1 /* 2 * Copyright (c) 2008, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang.invoke; 27 28 import java.lang.reflect.*; 29 import java.nio.ByteOrder; 30 import java.util.List; 31 import java.util.Arrays; 32 import java.util.ArrayList; 33 import java.util.NoSuchElementException; 34 35 import dalvik.system.VMStack; 36 import sun.invoke.util.VerifyAccess; 37 import sun.invoke.util.Wrapper; 38 import static java.lang.invoke.MethodHandleStatics.*; 39 40 /** 41 * This class consists exclusively of static methods that operate on or return 42 * method handles. They fall into several categories: 43 * <ul> 44 * <li>Lookup methods which help create method handles for methods and fields. 45 * <li>Combinator methods, which combine or transform pre-existing method handles into new ones. 46 * <li>Other factory methods to create method handles that emulate other common JVM operations or control flow patterns. 47 * </ul> 48 * <p> 49 * @author John Rose, JSR 292 EG 50 * @since 1.7 51 */ 52 public class MethodHandles { 53 54 private MethodHandles() { } // do not instantiate 55 56 // Android-changed: We do not use MemberName / MethodHandleImpl. 57 // 58 // private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory(); 59 // static { MethodHandleImpl.initStatics(); } 60 // See IMPL_LOOKUP below. 61 62 //// Method handle creation from ordinary methods. 63 64 /** 65 * Returns a {@link Lookup lookup object} with 66 * full capabilities to emulate all supported bytecode behaviors of the caller. 67 * These capabilities include <a href="MethodHandles.Lookup.html#privacc">private access</a> to the caller. 68 * Factory methods on the lookup object can create 69 * <a href="MethodHandleInfo.html#directmh">direct method handles</a> 70 * for any member that the caller has access to via bytecodes, 71 * including protected and private fields and methods. 72 * This lookup object is a <em>capability</em> which may be delegated to trusted agents. 73 * Do not store it in place where untrusted code can access it. 74 * <p> 75 * This method is caller sensitive, which means that it may return different 76 * values to different callers. 77 * <p> 78 * For any given caller class {@code C}, the lookup object returned by this call 79 * has equivalent capabilities to any lookup object 80 * supplied by the JVM to the bootstrap method of an 81 * <a href="package-summary.html#indyinsn">invokedynamic instruction</a> 82 * executing in the same caller class {@code C}. 83 * @return a lookup object for the caller of this method, with private access 84 */ 85 // Android-changed: Remove caller sensitive. 86 // @CallerSensitive 87 public static Lookup lookup() { 88 // Android-changed: Do not use Reflection.getCallerClass(). 89 return new Lookup(VMStack.getStackClass1()); 90 } 91 92 /** 93 * Returns a {@link Lookup lookup object} which is trusted minimally. 94 * It can only be used to create method handles to 95 * publicly accessible fields and methods. 96 * <p> 97 * As a matter of pure convention, the {@linkplain Lookup#lookupClass lookup class} 98 * of this lookup object will be {@link java.lang.Object}. 99 * 100 * <p style="font-size:smaller;"> 101 * <em>Discussion:</em> 102 * The lookup class can be changed to any other class {@code C} using an expression of the form 103 * {@link Lookup#in publicLookup().in(C.class)}. 104 * Since all classes have equal access to public names, 105 * such a change would confer no new access rights. 106 * A public lookup object is always subject to 107 * <a href="MethodHandles.Lookup.html#secmgr">security manager checks</a>. 108 * Also, it cannot access 109 * <a href="MethodHandles.Lookup.html#callsens">caller sensitive methods</a>. 110 * @return a lookup object which is trusted minimally 111 */ 112 public static Lookup publicLookup() { 113 return Lookup.PUBLIC_LOOKUP; 114 } 115 116 /** 117 * Performs an unchecked "crack" of a 118 * <a href="MethodHandleInfo.html#directmh">direct method handle</a>. 119 * The result is as if the user had obtained a lookup object capable enough 120 * to crack the target method handle, called 121 * {@link java.lang.invoke.MethodHandles.Lookup#revealDirect Lookup.revealDirect} 122 * on the target to obtain its symbolic reference, and then called 123 * {@link java.lang.invoke.MethodHandleInfo#reflectAs MethodHandleInfo.reflectAs} 124 * to resolve the symbolic reference to a member. 125 * <p> 126 * If there is a security manager, its {@code checkPermission} method 127 * is called with a {@code ReflectPermission("suppressAccessChecks")} permission. 128 * @param <T> the desired type of the result, either {@link Member} or a subtype 129 * @param target a direct method handle to crack into symbolic reference components 130 * @param expected a class object representing the desired result type {@code T} 131 * @return a reference to the method, constructor, or field object 132 * @exception SecurityException if the caller is not privileged to call {@code setAccessible} 133 * @exception NullPointerException if either argument is {@code null} 134 * @exception IllegalArgumentException if the target is not a direct method handle 135 * @exception ClassCastException if the member is not of the expected type 136 * @since 1.8 137 */ 138 public static <T extends Member> T 139 reflectAs(Class<T> expected, MethodHandle target) { 140 MethodHandleImpl directTarget = getMethodHandleImpl(target); 141 // Given that this is specified to be an "unchecked" crack, we can directly allocate 142 // a member from the underlying ArtField / Method and bypass all associated access checks. 143 return expected.cast(directTarget.getMemberInternal()); 144 } 145 146 /** 147 * A <em>lookup object</em> is a factory for creating method handles, 148 * when the creation requires access checking. 149 * Method handles do not perform 150 * access checks when they are called, but rather when they are created. 151 * Therefore, method handle access 152 * restrictions must be enforced when a method handle is created. 153 * The caller class against which those restrictions are enforced 154 * is known as the {@linkplain #lookupClass lookup class}. 155 * <p> 156 * A lookup class which needs to create method handles will call 157 * {@link #lookup MethodHandles.lookup} to create a factory for itself. 158 * When the {@code Lookup} factory object is created, the identity of the lookup class is 159 * determined, and securely stored in the {@code Lookup} object. 160 * The lookup class (or its delegates) may then use factory methods 161 * on the {@code Lookup} object to create method handles for access-checked members. 162 * This includes all methods, constructors, and fields which are allowed to the lookup class, 163 * even private ones. 164 * 165 * <h1><a name="lookups"></a>Lookup Factory Methods</h1> 166 * The factory methods on a {@code Lookup} object correspond to all major 167 * use cases for methods, constructors, and fields. 168 * Each method handle created by a factory method is the functional 169 * equivalent of a particular <em>bytecode behavior</em>. 170 * (Bytecode behaviors are described in section 5.4.3.5 of the Java Virtual Machine Specification.) 171 * Here is a summary of the correspondence between these factory methods and 172 * the behavior the resulting method handles: 173 * <table border=1 cellpadding=5 summary="lookup method behaviors"> 174 * <tr> 175 * <th><a name="equiv"></a>lookup expression</th> 176 * <th>member</th> 177 * <th>bytecode behavior</th> 178 * </tr> 179 * <tr> 180 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findGetter lookup.findGetter(C.class,"f",FT.class)}</td> 181 * <td>{@code FT f;}</td><td>{@code (T) this.f;}</td> 182 * </tr> 183 * <tr> 184 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findStaticGetter lookup.findStaticGetter(C.class,"f",FT.class)}</td> 185 * <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td> 186 * </tr> 187 * <tr> 188 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findSetter lookup.findSetter(C.class,"f",FT.class)}</td> 189 * <td>{@code FT f;}</td><td>{@code this.f = x;}</td> 190 * </tr> 191 * <tr> 192 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findStaticSetter lookup.findStaticSetter(C.class,"f",FT.class)}</td> 193 * <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td> 194 * </tr> 195 * <tr> 196 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findVirtual lookup.findVirtual(C.class,"m",MT)}</td> 197 * <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td> 198 * </tr> 199 * <tr> 200 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findStatic lookup.findStatic(C.class,"m",MT)}</td> 201 * <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td> 202 * </tr> 203 * <tr> 204 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findSpecial lookup.findSpecial(C.class,"m",MT,this.class)}</td> 205 * <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td> 206 * </tr> 207 * <tr> 208 * <td>{@link java.lang.invoke.MethodHandles.Lookup#findConstructor lookup.findConstructor(C.class,MT)}</td> 209 * <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td> 210 * </tr> 211 * <tr> 212 * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectGetter lookup.unreflectGetter(aField)}</td> 213 * <td>({@code static})?<br>{@code FT f;}</td><td>{@code (FT) aField.get(thisOrNull);}</td> 214 * </tr> 215 * <tr> 216 * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectSetter lookup.unreflectSetter(aField)}</td> 217 * <td>({@code static})?<br>{@code FT f;}</td><td>{@code aField.set(thisOrNull, arg);}</td> 218 * </tr> 219 * <tr> 220 * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflect lookup.unreflect(aMethod)}</td> 221 * <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td> 222 * </tr> 223 * <tr> 224 * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectConstructor lookup.unreflectConstructor(aConstructor)}</td> 225 * <td>{@code C(A*);}</td><td>{@code (C) aConstructor.newInstance(arg*);}</td> 226 * </tr> 227 * <tr> 228 * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflect lookup.unreflect(aMethod)}</td> 229 * <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td> 230 * </tr> 231 * </table> 232 * 233 * Here, the type {@code C} is the class or interface being searched for a member, 234 * documented as a parameter named {@code refc} in the lookup methods. 235 * The method type {@code MT} is composed from the return type {@code T} 236 * and the sequence of argument types {@code A*}. 237 * The constructor also has a sequence of argument types {@code A*} and 238 * is deemed to return the newly-created object of type {@code C}. 239 * Both {@code MT} and the field type {@code FT} are documented as a parameter named {@code type}. 240 * The formal parameter {@code this} stands for the self-reference of type {@code C}; 241 * if it is present, it is always the leading argument to the method handle invocation. 242 * (In the case of some {@code protected} members, {@code this} may be 243 * restricted in type to the lookup class; see below.) 244 * The name {@code arg} stands for all the other method handle arguments. 245 * In the code examples for the Core Reflection API, the name {@code thisOrNull} 246 * stands for a null reference if the accessed method or field is static, 247 * and {@code this} otherwise. 248 * The names {@code aMethod}, {@code aField}, and {@code aConstructor} stand 249 * for reflective objects corresponding to the given members. 250 * <p> 251 * In cases where the given member is of variable arity (i.e., a method or constructor) 252 * the returned method handle will also be of {@linkplain MethodHandle#asVarargsCollector variable arity}. 253 * In all other cases, the returned method handle will be of fixed arity. 254 * <p style="font-size:smaller;"> 255 * <em>Discussion:</em> 256 * The equivalence between looked-up method handles and underlying 257 * class members and bytecode behaviors 258 * can break down in a few ways: 259 * <ul style="font-size:smaller;"> 260 * <li>If {@code C} is not symbolically accessible from the lookup class's loader, 261 * the lookup can still succeed, even when there is no equivalent 262 * Java expression or bytecoded constant. 263 * <li>Likewise, if {@code T} or {@code MT} 264 * is not symbolically accessible from the lookup class's loader, 265 * the lookup can still succeed. 266 * For example, lookups for {@code MethodHandle.invokeExact} and 267 * {@code MethodHandle.invoke} will always succeed, regardless of requested type. 268 * <li>If there is a security manager installed, it can forbid the lookup 269 * on various grounds (<a href="MethodHandles.Lookup.html#secmgr">see below</a>). 270 * By contrast, the {@code ldc} instruction on a {@code CONSTANT_MethodHandle} 271 * constant is not subject to security manager checks. 272 * <li>If the looked-up method has a 273 * <a href="MethodHandle.html#maxarity">very large arity</a>, 274 * the method handle creation may fail, due to the method handle 275 * type having too many parameters. 276 * </ul> 277 * 278 * <h1><a name="access"></a>Access checking</h1> 279 * Access checks are applied in the factory methods of {@code Lookup}, 280 * when a method handle is created. 281 * This is a key difference from the Core Reflection API, since 282 * {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke} 283 * performs access checking against every caller, on every call. 284 * <p> 285 * All access checks start from a {@code Lookup} object, which 286 * compares its recorded lookup class against all requests to 287 * create method handles. 288 * A single {@code Lookup} object can be used to create any number 289 * of access-checked method handles, all checked against a single 290 * lookup class. 291 * <p> 292 * A {@code Lookup} object can be shared with other trusted code, 293 * such as a metaobject protocol. 294 * A shared {@code Lookup} object delegates the capability 295 * to create method handles on private members of the lookup class. 296 * Even if privileged code uses the {@code Lookup} object, 297 * the access checking is confined to the privileges of the 298 * original lookup class. 299 * <p> 300 * A lookup can fail, because 301 * the containing class is not accessible to the lookup class, or 302 * because the desired class member is missing, or because the 303 * desired class member is not accessible to the lookup class, or 304 * because the lookup object is not trusted enough to access the member. 305 * In any of these cases, a {@code ReflectiveOperationException} will be 306 * thrown from the attempted lookup. The exact class will be one of 307 * the following: 308 * <ul> 309 * <li>NoSuchMethodException — if a method is requested but does not exist 310 * <li>NoSuchFieldException — if a field is requested but does not exist 311 * <li>IllegalAccessException — if the member exists but an access check fails 312 * </ul> 313 * <p> 314 * In general, the conditions under which a method handle may be 315 * looked up for a method {@code M} are no more restrictive than the conditions 316 * under which the lookup class could have compiled, verified, and resolved a call to {@code M}. 317 * Where the JVM would raise exceptions like {@code NoSuchMethodError}, 318 * a method handle lookup will generally raise a corresponding 319 * checked exception, such as {@code NoSuchMethodException}. 320 * And the effect of invoking the method handle resulting from the lookup 321 * is <a href="MethodHandles.Lookup.html#equiv">exactly equivalent</a> 322 * to executing the compiled, verified, and resolved call to {@code M}. 323 * The same point is true of fields and constructors. 324 * <p style="font-size:smaller;"> 325 * <em>Discussion:</em> 326 * Access checks only apply to named and reflected methods, 327 * constructors, and fields. 328 * Other method handle creation methods, such as 329 * {@link MethodHandle#asType MethodHandle.asType}, 330 * do not require any access checks, and are used 331 * independently of any {@code Lookup} object. 332 * <p> 333 * If the desired member is {@code protected}, the usual JVM rules apply, 334 * including the requirement that the lookup class must be either be in the 335 * same package as the desired member, or must inherit that member. 336 * (See the Java Virtual Machine Specification, sections 4.9.2, 5.4.3.5, and 6.4.) 337 * In addition, if the desired member is a non-static field or method 338 * in a different package, the resulting method handle may only be applied 339 * to objects of the lookup class or one of its subclasses. 340 * This requirement is enforced by narrowing the type of the leading 341 * {@code this} parameter from {@code C} 342 * (which will necessarily be a superclass of the lookup class) 343 * to the lookup class itself. 344 * <p> 345 * The JVM imposes a similar requirement on {@code invokespecial} instruction, 346 * that the receiver argument must match both the resolved method <em>and</em> 347 * the current class. Again, this requirement is enforced by narrowing the 348 * type of the leading parameter to the resulting method handle. 349 * (See the Java Virtual Machine Specification, section 4.10.1.9.) 350 * <p> 351 * The JVM represents constructors and static initializer blocks as internal methods 352 * with special names ({@code "<init>"} and {@code "<clinit>"}). 353 * The internal syntax of invocation instructions allows them to refer to such internal 354 * methods as if they were normal methods, but the JVM bytecode verifier rejects them. 355 * A lookup of such an internal method will produce a {@code NoSuchMethodException}. 356 * <p> 357 * In some cases, access between nested classes is obtained by the Java compiler by creating 358 * an wrapper method to access a private method of another class 359 * in the same top-level declaration. 360 * For example, a nested class {@code C.D} 361 * can access private members within other related classes such as 362 * {@code C}, {@code C.D.E}, or {@code C.B}, 363 * but the Java compiler may need to generate wrapper methods in 364 * those related classes. In such cases, a {@code Lookup} object on 365 * {@code C.E} would be unable to those private members. 366 * A workaround for this limitation is the {@link Lookup#in Lookup.in} method, 367 * which can transform a lookup on {@code C.E} into one on any of those other 368 * classes, without special elevation of privilege. 369 * <p> 370 * The accesses permitted to a given lookup object may be limited, 371 * according to its set of {@link #lookupModes lookupModes}, 372 * to a subset of members normally accessible to the lookup class. 373 * For example, the {@link #publicLookup publicLookup} 374 * method produces a lookup object which is only allowed to access 375 * public members in public classes. 376 * The caller sensitive method {@link #lookup lookup} 377 * produces a lookup object with full capabilities relative to 378 * its caller class, to emulate all supported bytecode behaviors. 379 * Also, the {@link Lookup#in Lookup.in} method may produce a lookup object 380 * with fewer access modes than the original lookup object. 381 * 382 * <p style="font-size:smaller;"> 383 * <a name="privacc"></a> 384 * <em>Discussion of private access:</em> 385 * We say that a lookup has <em>private access</em> 386 * if its {@linkplain #lookupModes lookup modes} 387 * include the possibility of accessing {@code private} members. 388 * As documented in the relevant methods elsewhere, 389 * only lookups with private access possess the following capabilities: 390 * <ul style="font-size:smaller;"> 391 * <li>access private fields, methods, and constructors of the lookup class 392 * <li>create method handles which invoke <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a> methods, 393 * such as {@code Class.forName} 394 * <li>create method handles which {@link Lookup#findSpecial emulate invokespecial} instructions 395 * <li>avoid <a href="MethodHandles.Lookup.html#secmgr">package access checks</a> 396 * for classes accessible to the lookup class 397 * <li>create {@link Lookup#in delegated lookup objects} which have private access to other classes 398 * within the same package member 399 * </ul> 400 * <p style="font-size:smaller;"> 401 * Each of these permissions is a consequence of the fact that a lookup object 402 * with private access can be securely traced back to an originating class, 403 * whose <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> and Java language access permissions 404 * can be reliably determined and emulated by method handles. 405 * 406 * <h1><a name="secmgr"></a>Security manager interactions</h1> 407 * Although bytecode instructions can only refer to classes in 408 * a related class loader, this API can search for methods in any 409 * class, as long as a reference to its {@code Class} object is 410 * available. Such cross-loader references are also possible with the 411 * Core Reflection API, and are impossible to bytecode instructions 412 * such as {@code invokestatic} or {@code getfield}. 413 * There is a {@linkplain java.lang.SecurityManager security manager API} 414 * to allow applications to check such cross-loader references. 415 * These checks apply to both the {@code MethodHandles.Lookup} API 416 * and the Core Reflection API 417 * (as found on {@link java.lang.Class Class}). 418 * <p> 419 * If a security manager is present, member lookups are subject to 420 * additional checks. 421 * From one to three calls are made to the security manager. 422 * Any of these calls can refuse access by throwing a 423 * {@link java.lang.SecurityException SecurityException}. 424 * Define {@code smgr} as the security manager, 425 * {@code lookc} as the lookup class of the current lookup object, 426 * {@code refc} as the containing class in which the member 427 * is being sought, and {@code defc} as the class in which the 428 * member is actually defined. 429 * The value {@code lookc} is defined as <em>not present</em> 430 * if the current lookup object does not have 431 * <a href="MethodHandles.Lookup.html#privacc">private access</a>. 432 * The calls are made according to the following rules: 433 * <ul> 434 * <li><b>Step 1:</b> 435 * If {@code lookc} is not present, or if its class loader is not 436 * the same as or an ancestor of the class loader of {@code refc}, 437 * then {@link SecurityManager#checkPackageAccess 438 * smgr.checkPackageAccess(refcPkg)} is called, 439 * where {@code refcPkg} is the package of {@code refc}. 440 * <li><b>Step 2:</b> 441 * If the retrieved member is not public and 442 * {@code lookc} is not present, then 443 * {@link SecurityManager#checkPermission smgr.checkPermission} 444 * with {@code RuntimePermission("accessDeclaredMembers")} is called. 445 * <li><b>Step 3:</b> 446 * If the retrieved member is not public, 447 * and if {@code lookc} is not present, 448 * and if {@code defc} and {@code refc} are different, 449 * then {@link SecurityManager#checkPackageAccess 450 * smgr.checkPackageAccess(defcPkg)} is called, 451 * where {@code defcPkg} is the package of {@code defc}. 452 * </ul> 453 * Security checks are performed after other access checks have passed. 454 * Therefore, the above rules presuppose a member that is public, 455 * or else that is being accessed from a lookup class that has 456 * rights to access the member. 457 * 458 * <h1><a name="callsens"></a>Caller sensitive methods</h1> 459 * A small number of Java methods have a special property called caller sensitivity. 460 * A <em>caller-sensitive</em> method can behave differently depending on the 461 * identity of its immediate caller. 462 * <p> 463 * If a method handle for a caller-sensitive method is requested, 464 * the general rules for <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> apply, 465 * but they take account of the lookup class in a special way. 466 * The resulting method handle behaves as if it were called 467 * from an instruction contained in the lookup class, 468 * so that the caller-sensitive method detects the lookup class. 469 * (By contrast, the invoker of the method handle is disregarded.) 470 * Thus, in the case of caller-sensitive methods, 471 * different lookup classes may give rise to 472 * differently behaving method handles. 473 * <p> 474 * In cases where the lookup object is 475 * {@link #publicLookup publicLookup()}, 476 * or some other lookup object without 477 * <a href="MethodHandles.Lookup.html#privacc">private access</a>, 478 * the lookup class is disregarded. 479 * In such cases, no caller-sensitive method handle can be created, 480 * access is forbidden, and the lookup fails with an 481 * {@code IllegalAccessException}. 482 * <p style="font-size:smaller;"> 483 * <em>Discussion:</em> 484 * For example, the caller-sensitive method 485 * {@link java.lang.Class#forName(String) Class.forName(x)} 486 * can return varying classes or throw varying exceptions, 487 * depending on the class loader of the class that calls it. 488 * A public lookup of {@code Class.forName} will fail, because 489 * there is no reasonable way to determine its bytecode behavior. 490 * <p style="font-size:smaller;"> 491 * If an application caches method handles for broad sharing, 492 * it should use {@code publicLookup()} to create them. 493 * If there is a lookup of {@code Class.forName}, it will fail, 494 * and the application must take appropriate action in that case. 495 * It may be that a later lookup, perhaps during the invocation of a 496 * bootstrap method, can incorporate the specific identity 497 * of the caller, making the method accessible. 498 * <p style="font-size:smaller;"> 499 * The function {@code MethodHandles.lookup} is caller sensitive 500 * so that there can be a secure foundation for lookups. 501 * Nearly all other methods in the JSR 292 API rely on lookup 502 * objects to check access requests. 503 */ 504 // Android-changed: Change link targets from MethodHandles#[public]Lookup to 505 // #[public]Lookup to work around complaints from javadoc. 506 public static final 507 class Lookup { 508 /** The class on behalf of whom the lookup is being performed. */ 509 /* @NonNull */ private final Class<?> lookupClass; 510 511 /** The allowed sorts of members which may be looked up (PUBLIC, etc.). */ 512 private final int allowedModes; 513 514 /** A single-bit mask representing {@code public} access, 515 * which may contribute to the result of {@link #lookupModes lookupModes}. 516 * The value, {@code 0x01}, happens to be the same as the value of the 517 * {@code public} {@linkplain java.lang.reflect.Modifier#PUBLIC modifier bit}. 518 */ 519 public static final int PUBLIC = Modifier.PUBLIC; 520 521 /** A single-bit mask representing {@code private} access, 522 * which may contribute to the result of {@link #lookupModes lookupModes}. 523 * The value, {@code 0x02}, happens to be the same as the value of the 524 * {@code private} {@linkplain java.lang.reflect.Modifier#PRIVATE modifier bit}. 525 */ 526 public static final int PRIVATE = Modifier.PRIVATE; 527 528 /** A single-bit mask representing {@code protected} access, 529 * which may contribute to the result of {@link #lookupModes lookupModes}. 530 * The value, {@code 0x04}, happens to be the same as the value of the 531 * {@code protected} {@linkplain java.lang.reflect.Modifier#PROTECTED modifier bit}. 532 */ 533 public static final int PROTECTED = Modifier.PROTECTED; 534 535 /** A single-bit mask representing {@code package} access (default access), 536 * which may contribute to the result of {@link #lookupModes lookupModes}. 537 * The value is {@code 0x08}, which does not correspond meaningfully to 538 * any particular {@linkplain java.lang.reflect.Modifier modifier bit}. 539 */ 540 public static final int PACKAGE = Modifier.STATIC; 541 542 private static final int ALL_MODES = (PUBLIC | PRIVATE | PROTECTED | PACKAGE); 543 544 // Android-note: Android has no notion of a trusted lookup. If required, such lookups 545 // are performed by the runtime. As a result, we always use lookupClass, which will always 546 // be non-null in our implementation. 547 // 548 // private static final int TRUSTED = -1; 549 550 private static int fixmods(int mods) { 551 mods &= (ALL_MODES - PACKAGE); 552 return (mods != 0) ? mods : PACKAGE; 553 } 554 555 /** Tells which class is performing the lookup. It is this class against 556 * which checks are performed for visibility and access permissions. 557 * <p> 558 * The class implies a maximum level of access permission, 559 * but the permissions may be additionally limited by the bitmask 560 * {@link #lookupModes lookupModes}, which controls whether non-public members 561 * can be accessed. 562 * @return the lookup class, on behalf of which this lookup object finds members 563 */ 564 public Class<?> lookupClass() { 565 return lookupClass; 566 } 567 568 /** Tells which access-protection classes of members this lookup object can produce. 569 * The result is a bit-mask of the bits 570 * {@linkplain #PUBLIC PUBLIC (0x01)}, 571 * {@linkplain #PRIVATE PRIVATE (0x02)}, 572 * {@linkplain #PROTECTED PROTECTED (0x04)}, 573 * and {@linkplain #PACKAGE PACKAGE (0x08)}. 574 * <p> 575 * A freshly-created lookup object 576 * on the {@linkplain java.lang.invoke.MethodHandles#lookup() caller's class} 577 * has all possible bits set, since the caller class can access all its own members. 578 * A lookup object on a new lookup class 579 * {@linkplain java.lang.invoke.MethodHandles.Lookup#in created from a previous lookup object} 580 * may have some mode bits set to zero. 581 * The purpose of this is to restrict access via the new lookup object, 582 * so that it can access only names which can be reached by the original 583 * lookup object, and also by the new lookup class. 584 * @return the lookup modes, which limit the kinds of access performed by this lookup object 585 */ 586 public int lookupModes() { 587 return allowedModes & ALL_MODES; 588 } 589 590 /** Embody the current class (the lookupClass) as a lookup class 591 * for method handle creation. 592 * Must be called by from a method in this package, 593 * which in turn is called by a method not in this package. 594 */ 595 Lookup(Class<?> lookupClass) { 596 this(lookupClass, ALL_MODES); 597 // make sure we haven't accidentally picked up a privileged class: 598 checkUnprivilegedlookupClass(lookupClass, ALL_MODES); 599 } 600 601 private Lookup(Class<?> lookupClass, int allowedModes) { 602 this.lookupClass = lookupClass; 603 this.allowedModes = allowedModes; 604 } 605 606 /** 607 * Creates a lookup on the specified new lookup class. 608 * The resulting object will report the specified 609 * class as its own {@link #lookupClass lookupClass}. 610 * <p> 611 * However, the resulting {@code Lookup} object is guaranteed 612 * to have no more access capabilities than the original. 613 * In particular, access capabilities can be lost as follows:<ul> 614 * <li>If the new lookup class differs from the old one, 615 * protected members will not be accessible by virtue of inheritance. 616 * (Protected members may continue to be accessible because of package sharing.) 617 * <li>If the new lookup class is in a different package 618 * than the old one, protected and default (package) members will not be accessible. 619 * <li>If the new lookup class is not within the same package member 620 * as the old one, private members will not be accessible. 621 * <li>If the new lookup class is not accessible to the old lookup class, 622 * then no members, not even public members, will be accessible. 623 * (In all other cases, public members will continue to be accessible.) 624 * </ul> 625 * 626 * @param requestedLookupClass the desired lookup class for the new lookup object 627 * @return a lookup object which reports the desired lookup class 628 * @throws NullPointerException if the argument is null 629 */ 630 public Lookup in(Class<?> requestedLookupClass) { 631 requestedLookupClass.getClass(); // null check 632 // Android-changed: There's no notion of a trusted lookup. 633 // if (allowedModes == TRUSTED) // IMPL_LOOKUP can make any lookup at all 634 // return new Lookup(requestedLookupClass, ALL_MODES); 635 636 if (requestedLookupClass == this.lookupClass) 637 return this; // keep same capabilities 638 int newModes = (allowedModes & (ALL_MODES & ~PROTECTED)); 639 if ((newModes & PACKAGE) != 0 640 && !VerifyAccess.isSamePackage(this.lookupClass, requestedLookupClass)) { 641 newModes &= ~(PACKAGE|PRIVATE); 642 } 643 // Allow nestmate lookups to be created without special privilege: 644 if ((newModes & PRIVATE) != 0 645 && !VerifyAccess.isSamePackageMember(this.lookupClass, requestedLookupClass)) { 646 newModes &= ~PRIVATE; 647 } 648 if ((newModes & PUBLIC) != 0 649 && !VerifyAccess.isClassAccessible(requestedLookupClass, this.lookupClass, allowedModes)) { 650 // The requested class it not accessible from the lookup class. 651 // No permissions. 652 newModes = 0; 653 } 654 checkUnprivilegedlookupClass(requestedLookupClass, newModes); 655 return new Lookup(requestedLookupClass, newModes); 656 } 657 658 // Make sure outer class is initialized first. 659 // 660 // Android-changed: Removed unnecessary reference to IMPL_NAMES. 661 // static { IMPL_NAMES.getClass(); } 662 663 /** Version of lookup which is trusted minimally. 664 * It can only be used to create method handles to 665 * publicly accessible members. 666 */ 667 static final Lookup PUBLIC_LOOKUP = new Lookup(Object.class, PUBLIC); 668 669 /** Package-private version of lookup which is trusted. */ 670 static final Lookup IMPL_LOOKUP = new Lookup(Object.class, ALL_MODES); 671 672 private static void checkUnprivilegedlookupClass(Class<?> lookupClass, int allowedModes) { 673 String name = lookupClass.getName(); 674 if (name.startsWith("java.lang.invoke.")) 675 throw newIllegalArgumentException("illegal lookupClass: "+lookupClass); 676 677 // For caller-sensitive MethodHandles.lookup() 678 // disallow lookup more restricted packages 679 // 680 // Android-changed: The bootstrap classloader isn't null. 681 if (allowedModes == ALL_MODES && 682 lookupClass.getClassLoader() == Object.class.getClassLoader()) { 683 if (name.startsWith("java.") || 684 (name.startsWith("sun.") 685 && !name.startsWith("sun.invoke.") 686 && !name.equals("sun.reflect.ReflectionFactory"))) { 687 throw newIllegalArgumentException("illegal lookupClass: " + lookupClass); 688 } 689 } 690 } 691 692 /** 693 * Displays the name of the class from which lookups are to be made. 694 * (The name is the one reported by {@link java.lang.Class#getName() Class.getName}.) 695 * If there are restrictions on the access permitted to this lookup, 696 * this is indicated by adding a suffix to the class name, consisting 697 * of a slash and a keyword. The keyword represents the strongest 698 * allowed access, and is chosen as follows: 699 * <ul> 700 * <li>If no access is allowed, the suffix is "/noaccess". 701 * <li>If only public access is allowed, the suffix is "/public". 702 * <li>If only public and package access are allowed, the suffix is "/package". 703 * <li>If only public, package, and private access are allowed, the suffix is "/private". 704 * </ul> 705 * If none of the above cases apply, it is the case that full 706 * access (public, package, private, and protected) is allowed. 707 * In this case, no suffix is added. 708 * This is true only of an object obtained originally from 709 * {@link java.lang.invoke.MethodHandles#lookup MethodHandles.lookup}. 710 * Objects created by {@link java.lang.invoke.MethodHandles.Lookup#in Lookup.in} 711 * always have restricted access, and will display a suffix. 712 * <p> 713 * (It may seem strange that protected access should be 714 * stronger than private access. Viewed independently from 715 * package access, protected access is the first to be lost, 716 * because it requires a direct subclass relationship between 717 * caller and callee.) 718 * @see #in 719 */ 720 @Override 721 public String toString() { 722 String cname = lookupClass.getName(); 723 switch (allowedModes) { 724 case 0: // no privileges 725 return cname + "/noaccess"; 726 case PUBLIC: 727 return cname + "/public"; 728 case PUBLIC|PACKAGE: 729 return cname + "/package"; 730 case ALL_MODES & ~PROTECTED: 731 return cname + "/private"; 732 case ALL_MODES: 733 return cname; 734 // Android-changed: No support for TRUSTED callers. 735 // case TRUSTED: 736 // return "/trusted"; // internal only; not exported 737 default: // Should not happen, but it's a bitfield... 738 cname = cname + "/" + Integer.toHexString(allowedModes); 739 assert(false) : cname; 740 return cname; 741 } 742 } 743 744 /** 745 * Produces a method handle for a static method. 746 * The type of the method handle will be that of the method. 747 * (Since static methods do not take receivers, there is no 748 * additional receiver argument inserted into the method handle type, 749 * as there would be with {@link #findVirtual findVirtual} or {@link #findSpecial findSpecial}.) 750 * The method and all its argument types must be accessible to the lookup object. 751 * <p> 752 * The returned method handle will have 753 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 754 * the method's variable arity modifier bit ({@code 0x0080}) is set. 755 * <p> 756 * If the returned method handle is invoked, the method's class will 757 * be initialized, if it has not already been initialized. 758 * <p><b>Example:</b> 759 * <blockquote><pre>{@code 760 import static java.lang.invoke.MethodHandles.*; 761 import static java.lang.invoke.MethodType.*; 762 ... 763 MethodHandle MH_asList = publicLookup().findStatic(Arrays.class, 764 "asList", methodType(List.class, Object[].class)); 765 assertEquals("[x, y]", MH_asList.invoke("x", "y").toString()); 766 * }</pre></blockquote> 767 * @param refc the class from which the method is accessed 768 * @param name the name of the method 769 * @param type the type of the method 770 * @return the desired method handle 771 * @throws NoSuchMethodException if the method does not exist 772 * @throws IllegalAccessException if access checking fails, 773 * or if the method is not {@code static}, 774 * or if the method's variable arity modifier bit 775 * is set and {@code asVarargsCollector} fails 776 * @exception SecurityException if a security manager is present and it 777 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 778 * @throws NullPointerException if any argument is null 779 */ 780 public 781 MethodHandle findStatic(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException { 782 Method method = refc.getDeclaredMethod(name, type.ptypes()); 783 final int modifiers = method.getModifiers(); 784 if (!Modifier.isStatic(modifiers)) { 785 throw new IllegalAccessException("Method" + method + " is not static"); 786 } 787 checkReturnType(method, type); 788 checkAccess(refc, method.getDeclaringClass(), modifiers, method.getName()); 789 return createMethodHandle(method, MethodHandle.INVOKE_STATIC, type); 790 } 791 792 private MethodHandle findVirtualForMH(String name, MethodType type) { 793 // these names require special lookups because of the implicit MethodType argument 794 if ("invoke".equals(name)) 795 return invoker(type); 796 if ("invokeExact".equals(name)) 797 return exactInvoker(type); 798 return null; 799 } 800 801 private MethodHandle findVirtualForVH(String name, MethodType type) { 802 VarHandle.AccessMode accessMode; 803 try { 804 accessMode = VarHandle.AccessMode.valueFromMethodName(name); 805 } catch (IllegalArgumentException e) { 806 return null; 807 } 808 return varHandleInvoker(accessMode, type); 809 } 810 811 private static MethodHandle createMethodHandle(Method method, int handleKind, 812 MethodType methodType) { 813 MethodHandle mh = new MethodHandleImpl(method.getArtMethod(), handleKind, methodType); 814 if (method.isVarArgs()) { 815 return new Transformers.VarargsCollector(mh); 816 } else { 817 return mh; 818 } 819 } 820 821 /** 822 * Produces a method handle for a virtual method. 823 * The type of the method handle will be that of the method, 824 * with the receiver type (usually {@code refc}) prepended. 825 * The method and all its argument types must be accessible to the lookup object. 826 * <p> 827 * When called, the handle will treat the first argument as a receiver 828 * and dispatch on the receiver's type to determine which method 829 * implementation to enter. 830 * (The dispatching action is identical with that performed by an 831 * {@code invokevirtual} or {@code invokeinterface} instruction.) 832 * <p> 833 * The first argument will be of type {@code refc} if the lookup 834 * class has full privileges to access the member. Otherwise 835 * the member must be {@code protected} and the first argument 836 * will be restricted in type to the lookup class. 837 * <p> 838 * The returned method handle will have 839 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 840 * the method's variable arity modifier bit ({@code 0x0080}) is set. 841 * <p> 842 * Because of the general <a href="MethodHandles.Lookup.html#equiv">equivalence</a> between {@code invokevirtual} 843 * instructions and method handles produced by {@code findVirtual}, 844 * if the class is {@code MethodHandle} and the name string is 845 * {@code invokeExact} or {@code invoke}, the resulting 846 * method handle is equivalent to one produced by 847 * {@link java.lang.invoke.MethodHandles#exactInvoker MethodHandles.exactInvoker} or 848 * {@link java.lang.invoke.MethodHandles#invoker MethodHandles.invoker} 849 * with the same {@code type} argument. 850 * 851 * <b>Example:</b> 852 * <blockquote><pre>{@code 853 import static java.lang.invoke.MethodHandles.*; 854 import static java.lang.invoke.MethodType.*; 855 ... 856 MethodHandle MH_concat = publicLookup().findVirtual(String.class, 857 "concat", methodType(String.class, String.class)); 858 MethodHandle MH_hashCode = publicLookup().findVirtual(Object.class, 859 "hashCode", methodType(int.class)); 860 MethodHandle MH_hashCode_String = publicLookup().findVirtual(String.class, 861 "hashCode", methodType(int.class)); 862 assertEquals("xy", (String) MH_concat.invokeExact("x", "y")); 863 assertEquals("xy".hashCode(), (int) MH_hashCode.invokeExact((Object)"xy")); 864 assertEquals("xy".hashCode(), (int) MH_hashCode_String.invokeExact("xy")); 865 // interface method: 866 MethodHandle MH_subSequence = publicLookup().findVirtual(CharSequence.class, 867 "subSequence", methodType(CharSequence.class, int.class, int.class)); 868 assertEquals("def", MH_subSequence.invoke("abcdefghi", 3, 6).toString()); 869 // constructor "internal method" must be accessed differently: 870 MethodType MT_newString = methodType(void.class); //()V for new String() 871 try { assertEquals("impossible", lookup() 872 .findVirtual(String.class, "<init>", MT_newString)); 873 } catch (NoSuchMethodException ex) { } // OK 874 MethodHandle MH_newString = publicLookup() 875 .findConstructor(String.class, MT_newString); 876 assertEquals("", (String) MH_newString.invokeExact()); 877 * }</pre></blockquote> 878 * 879 * @param refc the class or interface from which the method is accessed 880 * @param name the name of the method 881 * @param type the type of the method, with the receiver argument omitted 882 * @return the desired method handle 883 * @throws NoSuchMethodException if the method does not exist 884 * @throws IllegalAccessException if access checking fails, 885 * or if the method is {@code static} 886 * or if the method's variable arity modifier bit 887 * is set and {@code asVarargsCollector} fails 888 * @exception SecurityException if a security manager is present and it 889 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 890 * @throws NullPointerException if any argument is null 891 */ 892 public MethodHandle findVirtual(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException { 893 // Special case : when we're looking up a virtual method on the MethodHandles class 894 // itself, we can return one of our specialized invokers. 895 if (refc == MethodHandle.class) { 896 MethodHandle mh = findVirtualForMH(name, type); 897 if (mh != null) { 898 return mh; 899 } 900 } else if (refc == VarHandle.class) { 901 // Returns an non-exact invoker. 902 MethodHandle mh = findVirtualForVH(name, type); 903 if (mh != null) { 904 return mh; 905 } 906 } 907 908 Method method = refc.getInstanceMethod(name, type.ptypes()); 909 if (method == null) { 910 // This is pretty ugly and a consequence of the MethodHandles API. We have to throw 911 // an IAE and not an NSME if the method exists but is static (even though the RI's 912 // IAE has a message that says "no such method"). We confine the ugliness and 913 // slowness to the failure case, and allow getInstanceMethod to remain fairly 914 // general. 915 try { 916 Method m = refc.getDeclaredMethod(name, type.ptypes()); 917 if (Modifier.isStatic(m.getModifiers())) { 918 throw new IllegalAccessException("Method" + m + " is static"); 919 } 920 } catch (NoSuchMethodException ignored) { 921 } 922 923 throw new NoSuchMethodException(name + " " + Arrays.toString(type.ptypes())); 924 } 925 checkReturnType(method, type); 926 927 // We have a valid method, perform access checks. 928 checkAccess(refc, method.getDeclaringClass(), method.getModifiers(), method.getName()); 929 930 // Insert the leading reference parameter. 931 MethodType handleType = type.insertParameterTypes(0, refc); 932 return createMethodHandle(method, MethodHandle.INVOKE_VIRTUAL, handleType); 933 } 934 935 /** 936 * Produces a method handle which creates an object and initializes it, using 937 * the constructor of the specified type. 938 * The parameter types of the method handle will be those of the constructor, 939 * while the return type will be a reference to the constructor's class. 940 * The constructor and all its argument types must be accessible to the lookup object. 941 * <p> 942 * The requested type must have a return type of {@code void}. 943 * (This is consistent with the JVM's treatment of constructor type descriptors.) 944 * <p> 945 * The returned method handle will have 946 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 947 * the constructor's variable arity modifier bit ({@code 0x0080}) is set. 948 * <p> 949 * If the returned method handle is invoked, the constructor's class will 950 * be initialized, if it has not already been initialized. 951 * <p><b>Example:</b> 952 * <blockquote><pre>{@code 953 import static java.lang.invoke.MethodHandles.*; 954 import static java.lang.invoke.MethodType.*; 955 ... 956 MethodHandle MH_newArrayList = publicLookup().findConstructor( 957 ArrayList.class, methodType(void.class, Collection.class)); 958 Collection orig = Arrays.asList("x", "y"); 959 Collection copy = (ArrayList) MH_newArrayList.invokeExact(orig); 960 assert(orig != copy); 961 assertEquals(orig, copy); 962 // a variable-arity constructor: 963 MethodHandle MH_newProcessBuilder = publicLookup().findConstructor( 964 ProcessBuilder.class, methodType(void.class, String[].class)); 965 ProcessBuilder pb = (ProcessBuilder) 966 MH_newProcessBuilder.invoke("x", "y", "z"); 967 assertEquals("[x, y, z]", pb.command().toString()); 968 * }</pre></blockquote> 969 * @param refc the class or interface from which the method is accessed 970 * @param type the type of the method, with the receiver argument omitted, and a void return type 971 * @return the desired method handle 972 * @throws NoSuchMethodException if the constructor does not exist 973 * @throws IllegalAccessException if access checking fails 974 * or if the method's variable arity modifier bit 975 * is set and {@code asVarargsCollector} fails 976 * @exception SecurityException if a security manager is present and it 977 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 978 * @throws NullPointerException if any argument is null 979 */ 980 public MethodHandle findConstructor(Class<?> refc, MethodType type) throws NoSuchMethodException, IllegalAccessException { 981 if (refc.isArray()) { 982 throw new NoSuchMethodException("no constructor for array class: " + refc.getName()); 983 } 984 // The queried |type| is (PT1,PT2,..)V 985 Constructor constructor = refc.getDeclaredConstructor(type.ptypes()); 986 if (constructor == null) { 987 throw new NoSuchMethodException( 988 "No constructor for " + constructor.getDeclaringClass() + " matching " + type); 989 } 990 checkAccess(refc, constructor.getDeclaringClass(), constructor.getModifiers(), 991 constructor.getName()); 992 993 return createMethodHandleForConstructor(constructor); 994 } 995 996 private MethodHandle createMethodHandleForConstructor(Constructor constructor) { 997 Class<?> refc = constructor.getDeclaringClass(); 998 MethodType constructorType = 999 MethodType.methodType(refc, constructor.getParameterTypes()); 1000 MethodHandle mh; 1001 if (refc == String.class) { 1002 // String constructors have optimized StringFactory methods 1003 // that matches returned type. These factory methods combine the 1004 // memory allocation and initialization calls for String objects. 1005 mh = new MethodHandleImpl(constructor.getArtMethod(), MethodHandle.INVOKE_DIRECT, 1006 constructorType); 1007 } else { 1008 // Constructors for all other classes use a Construct transformer to perform 1009 // their memory allocation and call to <init>. 1010 MethodType initType = initMethodType(constructorType); 1011 MethodHandle initHandle = new MethodHandleImpl( 1012 constructor.getArtMethod(), MethodHandle.INVOKE_DIRECT, initType); 1013 mh = new Transformers.Construct(initHandle, constructorType); 1014 } 1015 1016 if (constructor.isVarArgs()) { 1017 mh = new Transformers.VarargsCollector(mh); 1018 } 1019 return mh; 1020 } 1021 1022 private static MethodType initMethodType(MethodType constructorType) { 1023 // Returns a MethodType appropriate for class <init> 1024 // methods. Constructor MethodTypes have the form 1025 // (PT1,PT2,...)C and class <init> MethodTypes have the 1026 // form (C,PT1,PT2,...)V. 1027 assert constructorType.rtype() != void.class; 1028 1029 // Insert constructorType C as the first parameter type in 1030 // the MethodType for <init>. 1031 Class<?> [] initPtypes = new Class<?> [constructorType.ptypes().length + 1]; 1032 initPtypes[0] = constructorType.rtype(); 1033 System.arraycopy(constructorType.ptypes(), 0, initPtypes, 1, 1034 constructorType.ptypes().length); 1035 1036 // Set the return type for the <init> MethodType to be void. 1037 return MethodType.methodType(void.class, initPtypes); 1038 } 1039 1040 /** 1041 * Produces an early-bound method handle for a virtual method. 1042 * It will bypass checks for overriding methods on the receiver, 1043 * <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial} 1044 * instruction from within the explicitly specified {@code specialCaller}. 1045 * The type of the method handle will be that of the method, 1046 * with a suitably restricted receiver type prepended. 1047 * (The receiver type will be {@code specialCaller} or a subtype.) 1048 * The method and all its argument types must be accessible 1049 * to the lookup object. 1050 * <p> 1051 * Before method resolution, 1052 * if the explicitly specified caller class is not identical with the 1053 * lookup class, or if this lookup object does not have 1054 * <a href="MethodHandles.Lookup.html#privacc">private access</a> 1055 * privileges, the access fails. 1056 * <p> 1057 * The returned method handle will have 1058 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 1059 * the method's variable arity modifier bit ({@code 0x0080}) is set. 1060 * <p style="font-size:smaller;"> 1061 * <em>(Note: JVM internal methods named {@code "<init>"} are not visible to this API, 1062 * even though the {@code invokespecial} instruction can refer to them 1063 * in special circumstances. Use {@link #findConstructor findConstructor} 1064 * to access instance initialization methods in a safe manner.)</em> 1065 * <p><b>Example:</b> 1066 * <blockquote><pre>{@code 1067 import static java.lang.invoke.MethodHandles.*; 1068 import static java.lang.invoke.MethodType.*; 1069 ... 1070 static class Listie extends ArrayList { 1071 public String toString() { return "[wee Listie]"; } 1072 static Lookup lookup() { return MethodHandles.lookup(); } 1073 } 1074 ... 1075 // no access to constructor via invokeSpecial: 1076 MethodHandle MH_newListie = Listie.lookup() 1077 .findConstructor(Listie.class, methodType(void.class)); 1078 Listie l = (Listie) MH_newListie.invokeExact(); 1079 try { assertEquals("impossible", Listie.lookup().findSpecial( 1080 Listie.class, "<init>", methodType(void.class), Listie.class)); 1081 } catch (NoSuchMethodException ex) { } // OK 1082 // access to super and self methods via invokeSpecial: 1083 MethodHandle MH_super = Listie.lookup().findSpecial( 1084 ArrayList.class, "toString" , methodType(String.class), Listie.class); 1085 MethodHandle MH_this = Listie.lookup().findSpecial( 1086 Listie.class, "toString" , methodType(String.class), Listie.class); 1087 MethodHandle MH_duper = Listie.lookup().findSpecial( 1088 Object.class, "toString" , methodType(String.class), Listie.class); 1089 assertEquals("[]", (String) MH_super.invokeExact(l)); 1090 assertEquals(""+l, (String) MH_this.invokeExact(l)); 1091 assertEquals("[]", (String) MH_duper.invokeExact(l)); // ArrayList method 1092 try { assertEquals("inaccessible", Listie.lookup().findSpecial( 1093 String.class, "toString", methodType(String.class), Listie.class)); 1094 } catch (IllegalAccessException ex) { } // OK 1095 Listie subl = new Listie() { public String toString() { return "[subclass]"; } }; 1096 assertEquals(""+l, (String) MH_this.invokeExact(subl)); // Listie method 1097 * }</pre></blockquote> 1098 * 1099 * @param refc the class or interface from which the method is accessed 1100 * @param name the name of the method (which must not be "<init>") 1101 * @param type the type of the method, with the receiver argument omitted 1102 * @param specialCaller the proposed calling class to perform the {@code invokespecial} 1103 * @return the desired method handle 1104 * @throws NoSuchMethodException if the method does not exist 1105 * @throws IllegalAccessException if access checking fails 1106 * or if the method's variable arity modifier bit 1107 * is set and {@code asVarargsCollector} fails 1108 * @exception SecurityException if a security manager is present and it 1109 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1110 * @throws NullPointerException if any argument is null 1111 */ 1112 public MethodHandle findSpecial(Class<?> refc, String name, MethodType type, 1113 Class<?> specialCaller) throws NoSuchMethodException, IllegalAccessException { 1114 if (specialCaller == null) { 1115 throw new NullPointerException("specialCaller == null"); 1116 } 1117 1118 if (type == null) { 1119 throw new NullPointerException("type == null"); 1120 } 1121 1122 if (name == null) { 1123 throw new NullPointerException("name == null"); 1124 } 1125 1126 if (refc == null) { 1127 throw new NullPointerException("ref == null"); 1128 } 1129 1130 // Make sure that the special caller is identical to the lookup class or that we have 1131 // private access. 1132 checkSpecialCaller(specialCaller); 1133 1134 // Even though constructors are invoked using a "special" invoke, handles to them can't 1135 // be created using findSpecial. Callers must use findConstructor instead. Similarly, 1136 // there is no path for calling static class initializers. 1137 if (name.startsWith("<")) { 1138 throw new NoSuchMethodException(name + " is not a valid method name."); 1139 } 1140 1141 Method method = refc.getDeclaredMethod(name, type.ptypes()); 1142 checkReturnType(method, type); 1143 return findSpecial(method, type, refc, specialCaller); 1144 } 1145 1146 private MethodHandle findSpecial(Method method, MethodType type, 1147 Class<?> refc, Class<?> specialCaller) 1148 throws IllegalAccessException { 1149 if (Modifier.isStatic(method.getModifiers())) { 1150 throw new IllegalAccessException("expected a non-static method:" + method); 1151 } 1152 1153 if (Modifier.isPrivate(method.getModifiers())) { 1154 // Since this is a private method, we'll need to also make sure that the 1155 // lookup class is the same as the refering class. We've already checked that 1156 // the specialCaller is the same as the special lookup class, both of these must 1157 // be the same as the declaring class(*) in order to access the private method. 1158 // 1159 // (*) Well, this isn't true for nested classes but OpenJDK doesn't support those 1160 // either. 1161 if (refc != lookupClass()) { 1162 throw new IllegalAccessException("no private access for invokespecial : " 1163 + refc + ", from" + this); 1164 } 1165 1166 // This is a private method, so there's nothing special to do. 1167 MethodType handleType = type.insertParameterTypes(0, refc); 1168 return createMethodHandle(method, MethodHandle.INVOKE_DIRECT, handleType); 1169 } 1170 1171 // This is a public, protected or package-private method, which means we're expecting 1172 // invoke-super semantics. We'll have to restrict the receiver type appropriately on the 1173 // handle once we check that there really is a "super" relationship between them. 1174 if (!method.getDeclaringClass().isAssignableFrom(specialCaller)) { 1175 throw new IllegalAccessException(refc + "is not assignable from " + specialCaller); 1176 } 1177 1178 // Note that we restrict the receiver to "specialCaller" instances. 1179 MethodType handleType = type.insertParameterTypes(0, specialCaller); 1180 return createMethodHandle(method, MethodHandle.INVOKE_SUPER, handleType); 1181 } 1182 1183 /** 1184 * Produces a method handle giving read access to a non-static field. 1185 * The type of the method handle will have a return type of the field's 1186 * value type. 1187 * The method handle's single argument will be the instance containing 1188 * the field. 1189 * Access checking is performed immediately on behalf of the lookup class. 1190 * @param refc the class or interface from which the method is accessed 1191 * @param name the field's name 1192 * @param type the field's type 1193 * @return a method handle which can load values from the field 1194 * @throws NoSuchFieldException if the field does not exist 1195 * @throws IllegalAccessException if access checking fails, or if the field is {@code static} 1196 * @exception SecurityException if a security manager is present and it 1197 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1198 * @throws NullPointerException if any argument is null 1199 */ 1200 public MethodHandle findGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException { 1201 return findAccessor(refc, name, type, MethodHandle.IGET); 1202 } 1203 1204 private MethodHandle findAccessor(Class<?> refc, String name, Class<?> type, int kind) 1205 throws NoSuchFieldException, IllegalAccessException { 1206 final Field field = findFieldOfType(refc, name, type); 1207 return findAccessor(field, refc, type, kind, true /* performAccessChecks */); 1208 } 1209 1210 private MethodHandle findAccessor(Field field, Class<?> refc, Class<?> type, int kind, 1211 boolean performAccessChecks) 1212 throws IllegalAccessException { 1213 final boolean isSetterKind = kind == MethodHandle.IPUT || kind == MethodHandle.SPUT; 1214 final boolean isStaticKind = kind == MethodHandle.SGET || kind == MethodHandle.SPUT; 1215 commonFieldChecks(field, refc, type, isStaticKind, performAccessChecks); 1216 if (performAccessChecks) { 1217 final int modifiers = field.getModifiers(); 1218 if (isSetterKind && Modifier.isFinal(modifiers)) { 1219 throw new IllegalAccessException("Field " + field + " is final"); 1220 } 1221 } 1222 1223 final MethodType methodType; 1224 switch (kind) { 1225 case MethodHandle.SGET: 1226 methodType = MethodType.methodType(type); 1227 break; 1228 case MethodHandle.SPUT: 1229 methodType = MethodType.methodType(void.class, type); 1230 break; 1231 case MethodHandle.IGET: 1232 methodType = MethodType.methodType(type, refc); 1233 break; 1234 case MethodHandle.IPUT: 1235 methodType = MethodType.methodType(void.class, refc, type); 1236 break; 1237 default: 1238 throw new IllegalArgumentException("Invalid kind " + kind); 1239 } 1240 return new MethodHandleImpl(field.getArtField(), kind, methodType); 1241 } 1242 1243 /** 1244 * Produces a method handle giving write access to a non-static field. 1245 * The type of the method handle will have a void return type. 1246 * The method handle will take two arguments, the instance containing 1247 * the field, and the value to be stored. 1248 * The second argument will be of the field's value type. 1249 * Access checking is performed immediately on behalf of the lookup class. 1250 * @param refc the class or interface from which the method is accessed 1251 * @param name the field's name 1252 * @param type the field's type 1253 * @return a method handle which can store values into the field 1254 * @throws NoSuchFieldException if the field does not exist 1255 * @throws IllegalAccessException if access checking fails, or if the field is {@code static} 1256 * @exception SecurityException if a security manager is present and it 1257 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1258 * @throws NullPointerException if any argument is null 1259 */ 1260 public MethodHandle findSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException { 1261 return findAccessor(refc, name, type, MethodHandle.IPUT); 1262 } 1263 1264 // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory method. 1265 /** 1266 * Produces a VarHandle giving access to a non-static field {@code name} 1267 * of type {@code type} declared in a class of type {@code recv}. 1268 * The VarHandle's variable type is {@code type} and it has one 1269 * coordinate type, {@code recv}. 1270 * <p> 1271 * Access checking is performed immediately on behalf of the lookup 1272 * class. 1273 * <p> 1274 * Certain access modes of the returned VarHandle are unsupported under 1275 * the following conditions: 1276 * <ul> 1277 * <li>if the field is declared {@code final}, then the write, atomic 1278 * update, numeric atomic update, and bitwise atomic update access 1279 * modes are unsupported. 1280 * <li>if the field type is anything other than {@code byte}, 1281 * {@code short}, {@code char}, {@code int}, {@code long}, 1282 * {@code float}, or {@code double} then numeric atomic update 1283 * access modes are unsupported. 1284 * <li>if the field type is anything other than {@code boolean}, 1285 * {@code byte}, {@code short}, {@code char}, {@code int} or 1286 * {@code long} then bitwise atomic update access modes are 1287 * unsupported. 1288 * </ul> 1289 * <p> 1290 * If the field is declared {@code volatile} then the returned VarHandle 1291 * will override access to the field (effectively ignore the 1292 * {@code volatile} declaration) in accordance to its specified 1293 * access modes. 1294 * <p> 1295 * If the field type is {@code float} or {@code double} then numeric 1296 * and atomic update access modes compare values using their bitwise 1297 * representation (see {@link Float#floatToRawIntBits} and 1298 * {@link Double#doubleToRawLongBits}, respectively). 1299 * @apiNote 1300 * Bitwise comparison of {@code float} values or {@code double} values, 1301 * as performed by the numeric and atomic update access modes, differ 1302 * from the primitive {@code ==} operator and the {@link Float#equals} 1303 * and {@link Double#equals} methods, specifically with respect to 1304 * comparing NaN values or comparing {@code -0.0} with {@code +0.0}. 1305 * Care should be taken when performing a compare and set or a compare 1306 * and exchange operation with such values since the operation may 1307 * unexpectedly fail. 1308 * There are many possible NaN values that are considered to be 1309 * {@code NaN} in Java, although no IEEE 754 floating-point operation 1310 * provided by Java can distinguish between them. Operation failure can 1311 * occur if the expected or witness value is a NaN value and it is 1312 * transformed (perhaps in a platform specific manner) into another NaN 1313 * value, and thus has a different bitwise representation (see 1314 * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more 1315 * details). 1316 * The values {@code -0.0} and {@code +0.0} have different bitwise 1317 * representations but are considered equal when using the primitive 1318 * {@code ==} operator. Operation failure can occur if, for example, a 1319 * numeric algorithm computes an expected value to be say {@code -0.0} 1320 * and previously computed the witness value to be say {@code +0.0}. 1321 * @param recv the receiver class, of type {@code R}, that declares the 1322 * non-static field 1323 * @param name the field's name 1324 * @param type the field's type, of type {@code T} 1325 * @return a VarHandle giving access to non-static fields. 1326 * @throws NoSuchFieldException if the field does not exist 1327 * @throws IllegalAccessException if access checking fails, or if the field is {@code static} 1328 * @exception SecurityException if a security manager is present and it 1329 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1330 * @throws NullPointerException if any argument is null 1331 * @since 9 1332 * @hide 1333 */ 1334 public VarHandle findVarHandle(Class<?> recv, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException { 1335 final Field field = findFieldOfType(recv, name, type); 1336 final boolean isStatic = false; 1337 final boolean performAccessChecks = true; 1338 commonFieldChecks(field, recv, type, isStatic, performAccessChecks); 1339 return FieldVarHandle.create(field); 1340 } 1341 // END Android-changed: OpenJDK 9+181 VarHandle API factory method. 1342 1343 // BEGIN Android-added: Common field resolution and access check methods. 1344 private Field findFieldOfType(final Class<?> refc, String name, Class<?> type) 1345 throws NoSuchFieldException { 1346 Field field = null; 1347 1348 // Search refc and super classes for the field. 1349 for (Class<?> cls = refc; cls != null; cls = cls.getSuperclass()) { 1350 try { 1351 field = cls.getDeclaredField(name); 1352 break; 1353 } catch (NoSuchFieldException e) { 1354 } 1355 } 1356 1357 if (field == null) { 1358 // Force failure citing refc. 1359 field = refc.getDeclaredField(name); 1360 } 1361 1362 final Class<?> fieldType = field.getType(); 1363 if (fieldType != type) { 1364 throw new NoSuchFieldException(name); 1365 } 1366 return field; 1367 } 1368 1369 private void commonFieldChecks(Field field, Class<?> refc, Class<?> type, 1370 boolean isStatic, boolean performAccessChecks) 1371 throws IllegalAccessException { 1372 final int modifiers = field.getModifiers(); 1373 if (performAccessChecks) { 1374 checkAccess(refc, field.getDeclaringClass(), modifiers, field.getName()); 1375 } 1376 if (Modifier.isStatic(modifiers) != isStatic) { 1377 String reason = "Field " + field + " is " + 1378 (isStatic ? "not " : "") + "static"; 1379 throw new IllegalAccessException(reason); 1380 } 1381 } 1382 // END Android-added: Common field resolution and access check methods. 1383 1384 /** 1385 * Produces a method handle giving read access to a static field. 1386 * The type of the method handle will have a return type of the field's 1387 * value type. 1388 * The method handle will take no arguments. 1389 * Access checking is performed immediately on behalf of the lookup class. 1390 * <p> 1391 * If the returned method handle is invoked, the field's class will 1392 * be initialized, if it has not already been initialized. 1393 * @param refc the class or interface from which the method is accessed 1394 * @param name the field's name 1395 * @param type the field's type 1396 * @return a method handle which can load values from the field 1397 * @throws NoSuchFieldException if the field does not exist 1398 * @throws IllegalAccessException if access checking fails, or if the field is not {@code static} 1399 * @exception SecurityException if a security manager is present and it 1400 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1401 * @throws NullPointerException if any argument is null 1402 */ 1403 public MethodHandle findStaticGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException { 1404 return findAccessor(refc, name, type, MethodHandle.SGET); 1405 } 1406 1407 /** 1408 * Produces a method handle giving write access to a static field. 1409 * The type of the method handle will have a void return type. 1410 * The method handle will take a single 1411 * argument, of the field's value type, the value to be stored. 1412 * Access checking is performed immediately on behalf of the lookup class. 1413 * <p> 1414 * If the returned method handle is invoked, the field's class will 1415 * be initialized, if it has not already been initialized. 1416 * @param refc the class or interface from which the method is accessed 1417 * @param name the field's name 1418 * @param type the field's type 1419 * @return a method handle which can store values into the field 1420 * @throws NoSuchFieldException if the field does not exist 1421 * @throws IllegalAccessException if access checking fails, or if the field is not {@code static} 1422 * @exception SecurityException if a security manager is present and it 1423 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1424 * @throws NullPointerException if any argument is null 1425 */ 1426 public MethodHandle findStaticSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException { 1427 return findAccessor(refc, name, type, MethodHandle.SPUT); 1428 } 1429 1430 // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory method. 1431 /** 1432 * Produces a VarHandle giving access to a static field {@code name} of 1433 * type {@code type} declared in a class of type {@code decl}. 1434 * The VarHandle's variable type is {@code type} and it has no 1435 * coordinate types. 1436 * <p> 1437 * Access checking is performed immediately on behalf of the lookup 1438 * class. 1439 * <p> 1440 * If the returned VarHandle is operated on, the declaring class will be 1441 * initialized, if it has not already been initialized. 1442 * <p> 1443 * Certain access modes of the returned VarHandle are unsupported under 1444 * the following conditions: 1445 * <ul> 1446 * <li>if the field is declared {@code final}, then the write, atomic 1447 * update, numeric atomic update, and bitwise atomic update access 1448 * modes are unsupported. 1449 * <li>if the field type is anything other than {@code byte}, 1450 * {@code short}, {@code char}, {@code int}, {@code long}, 1451 * {@code float}, or {@code double}, then numeric atomic update 1452 * access modes are unsupported. 1453 * <li>if the field type is anything other than {@code boolean}, 1454 * {@code byte}, {@code short}, {@code char}, {@code int} or 1455 * {@code long} then bitwise atomic update access modes are 1456 * unsupported. 1457 * </ul> 1458 * <p> 1459 * If the field is declared {@code volatile} then the returned VarHandle 1460 * will override access to the field (effectively ignore the 1461 * {@code volatile} declaration) in accordance to its specified 1462 * access modes. 1463 * <p> 1464 * If the field type is {@code float} or {@code double} then numeric 1465 * and atomic update access modes compare values using their bitwise 1466 * representation (see {@link Float#floatToRawIntBits} and 1467 * {@link Double#doubleToRawLongBits}, respectively). 1468 * @apiNote 1469 * Bitwise comparison of {@code float} values or {@code double} values, 1470 * as performed by the numeric and atomic update access modes, differ 1471 * from the primitive {@code ==} operator and the {@link Float#equals} 1472 * and {@link Double#equals} methods, specifically with respect to 1473 * comparing NaN values or comparing {@code -0.0} with {@code +0.0}. 1474 * Care should be taken when performing a compare and set or a compare 1475 * and exchange operation with such values since the operation may 1476 * unexpectedly fail. 1477 * There are many possible NaN values that are considered to be 1478 * {@code NaN} in Java, although no IEEE 754 floating-point operation 1479 * provided by Java can distinguish between them. Operation failure can 1480 * occur if the expected or witness value is a NaN value and it is 1481 * transformed (perhaps in a platform specific manner) into another NaN 1482 * value, and thus has a different bitwise representation (see 1483 * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more 1484 * details). 1485 * The values {@code -0.0} and {@code +0.0} have different bitwise 1486 * representations but are considered equal when using the primitive 1487 * {@code ==} operator. Operation failure can occur if, for example, a 1488 * numeric algorithm computes an expected value to be say {@code -0.0} 1489 * and previously computed the witness value to be say {@code +0.0}. 1490 * @param decl the class that declares the static field 1491 * @param name the field's name 1492 * @param type the field's type, of type {@code T} 1493 * @return a VarHandle giving access to a static field 1494 * @throws NoSuchFieldException if the field does not exist 1495 * @throws IllegalAccessException if access checking fails, or if the field is not {@code static} 1496 * @exception SecurityException if a security manager is present and it 1497 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1498 * @throws NullPointerException if any argument is null 1499 * @since 9 1500 * @hide 1501 */ 1502 public VarHandle findStaticVarHandle(Class<?> decl, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException { 1503 final Field field = findFieldOfType(decl, name, type); 1504 final boolean isStatic = true; 1505 final boolean performAccessChecks = true; 1506 commonFieldChecks(field, decl, type, isStatic, performAccessChecks); 1507 return FieldVarHandle.create(field); 1508 } 1509 // END Android-changed: OpenJDK 9+181 VarHandle API factory method. 1510 1511 /** 1512 * Produces an early-bound method handle for a non-static method. 1513 * The receiver must have a supertype {@code defc} in which a method 1514 * of the given name and type is accessible to the lookup class. 1515 * The method and all its argument types must be accessible to the lookup object. 1516 * The type of the method handle will be that of the method, 1517 * without any insertion of an additional receiver parameter. 1518 * The given receiver will be bound into the method handle, 1519 * so that every call to the method handle will invoke the 1520 * requested method on the given receiver. 1521 * <p> 1522 * The returned method handle will have 1523 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 1524 * the method's variable arity modifier bit ({@code 0x0080}) is set 1525 * <em>and</em> the trailing array argument is not the only argument. 1526 * (If the trailing array argument is the only argument, 1527 * the given receiver value will be bound to it.) 1528 * <p> 1529 * This is equivalent to the following code: 1530 * <blockquote><pre>{@code 1531 import static java.lang.invoke.MethodHandles.*; 1532 import static java.lang.invoke.MethodType.*; 1533 ... 1534 MethodHandle mh0 = lookup().findVirtual(defc, name, type); 1535 MethodHandle mh1 = mh0.bindTo(receiver); 1536 MethodType mt1 = mh1.type(); 1537 if (mh0.isVarargsCollector()) 1538 mh1 = mh1.asVarargsCollector(mt1.parameterType(mt1.parameterCount()-1)); 1539 return mh1; 1540 * }</pre></blockquote> 1541 * where {@code defc} is either {@code receiver.getClass()} or a super 1542 * type of that class, in which the requested method is accessible 1543 * to the lookup class. 1544 * (Note that {@code bindTo} does not preserve variable arity.) 1545 * @param receiver the object from which the method is accessed 1546 * @param name the name of the method 1547 * @param type the type of the method, with the receiver argument omitted 1548 * @return the desired method handle 1549 * @throws NoSuchMethodException if the method does not exist 1550 * @throws IllegalAccessException if access checking fails 1551 * or if the method's variable arity modifier bit 1552 * is set and {@code asVarargsCollector} fails 1553 * @exception SecurityException if a security manager is present and it 1554 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1555 * @throws NullPointerException if any argument is null 1556 * @see MethodHandle#bindTo 1557 * @see #findVirtual 1558 */ 1559 public MethodHandle bind(Object receiver, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException { 1560 MethodHandle handle = findVirtual(receiver.getClass(), name, type); 1561 MethodHandle adapter = handle.bindTo(receiver); 1562 MethodType adapterType = adapter.type(); 1563 if (handle.isVarargsCollector()) { 1564 adapter = adapter.asVarargsCollector( 1565 adapterType.parameterType(adapterType.parameterCount() - 1)); 1566 } 1567 1568 return adapter; 1569 } 1570 1571 /** 1572 * Makes a <a href="MethodHandleInfo.html#directmh">direct method handle</a> 1573 * to <i>m</i>, if the lookup class has permission. 1574 * If <i>m</i> is non-static, the receiver argument is treated as an initial argument. 1575 * If <i>m</i> is virtual, overriding is respected on every call. 1576 * Unlike the Core Reflection API, exceptions are <em>not</em> wrapped. 1577 * The type of the method handle will be that of the method, 1578 * with the receiver type prepended (but only if it is non-static). 1579 * If the method's {@code accessible} flag is not set, 1580 * access checking is performed immediately on behalf of the lookup class. 1581 * If <i>m</i> is not public, do not share the resulting handle with untrusted parties. 1582 * <p> 1583 * The returned method handle will have 1584 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 1585 * the method's variable arity modifier bit ({@code 0x0080}) is set. 1586 * <p> 1587 * If <i>m</i> is static, and 1588 * if the returned method handle is invoked, the method's class will 1589 * be initialized, if it has not already been initialized. 1590 * @param m the reflected method 1591 * @return a method handle which can invoke the reflected method 1592 * @throws IllegalAccessException if access checking fails 1593 * or if the method's variable arity modifier bit 1594 * is set and {@code asVarargsCollector} fails 1595 * @throws NullPointerException if the argument is null 1596 */ 1597 public MethodHandle unreflect(Method m) throws IllegalAccessException { 1598 if (m == null) { 1599 throw new NullPointerException("m == null"); 1600 } 1601 1602 MethodType methodType = MethodType.methodType(m.getReturnType(), 1603 m.getParameterTypes()); 1604 1605 // We should only perform access checks if setAccessible hasn't been called yet. 1606 if (!m.isAccessible()) { 1607 checkAccess(m.getDeclaringClass(), m.getDeclaringClass(), m.getModifiers(), 1608 m.getName()); 1609 } 1610 1611 if (Modifier.isStatic(m.getModifiers())) { 1612 return createMethodHandle(m, MethodHandle.INVOKE_STATIC, methodType); 1613 } else { 1614 methodType = methodType.insertParameterTypes(0, m.getDeclaringClass()); 1615 return createMethodHandle(m, MethodHandle.INVOKE_VIRTUAL, methodType); 1616 } 1617 } 1618 1619 /** 1620 * Produces a method handle for a reflected method. 1621 * It will bypass checks for overriding methods on the receiver, 1622 * <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial} 1623 * instruction from within the explicitly specified {@code specialCaller}. 1624 * The type of the method handle will be that of the method, 1625 * with a suitably restricted receiver type prepended. 1626 * (The receiver type will be {@code specialCaller} or a subtype.) 1627 * If the method's {@code accessible} flag is not set, 1628 * access checking is performed immediately on behalf of the lookup class, 1629 * as if {@code invokespecial} instruction were being linked. 1630 * <p> 1631 * Before method resolution, 1632 * if the explicitly specified caller class is not identical with the 1633 * lookup class, or if this lookup object does not have 1634 * <a href="MethodHandles.Lookup.html#privacc">private access</a> 1635 * privileges, the access fails. 1636 * <p> 1637 * The returned method handle will have 1638 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 1639 * the method's variable arity modifier bit ({@code 0x0080}) is set. 1640 * @param m the reflected method 1641 * @param specialCaller the class nominally calling the method 1642 * @return a method handle which can invoke the reflected method 1643 * @throws IllegalAccessException if access checking fails 1644 * or if the method's variable arity modifier bit 1645 * is set and {@code asVarargsCollector} fails 1646 * @throws NullPointerException if any argument is null 1647 */ 1648 public MethodHandle unreflectSpecial(Method m, Class<?> specialCaller) throws IllegalAccessException { 1649 if (m == null) { 1650 throw new NullPointerException("m == null"); 1651 } 1652 1653 if (specialCaller == null) { 1654 throw new NullPointerException("specialCaller == null"); 1655 } 1656 1657 if (!m.isAccessible()) { 1658 checkSpecialCaller(specialCaller); 1659 } 1660 1661 final MethodType methodType = MethodType.methodType(m.getReturnType(), 1662 m.getParameterTypes()); 1663 return findSpecial(m, methodType, m.getDeclaringClass() /* refc */, specialCaller); 1664 } 1665 1666 /** 1667 * Produces a method handle for a reflected constructor. 1668 * The type of the method handle will be that of the constructor, 1669 * with the return type changed to the declaring class. 1670 * The method handle will perform a {@code newInstance} operation, 1671 * creating a new instance of the constructor's class on the 1672 * arguments passed to the method handle. 1673 * <p> 1674 * If the constructor's {@code accessible} flag is not set, 1675 * access checking is performed immediately on behalf of the lookup class. 1676 * <p> 1677 * The returned method handle will have 1678 * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if 1679 * the constructor's variable arity modifier bit ({@code 0x0080}) is set. 1680 * <p> 1681 * If the returned method handle is invoked, the constructor's class will 1682 * be initialized, if it has not already been initialized. 1683 * @param c the reflected constructor 1684 * @return a method handle which can invoke the reflected constructor 1685 * @throws IllegalAccessException if access checking fails 1686 * or if the method's variable arity modifier bit 1687 * is set and {@code asVarargsCollector} fails 1688 * @throws NullPointerException if the argument is null 1689 */ 1690 public MethodHandle unreflectConstructor(Constructor<?> c) throws IllegalAccessException { 1691 if (c == null) { 1692 throw new NullPointerException("c == null"); 1693 } 1694 1695 if (!c.isAccessible()) { 1696 checkAccess(c.getDeclaringClass(), c.getDeclaringClass(), c.getModifiers(), 1697 c.getName()); 1698 } 1699 1700 return createMethodHandleForConstructor(c); 1701 } 1702 1703 /** 1704 * Produces a method handle giving read access to a reflected field. 1705 * The type of the method handle will have a return type of the field's 1706 * value type. 1707 * If the field is static, the method handle will take no arguments. 1708 * Otherwise, its single argument will be the instance containing 1709 * the field. 1710 * If the field's {@code accessible} flag is not set, 1711 * access checking is performed immediately on behalf of the lookup class. 1712 * <p> 1713 * If the field is static, and 1714 * if the returned method handle is invoked, the field's class will 1715 * be initialized, if it has not already been initialized. 1716 * @param f the reflected field 1717 * @return a method handle which can load values from the reflected field 1718 * @throws IllegalAccessException if access checking fails 1719 * @throws NullPointerException if the argument is null 1720 */ 1721 public MethodHandle unreflectGetter(Field f) throws IllegalAccessException { 1722 return findAccessor(f, f.getDeclaringClass(), f.getType(), 1723 Modifier.isStatic(f.getModifiers()) ? MethodHandle.SGET : MethodHandle.IGET, 1724 !f.isAccessible() /* performAccessChecks */); 1725 } 1726 1727 /** 1728 * Produces a method handle giving write access to a reflected field. 1729 * The type of the method handle will have a void return type. 1730 * If the field is static, the method handle will take a single 1731 * argument, of the field's value type, the value to be stored. 1732 * Otherwise, the two arguments will be the instance containing 1733 * the field, and the value to be stored. 1734 * If the field's {@code accessible} flag is not set, 1735 * access checking is performed immediately on behalf of the lookup class. 1736 * <p> 1737 * If the field is static, and 1738 * if the returned method handle is invoked, the field's class will 1739 * be initialized, if it has not already been initialized. 1740 * @param f the reflected field 1741 * @return a method handle which can store values into the reflected field 1742 * @throws IllegalAccessException if access checking fails 1743 * @throws NullPointerException if the argument is null 1744 */ 1745 public MethodHandle unreflectSetter(Field f) throws IllegalAccessException { 1746 return findAccessor(f, f.getDeclaringClass(), f.getType(), 1747 Modifier.isStatic(f.getModifiers()) ? MethodHandle.SPUT : MethodHandle.IPUT, 1748 !f.isAccessible() /* performAccessChecks */); 1749 } 1750 1751 // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory method. 1752 /** 1753 * Produces a VarHandle giving access to a reflected field {@code f} 1754 * of type {@code T} declared in a class of type {@code R}. 1755 * The VarHandle's variable type is {@code T}. 1756 * If the field is non-static the VarHandle has one coordinate type, 1757 * {@code R}. Otherwise, the field is static, and the VarHandle has no 1758 * coordinate types. 1759 * <p> 1760 * Access checking is performed immediately on behalf of the lookup 1761 * class, regardless of the value of the field's {@code accessible} 1762 * flag. 1763 * <p> 1764 * If the field is static, and if the returned VarHandle is operated 1765 * on, the field's declaring class will be initialized, if it has not 1766 * already been initialized. 1767 * <p> 1768 * Certain access modes of the returned VarHandle are unsupported under 1769 * the following conditions: 1770 * <ul> 1771 * <li>if the field is declared {@code final}, then the write, atomic 1772 * update, numeric atomic update, and bitwise atomic update access 1773 * modes are unsupported. 1774 * <li>if the field type is anything other than {@code byte}, 1775 * {@code short}, {@code char}, {@code int}, {@code long}, 1776 * {@code float}, or {@code double} then numeric atomic update 1777 * access modes are unsupported. 1778 * <li>if the field type is anything other than {@code boolean}, 1779 * {@code byte}, {@code short}, {@code char}, {@code int} or 1780 * {@code long} then bitwise atomic update access modes are 1781 * unsupported. 1782 * </ul> 1783 * <p> 1784 * If the field is declared {@code volatile} then the returned VarHandle 1785 * will override access to the field (effectively ignore the 1786 * {@code volatile} declaration) in accordance to its specified 1787 * access modes. 1788 * <p> 1789 * If the field type is {@code float} or {@code double} then numeric 1790 * and atomic update access modes compare values using their bitwise 1791 * representation (see {@link Float#floatToRawIntBits} and 1792 * {@link Double#doubleToRawLongBits}, respectively). 1793 * @apiNote 1794 * Bitwise comparison of {@code float} values or {@code double} values, 1795 * as performed by the numeric and atomic update access modes, differ 1796 * from the primitive {@code ==} operator and the {@link Float#equals} 1797 * and {@link Double#equals} methods, specifically with respect to 1798 * comparing NaN values or comparing {@code -0.0} with {@code +0.0}. 1799 * Care should be taken when performing a compare and set or a compare 1800 * and exchange operation with such values since the operation may 1801 * unexpectedly fail. 1802 * There are many possible NaN values that are considered to be 1803 * {@code NaN} in Java, although no IEEE 754 floating-point operation 1804 * provided by Java can distinguish between them. Operation failure can 1805 * occur if the expected or witness value is a NaN value and it is 1806 * transformed (perhaps in a platform specific manner) into another NaN 1807 * value, and thus has a different bitwise representation (see 1808 * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more 1809 * details). 1810 * The values {@code -0.0} and {@code +0.0} have different bitwise 1811 * representations but are considered equal when using the primitive 1812 * {@code ==} operator. Operation failure can occur if, for example, a 1813 * numeric algorithm computes an expected value to be say {@code -0.0} 1814 * and previously computed the witness value to be say {@code +0.0}. 1815 * @param f the reflected field, with a field of type {@code T}, and 1816 * a declaring class of type {@code R} 1817 * @return a VarHandle giving access to non-static fields or a static 1818 * field 1819 * @throws IllegalAccessException if access checking fails 1820 * @throws NullPointerException if the argument is null 1821 * @since 9 1822 * @hide 1823 */ 1824 public VarHandle unreflectVarHandle(Field f) throws IllegalAccessException { 1825 final boolean isStatic = Modifier.isStatic(f.getModifiers()); 1826 final boolean performAccessChecks = true; 1827 commonFieldChecks(f, f.getDeclaringClass(), f.getType(), isStatic, performAccessChecks); 1828 return FieldVarHandle.create(f); 1829 } 1830 // END Android-changed: OpenJDK 9+181 VarHandle API factory method. 1831 1832 /** 1833 * Cracks a <a href="MethodHandleInfo.html#directmh">direct method handle</a> 1834 * created by this lookup object or a similar one. 1835 * Security and access checks are performed to ensure that this lookup object 1836 * is capable of reproducing the target method handle. 1837 * This means that the cracking may fail if target is a direct method handle 1838 * but was created by an unrelated lookup object. 1839 * This can happen if the method handle is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a> 1840 * and was created by a lookup object for a different class. 1841 * @param target a direct method handle to crack into symbolic reference components 1842 * @return a symbolic reference which can be used to reconstruct this method handle from this lookup object 1843 * @exception SecurityException if a security manager is present and it 1844 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a> 1845 * @throws IllegalArgumentException if the target is not a direct method handle or if access checking fails 1846 * @exception NullPointerException if the target is {@code null} 1847 * @see MethodHandleInfo 1848 * @since 1.8 1849 */ 1850 public MethodHandleInfo revealDirect(MethodHandle target) { 1851 MethodHandleImpl directTarget = getMethodHandleImpl(target); 1852 MethodHandleInfo info = directTarget.reveal(); 1853 1854 try { 1855 checkAccess(lookupClass(), info.getDeclaringClass(), info.getModifiers(), 1856 info.getName()); 1857 } catch (IllegalAccessException exception) { 1858 throw new IllegalArgumentException("Unable to access memeber.", exception); 1859 } 1860 1861 return info; 1862 } 1863 1864 private boolean hasPrivateAccess() { 1865 return (allowedModes & PRIVATE) != 0; 1866 } 1867 1868 /** Check public/protected/private bits on the symbolic reference class and its member. */ 1869 void checkAccess(Class<?> refc, Class<?> defc, int mods, String methName) 1870 throws IllegalAccessException { 1871 int allowedModes = this.allowedModes; 1872 1873 if (Modifier.isProtected(mods) && 1874 defc == Object.class && 1875 "clone".equals(methName) && 1876 refc.isArray()) { 1877 // The JVM does this hack also. 1878 // (See ClassVerifier::verify_invoke_instructions 1879 // and LinkResolver::check_method_accessability.) 1880 // Because the JVM does not allow separate methods on array types, 1881 // there is no separate method for int[].clone. 1882 // All arrays simply inherit Object.clone. 1883 // But for access checking logic, we make Object.clone 1884 // (normally protected) appear to be public. 1885 // Later on, when the DirectMethodHandle is created, 1886 // its leading argument will be restricted to the 1887 // requested array type. 1888 // N.B. The return type is not adjusted, because 1889 // that is *not* the bytecode behavior. 1890 mods ^= Modifier.PROTECTED | Modifier.PUBLIC; 1891 } 1892 1893 if (Modifier.isProtected(mods) && Modifier.isConstructor(mods)) { 1894 // cannot "new" a protected ctor in a different package 1895 mods ^= Modifier.PROTECTED; 1896 } 1897 1898 if (Modifier.isPublic(mods) && Modifier.isPublic(refc.getModifiers()) && allowedModes != 0) 1899 return; // common case 1900 int requestedModes = fixmods(mods); // adjust 0 => PACKAGE 1901 if ((requestedModes & allowedModes) != 0) { 1902 if (VerifyAccess.isMemberAccessible(refc, defc, mods, lookupClass(), allowedModes)) 1903 return; 1904 } else { 1905 // Protected members can also be checked as if they were package-private. 1906 if ((requestedModes & PROTECTED) != 0 && (allowedModes & PACKAGE) != 0 1907 && VerifyAccess.isSamePackage(defc, lookupClass())) 1908 return; 1909 } 1910 1911 throwMakeAccessException(accessFailedMessage(refc, defc, mods), this); 1912 } 1913 1914 String accessFailedMessage(Class<?> refc, Class<?> defc, int mods) { 1915 // check the class first: 1916 boolean classOK = (Modifier.isPublic(defc.getModifiers()) && 1917 (defc == refc || 1918 Modifier.isPublic(refc.getModifiers()))); 1919 if (!classOK && (allowedModes & PACKAGE) != 0) { 1920 classOK = (VerifyAccess.isClassAccessible(defc, lookupClass(), ALL_MODES) && 1921 (defc == refc || 1922 VerifyAccess.isClassAccessible(refc, lookupClass(), ALL_MODES))); 1923 } 1924 if (!classOK) 1925 return "class is not public"; 1926 if (Modifier.isPublic(mods)) 1927 return "access to public member failed"; // (how?) 1928 if (Modifier.isPrivate(mods)) 1929 return "member is private"; 1930 if (Modifier.isProtected(mods)) 1931 return "member is protected"; 1932 return "member is private to package"; 1933 } 1934 1935 // Android-changed: checkSpecialCaller assumes that ALLOW_NESTMATE_ACCESS = false, 1936 // as in upstream OpenJDK. 1937 // 1938 // private static final boolean ALLOW_NESTMATE_ACCESS = false; 1939 1940 private void checkSpecialCaller(Class<?> specialCaller) throws IllegalAccessException { 1941 // Android-changed: No support for TRUSTED lookups. Also construct the 1942 // IllegalAccessException by hand because the upstream code implicitly assumes 1943 // that the lookupClass == specialCaller. 1944 // 1945 // if (allowedModes == TRUSTED) return; 1946 if (!hasPrivateAccess() || (specialCaller != lookupClass())) { 1947 throw new IllegalAccessException("no private access for invokespecial : " 1948 + specialCaller + ", from" + this); 1949 } 1950 } 1951 1952 private void throwMakeAccessException(String message, Object from) throws 1953 IllegalAccessException{ 1954 message = message + ": "+ toString(); 1955 if (from != null) message += ", from " + from; 1956 throw new IllegalAccessException(message); 1957 } 1958 1959 private void checkReturnType(Method method, MethodType methodType) 1960 throws NoSuchMethodException { 1961 if (method.getReturnType() != methodType.rtype()) { 1962 throw new NoSuchMethodException(method.getName() + methodType); 1963 } 1964 } 1965 } 1966 1967 /** 1968 * "Cracks" {@code target} to reveal the underlying {@code MethodHandleImpl}. 1969 */ 1970 private static MethodHandleImpl getMethodHandleImpl(MethodHandle target) { 1971 // Special case : We implement handles to constructors as transformers, 1972 // so we must extract the underlying handle from the transformer. 1973 if (target instanceof Transformers.Construct) { 1974 target = ((Transformers.Construct) target).getConstructorHandle(); 1975 } 1976 1977 // Special case: Var-args methods are also implemented as Transformers, 1978 // so we should get the underlying handle in that case as well. 1979 if (target instanceof Transformers.VarargsCollector) { 1980 target = target.asFixedArity(); 1981 } 1982 1983 if (target instanceof MethodHandleImpl) { 1984 return (MethodHandleImpl) target; 1985 } 1986 1987 throw new IllegalArgumentException(target + " is not a direct handle"); 1988 } 1989 1990 // BEGIN Android-added: method to check if a class is an array. 1991 private static void checkClassIsArray(Class<?> c) { 1992 if (!c.isArray()) { 1993 throw new IllegalArgumentException("Not an array type: " + c); 1994 } 1995 } 1996 1997 private static void checkTypeIsViewable(Class<?> componentType) { 1998 if (componentType == short.class || 1999 componentType == char.class || 2000 componentType == int.class || 2001 componentType == long.class || 2002 componentType == float.class || 2003 componentType == double.class) { 2004 return; 2005 } 2006 throw new UnsupportedOperationException("Component type not supported: " + componentType); 2007 } 2008 // END Android-added: method to check if a class is an array. 2009 2010 /** 2011 * Produces a method handle giving read access to elements of an array. 2012 * The type of the method handle will have a return type of the array's 2013 * element type. Its first argument will be the array type, 2014 * and the second will be {@code int}. 2015 * @param arrayClass an array type 2016 * @return a method handle which can load values from the given array type 2017 * @throws NullPointerException if the argument is null 2018 * @throws IllegalArgumentException if arrayClass is not an array type 2019 */ 2020 public static 2021 MethodHandle arrayElementGetter(Class<?> arrayClass) throws IllegalArgumentException { 2022 checkClassIsArray(arrayClass); 2023 final Class<?> componentType = arrayClass.getComponentType(); 2024 if (componentType.isPrimitive()) { 2025 try { 2026 return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class, 2027 "arrayElementGetter", 2028 MethodType.methodType(componentType, arrayClass, int.class)); 2029 } catch (NoSuchMethodException | IllegalAccessException exception) { 2030 throw new AssertionError(exception); 2031 } 2032 } 2033 2034 return new Transformers.ReferenceArrayElementGetter(arrayClass); 2035 } 2036 2037 /** @hide */ public static byte arrayElementGetter(byte[] array, int i) { return array[i]; } 2038 /** @hide */ public static boolean arrayElementGetter(boolean[] array, int i) { return array[i]; } 2039 /** @hide */ public static char arrayElementGetter(char[] array, int i) { return array[i]; } 2040 /** @hide */ public static short arrayElementGetter(short[] array, int i) { return array[i]; } 2041 /** @hide */ public static int arrayElementGetter(int[] array, int i) { return array[i]; } 2042 /** @hide */ public static long arrayElementGetter(long[] array, int i) { return array[i]; } 2043 /** @hide */ public static float arrayElementGetter(float[] array, int i) { return array[i]; } 2044 /** @hide */ public static double arrayElementGetter(double[] array, int i) { return array[i]; } 2045 2046 /** 2047 * Produces a method handle giving write access to elements of an array. 2048 * The type of the method handle will have a void return type. 2049 * Its last argument will be the array's element type. 2050 * The first and second arguments will be the array type and int. 2051 * @param arrayClass the class of an array 2052 * @return a method handle which can store values into the array type 2053 * @throws NullPointerException if the argument is null 2054 * @throws IllegalArgumentException if arrayClass is not an array type 2055 */ 2056 public static 2057 MethodHandle arrayElementSetter(Class<?> arrayClass) throws IllegalArgumentException { 2058 checkClassIsArray(arrayClass); 2059 final Class<?> componentType = arrayClass.getComponentType(); 2060 if (componentType.isPrimitive()) { 2061 try { 2062 return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class, 2063 "arrayElementSetter", 2064 MethodType.methodType(void.class, arrayClass, int.class, componentType)); 2065 } catch (NoSuchMethodException | IllegalAccessException exception) { 2066 throw new AssertionError(exception); 2067 } 2068 } 2069 2070 return new Transformers.ReferenceArrayElementSetter(arrayClass); 2071 } 2072 2073 /** @hide */ 2074 public static void arrayElementSetter(byte[] array, int i, byte val) { array[i] = val; } 2075 /** @hide */ 2076 public static void arrayElementSetter(boolean[] array, int i, boolean val) { array[i] = val; } 2077 /** @hide */ 2078 public static void arrayElementSetter(char[] array, int i, char val) { array[i] = val; } 2079 /** @hide */ 2080 public static void arrayElementSetter(short[] array, int i, short val) { array[i] = val; } 2081 /** @hide */ 2082 public static void arrayElementSetter(int[] array, int i, int val) { array[i] = val; } 2083 /** @hide */ 2084 public static void arrayElementSetter(long[] array, int i, long val) { array[i] = val; } 2085 /** @hide */ 2086 public static void arrayElementSetter(float[] array, int i, float val) { array[i] = val; } 2087 /** @hide */ 2088 public static void arrayElementSetter(double[] array, int i, double val) { array[i] = val; } 2089 2090 // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory methods. 2091 /** 2092 * Produces a VarHandle giving access to elements of an array of type 2093 * {@code arrayClass}. The VarHandle's variable type is the component type 2094 * of {@code arrayClass} and the list of coordinate types is 2095 * {@code (arrayClass, int)}, where the {@code int} coordinate type 2096 * corresponds to an argument that is an index into an array. 2097 * <p> 2098 * Certain access modes of the returned VarHandle are unsupported under 2099 * the following conditions: 2100 * <ul> 2101 * <li>if the component type is anything other than {@code byte}, 2102 * {@code short}, {@code char}, {@code int}, {@code long}, 2103 * {@code float}, or {@code double} then numeric atomic update access 2104 * modes are unsupported. 2105 * <li>if the field type is anything other than {@code boolean}, 2106 * {@code byte}, {@code short}, {@code char}, {@code int} or 2107 * {@code long} then bitwise atomic update access modes are 2108 * unsupported. 2109 * </ul> 2110 * <p> 2111 * If the component type is {@code float} or {@code double} then numeric 2112 * and atomic update access modes compare values using their bitwise 2113 * representation (see {@link Float#floatToRawIntBits} and 2114 * {@link Double#doubleToRawLongBits}, respectively). 2115 * @apiNote 2116 * Bitwise comparison of {@code float} values or {@code double} values, 2117 * as performed by the numeric and atomic update access modes, differ 2118 * from the primitive {@code ==} operator and the {@link Float#equals} 2119 * and {@link Double#equals} methods, specifically with respect to 2120 * comparing NaN values or comparing {@code -0.0} with {@code +0.0}. 2121 * Care should be taken when performing a compare and set or a compare 2122 * and exchange operation with such values since the operation may 2123 * unexpectedly fail. 2124 * There are many possible NaN values that are considered to be 2125 * {@code NaN} in Java, although no IEEE 754 floating-point operation 2126 * provided by Java can distinguish between them. Operation failure can 2127 * occur if the expected or witness value is a NaN value and it is 2128 * transformed (perhaps in a platform specific manner) into another NaN 2129 * value, and thus has a different bitwise representation (see 2130 * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more 2131 * details). 2132 * The values {@code -0.0} and {@code +0.0} have different bitwise 2133 * representations but are considered equal when using the primitive 2134 * {@code ==} operator. Operation failure can occur if, for example, a 2135 * numeric algorithm computes an expected value to be say {@code -0.0} 2136 * and previously computed the witness value to be say {@code +0.0}. 2137 * @param arrayClass the class of an array, of type {@code T[]} 2138 * @return a VarHandle giving access to elements of an array 2139 * @throws NullPointerException if the arrayClass is null 2140 * @throws IllegalArgumentException if arrayClass is not an array type 2141 * @since 9 2142 * @hide 2143 */ 2144 public static 2145 VarHandle arrayElementVarHandle(Class<?> arrayClass) throws IllegalArgumentException { 2146 checkClassIsArray(arrayClass); 2147 return ArrayElementVarHandle.create(arrayClass); 2148 } 2149 2150 /** 2151 * Produces a VarHandle giving access to elements of a {@code byte[]} array 2152 * viewed as if it were a different primitive array type, such as 2153 * {@code int[]} or {@code long[]}. 2154 * The VarHandle's variable type is the component type of 2155 * {@code viewArrayClass} and the list of coordinate types is 2156 * {@code (byte[], int)}, where the {@code int} coordinate type 2157 * corresponds to an argument that is an index into a {@code byte[]} array. 2158 * The returned VarHandle accesses bytes at an index in a {@code byte[]} 2159 * array, composing bytes to or from a value of the component type of 2160 * {@code viewArrayClass} according to the given endianness. 2161 * <p> 2162 * The supported component types (variables types) are {@code short}, 2163 * {@code char}, {@code int}, {@code long}, {@code float} and 2164 * {@code double}. 2165 * <p> 2166 * Access of bytes at a given index will result in an 2167 * {@code IndexOutOfBoundsException} if the index is less than {@code 0} 2168 * or greater than the {@code byte[]} array length minus the size (in bytes) 2169 * of {@code T}. 2170 * <p> 2171 * Access of bytes at an index may be aligned or misaligned for {@code T}, 2172 * with respect to the underlying memory address, {@code A} say, associated 2173 * with the array and index. 2174 * If access is misaligned then access for anything other than the 2175 * {@code get} and {@code set} access modes will result in an 2176 * {@code IllegalStateException}. In such cases atomic access is only 2177 * guaranteed with respect to the largest power of two that divides the GCD 2178 * of {@code A} and the size (in bytes) of {@code T}. 2179 * If access is aligned then following access modes are supported and are 2180 * guaranteed to support atomic access: 2181 * <ul> 2182 * <li>read write access modes for all {@code T}, with the exception of 2183 * access modes {@code get} and {@code set} for {@code long} and 2184 * {@code double} on 32-bit platforms. 2185 * <li>atomic update access modes for {@code int}, {@code long}, 2186 * {@code float} or {@code double}. 2187 * (Future major platform releases of the JDK may support additional 2188 * types for certain currently unsupported access modes.) 2189 * <li>numeric atomic update access modes for {@code int} and {@code long}. 2190 * (Future major platform releases of the JDK may support additional 2191 * numeric types for certain currently unsupported access modes.) 2192 * <li>bitwise atomic update access modes for {@code int} and {@code long}. 2193 * (Future major platform releases of the JDK may support additional 2194 * numeric types for certain currently unsupported access modes.) 2195 * </ul> 2196 * <p> 2197 * Misaligned access, and therefore atomicity guarantees, may be determined 2198 * for {@code byte[]} arrays without operating on a specific array. Given 2199 * an {@code index}, {@code T} and it's corresponding boxed type, 2200 * {@code T_BOX}, misalignment may be determined as follows: 2201 * <pre>{@code 2202 * int sizeOfT = T_BOX.BYTES; // size in bytes of T 2203 * int misalignedAtZeroIndex = ByteBuffer.wrap(new byte[0]). 2204 * alignmentOffset(0, sizeOfT); 2205 * int misalignedAtIndex = (misalignedAtZeroIndex + index) % sizeOfT; 2206 * boolean isMisaligned = misalignedAtIndex != 0; 2207 * }</pre> 2208 * <p> 2209 * If the variable type is {@code float} or {@code double} then atomic 2210 * update access modes compare values using their bitwise representation 2211 * (see {@link Float#floatToRawIntBits} and 2212 * {@link Double#doubleToRawLongBits}, respectively). 2213 * @param viewArrayClass the view array class, with a component type of 2214 * type {@code T} 2215 * @param byteOrder the endianness of the view array elements, as 2216 * stored in the underlying {@code byte} array 2217 * @return a VarHandle giving access to elements of a {@code byte[]} array 2218 * viewed as if elements corresponding to the components type of the view 2219 * array class 2220 * @throws NullPointerException if viewArrayClass or byteOrder is null 2221 * @throws IllegalArgumentException if viewArrayClass is not an array type 2222 * @throws UnsupportedOperationException if the component type of 2223 * viewArrayClass is not supported as a variable type 2224 * @since 9 2225 * @hide 2226 */ 2227 public static 2228 VarHandle byteArrayViewVarHandle(Class<?> viewArrayClass, 2229 ByteOrder byteOrder) throws IllegalArgumentException { 2230 checkClassIsArray(viewArrayClass); 2231 checkTypeIsViewable(viewArrayClass.getComponentType()); 2232 return ByteArrayViewVarHandle.create(viewArrayClass, byteOrder); 2233 } 2234 2235 /** 2236 * Produces a VarHandle giving access to elements of a {@code ByteBuffer} 2237 * viewed as if it were an array of elements of a different primitive 2238 * component type to that of {@code byte}, such as {@code int[]} or 2239 * {@code long[]}. 2240 * The VarHandle's variable type is the component type of 2241 * {@code viewArrayClass} and the list of coordinate types is 2242 * {@code (ByteBuffer, int)}, where the {@code int} coordinate type 2243 * corresponds to an argument that is an index into a {@code byte[]} array. 2244 * The returned VarHandle accesses bytes at an index in a 2245 * {@code ByteBuffer}, composing bytes to or from a value of the component 2246 * type of {@code viewArrayClass} according to the given endianness. 2247 * <p> 2248 * The supported component types (variables types) are {@code short}, 2249 * {@code char}, {@code int}, {@code long}, {@code float} and 2250 * {@code double}. 2251 * <p> 2252 * Access will result in a {@code ReadOnlyBufferException} for anything 2253 * other than the read access modes if the {@code ByteBuffer} is read-only. 2254 * <p> 2255 * Access of bytes at a given index will result in an 2256 * {@code IndexOutOfBoundsException} if the index is less than {@code 0} 2257 * or greater than the {@code ByteBuffer} limit minus the size (in bytes) of 2258 * {@code T}. 2259 * <p> 2260 * Access of bytes at an index may be aligned or misaligned for {@code T}, 2261 * with respect to the underlying memory address, {@code A} say, associated 2262 * with the {@code ByteBuffer} and index. 2263 * If access is misaligned then access for anything other than the 2264 * {@code get} and {@code set} access modes will result in an 2265 * {@code IllegalStateException}. In such cases atomic access is only 2266 * guaranteed with respect to the largest power of two that divides the GCD 2267 * of {@code A} and the size (in bytes) of {@code T}. 2268 * If access is aligned then following access modes are supported and are 2269 * guaranteed to support atomic access: 2270 * <ul> 2271 * <li>read write access modes for all {@code T}, with the exception of 2272 * access modes {@code get} and {@code set} for {@code long} and 2273 * {@code double} on 32-bit platforms. 2274 * <li>atomic update access modes for {@code int}, {@code long}, 2275 * {@code float} or {@code double}. 2276 * (Future major platform releases of the JDK may support additional 2277 * types for certain currently unsupported access modes.) 2278 * <li>numeric atomic update access modes for {@code int} and {@code long}. 2279 * (Future major platform releases of the JDK may support additional 2280 * numeric types for certain currently unsupported access modes.) 2281 * <li>bitwise atomic update access modes for {@code int} and {@code long}. 2282 * (Future major platform releases of the JDK may support additional 2283 * numeric types for certain currently unsupported access modes.) 2284 * </ul> 2285 * <p> 2286 * Misaligned access, and therefore atomicity guarantees, may be determined 2287 * for a {@code ByteBuffer}, {@code bb} (direct or otherwise), an 2288 * {@code index}, {@code T} and it's corresponding boxed type, 2289 * {@code T_BOX}, as follows: 2290 * <pre>{@code 2291 * int sizeOfT = T_BOX.BYTES; // size in bytes of T 2292 * ByteBuffer bb = ... 2293 * int misalignedAtIndex = bb.alignmentOffset(index, sizeOfT); 2294 * boolean isMisaligned = misalignedAtIndex != 0; 2295 * }</pre> 2296 * <p> 2297 * If the variable type is {@code float} or {@code double} then atomic 2298 * update access modes compare values using their bitwise representation 2299 * (see {@link Float#floatToRawIntBits} and 2300 * {@link Double#doubleToRawLongBits}, respectively). 2301 * @param viewArrayClass the view array class, with a component type of 2302 * type {@code T} 2303 * @param byteOrder the endianness of the view array elements, as 2304 * stored in the underlying {@code ByteBuffer} (Note this overrides the 2305 * endianness of a {@code ByteBuffer}) 2306 * @return a VarHandle giving access to elements of a {@code ByteBuffer} 2307 * viewed as if elements corresponding to the components type of the view 2308 * array class 2309 * @throws NullPointerException if viewArrayClass or byteOrder is null 2310 * @throws IllegalArgumentException if viewArrayClass is not an array type 2311 * @throws UnsupportedOperationException if the component type of 2312 * viewArrayClass is not supported as a variable type 2313 * @since 9 2314 * @hide 2315 */ 2316 public static 2317 VarHandle byteBufferViewVarHandle(Class<?> viewArrayClass, 2318 ByteOrder byteOrder) throws IllegalArgumentException { 2319 checkClassIsArray(viewArrayClass); 2320 checkTypeIsViewable(viewArrayClass.getComponentType()); 2321 return ByteBufferViewVarHandle.create(viewArrayClass, byteOrder); 2322 } 2323 // END Android-changed: OpenJDK 9+181 VarHandle API factory methods. 2324 2325 /// method handle invocation (reflective style) 2326 2327 /** 2328 * Produces a method handle which will invoke any method handle of the 2329 * given {@code type}, with a given number of trailing arguments replaced by 2330 * a single trailing {@code Object[]} array. 2331 * The resulting invoker will be a method handle with the following 2332 * arguments: 2333 * <ul> 2334 * <li>a single {@code MethodHandle} target 2335 * <li>zero or more leading values (counted by {@code leadingArgCount}) 2336 * <li>an {@code Object[]} array containing trailing arguments 2337 * </ul> 2338 * <p> 2339 * The invoker will invoke its target like a call to {@link MethodHandle#invoke invoke} with 2340 * the indicated {@code type}. 2341 * That is, if the target is exactly of the given {@code type}, it will behave 2342 * like {@code invokeExact}; otherwise it behave as if {@link MethodHandle#asType asType} 2343 * is used to convert the target to the required {@code type}. 2344 * <p> 2345 * The type of the returned invoker will not be the given {@code type}, but rather 2346 * will have all parameters except the first {@code leadingArgCount} 2347 * replaced by a single array of type {@code Object[]}, which will be 2348 * the final parameter. 2349 * <p> 2350 * Before invoking its target, the invoker will spread the final array, apply 2351 * reference casts as necessary, and unbox and widen primitive arguments. 2352 * If, when the invoker is called, the supplied array argument does 2353 * not have the correct number of elements, the invoker will throw 2354 * an {@link IllegalArgumentException} instead of invoking the target. 2355 * <p> 2356 * This method is equivalent to the following code (though it may be more efficient): 2357 * <blockquote><pre>{@code 2358 MethodHandle invoker = MethodHandles.invoker(type); 2359 int spreadArgCount = type.parameterCount() - leadingArgCount; 2360 invoker = invoker.asSpreader(Object[].class, spreadArgCount); 2361 return invoker; 2362 * }</pre></blockquote> 2363 * This method throws no reflective or security exceptions. 2364 * @param type the desired target type 2365 * @param leadingArgCount number of fixed arguments, to be passed unchanged to the target 2366 * @return a method handle suitable for invoking any method handle of the given type 2367 * @throws NullPointerException if {@code type} is null 2368 * @throws IllegalArgumentException if {@code leadingArgCount} is not in 2369 * the range from 0 to {@code type.parameterCount()} inclusive, 2370 * or if the resulting method handle's type would have 2371 * <a href="MethodHandle.html#maxarity">too many parameters</a> 2372 */ 2373 static public 2374 MethodHandle spreadInvoker(MethodType type, int leadingArgCount) { 2375 if (leadingArgCount < 0 || leadingArgCount > type.parameterCount()) 2376 throw newIllegalArgumentException("bad argument count", leadingArgCount); 2377 2378 MethodHandle invoker = MethodHandles.invoker(type); 2379 int spreadArgCount = type.parameterCount() - leadingArgCount; 2380 invoker = invoker.asSpreader(Object[].class, spreadArgCount); 2381 return invoker; 2382 } 2383 2384 /** 2385 * Produces a special <em>invoker method handle</em> which can be used to 2386 * invoke any method handle of the given type, as if by {@link MethodHandle#invokeExact invokeExact}. 2387 * The resulting invoker will have a type which is 2388 * exactly equal to the desired type, except that it will accept 2389 * an additional leading argument of type {@code MethodHandle}. 2390 * <p> 2391 * This method is equivalent to the following code (though it may be more efficient): 2392 * {@code publicLookup().findVirtual(MethodHandle.class, "invokeExact", type)} 2393 * 2394 * <p style="font-size:smaller;"> 2395 * <em>Discussion:</em> 2396 * Invoker method handles can be useful when working with variable method handles 2397 * of unknown types. 2398 * For example, to emulate an {@code invokeExact} call to a variable method 2399 * handle {@code M}, extract its type {@code T}, 2400 * look up the invoker method {@code X} for {@code T}, 2401 * and call the invoker method, as {@code X.invoke(T, A...)}. 2402 * (It would not work to call {@code X.invokeExact}, since the type {@code T} 2403 * is unknown.) 2404 * If spreading, collecting, or other argument transformations are required, 2405 * they can be applied once to the invoker {@code X} and reused on many {@code M} 2406 * method handle values, as long as they are compatible with the type of {@code X}. 2407 * <p style="font-size:smaller;"> 2408 * <em>(Note: The invoker method is not available via the Core Reflection API. 2409 * An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke} 2410 * on the declared {@code invokeExact} or {@code invoke} method will raise an 2411 * {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)</em> 2412 * <p> 2413 * This method throws no reflective or security exceptions. 2414 * @param type the desired target type 2415 * @return a method handle suitable for invoking any method handle of the given type 2416 * @throws IllegalArgumentException if the resulting method handle's type would have 2417 * <a href="MethodHandle.html#maxarity">too many parameters</a> 2418 */ 2419 static public 2420 MethodHandle exactInvoker(MethodType type) { 2421 return new Transformers.Invoker(type, true /* isExactInvoker */); 2422 } 2423 2424 /** 2425 * Produces a special <em>invoker method handle</em> which can be used to 2426 * invoke any method handle compatible with the given type, as if by {@link MethodHandle#invoke invoke}. 2427 * The resulting invoker will have a type which is 2428 * exactly equal to the desired type, except that it will accept 2429 * an additional leading argument of type {@code MethodHandle}. 2430 * <p> 2431 * Before invoking its target, if the target differs from the expected type, 2432 * the invoker will apply reference casts as 2433 * necessary and box, unbox, or widen primitive values, as if by {@link MethodHandle#asType asType}. 2434 * Similarly, the return value will be converted as necessary. 2435 * If the target is a {@linkplain MethodHandle#asVarargsCollector variable arity method handle}, 2436 * the required arity conversion will be made, again as if by {@link MethodHandle#asType asType}. 2437 * <p> 2438 * This method is equivalent to the following code (though it may be more efficient): 2439 * {@code publicLookup().findVirtual(MethodHandle.class, "invoke", type)} 2440 * <p style="font-size:smaller;"> 2441 * <em>Discussion:</em> 2442 * A {@linkplain MethodType#genericMethodType general method type} is one which 2443 * mentions only {@code Object} arguments and return values. 2444 * An invoker for such a type is capable of calling any method handle 2445 * of the same arity as the general type. 2446 * <p style="font-size:smaller;"> 2447 * <em>(Note: The invoker method is not available via the Core Reflection API. 2448 * An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke} 2449 * on the declared {@code invokeExact} or {@code invoke} method will raise an 2450 * {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)</em> 2451 * <p> 2452 * This method throws no reflective or security exceptions. 2453 * @param type the desired target type 2454 * @return a method handle suitable for invoking any method handle convertible to the given type 2455 * @throws IllegalArgumentException if the resulting method handle's type would have 2456 * <a href="MethodHandle.html#maxarity">too many parameters</a> 2457 */ 2458 static public 2459 MethodHandle invoker(MethodType type) { 2460 return new Transformers.Invoker(type, false /* isExactInvoker */); 2461 } 2462 2463 // BEGIN Android-added: resolver for VarHandle accessor methods. 2464 static private MethodHandle methodHandleForVarHandleAccessor(VarHandle.AccessMode accessMode, 2465 MethodType type, 2466 boolean isExactInvoker) { 2467 Class<?> refc = VarHandle.class; 2468 Method method; 2469 try { 2470 method = refc.getDeclaredMethod(accessMode.methodName(), Object[].class); 2471 } catch (NoSuchMethodException e) { 2472 throw new InternalError("No method for AccessMode " + accessMode, e); 2473 } 2474 MethodType methodType = type.insertParameterTypes(0, VarHandle.class); 2475 int kind = isExactInvoker ? MethodHandle.INVOKE_VAR_HANDLE_EXACT 2476 : MethodHandle.INVOKE_VAR_HANDLE; 2477 return new MethodHandleImpl(method.getArtMethod(), kind, methodType); 2478 } 2479 // END Android-added: resolver for VarHandle accessor methods. 2480 2481 /** 2482 * Produces a special <em>invoker method handle</em> which can be used to 2483 * invoke a signature-polymorphic access mode method on any VarHandle whose 2484 * associated access mode type is compatible with the given type. 2485 * The resulting invoker will have a type which is exactly equal to the 2486 * desired given type, except that it will accept an additional leading 2487 * argument of type {@code VarHandle}. 2488 * 2489 * @param accessMode the VarHandle access mode 2490 * @param type the desired target type 2491 * @return a method handle suitable for invoking an access mode method of 2492 * any VarHandle whose access mode type is of the given type. 2493 * @since 9 2494 * @hide 2495 */ 2496 static public 2497 MethodHandle varHandleExactInvoker(VarHandle.AccessMode accessMode, MethodType type) { 2498 return methodHandleForVarHandleAccessor(accessMode, type, true /* isExactInvoker */); 2499 } 2500 2501 /** 2502 * Produces a special <em>invoker method handle</em> which can be used to 2503 * invoke a signature-polymorphic access mode method on any VarHandle whose 2504 * associated access mode type is compatible with the given type. 2505 * The resulting invoker will have a type which is exactly equal to the 2506 * desired given type, except that it will accept an additional leading 2507 * argument of type {@code VarHandle}. 2508 * <p> 2509 * Before invoking its target, if the access mode type differs from the 2510 * desired given type, the invoker will apply reference casts as necessary 2511 * and box, unbox, or widen primitive values, as if by 2512 * {@link MethodHandle#asType asType}. Similarly, the return value will be 2513 * converted as necessary. 2514 * <p> 2515 * This method is equivalent to the following code (though it may be more 2516 * efficient): {@code publicLookup().findVirtual(VarHandle.class, accessMode.name(), type)} 2517 * 2518 * @param accessMode the VarHandle access mode 2519 * @param type the desired target type 2520 * @return a method handle suitable for invoking an access mode method of 2521 * any VarHandle whose access mode type is convertible to the given 2522 * type. 2523 * @since 9 2524 * @hide 2525 */ 2526 static public 2527 MethodHandle varHandleInvoker(VarHandle.AccessMode accessMode, MethodType type) { 2528 return methodHandleForVarHandleAccessor(accessMode, type, false /* isExactInvoker */); 2529 } 2530 2531 // Android-changed: Basic invokers are not supported. 2532 // 2533 // static /*non-public*/ 2534 // MethodHandle basicInvoker(MethodType type) { 2535 // return type.invokers().basicInvoker(); 2536 // } 2537 2538 /// method handle modification (creation from other method handles) 2539 2540 /** 2541 * Produces a method handle which adapts the type of the 2542 * given method handle to a new type by pairwise argument and return type conversion. 2543 * The original type and new type must have the same number of arguments. 2544 * The resulting method handle is guaranteed to report a type 2545 * which is equal to the desired new type. 2546 * <p> 2547 * If the original type and new type are equal, returns target. 2548 * <p> 2549 * The same conversions are allowed as for {@link MethodHandle#asType MethodHandle.asType}, 2550 * and some additional conversions are also applied if those conversions fail. 2551 * Given types <em>T0</em>, <em>T1</em>, one of the following conversions is applied 2552 * if possible, before or instead of any conversions done by {@code asType}: 2553 * <ul> 2554 * <li>If <em>T0</em> and <em>T1</em> are references, and <em>T1</em> is an interface type, 2555 * then the value of type <em>T0</em> is passed as a <em>T1</em> without a cast. 2556 * (This treatment of interfaces follows the usage of the bytecode verifier.) 2557 * <li>If <em>T0</em> is boolean and <em>T1</em> is another primitive, 2558 * the boolean is converted to a byte value, 1 for true, 0 for false. 2559 * (This treatment follows the usage of the bytecode verifier.) 2560 * <li>If <em>T1</em> is boolean and <em>T0</em> is another primitive, 2561 * <em>T0</em> is converted to byte via Java casting conversion (JLS 5.5), 2562 * and the low order bit of the result is tested, as if by {@code (x & 1) != 0}. 2563 * <li>If <em>T0</em> and <em>T1</em> are primitives other than boolean, 2564 * then a Java casting conversion (JLS 5.5) is applied. 2565 * (Specifically, <em>T0</em> will convert to <em>T1</em> by 2566 * widening and/or narrowing.) 2567 * <li>If <em>T0</em> is a reference and <em>T1</em> a primitive, an unboxing 2568 * conversion will be applied at runtime, possibly followed 2569 * by a Java casting conversion (JLS 5.5) on the primitive value, 2570 * possibly followed by a conversion from byte to boolean by testing 2571 * the low-order bit. 2572 * <li>If <em>T0</em> is a reference and <em>T1</em> a primitive, 2573 * and if the reference is null at runtime, a zero value is introduced. 2574 * </ul> 2575 * @param target the method handle to invoke after arguments are retyped 2576 * @param newType the expected type of the new method handle 2577 * @return a method handle which delegates to the target after performing 2578 * any necessary argument conversions, and arranges for any 2579 * necessary return value conversions 2580 * @throws NullPointerException if either argument is null 2581 * @throws WrongMethodTypeException if the conversion cannot be made 2582 * @see MethodHandle#asType 2583 */ 2584 public static 2585 MethodHandle explicitCastArguments(MethodHandle target, MethodType newType) { 2586 explicitCastArgumentsChecks(target, newType); 2587 // use the asTypeCache when possible: 2588 MethodType oldType = target.type(); 2589 if (oldType == newType) return target; 2590 if (oldType.explicitCastEquivalentToAsType(newType)) { 2591 return target.asFixedArity().asType(newType); 2592 } 2593 2594 return new Transformers.ExplicitCastArguments(target, newType); 2595 } 2596 2597 private static void explicitCastArgumentsChecks(MethodHandle target, MethodType newType) { 2598 if (target.type().parameterCount() != newType.parameterCount()) { 2599 throw new WrongMethodTypeException("cannot explicitly cast " + target + " to " + newType); 2600 } 2601 } 2602 2603 /** 2604 * Produces a method handle which adapts the calling sequence of the 2605 * given method handle to a new type, by reordering the arguments. 2606 * The resulting method handle is guaranteed to report a type 2607 * which is equal to the desired new type. 2608 * <p> 2609 * The given array controls the reordering. 2610 * Call {@code #I} the number of incoming parameters (the value 2611 * {@code newType.parameterCount()}, and call {@code #O} the number 2612 * of outgoing parameters (the value {@code target.type().parameterCount()}). 2613 * Then the length of the reordering array must be {@code #O}, 2614 * and each element must be a non-negative number less than {@code #I}. 2615 * For every {@code N} less than {@code #O}, the {@code N}-th 2616 * outgoing argument will be taken from the {@code I}-th incoming 2617 * argument, where {@code I} is {@code reorder[N]}. 2618 * <p> 2619 * No argument or return value conversions are applied. 2620 * The type of each incoming argument, as determined by {@code newType}, 2621 * must be identical to the type of the corresponding outgoing parameter 2622 * or parameters in the target method handle. 2623 * The return type of {@code newType} must be identical to the return 2624 * type of the original target. 2625 * <p> 2626 * The reordering array need not specify an actual permutation. 2627 * An incoming argument will be duplicated if its index appears 2628 * more than once in the array, and an incoming argument will be dropped 2629 * if its index does not appear in the array. 2630 * As in the case of {@link #dropArguments(MethodHandle,int,List) dropArguments}, 2631 * incoming arguments which are not mentioned in the reordering array 2632 * are may be any type, as determined only by {@code newType}. 2633 * <blockquote><pre>{@code 2634 import static java.lang.invoke.MethodHandles.*; 2635 import static java.lang.invoke.MethodType.*; 2636 ... 2637 MethodType intfn1 = methodType(int.class, int.class); 2638 MethodType intfn2 = methodType(int.class, int.class, int.class); 2639 MethodHandle sub = ... (int x, int y) -> (x-y) ...; 2640 assert(sub.type().equals(intfn2)); 2641 MethodHandle sub1 = permuteArguments(sub, intfn2, 0, 1); 2642 MethodHandle rsub = permuteArguments(sub, intfn2, 1, 0); 2643 assert((int)rsub.invokeExact(1, 100) == 99); 2644 MethodHandle add = ... (int x, int y) -> (x+y) ...; 2645 assert(add.type().equals(intfn2)); 2646 MethodHandle twice = permuteArguments(add, intfn1, 0, 0); 2647 assert(twice.type().equals(intfn1)); 2648 assert((int)twice.invokeExact(21) == 42); 2649 * }</pre></blockquote> 2650 * @param target the method handle to invoke after arguments are reordered 2651 * @param newType the expected type of the new method handle 2652 * @param reorder an index array which controls the reordering 2653 * @return a method handle which delegates to the target after it 2654 * drops unused arguments and moves and/or duplicates the other arguments 2655 * @throws NullPointerException if any argument is null 2656 * @throws IllegalArgumentException if the index array length is not equal to 2657 * the arity of the target, or if any index array element 2658 * not a valid index for a parameter of {@code newType}, 2659 * or if two corresponding parameter types in 2660 * {@code target.type()} and {@code newType} are not identical, 2661 */ 2662 public static 2663 MethodHandle permuteArguments(MethodHandle target, MethodType newType, int... reorder) { 2664 reorder = reorder.clone(); // get a private copy 2665 MethodType oldType = target.type(); 2666 permuteArgumentChecks(reorder, newType, oldType); 2667 2668 return new Transformers.PermuteArguments(newType, target, reorder); 2669 } 2670 2671 // Android-changed: findFirstDupOrDrop is unused and removed. 2672 // private static int findFirstDupOrDrop(int[] reorder, int newArity); 2673 2674 private static boolean permuteArgumentChecks(int[] reorder, MethodType newType, MethodType oldType) { 2675 if (newType.returnType() != oldType.returnType()) 2676 throw newIllegalArgumentException("return types do not match", 2677 oldType, newType); 2678 if (reorder.length == oldType.parameterCount()) { 2679 int limit = newType.parameterCount(); 2680 boolean bad = false; 2681 for (int j = 0; j < reorder.length; j++) { 2682 int i = reorder[j]; 2683 if (i < 0 || i >= limit) { 2684 bad = true; break; 2685 } 2686 Class<?> src = newType.parameterType(i); 2687 Class<?> dst = oldType.parameterType(j); 2688 if (src != dst) 2689 throw newIllegalArgumentException("parameter types do not match after reorder", 2690 oldType, newType); 2691 } 2692 if (!bad) return true; 2693 } 2694 throw newIllegalArgumentException("bad reorder array: "+Arrays.toString(reorder)); 2695 } 2696 2697 /** 2698 * Produces a method handle of the requested return type which returns the given 2699 * constant value every time it is invoked. 2700 * <p> 2701 * Before the method handle is returned, the passed-in value is converted to the requested type. 2702 * If the requested type is primitive, widening primitive conversions are attempted, 2703 * else reference conversions are attempted. 2704 * <p>The returned method handle is equivalent to {@code identity(type).bindTo(value)}. 2705 * @param type the return type of the desired method handle 2706 * @param value the value to return 2707 * @return a method handle of the given return type and no arguments, which always returns the given value 2708 * @throws NullPointerException if the {@code type} argument is null 2709 * @throws ClassCastException if the value cannot be converted to the required return type 2710 * @throws IllegalArgumentException if the given type is {@code void.class} 2711 */ 2712 public static 2713 MethodHandle constant(Class<?> type, Object value) { 2714 if (type.isPrimitive()) { 2715 if (type == void.class) 2716 throw newIllegalArgumentException("void type"); 2717 Wrapper w = Wrapper.forPrimitiveType(type); 2718 value = w.convert(value, type); 2719 } 2720 2721 return new Transformers.Constant(type, value); 2722 } 2723 2724 /** 2725 * Produces a method handle which returns its sole argument when invoked. 2726 * @param type the type of the sole parameter and return value of the desired method handle 2727 * @return a unary method handle which accepts and returns the given type 2728 * @throws NullPointerException if the argument is null 2729 * @throws IllegalArgumentException if the given type is {@code void.class} 2730 */ 2731 public static 2732 MethodHandle identity(Class<?> type) { 2733 if (type == null) { 2734 throw new NullPointerException("type == null"); 2735 } 2736 2737 if (type.isPrimitive()) { 2738 try { 2739 return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class, "identity", 2740 MethodType.methodType(type, type)); 2741 } catch (NoSuchMethodException | IllegalAccessException e) { 2742 throw new AssertionError(e); 2743 } 2744 } 2745 2746 return new Transformers.ReferenceIdentity(type); 2747 } 2748 2749 /** @hide */ public static byte identity(byte val) { return val; } 2750 /** @hide */ public static boolean identity(boolean val) { return val; } 2751 /** @hide */ public static char identity(char val) { return val; } 2752 /** @hide */ public static short identity(short val) { return val; } 2753 /** @hide */ public static int identity(int val) { return val; } 2754 /** @hide */ public static long identity(long val) { return val; } 2755 /** @hide */ public static float identity(float val) { return val; } 2756 /** @hide */ public static double identity(double val) { return val; } 2757 2758 /** 2759 * Provides a target method handle with one or more <em>bound arguments</em> 2760 * in advance of the method handle's invocation. 2761 * The formal parameters to the target corresponding to the bound 2762 * arguments are called <em>bound parameters</em>. 2763 * Returns a new method handle which saves away the bound arguments. 2764 * When it is invoked, it receives arguments for any non-bound parameters, 2765 * binds the saved arguments to their corresponding parameters, 2766 * and calls the original target. 2767 * <p> 2768 * The type of the new method handle will drop the types for the bound 2769 * parameters from the original target type, since the new method handle 2770 * will no longer require those arguments to be supplied by its callers. 2771 * <p> 2772 * Each given argument object must match the corresponding bound parameter type. 2773 * If a bound parameter type is a primitive, the argument object 2774 * must be a wrapper, and will be unboxed to produce the primitive value. 2775 * <p> 2776 * The {@code pos} argument selects which parameters are to be bound. 2777 * It may range between zero and <i>N-L</i> (inclusively), 2778 * where <i>N</i> is the arity of the target method handle 2779 * and <i>L</i> is the length of the values array. 2780 * @param target the method handle to invoke after the argument is inserted 2781 * @param pos where to insert the argument (zero for the first) 2782 * @param values the series of arguments to insert 2783 * @return a method handle which inserts an additional argument, 2784 * before calling the original method handle 2785 * @throws NullPointerException if the target or the {@code values} array is null 2786 * @see MethodHandle#bindTo 2787 */ 2788 public static 2789 MethodHandle insertArguments(MethodHandle target, int pos, Object... values) { 2790 int insCount = values.length; 2791 Class<?>[] ptypes = insertArgumentsChecks(target, insCount, pos); 2792 if (insCount == 0) { 2793 return target; 2794 } 2795 2796 // Throw ClassCastExceptions early if we can't cast any of the provided values 2797 // to the required type. 2798 for (int i = 0; i < insCount; i++) { 2799 final Class<?> ptype = ptypes[pos + i]; 2800 if (!ptype.isPrimitive()) { 2801 ptypes[pos + i].cast(values[i]); 2802 } else { 2803 // Will throw a ClassCastException if something terrible happens. 2804 values[i] = Wrapper.forPrimitiveType(ptype).convert(values[i], ptype); 2805 } 2806 } 2807 2808 return new Transformers.InsertArguments(target, pos, values); 2809 } 2810 2811 // Android-changed: insertArgumentPrimitive is unused. 2812 // 2813 // private static BoundMethodHandle insertArgumentPrimitive(BoundMethodHandle result, int pos, 2814 // Class<?> ptype, Object value) { 2815 // Wrapper w = Wrapper.forPrimitiveType(ptype); 2816 // // perform unboxing and/or primitive conversion 2817 // value = w.convert(value, ptype); 2818 // switch (w) { 2819 // case INT: return result.bindArgumentI(pos, (int)value); 2820 // case LONG: return result.bindArgumentJ(pos, (long)value); 2821 // case FLOAT: return result.bindArgumentF(pos, (float)value); 2822 // case DOUBLE: return result.bindArgumentD(pos, (double)value); 2823 // default: return result.bindArgumentI(pos, ValueConversions.widenSubword(value)); 2824 // } 2825 // } 2826 2827 private static Class<?>[] insertArgumentsChecks(MethodHandle target, int insCount, int pos) throws RuntimeException { 2828 MethodType oldType = target.type(); 2829 int outargs = oldType.parameterCount(); 2830 int inargs = outargs - insCount; 2831 if (inargs < 0) 2832 throw newIllegalArgumentException("too many values to insert"); 2833 if (pos < 0 || pos > inargs) 2834 throw newIllegalArgumentException("no argument type to append"); 2835 return oldType.ptypes(); 2836 } 2837 2838 /** 2839 * Produces a method handle which will discard some dummy arguments 2840 * before calling some other specified <i>target</i> method handle. 2841 * The type of the new method handle will be the same as the target's type, 2842 * except it will also include the dummy argument types, 2843 * at some given position. 2844 * <p> 2845 * The {@code pos} argument may range between zero and <i>N</i>, 2846 * where <i>N</i> is the arity of the target. 2847 * If {@code pos} is zero, the dummy arguments will precede 2848 * the target's real arguments; if {@code pos} is <i>N</i> 2849 * they will come after. 2850 * <p> 2851 * <b>Example:</b> 2852 * <blockquote><pre>{@code 2853 import static java.lang.invoke.MethodHandles.*; 2854 import static java.lang.invoke.MethodType.*; 2855 ... 2856 MethodHandle cat = lookup().findVirtual(String.class, 2857 "concat", methodType(String.class, String.class)); 2858 assertEquals("xy", (String) cat.invokeExact("x", "y")); 2859 MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class); 2860 MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2)); 2861 assertEquals(bigType, d0.type()); 2862 assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z")); 2863 * }</pre></blockquote> 2864 * <p> 2865 * This method is also equivalent to the following code: 2866 * <blockquote><pre> 2867 * {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))} 2868 * </pre></blockquote> 2869 * @param target the method handle to invoke after the arguments are dropped 2870 * @param valueTypes the type(s) of the argument(s) to drop 2871 * @param pos position of first argument to drop (zero for the leftmost) 2872 * @return a method handle which drops arguments of the given types, 2873 * before calling the original method handle 2874 * @throws NullPointerException if the target is null, 2875 * or if the {@code valueTypes} list or any of its elements is null 2876 * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class}, 2877 * or if {@code pos} is negative or greater than the arity of the target, 2878 * or if the new method handle's type would have too many parameters 2879 */ 2880 public static 2881 MethodHandle dropArguments(MethodHandle target, int pos, List<Class<?>> valueTypes) { 2882 valueTypes = copyTypes(valueTypes); 2883 MethodType oldType = target.type(); // get NPE 2884 int dropped = dropArgumentChecks(oldType, pos, valueTypes); 2885 2886 MethodType newType = oldType.insertParameterTypes(pos, valueTypes); 2887 if (dropped == 0) { 2888 return target; 2889 } 2890 2891 return new Transformers.DropArguments(newType, target, pos, valueTypes.size()); 2892 } 2893 2894 private static List<Class<?>> copyTypes(List<Class<?>> types) { 2895 Object[] a = types.toArray(); 2896 return Arrays.asList(Arrays.copyOf(a, a.length, Class[].class)); 2897 } 2898 2899 private static int dropArgumentChecks(MethodType oldType, int pos, List<Class<?>> valueTypes) { 2900 int dropped = valueTypes.size(); 2901 MethodType.checkSlotCount(dropped); 2902 int outargs = oldType.parameterCount(); 2903 int inargs = outargs + dropped; 2904 if (pos < 0 || pos > outargs) 2905 throw newIllegalArgumentException("no argument type to remove" 2906 + Arrays.asList(oldType, pos, valueTypes, inargs, outargs) 2907 ); 2908 return dropped; 2909 } 2910 2911 /** 2912 * Produces a method handle which will discard some dummy arguments 2913 * before calling some other specified <i>target</i> method handle. 2914 * The type of the new method handle will be the same as the target's type, 2915 * except it will also include the dummy argument types, 2916 * at some given position. 2917 * <p> 2918 * The {@code pos} argument may range between zero and <i>N</i>, 2919 * where <i>N</i> is the arity of the target. 2920 * If {@code pos} is zero, the dummy arguments will precede 2921 * the target's real arguments; if {@code pos} is <i>N</i> 2922 * they will come after. 2923 * <p> 2924 * <b>Example:</b> 2925 * <blockquote><pre>{@code 2926 import static java.lang.invoke.MethodHandles.*; 2927 import static java.lang.invoke.MethodType.*; 2928 ... 2929 MethodHandle cat = lookup().findVirtual(String.class, 2930 "concat", methodType(String.class, String.class)); 2931 assertEquals("xy", (String) cat.invokeExact("x", "y")); 2932 MethodHandle d0 = dropArguments(cat, 0, String.class); 2933 assertEquals("yz", (String) d0.invokeExact("x", "y", "z")); 2934 MethodHandle d1 = dropArguments(cat, 1, String.class); 2935 assertEquals("xz", (String) d1.invokeExact("x", "y", "z")); 2936 MethodHandle d2 = dropArguments(cat, 2, String.class); 2937 assertEquals("xy", (String) d2.invokeExact("x", "y", "z")); 2938 MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class); 2939 assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z")); 2940 * }</pre></blockquote> 2941 * <p> 2942 * This method is also equivalent to the following code: 2943 * <blockquote><pre> 2944 * {@link #dropArguments(MethodHandle,int,List) dropArguments}{@code (target, pos, Arrays.asList(valueTypes))} 2945 * </pre></blockquote> 2946 * @param target the method handle to invoke after the arguments are dropped 2947 * @param valueTypes the type(s) of the argument(s) to drop 2948 * @param pos position of first argument to drop (zero for the leftmost) 2949 * @return a method handle which drops arguments of the given types, 2950 * before calling the original method handle 2951 * @throws NullPointerException if the target is null, 2952 * or if the {@code valueTypes} array or any of its elements is null 2953 * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class}, 2954 * or if {@code pos} is negative or greater than the arity of the target, 2955 * or if the new method handle's type would have 2956 * <a href="MethodHandle.html#maxarity">too many parameters</a> 2957 */ 2958 public static 2959 MethodHandle dropArguments(MethodHandle target, int pos, Class<?>... valueTypes) { 2960 return dropArguments(target, pos, Arrays.asList(valueTypes)); 2961 } 2962 2963 /** 2964 * Adapts a target method handle by pre-processing 2965 * one or more of its arguments, each with its own unary filter function, 2966 * and then calling the target with each pre-processed argument 2967 * replaced by the result of its corresponding filter function. 2968 * <p> 2969 * The pre-processing is performed by one or more method handles, 2970 * specified in the elements of the {@code filters} array. 2971 * The first element of the filter array corresponds to the {@code pos} 2972 * argument of the target, and so on in sequence. 2973 * <p> 2974 * Null arguments in the array are treated as identity functions, 2975 * and the corresponding arguments left unchanged. 2976 * (If there are no non-null elements in the array, the original target is returned.) 2977 * Each filter is applied to the corresponding argument of the adapter. 2978 * <p> 2979 * If a filter {@code F} applies to the {@code N}th argument of 2980 * the target, then {@code F} must be a method handle which 2981 * takes exactly one argument. The type of {@code F}'s sole argument 2982 * replaces the corresponding argument type of the target 2983 * in the resulting adapted method handle. 2984 * The return type of {@code F} must be identical to the corresponding 2985 * parameter type of the target. 2986 * <p> 2987 * It is an error if there are elements of {@code filters} 2988 * (null or not) 2989 * which do not correspond to argument positions in the target. 2990 * <p><b>Example:</b> 2991 * <blockquote><pre>{@code 2992 import static java.lang.invoke.MethodHandles.*; 2993 import static java.lang.invoke.MethodType.*; 2994 ... 2995 MethodHandle cat = lookup().findVirtual(String.class, 2996 "concat", methodType(String.class, String.class)); 2997 MethodHandle upcase = lookup().findVirtual(String.class, 2998 "toUpperCase", methodType(String.class)); 2999 assertEquals("xy", (String) cat.invokeExact("x", "y")); 3000 MethodHandle f0 = filterArguments(cat, 0, upcase); 3001 assertEquals("Xy", (String) f0.invokeExact("x", "y")); // Xy 3002 MethodHandle f1 = filterArguments(cat, 1, upcase); 3003 assertEquals("xY", (String) f1.invokeExact("x", "y")); // xY 3004 MethodHandle f2 = filterArguments(cat, 0, upcase, upcase); 3005 assertEquals("XY", (String) f2.invokeExact("x", "y")); // XY 3006 * }</pre></blockquote> 3007 * <p> Here is pseudocode for the resulting adapter: 3008 * <blockquote><pre>{@code 3009 * V target(P... p, A[i]... a[i], B... b); 3010 * A[i] filter[i](V[i]); 3011 * T adapter(P... p, V[i]... v[i], B... b) { 3012 * return target(p..., f[i](v[i])..., b...); 3013 * } 3014 * }</pre></blockquote> 3015 * 3016 * @param target the method handle to invoke after arguments are filtered 3017 * @param pos the position of the first argument to filter 3018 * @param filters method handles to call initially on filtered arguments 3019 * @return method handle which incorporates the specified argument filtering logic 3020 * @throws NullPointerException if the target is null 3021 * or if the {@code filters} array is null 3022 * @throws IllegalArgumentException if a non-null element of {@code filters} 3023 * does not match a corresponding argument type of target as described above, 3024 * or if the {@code pos+filters.length} is greater than {@code target.type().parameterCount()}, 3025 * or if the resulting method handle's type would have 3026 * <a href="MethodHandle.html#maxarity">too many parameters</a> 3027 */ 3028 public static 3029 MethodHandle filterArguments(MethodHandle target, int pos, MethodHandle... filters) { 3030 filterArgumentsCheckArity(target, pos, filters); 3031 3032 for (int i = 0; i < filters.length; ++i) { 3033 filterArgumentChecks(target, i + pos, filters[i]); 3034 } 3035 3036 return new Transformers.FilterArguments(target, pos, filters); 3037 } 3038 3039 private static void filterArgumentsCheckArity(MethodHandle target, int pos, MethodHandle[] filters) { 3040 MethodType targetType = target.type(); 3041 int maxPos = targetType.parameterCount(); 3042 if (pos + filters.length > maxPos) 3043 throw newIllegalArgumentException("too many filters"); 3044 } 3045 3046 private static void filterArgumentChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException { 3047 MethodType targetType = target.type(); 3048 MethodType filterType = filter.type(); 3049 if (filterType.parameterCount() != 1 3050 || filterType.returnType() != targetType.parameterType(pos)) 3051 throw newIllegalArgumentException("target and filter types do not match", targetType, filterType); 3052 } 3053 3054 /** 3055 * Adapts a target method handle by pre-processing 3056 * a sub-sequence of its arguments with a filter (another method handle). 3057 * The pre-processed arguments are replaced by the result (if any) of the 3058 * filter function. 3059 * The target is then called on the modified (usually shortened) argument list. 3060 * <p> 3061 * If the filter returns a value, the target must accept that value as 3062 * its argument in position {@code pos}, preceded and/or followed by 3063 * any arguments not passed to the filter. 3064 * If the filter returns void, the target must accept all arguments 3065 * not passed to the filter. 3066 * No arguments are reordered, and a result returned from the filter 3067 * replaces (in order) the whole subsequence of arguments originally 3068 * passed to the adapter. 3069 * <p> 3070 * The argument types (if any) of the filter 3071 * replace zero or one argument types of the target, at position {@code pos}, 3072 * in the resulting adapted method handle. 3073 * The return type of the filter (if any) must be identical to the 3074 * argument type of the target at position {@code pos}, and that target argument 3075 * is supplied by the return value of the filter. 3076 * <p> 3077 * In all cases, {@code pos} must be greater than or equal to zero, and 3078 * {@code pos} must also be less than or equal to the target's arity. 3079 * <p><b>Example:</b> 3080 * <blockquote><pre>{@code 3081 import static java.lang.invoke.MethodHandles.*; 3082 import static java.lang.invoke.MethodType.*; 3083 ... 3084 MethodHandle deepToString = publicLookup() 3085 .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class)); 3086 3087 MethodHandle ts1 = deepToString.asCollector(String[].class, 1); 3088 assertEquals("[strange]", (String) ts1.invokeExact("strange")); 3089 3090 MethodHandle ts2 = deepToString.asCollector(String[].class, 2); 3091 assertEquals("[up, down]", (String) ts2.invokeExact("up", "down")); 3092 3093 MethodHandle ts3 = deepToString.asCollector(String[].class, 3); 3094 MethodHandle ts3_ts2 = collectArguments(ts3, 1, ts2); 3095 assertEquals("[top, [up, down], strange]", 3096 (String) ts3_ts2.invokeExact("top", "up", "down", "strange")); 3097 3098 MethodHandle ts3_ts2_ts1 = collectArguments(ts3_ts2, 3, ts1); 3099 assertEquals("[top, [up, down], [strange]]", 3100 (String) ts3_ts2_ts1.invokeExact("top", "up", "down", "strange")); 3101 3102 MethodHandle ts3_ts2_ts3 = collectArguments(ts3_ts2, 1, ts3); 3103 assertEquals("[top, [[up, down, strange], charm], bottom]", 3104 (String) ts3_ts2_ts3.invokeExact("top", "up", "down", "strange", "charm", "bottom")); 3105 * }</pre></blockquote> 3106 * <p> Here is pseudocode for the resulting adapter: 3107 * <blockquote><pre>{@code 3108 * T target(A...,V,C...); 3109 * V filter(B...); 3110 * T adapter(A... a,B... b,C... c) { 3111 * V v = filter(b...); 3112 * return target(a...,v,c...); 3113 * } 3114 * // and if the filter has no arguments: 3115 * T target2(A...,V,C...); 3116 * V filter2(); 3117 * T adapter2(A... a,C... c) { 3118 * V v = filter2(); 3119 * return target2(a...,v,c...); 3120 * } 3121 * // and if the filter has a void return: 3122 * T target3(A...,C...); 3123 * void filter3(B...); 3124 * void adapter3(A... a,B... b,C... c) { 3125 * filter3(b...); 3126 * return target3(a...,c...); 3127 * } 3128 * }</pre></blockquote> 3129 * <p> 3130 * A collection adapter {@code collectArguments(mh, 0, coll)} is equivalent to 3131 * one which first "folds" the affected arguments, and then drops them, in separate 3132 * steps as follows: 3133 * <blockquote><pre>{@code 3134 * mh = MethodHandles.dropArguments(mh, 1, coll.type().parameterList()); //step 2 3135 * mh = MethodHandles.foldArguments(mh, coll); //step 1 3136 * }</pre></blockquote> 3137 * If the target method handle consumes no arguments besides than the result 3138 * (if any) of the filter {@code coll}, then {@code collectArguments(mh, 0, coll)} 3139 * is equivalent to {@code filterReturnValue(coll, mh)}. 3140 * If the filter method handle {@code coll} consumes one argument and produces 3141 * a non-void result, then {@code collectArguments(mh, N, coll)} 3142 * is equivalent to {@code filterArguments(mh, N, coll)}. 3143 * Other equivalences are possible but would require argument permutation. 3144 * 3145 * @param target the method handle to invoke after filtering the subsequence of arguments 3146 * @param pos the position of the first adapter argument to pass to the filter, 3147 * and/or the target argument which receives the result of the filter 3148 * @param filter method handle to call on the subsequence of arguments 3149 * @return method handle which incorporates the specified argument subsequence filtering logic 3150 * @throws NullPointerException if either argument is null 3151 * @throws IllegalArgumentException if the return type of {@code filter} 3152 * is non-void and is not the same as the {@code pos} argument of the target, 3153 * or if {@code pos} is not between 0 and the target's arity, inclusive, 3154 * or if the resulting method handle's type would have 3155 * <a href="MethodHandle.html#maxarity">too many parameters</a> 3156 * @see MethodHandles#foldArguments 3157 * @see MethodHandles#filterArguments 3158 * @see MethodHandles#filterReturnValue 3159 */ 3160 public static 3161 MethodHandle collectArguments(MethodHandle target, int pos, MethodHandle filter) { 3162 MethodType newType = collectArgumentsChecks(target, pos, filter); 3163 return new Transformers.CollectArguments(target, filter, pos, newType); 3164 } 3165 3166 private static MethodType collectArgumentsChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException { 3167 MethodType targetType = target.type(); 3168 MethodType filterType = filter.type(); 3169 Class<?> rtype = filterType.returnType(); 3170 List<Class<?>> filterArgs = filterType.parameterList(); 3171 if (rtype == void.class) { 3172 return targetType.insertParameterTypes(pos, filterArgs); 3173 } 3174 if (rtype != targetType.parameterType(pos)) { 3175 throw newIllegalArgumentException("target and filter types do not match", targetType, filterType); 3176 } 3177 return targetType.dropParameterTypes(pos, pos+1).insertParameterTypes(pos, filterArgs); 3178 } 3179 3180 /** 3181 * Adapts a target method handle by post-processing 3182 * its return value (if any) with a filter (another method handle). 3183 * The result of the filter is returned from the adapter. 3184 * <p> 3185 * If the target returns a value, the filter must accept that value as 3186 * its only argument. 3187 * If the target returns void, the filter must accept no arguments. 3188 * <p> 3189 * The return type of the filter 3190 * replaces the return type of the target 3191 * in the resulting adapted method handle. 3192 * The argument type of the filter (if any) must be identical to the 3193 * return type of the target. 3194 * <p><b>Example:</b> 3195 * <blockquote><pre>{@code 3196 import static java.lang.invoke.MethodHandles.*; 3197 import static java.lang.invoke.MethodType.*; 3198 ... 3199 MethodHandle cat = lookup().findVirtual(String.class, 3200 "concat", methodType(String.class, String.class)); 3201 MethodHandle length = lookup().findVirtual(String.class, 3202 "length", methodType(int.class)); 3203 System.out.println((String) cat.invokeExact("x", "y")); // xy 3204 MethodHandle f0 = filterReturnValue(cat, length); 3205 System.out.println((int) f0.invokeExact("x", "y")); // 2 3206 * }</pre></blockquote> 3207 * <p> Here is pseudocode for the resulting adapter: 3208 * <blockquote><pre>{@code 3209 * V target(A...); 3210 * T filter(V); 3211 * T adapter(A... a) { 3212 * V v = target(a...); 3213 * return filter(v); 3214 * } 3215 * // and if the target has a void return: 3216 * void target2(A...); 3217 * T filter2(); 3218 * T adapter2(A... a) { 3219 * target2(a...); 3220 * return filter2(); 3221 * } 3222 * // and if the filter has a void return: 3223 * V target3(A...); 3224 * void filter3(V); 3225 * void adapter3(A... a) { 3226 * V v = target3(a...); 3227 * filter3(v); 3228 * } 3229 * }</pre></blockquote> 3230 * @param target the method handle to invoke before filtering the return value 3231 * @param filter method handle to call on the return value 3232 * @return method handle which incorporates the specified return value filtering logic 3233 * @throws NullPointerException if either argument is null 3234 * @throws IllegalArgumentException if the argument list of {@code filter} 3235 * does not match the return type of target as described above 3236 */ 3237 public static 3238 MethodHandle filterReturnValue(MethodHandle target, MethodHandle filter) { 3239 MethodType targetType = target.type(); 3240 MethodType filterType = filter.type(); 3241 filterReturnValueChecks(targetType, filterType); 3242 3243 return new Transformers.FilterReturnValue(target, filter); 3244 } 3245 3246 private static void filterReturnValueChecks(MethodType targetType, MethodType filterType) throws RuntimeException { 3247 Class<?> rtype = targetType.returnType(); 3248 int filterValues = filterType.parameterCount(); 3249 if (filterValues == 0 3250 ? (rtype != void.class) 3251 : (rtype != filterType.parameterType(0) || filterValues != 1)) 3252 throw newIllegalArgumentException("target and filter types do not match", targetType, filterType); 3253 } 3254 3255 /** 3256 * Adapts a target method handle by pre-processing 3257 * some of its arguments, and then calling the target with 3258 * the result of the pre-processing, inserted into the original 3259 * sequence of arguments. 3260 * <p> 3261 * The pre-processing is performed by {@code combiner}, a second method handle. 3262 * Of the arguments passed to the adapter, the first {@code N} arguments 3263 * are copied to the combiner, which is then called. 3264 * (Here, {@code N} is defined as the parameter count of the combiner.) 3265 * After this, control passes to the target, with any result 3266 * from the combiner inserted before the original {@code N} incoming 3267 * arguments. 3268 * <p> 3269 * If the combiner returns a value, the first parameter type of the target 3270 * must be identical with the return type of the combiner, and the next 3271 * {@code N} parameter types of the target must exactly match the parameters 3272 * of the combiner. 3273 * <p> 3274 * If the combiner has a void return, no result will be inserted, 3275 * and the first {@code N} parameter types of the target 3276 * must exactly match the parameters of the combiner. 3277 * <p> 3278 * The resulting adapter is the same type as the target, except that the 3279 * first parameter type is dropped, 3280 * if it corresponds to the result of the combiner. 3281 * <p> 3282 * (Note that {@link #dropArguments(MethodHandle,int,List) dropArguments} can be used to remove any arguments 3283 * that either the combiner or the target does not wish to receive. 3284 * If some of the incoming arguments are destined only for the combiner, 3285 * consider using {@link MethodHandle#asCollector asCollector} instead, since those 3286 * arguments will not need to be live on the stack on entry to the 3287 * target.) 3288 * <p><b>Example:</b> 3289 * <blockquote><pre>{@code 3290 import static java.lang.invoke.MethodHandles.*; 3291 import static java.lang.invoke.MethodType.*; 3292 ... 3293 MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class, 3294 "println", methodType(void.class, String.class)) 3295 .bindTo(System.out); 3296 MethodHandle cat = lookup().findVirtual(String.class, 3297 "concat", methodType(String.class, String.class)); 3298 assertEquals("boojum", (String) cat.invokeExact("boo", "jum")); 3299 MethodHandle catTrace = foldArguments(cat, trace); 3300 // also prints "boo": 3301 assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum")); 3302 * }</pre></blockquote> 3303 * <p> Here is pseudocode for the resulting adapter: 3304 * <blockquote><pre>{@code 3305 * // there are N arguments in A... 3306 * T target(V, A[N]..., B...); 3307 * V combiner(A...); 3308 * T adapter(A... a, B... b) { 3309 * V v = combiner(a...); 3310 * return target(v, a..., b...); 3311 * } 3312 * // and if the combiner has a void return: 3313 * T target2(A[N]..., B...); 3314 * void combiner2(A...); 3315 * T adapter2(A... a, B... b) { 3316 * combiner2(a...); 3317 * return target2(a..., b...); 3318 * } 3319 * }</pre></blockquote> 3320 * @param target the method handle to invoke after arguments are combined 3321 * @param combiner method handle to call initially on the incoming arguments 3322 * @return method handle which incorporates the specified argument folding logic 3323 * @throws NullPointerException if either argument is null 3324 * @throws IllegalArgumentException if {@code combiner}'s return type 3325 * is non-void and not the same as the first argument type of 3326 * the target, or if the initial {@code N} argument types 3327 * of the target 3328 * (skipping one matching the {@code combiner}'s return type) 3329 * are not identical with the argument types of {@code combiner} 3330 */ 3331 public static 3332 MethodHandle foldArguments(MethodHandle target, MethodHandle combiner) { 3333 int foldPos = 0; 3334 MethodType targetType = target.type(); 3335 MethodType combinerType = combiner.type(); 3336 Class<?> rtype = foldArgumentChecks(foldPos, targetType, combinerType); 3337 3338 return new Transformers.FoldArguments(target, combiner); 3339 } 3340 3341 private static Class<?> foldArgumentChecks(int foldPos, MethodType targetType, MethodType combinerType) { 3342 int foldArgs = combinerType.parameterCount(); 3343 Class<?> rtype = combinerType.returnType(); 3344 int foldVals = rtype == void.class ? 0 : 1; 3345 int afterInsertPos = foldPos + foldVals; 3346 boolean ok = (targetType.parameterCount() >= afterInsertPos + foldArgs); 3347 if (ok && !(combinerType.parameterList() 3348 .equals(targetType.parameterList().subList(afterInsertPos, 3349 afterInsertPos + foldArgs)))) 3350 ok = false; 3351 if (ok && foldVals != 0 && combinerType.returnType() != targetType.parameterType(0)) 3352 ok = false; 3353 if (!ok) 3354 throw misMatchedTypes("target and combiner types", targetType, combinerType); 3355 return rtype; 3356 } 3357 3358 /** 3359 * Makes a method handle which adapts a target method handle, 3360 * by guarding it with a test, a boolean-valued method handle. 3361 * If the guard fails, a fallback handle is called instead. 3362 * All three method handles must have the same corresponding 3363 * argument and return types, except that the return type 3364 * of the test must be boolean, and the test is allowed 3365 * to have fewer arguments than the other two method handles. 3366 * <p> Here is pseudocode for the resulting adapter: 3367 * <blockquote><pre>{@code 3368 * boolean test(A...); 3369 * T target(A...,B...); 3370 * T fallback(A...,B...); 3371 * T adapter(A... a,B... b) { 3372 * if (test(a...)) 3373 * return target(a..., b...); 3374 * else 3375 * return fallback(a..., b...); 3376 * } 3377 * }</pre></blockquote> 3378 * Note that the test arguments ({@code a...} in the pseudocode) cannot 3379 * be modified by execution of the test, and so are passed unchanged 3380 * from the caller to the target or fallback as appropriate. 3381 * @param test method handle used for test, must return boolean 3382 * @param target method handle to call if test passes 3383 * @param fallback method handle to call if test fails 3384 * @return method handle which incorporates the specified if/then/else logic 3385 * @throws NullPointerException if any argument is null 3386 * @throws IllegalArgumentException if {@code test} does not return boolean, 3387 * or if all three method types do not match (with the return 3388 * type of {@code test} changed to match that of the target). 3389 */ 3390 public static 3391 MethodHandle guardWithTest(MethodHandle test, 3392 MethodHandle target, 3393 MethodHandle fallback) { 3394 MethodType gtype = test.type(); 3395 MethodType ttype = target.type(); 3396 MethodType ftype = fallback.type(); 3397 if (!ttype.equals(ftype)) 3398 throw misMatchedTypes("target and fallback types", ttype, ftype); 3399 if (gtype.returnType() != boolean.class) 3400 throw newIllegalArgumentException("guard type is not a predicate "+gtype); 3401 List<Class<?>> targs = ttype.parameterList(); 3402 List<Class<?>> gargs = gtype.parameterList(); 3403 if (!targs.equals(gargs)) { 3404 int gpc = gargs.size(), tpc = targs.size(); 3405 if (gpc >= tpc || !targs.subList(0, gpc).equals(gargs)) 3406 throw misMatchedTypes("target and test types", ttype, gtype); 3407 test = dropArguments(test, gpc, targs.subList(gpc, tpc)); 3408 gtype = test.type(); 3409 } 3410 3411 return new Transformers.GuardWithTest(test, target, fallback); 3412 } 3413 3414 static RuntimeException misMatchedTypes(String what, MethodType t1, MethodType t2) { 3415 return newIllegalArgumentException(what + " must match: " + t1 + " != " + t2); 3416 } 3417 3418 /** 3419 * Makes a method handle which adapts a target method handle, 3420 * by running it inside an exception handler. 3421 * If the target returns normally, the adapter returns that value. 3422 * If an exception matching the specified type is thrown, the fallback 3423 * handle is called instead on the exception, plus the original arguments. 3424 * <p> 3425 * The target and handler must have the same corresponding 3426 * argument and return types, except that handler may omit trailing arguments 3427 * (similarly to the predicate in {@link #guardWithTest guardWithTest}). 3428 * Also, the handler must have an extra leading parameter of {@code exType} or a supertype. 3429 * <p> Here is pseudocode for the resulting adapter: 3430 * <blockquote><pre>{@code 3431 * T target(A..., B...); 3432 * T handler(ExType, A...); 3433 * T adapter(A... a, B... b) { 3434 * try { 3435 * return target(a..., b...); 3436 * } catch (ExType ex) { 3437 * return handler(ex, a...); 3438 * } 3439 * } 3440 * }</pre></blockquote> 3441 * Note that the saved arguments ({@code a...} in the pseudocode) cannot 3442 * be modified by execution of the target, and so are passed unchanged 3443 * from the caller to the handler, if the handler is invoked. 3444 * <p> 3445 * The target and handler must return the same type, even if the handler 3446 * always throws. (This might happen, for instance, because the handler 3447 * is simulating a {@code finally} clause). 3448 * To create such a throwing handler, compose the handler creation logic 3449 * with {@link #throwException throwException}, 3450 * in order to create a method handle of the correct return type. 3451 * @param target method handle to call 3452 * @param exType the type of exception which the handler will catch 3453 * @param handler method handle to call if a matching exception is thrown 3454 * @return method handle which incorporates the specified try/catch logic 3455 * @throws NullPointerException if any argument is null 3456 * @throws IllegalArgumentException if {@code handler} does not accept 3457 * the given exception type, or if the method handle types do 3458 * not match in their return types and their 3459 * corresponding parameters 3460 */ 3461 public static 3462 MethodHandle catchException(MethodHandle target, 3463 Class<? extends Throwable> exType, 3464 MethodHandle handler) { 3465 MethodType ttype = target.type(); 3466 MethodType htype = handler.type(); 3467 if (htype.parameterCount() < 1 || 3468 !htype.parameterType(0).isAssignableFrom(exType)) 3469 throw newIllegalArgumentException("handler does not accept exception type "+exType); 3470 if (htype.returnType() != ttype.returnType()) 3471 throw misMatchedTypes("target and handler return types", ttype, htype); 3472 List<Class<?>> targs = ttype.parameterList(); 3473 List<Class<?>> hargs = htype.parameterList(); 3474 hargs = hargs.subList(1, hargs.size()); // omit leading parameter from handler 3475 if (!targs.equals(hargs)) { 3476 int hpc = hargs.size(), tpc = targs.size(); 3477 if (hpc >= tpc || !targs.subList(0, hpc).equals(hargs)) 3478 throw misMatchedTypes("target and handler types", ttype, htype); 3479 } 3480 3481 return new Transformers.CatchException(target, handler, exType); 3482 } 3483 3484 /** 3485 * Produces a method handle which will throw exceptions of the given {@code exType}. 3486 * The method handle will accept a single argument of {@code exType}, 3487 * and immediately throw it as an exception. 3488 * The method type will nominally specify a return of {@code returnType}. 3489 * The return type may be anything convenient: It doesn't matter to the 3490 * method handle's behavior, since it will never return normally. 3491 * @param returnType the return type of the desired method handle 3492 * @param exType the parameter type of the desired method handle 3493 * @return method handle which can throw the given exceptions 3494 * @throws NullPointerException if either argument is null 3495 */ 3496 public static 3497 MethodHandle throwException(Class<?> returnType, Class<? extends Throwable> exType) { 3498 if (!Throwable.class.isAssignableFrom(exType)) 3499 throw new ClassCastException(exType.getName()); 3500 3501 return new Transformers.AlwaysThrow(returnType, exType); 3502 } 3503 } 3504
