1 // Copyright 2011 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #ifndef V8_HANDLES_H_ 29 #define V8_HANDLES_H_ 30 31 #include "allocation.h" 32 #include "apiutils.h" 33 #include "objects.h" 34 35 namespace v8 { 36 namespace internal { 37 38 // ---------------------------------------------------------------------------- 39 // A Handle provides a reference to an object that survives relocation by 40 // the garbage collector. 41 // Handles are only valid within a HandleScope. 42 // When a handle is created for an object a cell is allocated in the heap. 43 44 template<typename T> 45 class Handle { 46 public: 47 INLINE(explicit Handle(T** location)) { location_ = location; } 48 INLINE(explicit Handle(T* obj)); 49 INLINE(Handle(T* obj, Isolate* isolate)); 50 51 INLINE(Handle()) : location_(NULL) {} 52 53 // Constructor for handling automatic up casting. 54 // Ex. Handle<JSFunction> can be passed when Handle<Object> is expected. 55 template <class S> Handle(Handle<S> handle) { 56 #ifdef DEBUG 57 T* a = NULL; 58 S* b = NULL; 59 a = b; // Fake assignment to enforce type checks. 60 USE(a); 61 #endif 62 location_ = reinterpret_cast<T**>(handle.location_); 63 } 64 65 INLINE(T* operator->() const) { return operator*(); } 66 67 // Check if this handle refers to the exact same object as the other handle. 68 INLINE(bool is_identical_to(const Handle<T> other) const); 69 70 // Provides the C++ dereference operator. 71 INLINE(T* operator*() const); 72 73 // Returns the address to where the raw pointer is stored. 74 INLINE(T** location() const); 75 76 template <class S> static Handle<T> cast(Handle<S> that) { 77 T::cast(*reinterpret_cast<T**>(that.location_)); 78 return Handle<T>(reinterpret_cast<T**>(that.location_)); 79 } 80 81 static Handle<T> null() { return Handle<T>(); } 82 bool is_null() const { return location_ == NULL; } 83 84 // Closes the given scope, but lets this handle escape. See 85 // implementation in api.h. 86 inline Handle<T> EscapeFrom(v8::EscapableHandleScope* scope); 87 88 #ifdef DEBUG 89 enum DereferenceCheckMode { INCLUDE_DEFERRED_CHECK, NO_DEFERRED_CHECK }; 90 91 bool IsDereferenceAllowed(DereferenceCheckMode mode) const; 92 #endif // DEBUG 93 94 private: 95 T** location_; 96 97 // Handles of different classes are allowed to access each other's location_. 98 template<class S> friend class Handle; 99 }; 100 101 102 // Convenience wrapper. 103 template<class T> 104 inline Handle<T> handle(T* t, Isolate* isolate) { 105 return Handle<T>(t, isolate); 106 } 107 108 109 // Convenience wrapper. 110 template<class T> 111 inline Handle<T> handle(T* t) { 112 return Handle<T>(t, t->GetIsolate()); 113 } 114 115 116 class DeferredHandles; 117 class HandleScopeImplementer; 118 119 120 // A stack-allocated class that governs a number of local handles. 121 // After a handle scope has been created, all local handles will be 122 // allocated within that handle scope until either the handle scope is 123 // deleted or another handle scope is created. If there is already a 124 // handle scope and a new one is created, all allocations will take 125 // place in the new handle scope until it is deleted. After that, 126 // new handles will again be allocated in the original handle scope. 127 // 128 // After the handle scope of a local handle has been deleted the 129 // garbage collector will no longer track the object stored in the 130 // handle and may deallocate it. The behavior of accessing a handle 131 // for which the handle scope has been deleted is undefined. 132 class HandleScope { 133 public: 134 explicit inline HandleScope(Isolate* isolate); 135 136 inline ~HandleScope(); 137 138 // Counts the number of allocated handles. 139 static int NumberOfHandles(Isolate* isolate); 140 141 // Creates a new handle with the given value. 142 template <typename T> 143 static inline T** CreateHandle(Isolate* isolate, T* value); 144 145 // Deallocates any extensions used by the current scope. 146 static void DeleteExtensions(Isolate* isolate); 147 148 static Address current_next_address(Isolate* isolate); 149 static Address current_limit_address(Isolate* isolate); 150 static Address current_level_address(Isolate* isolate); 151 152 // Closes the HandleScope (invalidating all handles 153 // created in the scope of the HandleScope) and returns 154 // a Handle backed by the parent scope holding the 155 // value of the argument handle. 156 template <typename T> 157 Handle<T> CloseAndEscape(Handle<T> handle_value); 158 159 Isolate* isolate() { return isolate_; } 160 161 private: 162 // Prevent heap allocation or illegal handle scopes. 163 HandleScope(const HandleScope&); 164 void operator=(const HandleScope&); 165 void* operator new(size_t size); 166 void operator delete(void* size_t); 167 168 Isolate* isolate_; 169 Object** prev_next_; 170 Object** prev_limit_; 171 172 // Close the handle scope resetting limits to a previous state. 173 static inline void CloseScope(Isolate* isolate, 174 Object** prev_next, 175 Object** prev_limit); 176 177 // Extend the handle scope making room for more handles. 178 static internal::Object** Extend(Isolate* isolate); 179 180 #ifdef ENABLE_HANDLE_ZAPPING 181 // Zaps the handles in the half-open interval [start, end). 182 static void ZapRange(Object** start, Object** end); 183 #endif 184 185 friend class v8::HandleScope; 186 friend class v8::internal::DeferredHandles; 187 friend class v8::internal::HandleScopeImplementer; 188 friend class v8::internal::Isolate; 189 }; 190 191 192 class DeferredHandles; 193 194 195 class DeferredHandleScope { 196 public: 197 explicit DeferredHandleScope(Isolate* isolate); 198 // The DeferredHandles object returned stores the Handles created 199 // since the creation of this DeferredHandleScope. The Handles are 200 // alive as long as the DeferredHandles object is alive. 201 DeferredHandles* Detach(); 202 ~DeferredHandleScope(); 203 204 private: 205 Object** prev_limit_; 206 Object** prev_next_; 207 HandleScopeImplementer* impl_; 208 209 #ifdef DEBUG 210 bool handles_detached_; 211 int prev_level_; 212 #endif 213 214 friend class HandleScopeImplementer; 215 }; 216 217 218 // ---------------------------------------------------------------------------- 219 // Handle operations. 220 // They might invoke garbage collection. The result is an handle to 221 // an object of expected type, or the handle is an error if running out 222 // of space or encountering an internal error. 223 224 // Flattens a string. 225 void FlattenString(Handle<String> str); 226 227 // Flattens a string and returns the underlying external or sequential 228 // string. 229 Handle<String> FlattenGetString(Handle<String> str); 230 231 Handle<Object> ForceSetProperty(Handle<JSObject> object, 232 Handle<Object> key, 233 Handle<Object> value, 234 PropertyAttributes attributes); 235 236 Handle<Object> DeleteProperty(Handle<JSObject> object, Handle<Object> key); 237 238 Handle<Object> ForceDeleteProperty(Handle<JSObject> object, Handle<Object> key); 239 240 Handle<Object> HasProperty(Handle<JSReceiver> obj, Handle<Object> key); 241 242 Handle<Object> GetProperty(Handle<JSReceiver> obj, const char* name); 243 244 Handle<Object> GetProperty(Isolate* isolate, 245 Handle<Object> obj, 246 Handle<Object> key); 247 248 Handle<Object> LookupSingleCharacterStringFromCode(Isolate* isolate, 249 uint32_t index); 250 251 Handle<FixedArray> AddKeysFromJSArray(Handle<FixedArray>, 252 Handle<JSArray> array); 253 254 // Get the JS object corresponding to the given script; create it 255 // if none exists. 256 Handle<JSValue> GetScriptWrapper(Handle<Script> script); 257 258 // Script line number computations. Note that the line number is zero-based. 259 void InitScriptLineEnds(Handle<Script> script); 260 // For string calculates an array of line end positions. If the string 261 // does not end with a new line character, this character may optionally be 262 // imagined. 263 Handle<FixedArray> CalculateLineEnds(Handle<String> string, 264 bool with_imaginary_last_new_line); 265 int GetScriptLineNumber(Handle<Script> script, int code_position); 266 // The safe version does not make heap allocations but may work much slower. 267 int GetScriptLineNumberSafe(Handle<Script> script, int code_position); 268 int GetScriptColumnNumber(Handle<Script> script, int code_position); 269 Handle<Object> GetScriptNameOrSourceURL(Handle<Script> script); 270 271 // Computes the enumerable keys from interceptors. Used for debug mirrors and 272 // by GetKeysInFixedArrayFor below. 273 v8::Handle<v8::Array> GetKeysForNamedInterceptor(Handle<JSReceiver> receiver, 274 Handle<JSObject> object); 275 v8::Handle<v8::Array> GetKeysForIndexedInterceptor(Handle<JSReceiver> receiver, 276 Handle<JSObject> object); 277 278 enum KeyCollectionType { LOCAL_ONLY, INCLUDE_PROTOS }; 279 280 // Computes the enumerable keys for a JSObject. Used for implementing 281 // "for (n in object) { }". 282 Handle<FixedArray> GetKeysInFixedArrayFor(Handle<JSReceiver> object, 283 KeyCollectionType type, 284 bool* threw); 285 Handle<JSArray> GetKeysFor(Handle<JSReceiver> object, bool* threw); 286 Handle<FixedArray> ReduceFixedArrayTo(Handle<FixedArray> array, int length); 287 Handle<FixedArray> GetEnumPropertyKeys(Handle<JSObject> object, 288 bool cache_result); 289 290 // Computes the union of keys and return the result. 291 // Used for implementing "for (n in object) { }" 292 Handle<FixedArray> UnionOfKeys(Handle<FixedArray> first, 293 Handle<FixedArray> second); 294 295 Handle<JSGlobalProxy> ReinitializeJSGlobalProxy( 296 Handle<JSFunction> constructor, 297 Handle<JSGlobalProxy> global); 298 299 void AddWeakObjectToCodeDependency(Heap* heap, 300 Handle<Object> object, 301 Handle<Code> code); 302 303 // Seal off the current HandleScope so that new handles can only be created 304 // if a new HandleScope is entered. 305 class SealHandleScope BASE_EMBEDDED { 306 public: 307 #ifndef DEBUG 308 explicit SealHandleScope(Isolate* isolate) {} 309 ~SealHandleScope() {} 310 #else 311 explicit inline SealHandleScope(Isolate* isolate); 312 inline ~SealHandleScope(); 313 private: 314 Isolate* isolate_; 315 Object** limit_; 316 int level_; 317 #endif 318 }; 319 320 } } // namespace v8::internal 321 322 #endif // V8_HANDLES_H_ 323
