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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 /*
     18  * This uses the FFI (Foreign Function Interface) library to abstract away
     19  * the system-dependent stuff.  The FFI code is slower than a custom
     20  * assembly version, but has the distinct advantage of having been
     21  * written already for several platforms.
     22  */
     23 #include "Dalvik.h"
     24 #include "ffi.h"
     25 
     26 /*
     27  * Convert a signature type character to an FFI type.
     28  */
     29 static ffi_type* getFfiType(char sigType)
     30 {
     31     switch (sigType) {
     32     case 'V': return &ffi_type_void;
     33     case 'Z': return &ffi_type_uint8;
     34     case 'B': return &ffi_type_sint8;
     35     case 'C': return &ffi_type_uint16;
     36     case 'S': return &ffi_type_sint16;
     37     case 'I': return &ffi_type_sint32;
     38     case 'F': return &ffi_type_float;
     39     case 'J': return &ffi_type_sint64;
     40     case 'D': return &ffi_type_double;
     41     case '[':
     42     case 'L': return &ffi_type_pointer;
     43     default:
     44         ALOGE("bad ffitype 0x%02x", sigType);
     45         dvmAbort();
     46         return NULL;
     47     }
     48 }
     49 
     50 /*
     51  * Call "func" with the specified arguments.
     52  *
     53  * The second argument to JNI native functions is either the object (the
     54  * "this" pointer) or, for static functions, a pointer to the class object.
     55  * The Dalvik instructions will push "this" into argv[0], but it's up to
     56  * us to insert the class object.
     57  *
     58  * Because there is no such thing in as a null "this" pointer, we use
     59  * the non-NULL state of "clazz" to determine whether or not it's static.
     60  *
     61  * For maximum efficiency we should compute the CIF once and save it with
     62  * the method.  However, this requires storing the data with every native
     63  * method.  Since the goal is to have custom assembly versions of this
     64  * on the platforms where performance matters, I'm recomputing the CIF on
     65  * every call.
     66  */
     67 void dvmPlatformInvoke(void* pEnv, ClassObject* clazz, int argInfo, int argc,
     68     const u4* argv, const char* shorty, void* func, JValue* pReturn)
     69 {
     70     const int kMaxArgs = argc+2;    /* +1 for env, maybe +1 for clazz */
     71     ffi_cif cif;
     72     ffi_type* types[kMaxArgs];
     73     void* values[kMaxArgs];
     74     ffi_type* retType;
     75     char sigByte;
     76     int srcArg, dstArg;
     77 
     78     types[0] = &ffi_type_pointer;
     79     values[0] = &pEnv;
     80 
     81     types[1] = &ffi_type_pointer;
     82     if (clazz != NULL) {
     83         values[1] = &clazz;
     84         srcArg = 0;
     85     } else {
     86         values[1] = (void*) argv++;
     87         srcArg = 1;
     88     }
     89     dstArg = 2;
     90 
     91     /*
     92      * Scan the types out of the short signature.  Use them to fill out the
     93      * "types" array.  Store the start address of the argument in "values".
     94      */
     95     retType = getFfiType(*shorty);
     96     while ((sigByte = *++shorty) != '\0') {
     97         types[dstArg] = getFfiType(sigByte);
     98         values[dstArg++] = (void*) argv++;
     99         if (sigByte == 'D' || sigByte == 'J')
    100             argv++;
    101     }
    102 
    103     /*
    104      * Prep the CIF (Call InterFace object).
    105      */
    106     if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, dstArg, retType, types) != FFI_OK) {
    107         ALOGE("ffi_prep_cif failed");
    108         dvmAbort();
    109     }
    110 
    111     ffi_call(&cif, FFI_FN(func), pReturn, values);
    112 }
    113