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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  * This uses the FFI (Foreign Function Interface) library to abstract away
18  * the system-dependent stuff.  The FFI code is slower than a custom
19  * assembly version, but has the distinct advantage of having been
20  * written already for several platforms.
21  */
22 #include "Dalvik.h"
23 #include "ffi.h"
24 
25 /*
26  * Convert a signature type character to an FFI type.
27  */
getFfiType(char sigType)28 static ffi_type* getFfiType(char sigType)
29 {
30     switch (sigType) {
31     case 'V': return &ffi_type_void;
32     case 'F': return &ffi_type_float;
33     case 'D': return &ffi_type_double;
34     case 'J': return &ffi_type_sint64;
35     case '[':
36     case 'L': return &ffi_type_pointer;
37     default:  return &ffi_type_uint32;
38     }
39 }
40 
41 /*
42  * Call "func" with the specified arguments.
43  *
44  * The second argument to JNI native functions is either the object (the
45  * "this" pointer) or, for static functions, a pointer to the class object.
46  * The Dalvik instructions will push "this" into argv[0], but it's up to
47  * us to insert the class object.
48  *
49  * Because there is no such thing in as a null "this" pointer, we use
50  * the non-NULL state of "clazz" to determine whether or not it's static.
51  *
52  * For maximum efficiency we should compute the CIF once and save it with
53  * the method.  However, this requires storing the data with every native
54  * method.  Since the goal is to have custom assembly versions of this
55  * on the platforms where performance matters, I'm recomputing the CIF on
56  * every call.
57  */
dvmPlatformInvoke(void * pEnv,ClassObject * clazz,int argInfo,int argc,const u4 * argv,const char * shorty,void * func,JValue * pReturn)58 void dvmPlatformInvoke(void* pEnv, ClassObject* clazz, int argInfo, int argc,
59     const u4* argv, const char* shorty, void* func, JValue* pReturn)
60 {
61     const int kMaxArgs = argc+2;    /* +1 for env, maybe +1 for clazz */
62     ffi_cif cif;
63     ffi_type* types[kMaxArgs];
64     void* values[kMaxArgs];
65     ffi_type* retType;
66     const char* sig;
67     char sigByte;
68     int srcArg, dstArg;
69 
70     types[0] = &ffi_type_pointer;
71     values[0] = &pEnv;
72 
73     types[1] = &ffi_type_pointer;
74     if (clazz != NULL) {
75         values[1] = &clazz;
76         srcArg = 0;
77     } else {
78         values[1] = (void*) argv++;
79         srcArg = 1;
80     }
81     dstArg = 2;
82 
83     /*
84      * Scan the types out of the short signature.  Use them to fill out the
85      * "types" array.  Store the start address of the argument in "values".
86      */
87     retType = getFfiType(*shorty);
88     while ((sigByte = *++shorty) != '\0') {
89         types[dstArg] = getFfiType(sigByte);
90         values[dstArg++] = (void*) argv++;
91         if (sigByte == 'D' || sigByte == 'J')
92             argv++;
93     }
94 
95     /*
96      * Prep the CIF (Call InterFace object).
97      */
98     if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, dstArg, retType, types) != FFI_OK) {
99         LOGE("ffi_prep_cif failed\n");
100         dvmAbort();
101     }
102 
103     ffi_call(&cif, FFI_FN(func), pReturn, values);
104 }
105