Call.cpp revision 60fc806b679a3655c228b4093058c59941a49cfe 
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 */
29static 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        LOGE("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 */
67void 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        LOGE("ffi_prep_cif failed");
108        dvmAbort();
109    }
110
111    ffi_call(&cif, FFI_FN(func), pReturn, values);
112}
113