1 /* Copyright (c) 2008 The Android Open Source Project
2 *
3 * Permission is hereby granted, free of charge, to any person obtaining a copy
4 * of this software and associated documentation files (the "Software"), to deal
5 * in the Software without restriction, including without limitation the rights
6 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
7 * copies of the Software, and to permit persons to whom the Software is
8 * furnished to do so, subject to the following conditions:
9 *
10 * The above copyright notice and this permission notice shall be included in
11 * all copies or substantial portions of the Software.
12 *
13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
16 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
18 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
19 * THE SOFTWARE.
20 */
21
22 /*
23 * Lazy Dynamic Linking Support
24 *
25 * This header file is meant to be included multiple times.
26 *
27 * It is used to define function pointers to symbols in external
28 * shared objects (Unix dynamic libraries) which will be lazily resolved
29 * at runtime, by calling a specific initialization function.
30 *
31 * You must define, before including this header, a DYNLINK_FUNCTIONS
32 * macro which must contain a sequence of DYNLINK_FUNC(ret,name,sig)
33 * statements.
34 *
35 * In each statement, 'ret' is a function return type, 'name' is
36 * the function's name as provided by the library, and 'sig' is
37 * the function signature, including enclosing parentheses.
38 *
39 * Here's an example:
40 *
41 * #define DYNLINK_FUNCTIONS \
42 * DYNLINK_FUNC(int,open,(const char*, int)) \
43 * DYNLINK_FUNC(int,read,(int,char*,int)) \
44 * DYNLINK_FUNC(int,close,(int)) \
45 *
46 *
47 * You must also define a DYNLINK_FUNCTIONS_INIT macro which contains the
48 * name of a generated function used to initialize the function pointers.
49 * (see below)
50 */
51
52 #ifndef DYNLINK_FUNCTIONS
53 #error DYNLINK_FUNCTIONS should be defined when including this file
54 #endif
55
56 #ifndef DYNLINK_FUNCTIONS_INIT
57 #error DYNLINK_FUNCTIONS_INIT should be defined when including this file
58 #endif
59
60 /* just in case */
61 #undef DYNLINK_FUNC
62
63 /* define pointers to dynamic library functions as static pointers.
64 */
65 #define DYNLINK_FUNC(ret,name,sig) \
66 static ret (*_dynlink_##name) sig ;
67
68 #define DYNLINK_STR(name) DYNLINK_STR_(name)
69 #define DYNLINK_STR_(name) #name
70
71 DYNLINK_FUNCTIONS
72 #undef DYNLINK_FUNC
73
74 /* now define a function that tries to load all dynlink function
75 * pointers. returns 0 on success, or -1 on error (i.e. if any of
76 * the functions could not be loaded).
77 *
78 * 'library' must be the result of a succesful dlopen() call
79 *
80 * You must define DYNLINK_FUNCTIONS_INIT
81 */
82 static int
DYNLINK_FUNCTIONS_INIT(void * library)83 DYNLINK_FUNCTIONS_INIT(void* library)
84 {
85 #define DYNLINK_FUNC(ret,name,sig) \
86 do { \
87 _dynlink_##name = dlsym( library, DYNLINK_STR(name) ); \
88 if (_dynlink_##name == NULL) goto Fail; \
89 } while (0);
90
91 DYNLINK_FUNCTIONS
92 #undef DYNLINK_FUNC
93
94 return 0;
95 Fail:
96 return -1;
97 }
98
99 /* in user code, use FF(function_name) to invoke the
100 * corresponding dynamic function named 'function_name'
101 * after initialization succeeded.
102 */
103 #ifndef FF
104 #define FF(name) (*_dynlink_##name)
105 #endif
106
107 /* clear macros */
108 #undef DYNLINK_FUNC
109 #undef DYNLINK_FUNCTIONS
110 #undef DYNLINK_FUNCTIONS_INIT
111