SDL  2.0
SDL_dynapi.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
4 
5  This software is provided 'as-is', without any express or implied
6  warranty. In no event will the authors be held liable for any damages
7  arising from the use of this software.
8 
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12 
13  1. The origin of this software must not be misrepresented; you must not
14  claim that you wrote the original software. If you use this software
15  in a product, an acknowledgment in the product documentation would be
16  appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18  misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20 */
21 
22 #include "SDL_config.h"
23 #include "SDL_dynapi.h"
24 
25 #if SDL_DYNAMIC_API
26 
27 #include "SDL.h"
28 
29 /* !!! FIXME: Shouldn't these be included in SDL.h? */
30 #include "SDL_shape.h"
31 #include "SDL_syswm.h"
32 
33 /* This is the version of the dynamic API. This doesn't match the SDL version
34  and should not change until there's been a major revamp in API/ABI.
35  So 2.0.5 adds functions over 2.0.4? This number doesn't change;
36  the sizeof (jump_table) changes instead. But 2.1.0 changes how a function
37  works in an incompatible way or removes a function? This number changes,
38  since sizeof (jump_table) isn't sufficient anymore. It's likely
39  we'll forget to bump every time we add a function, so this is the
40  failsafe switch for major API change decisions. Respect it and use it
41  sparingly. */
42 #define SDL_DYNAPI_VERSION 1
43 
44 static void SDL_InitDynamicAPI(void);
45 
46 
47 /* BE CAREFUL CALLING ANY SDL CODE IN HERE, IT WILL BLOW UP.
48  Even self-contained stuff might call SDL_Error and break everything. */
49 
50 
51 /* behold, the macro salsa! */
52 
53 /* !!! FIXME: ...disabled...until we write it. :) */
54 #define DISABLE_JUMP_MAGIC 1
55 
56 #if DISABLE_JUMP_MAGIC
57 /* Can't use the macro for varargs nonsense. This is atrocious. */
58 #define SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, logname, prio) \
59  _static void SDL_Log##logname##name(int category, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
60  va_list ap; initcall; va_start(ap, fmt); \
61  jump_table.SDL_LogMessageV(category, SDL_LOG_PRIORITY_##prio, fmt, ap); \
62  va_end(ap); \
63  }
64 
65 #define SDL_DYNAPI_VARARGS(_static, name, initcall) \
66  _static int SDL_SetError##name(SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
67  char buf[512]; /* !!! FIXME: dynamic allocation */ \
68  va_list ap; initcall; va_start(ap, fmt); \
69  jump_table.SDL_vsnprintf(buf, sizeof (buf), fmt, ap); \
70  va_end(ap); \
71  return jump_table.SDL_SetError("%s", buf); \
72  } \
73  _static int SDL_sscanf##name(const char *buf, SDL_SCANF_FORMAT_STRING const char *fmt, ...) { \
74  int retval; va_list ap; initcall; va_start(ap, fmt); \
75  retval = jump_table.SDL_vsscanf(buf, fmt, ap); \
76  va_end(ap); \
77  return retval; \
78  } \
79  _static int SDL_snprintf##name(SDL_OUT_Z_CAP(maxlen) char *buf, size_t maxlen, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
80  int retval; va_list ap; initcall; va_start(ap, fmt); \
81  retval = jump_table.SDL_vsnprintf(buf, maxlen, fmt, ap); \
82  va_end(ap); \
83  return retval; \
84  } \
85  _static void SDL_Log##name(SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
86  va_list ap; initcall; va_start(ap, fmt); \
87  jump_table.SDL_LogMessageV(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO, fmt, ap); \
88  va_end(ap); \
89  } \
90  _static void SDL_LogMessage##name(int category, SDL_LogPriority priority, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
91  va_list ap; initcall; va_start(ap, fmt); \
92  jump_table.SDL_LogMessageV(category, priority, fmt, ap); \
93  va_end(ap); \
94  } \
95  SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Verbose, VERBOSE) \
96  SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Debug, DEBUG) \
97  SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Info, INFO) \
98  SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Warn, WARN) \
99  SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Error, ERROR) \
100  SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Critical, CRITICAL)
101 #endif
103 
104 /* Typedefs for function pointers for jump table, and predeclare funcs */
105 /* The DEFAULT funcs will init jump table and then call real function. */
106 /* The REAL funcs are the actual functions, name-mangled to not clash. */
107 #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
108  typedef rc (*SDL_DYNAPIFN_##fn) params; \
109  static rc fn##_DEFAULT params; \
110  extern rc fn##_REAL params;
111 #include "SDL_dynapi_procs.h"
112 #undef SDL_DYNAPI_PROC
113 
114 /* The jump table! */
115 typedef struct {
116  #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) SDL_DYNAPIFN_##fn fn;
117  #include "SDL_dynapi_procs.h"
118  #undef SDL_DYNAPI_PROC
121 /* Predeclare the default functions for initializing the jump table. */
122 #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) static rc fn##_DEFAULT params;
123 #include "SDL_dynapi_procs.h"
124 #undef SDL_DYNAPI_PROC
125 
126 /* The actual jump table. */
128  #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) fn##_DEFAULT,
129  #include "SDL_dynapi_procs.h"
130  #undef SDL_DYNAPI_PROC
131 };
133 /* Default functions init the function table then call right thing. */
134 #if DISABLE_JUMP_MAGIC
135 #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
136  static rc fn##_DEFAULT params { \
137  SDL_InitDynamicAPI(); \
138  ret jump_table.fn args; \
139  }
140 #define SDL_DYNAPI_PROC_NO_VARARGS 1
141 #include "SDL_dynapi_procs.h"
142 #undef SDL_DYNAPI_PROC
143 #undef SDL_DYNAPI_PROC_NO_VARARGS
145 #else
146 /* !!! FIXME: need the jump magic. */
147 #error Write me.
148 #endif
149 
150 /* Public API functions to jump into the jump table. */
151 #if DISABLE_JUMP_MAGIC
152 #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
153  rc fn params { ret jump_table.fn args; }
154 #define SDL_DYNAPI_PROC_NO_VARARGS 1
155 #include "SDL_dynapi_procs.h"
156 #undef SDL_DYNAPI_PROC
157 #undef SDL_DYNAPI_PROC_NO_VARARGS
159 #else
160 /* !!! FIXME: need the jump magic. */
161 #error Write me.
162 #endif
163 
165 
166 /* Here's the exported entry point that fills in the jump table. */
167 /* Use specific types when an "int" might suffice to keep this sane. */
168 typedef Sint32 (SDLCALL *SDL_DYNAPI_ENTRYFN)(Uint32 apiver, void *table, Uint32 tablesize);
171 Sint32
172 SDL_DYNAPI_entry(Uint32 apiver, void *table, Uint32 tablesize)
173 {
174  SDL_DYNAPI_jump_table *output_jump_table = (SDL_DYNAPI_jump_table *) table;
175 
176  if (apiver != SDL_DYNAPI_VERSION) {
177  /* !!! FIXME: can maybe handle older versions? */
178  return -1; /* not compatible. */
179  } else if (tablesize > sizeof (jump_table)) {
180  return -1; /* newer version of SDL with functions we can't provide. */
181  }
183  /* Init our jump table first. */
184  #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) jump_table.fn = fn##_REAL;
185  #include "SDL_dynapi_procs.h"
186  #undef SDL_DYNAPI_PROC
187 
188  /* Then the external table... */
189  if (output_jump_table != &jump_table) {
190  jump_table.SDL_memcpy(output_jump_table, &jump_table, tablesize);
191  }
193  /* Safe to call SDL functions now; jump table is initialized! */
195  return 0; /* success! */
196 }
197 
199 /* Obviously we can't use SDL_LoadObject() to load SDL. :) */
200 /* Also obviously, we never close the loaded library. */
201 #if defined(WIN32) || defined(_WIN32) || defined(__CYGWIN__)
202 #ifndef WIN32_LEAN_AND_MEAN
203 #define WIN32_LEAN_AND_MEAN 1
204 #endif
205 #include <windows.h>
206 static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
207 {
208  HANDLE lib = LoadLibraryA(fname);
209  void *retval = NULL;
210  if (lib) {
211  retval = GetProcAddress(lib, sym);
212  if (retval == NULL) {
213  FreeLibrary(lib);
214  }
215  }
216  return retval;
217 }
219 #elif defined(__HAIKU__)
220 #include <os/kernel/image.h>
221 static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
222 {
223  image_id lib = load_add_on(fname);
224  void *retval = NULL;
225  if (lib >= 0) {
226  if (get_image_symbol(lib, sym, B_SYMBOL_TYPE_TEXT, &retval) != B_NO_ERROR) {
227  unload_add_on(lib);
228  retval = NULL;
229  }
230  }
231  return retval;
232 }
233 #elif defined(unix) || defined(__unix__) || defined(__APPLE__)
234 #include <dlfcn.h>
235 static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
236 {
237  void *lib = dlopen(fname, RTLD_NOW | RTLD_LOCAL);
238  void *retval = NULL;
239  if (lib != NULL) {
240  retval = dlsym(lib, sym);
241  if (retval == NULL) {
242  dlclose(lib);
243  }
244  }
245  return retval;
246 }
247 #else
248 #error Please define your platform.
249 #endif
251 
252 static void
254 {
255  const char *libname = SDL_getenv_REAL("SDL_DYNAMIC_API");
256  SDL_DYNAPI_ENTRYFN entry = SDL_DYNAPI_entry; /* funcs from here by default. */
257 
258  if (libname) {
259  entry = (SDL_DYNAPI_ENTRYFN) get_sdlapi_entry(libname, "SDL_DYNAPI_entry");
260  if (!entry) {
261  /* !!! FIXME: fail to startup here instead? */
262  /* !!! FIXME: definitely warn user. */
263  /* Just fill in the function pointers from this library. */
265  }
266  }
267 
268  if (entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table)) < 0) {
269  /* !!! FIXME: fail to startup here instead? */
270  /* !!! FIXME: definitely warn user. */
271  /* Just fill in the function pointers from this library. */
272  if (entry != SDL_DYNAPI_entry) {
273  if (!SDL_DYNAPI_entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table))) {
274  /* !!! FIXME: now we're screwed. Should definitely abort now. */
275  }
276  }
277  }
279  /* we intentionally never close the newly-loaded lib, of course. */
280 }
281 
282 static void
284 {
285  /* So the theory is that every function in the jump table defaults to
286  * calling this function, and then replaces itself with a version that
287  * doesn't call this function anymore. But it's possible that, in an
288  * extreme corner case, you can have a second thread hit this function
289  * while the jump table is being initialized by the first.
290  * In this case, a spinlock is really painful compared to what spinlocks
291  * _should_ be used for, but this would only happen once, and should be
292  * insanely rare, as you would have to spin a thread outside of SDL (as
293  * SDL_CreateThread() would also call this function before building the
294  * new thread).
295  */
296  static volatile SDL_bool already_initialized = SDL_FALSE;
297 
298  /* SDL_AtomicLock calls SDL mutex functions to emulate if
299  SDL_ATOMIC_DISABLED, which we can't do here, so in such a
300  configuration, you're on your own. */
301  #if !SDL_ATOMIC_DISABLED
302  static SDL_SpinLock lock = 0;
303  SDL_AtomicLock_REAL(&lock);
304  #endif
305 
306  if (!already_initialized) {
308  already_initialized = SDL_TRUE;
309  }
311  #if !SDL_ATOMIC_DISABLED
312  SDL_AtomicUnlock_REAL(&lock);
313  #endif
314 }
315 
316 #endif /* SDL_DYNAMIC_API */
317 
318 /* vi: set ts=4 sw=4 expandtab: */
319 
GLenum GLsizei GLenum GLenum const void * table
uint32_t Uint32
An unsigned 32-bit integer type.
Definition: SDL_stdinc.h:155
static SDL_INLINE void * get_sdlapi_entry(const char *fname, const char *sym)
Definition: SDL_dynapi.c:206
Sint32(* SDL_DYNAPI_ENTRYFN)(Uint32 apiver, void *table, Uint32 tablesize)
Definition: SDL_dynapi.c:168
#define SDL_DYNAPI_VERSION
Definition: SDL_dynapi.c:42
SDL_bool
Definition: SDL_stdinc.h:126
SDL_bool retval
#define DECLSPEC
Definition: SDL_internal.h:30
static void SDL_InitDynamicAPI(void)
Definition: SDL_dynapi.c:283
static SDL_DYNAPI_jump_table jump_table
Definition: SDL_dynapi.c:127
static void SDL_InitDynamicAPILocked(void)
Definition: SDL_dynapi.c:253
int32_t Sint32
A signed 32-bit integer type.
Definition: SDL_stdinc.h:151
#define NULL
Definition: begin_code.h:143
SDL_mutex * lock
Definition: SDL_events.c:75
Sint32 SDL_DYNAPI_entry(Uint32, void *, Uint32)
Definition: SDL_dynapi.c:172
#define SDL_INLINE
Definition: begin_code.h:120
int SDL_SpinLock
Definition: SDL_atomic.h:89
#define SDL_DYNAPI_VARARGS(_static, name, initcall)
Definition: SDL_dynapi.c:65
#define SDLCALL
Definition: SDL_internal.h:31