src/dynapi/SDL_dynapi.c
author Sam Lantinga
Wed, 18 Jan 2017 12:19:57 -0800
changeset 10821 b0b8395f5cf9
parent 10737 3406a0f8b041
child 11119 28d3a50e276e
permissions -rw-r--r--
Removed unused variable
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2017 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
   102 
   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
   119 } SDL_DYNAPI_jump_table;
   120 
   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. */
   127 static SDL_DYNAPI_jump_table 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 };
   132 
   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
   144 SDL_DYNAPI_VARARGS(static, _DEFAULT, SDL_InitDynamicAPI())
   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
   158 SDL_DYNAPI_VARARGS(,,)
   159 #else
   160 /* !!! FIXME: need the jump magic. */
   161 #error Write me.
   162 #endif
   163 
   164 
   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);
   169 extern DECLSPEC Sint32 SDLCALL SDL_DYNAPI_entry(Uint32, void *, Uint32);
   170 
   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     }
   182 
   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     }
   192 
   193     /* Safe to call SDL functions now; jump table is initialized! */
   194 
   195     return 0;  /* success! */
   196 }
   197 
   198 
   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 }
   218 
   219 #elif defined(unix) || defined(__unix__) || defined(__APPLE__) || defined(__HAIKU__)
   220 #include <dlfcn.h>
   221 static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
   222 {
   223     void *lib = dlopen(fname, RTLD_NOW | RTLD_LOCAL);
   224     void *retval = NULL;
   225     if (lib != NULL) {
   226         retval = dlsym(lib, sym);
   227         if (retval == NULL) {
   228             dlclose(lib);
   229         }
   230     }
   231     return retval;
   232 }
   233 #else
   234 #error Please define your platform.
   235 #endif
   236 
   237 
   238 static void
   239 SDL_InitDynamicAPILocked(void)
   240 {
   241     const char *libname = SDL_getenv_REAL("SDL_DYNAMIC_API");
   242     SDL_DYNAPI_ENTRYFN entry = SDL_DYNAPI_entry;  /* funcs from here by default. */
   243 
   244     if (libname) {
   245         entry = (SDL_DYNAPI_ENTRYFN) get_sdlapi_entry(libname, "SDL_DYNAPI_entry");
   246         if (!entry) {
   247             /* !!! FIXME: fail to startup here instead? */
   248             /* !!! FIXME: definitely warn user. */
   249             /* Just fill in the function pointers from this library. */
   250             entry = SDL_DYNAPI_entry;
   251         }
   252     }
   253 
   254     if (entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table)) < 0) {
   255         /* !!! FIXME: fail to startup here instead? */
   256         /* !!! FIXME: definitely warn user. */
   257         /* Just fill in the function pointers from this library. */
   258         if (entry != SDL_DYNAPI_entry) {
   259             if (!SDL_DYNAPI_entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table))) {
   260                 /* !!! FIXME: now we're screwed. Should definitely abort now. */
   261             }
   262         }
   263     }
   264 
   265     /* we intentionally never close the newly-loaded lib, of course. */
   266 }
   267 
   268 static void
   269 SDL_InitDynamicAPI(void)
   270 {
   271     /* So the theory is that every function in the jump table defaults to
   272      *  calling this function, and then replaces itself with a version that
   273      *  doesn't call this function anymore. But it's possible that, in an
   274      *  extreme corner case, you can have a second thread hit this function
   275      *  while the jump table is being initialized by the first.
   276      * In this case, a spinlock is really painful compared to what spinlocks
   277      *  _should_ be used for, but this would only happen once, and should be
   278      *  insanely rare, as you would have to spin a thread outside of SDL (as
   279      *  SDL_CreateThread() would also call this function before building the
   280      *  new thread).
   281      */
   282     static SDL_bool already_initialized = SDL_FALSE;
   283 
   284     /* SDL_AtomicLock calls SDL mutex functions to emulate if
   285        SDL_ATOMIC_DISABLED, which we can't do here, so in such a
   286        configuration, you're on your own. */
   287     #if !SDL_ATOMIC_DISABLED
   288     static SDL_SpinLock lock = 0;
   289     SDL_AtomicLock_REAL(&lock);
   290     #endif
   291 
   292     if (!already_initialized) {
   293         SDL_InitDynamicAPILocked();
   294         already_initialized = SDL_TRUE;
   295     }
   296 
   297     #if !SDL_ATOMIC_DISABLED
   298     SDL_AtomicUnlock_REAL(&lock);
   299     #endif
   300 }
   301 
   302 #endif  /* SDL_DYNAMIC_API */
   303 
   304 /* vi: set ts=4 sw=4 expandtab: */
   305