Atlas - SDL_dynapi.c
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <[email protected]>
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#if defined(__OS2__)
28#define INCL_DOS
29#define INCL_DOSERRORS
30#include <dos.h>
31#endif
32
33#include "SDL.h"
34
35/* These headers have system specific definitions, so aren't included above */
36#include "SDL_syswm.h"
37#include "SDL_vulkan.h"
38
39/* This is the version of the dynamic API. This doesn't match the SDL version
40   and should not change until there's been a major revamp in API/ABI.
41   So 2.0.5 adds functions over 2.0.4? This number doesn't change;
42   the sizeof (jump_table) changes instead. But 2.1.0 changes how a function
43   works in an incompatible way or removes a function? This number changes,
44   since sizeof (jump_table) isn't sufficient anymore. It's likely
45   we'll forget to bump every time we add a function, so this is the
46   failsafe switch for major API change decisions. Respect it and use it
47   sparingly. */
48#define SDL_DYNAPI_VERSION 1
49
50static void SDL_InitDynamicAPI(void);
51
52
53/* BE CAREFUL CALLING ANY SDL CODE IN HERE, IT WILL BLOW UP.
54   Even self-contained stuff might call SDL_Error and break everything. */
55
56
57/* behold, the macro salsa! */
58
59/* !!! FIXME: ...disabled...until we write it.  :) */
60#define DISABLE_JUMP_MAGIC 1
61
62#if DISABLE_JUMP_MAGIC
63/* Can't use the macro for varargs nonsense. This is atrocious. */
64#define SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, logname, prio) \
65    _static void SDLCALL SDL_Log##logname##name(int category, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
66        va_list ap; initcall; va_start(ap, fmt); \
67        jump_table.SDL_LogMessageV(category, SDL_LOG_PRIORITY_##prio, fmt, ap); \
68        va_end(ap); \
69    }
70
71#define SDL_DYNAPI_VARARGS(_static, name, initcall) \
72    _static int SDLCALL SDL_SetError##name(SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
73        char buf[512]; /* !!! FIXME: dynamic allocation */ \
74        va_list ap; initcall; va_start(ap, fmt); \
75        jump_table.SDL_vsnprintf(buf, sizeof (buf), fmt, ap); \
76        va_end(ap); \
77        return jump_table.SDL_SetError("%s", buf); \
78    } \
79    _static int SDLCALL SDL_sscanf##name(const char *buf, SDL_SCANF_FORMAT_STRING const char *fmt, ...) { \
80        int retval; va_list ap; initcall; va_start(ap, fmt); \
81        retval = jump_table.SDL_vsscanf(buf, fmt, ap); \
82        va_end(ap); \
83        return retval; \
84    } \
85    _static int SDLCALL SDL_snprintf##name(SDL_OUT_Z_CAP(maxlen) char *buf, size_t maxlen, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
86        int retval; va_list ap; initcall; va_start(ap, fmt); \
87        retval = jump_table.SDL_vsnprintf(buf, maxlen, fmt, ap); \
88        va_end(ap); \
89        return retval; \
90    } \
91    _static void SDLCALL SDL_Log##name(SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
92        va_list ap; initcall; va_start(ap, fmt); \
93        jump_table.SDL_LogMessageV(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO, fmt, ap); \
94        va_end(ap); \
95    } \
96    _static void SDLCALL SDL_LogMessage##name(int category, SDL_LogPriority priority, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) { \
97        va_list ap; initcall; va_start(ap, fmt); \
98        jump_table.SDL_LogMessageV(category, priority, fmt, ap); \
99        va_end(ap); \
100    } \
101    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Verbose, VERBOSE) \
102    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Debug, DEBUG) \
103    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Info, INFO) \
104    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Warn, WARN) \
105    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Error, ERROR) \
106    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Critical, CRITICAL)
107#endif
108
109
110/* Typedefs for function pointers for jump table, and predeclare funcs */
111/* The DEFAULT funcs will init jump table and then call real function. */
112/* The REAL funcs are the actual functions, name-mangled to not clash. */
113#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
114    typedef rc (SDLCALL *SDL_DYNAPIFN_##fn) params; \
115    static rc SDLCALL fn##_DEFAULT params; \
116    extern rc SDLCALL fn##_REAL params;
117#include "SDL_dynapi_procs.h"
118#undef SDL_DYNAPI_PROC
119
120/* The jump table! */
121typedef struct {
122    #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) SDL_DYNAPIFN_##fn fn;
123    #include "SDL_dynapi_procs.h"
124    #undef SDL_DYNAPI_PROC
125} SDL_DYNAPI_jump_table;
126
127/* Predeclare the default functions for initializing the jump table. */
128#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) static rc SDLCALL fn##_DEFAULT params;
129#include "SDL_dynapi_procs.h"
130#undef SDL_DYNAPI_PROC
131
132/* The actual jump table. */
133static SDL_DYNAPI_jump_table jump_table = {
134    #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) fn##_DEFAULT,
135    #include "SDL_dynapi_procs.h"
136    #undef SDL_DYNAPI_PROC
137};
138
139/* Default functions init the function table then call right thing. */
140#if DISABLE_JUMP_MAGIC
141#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
142    static rc SDLCALL fn##_DEFAULT params { \
143        SDL_InitDynamicAPI(); \
144        ret jump_table.fn args; \
145    }
146#define SDL_DYNAPI_PROC_NO_VARARGS 1
147#include "SDL_dynapi_procs.h"
148#undef SDL_DYNAPI_PROC
149#undef SDL_DYNAPI_PROC_NO_VARARGS
150SDL_DYNAPI_VARARGS(static, _DEFAULT, SDL_InitDynamicAPI())
151#else
152/* !!! FIXME: need the jump magic. */
153#error Write me.
154#endif
155
156/* Public API functions to jump into the jump table. */
157#if DISABLE_JUMP_MAGIC
158#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
159    rc SDLCALL fn params { ret jump_table.fn args; }
160#define SDL_DYNAPI_PROC_NO_VARARGS 1
161#include "SDL_dynapi_procs.h"
162#undef SDL_DYNAPI_PROC
163#undef SDL_DYNAPI_PROC_NO_VARARGS
164SDL_DYNAPI_VARARGS(,,)
165#else
166/* !!! FIXME: need the jump magic. */
167#error Write me.
168#endif
169
170/* we make this a static function so we can call the correct one without the
171   system's dynamic linker resolving to the wrong version of this. */
172static Sint32
173initialize_jumptable(Uint32 apiver, void *table, Uint32 tablesize)
174{
175    SDL_DYNAPI_jump_table *output_jump_table = (SDL_DYNAPI_jump_table *) table;
176
177    if (apiver != SDL_DYNAPI_VERSION) {
178        /* !!! FIXME: can maybe handle older versions? */
179        return -1;  /* not compatible. */
180    } else if (tablesize > sizeof (jump_table)) {
181        return -1;  /* newer version of SDL with functions we can't provide. */
182    }
183
184    /* Init our jump table first. */
185    #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) jump_table.fn = fn##_REAL;
186    #include "SDL_dynapi_procs.h"
187    #undef SDL_DYNAPI_PROC
188
189    /* Then the external table... */
190    if (output_jump_table != &jump_table) {
191        jump_table.SDL_memcpy(output_jump_table, &jump_table, tablesize);
192    }
193
194    /* Safe to call SDL functions now; jump table is initialized! */
195
196    return 0;  /* success! */
197}
198
199
200/* Here's the exported entry point that fills in the jump table. */
201/*  Use specific types when an "int" might suffice to keep this sane. */
202typedef Sint32 (SDLCALL *SDL_DYNAPI_ENTRYFN)(Uint32 apiver, void *table, Uint32 tablesize);
203extern DECLSPEC Sint32 SDLCALL SDL_DYNAPI_entry(Uint32, void *, Uint32);
204
205Sint32
206SDL_DYNAPI_entry(Uint32 apiver, void *table, Uint32 tablesize)
207{
208    return initialize_jumptable(apiver, table, tablesize);
209}
210
211
212/* Obviously we can't use SDL_LoadObject() to load SDL.  :)  */
213/* Also obviously, we never close the loaded library. */
214#if defined(WIN32) || defined(_WIN32) || defined(__CYGWIN__)
215#ifndef WIN32_LEAN_AND_MEAN
216#define WIN32_LEAN_AND_MEAN 1
217#endif
218#include <windows.h>
219static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
220{
221    HANDLE lib = LoadLibraryA(fname);
222    void *retval = NULL;
223    if (lib) {
224        retval = GetProcAddress(lib, sym);
225        if (retval == NULL) {
226            FreeLibrary(lib);
227        }
228    }
229    return retval;
230}
231
232#elif defined(unix) || defined(__unix__) || defined(__APPLE__) || defined(__HAIKU__) || defined(__QNX__)
233#include <dlfcn.h>
234static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
235{
236    void *lib = dlopen(fname, RTLD_NOW | RTLD_LOCAL);
237    void *retval = NULL;
238    if (lib != NULL) {
239        retval = dlsym(lib, sym);
240        if (retval == NULL) {
241            dlclose(lib);
242        }
243    }
244    return retval;
245}
246
247#elif defined(__OS2__)
248static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
249{
250    HMODULE hmodule;
251    PFN retval = NULL;
252    char error[256];
253    if (DosLoadModule(&error, sizeof(error), fname, &hmodule) == NO_ERROR) {
254        if (DosQueryProcAddr(hmodule, 0, sym, &retval) != NO_ERROR) {
255            DosFreeModule(hmodule);
256        }
257    }
258    return (void *) retval;
259}
260
261#else
262#error Please define your platform.
263#endif
264
265
266static void
267SDL_InitDynamicAPILocked(void)
268{
269    const char *libname = SDL_getenv_REAL("SDL_DYNAMIC_API");
270    SDL_DYNAPI_ENTRYFN entry = NULL;  /* funcs from here by default. */
271
272    if (libname) {
273        entry = (SDL_DYNAPI_ENTRYFN) get_sdlapi_entry(libname, "SDL_DYNAPI_entry");
274        if (!entry) {
275            /* !!! FIXME: fail to startup here instead? */
276            /* !!! FIXME: definitely warn user. */
277            /* Just fill in the function pointers from this library. */
278        }
279    }
280
281    if (!entry || (entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table)) < 0)) {
282        /* !!! FIXME: fail to startup here instead? */
283        /* !!! FIXME: definitely warn user. */
284        /* Just fill in the function pointers from this library. */
285        if (!entry) {
286            if (!initialize_jumptable(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table))) {
287                /* !!! FIXME: now we're screwed. Should definitely abort now. */
288            }
289        }
290    }
291
292    /* we intentionally never close the newly-loaded lib, of course. */
293}
294
295static void
296SDL_InitDynamicAPI(void)
297{
298    /* So the theory is that every function in the jump table defaults to
299     *  calling this function, and then replaces itself with a version that
300     *  doesn't call this function anymore. But it's possible that, in an
301     *  extreme corner case, you can have a second thread hit this function
302     *  while the jump table is being initialized by the first.
303     * In this case, a spinlock is really painful compared to what spinlocks
304     *  _should_ be used for, but this would only happen once, and should be
305     *  insanely rare, as you would have to spin a thread outside of SDL (as
306     *  SDL_CreateThread() would also call this function before building the
307     *  new thread).
308     */
309    static SDL_bool already_initialized = SDL_FALSE;
310
311    /* SDL_AtomicLock calls SDL mutex functions to emulate if
312       SDL_ATOMIC_DISABLED, which we can't do here, so in such a
313       configuration, you're on your own. */
314    #if !SDL_ATOMIC_DISABLED
315    static SDL_SpinLock lock = 0;
316    SDL_AtomicLock_REAL(&lock);
317    #endif
318
319    if (!already_initialized) {
320        SDL_InitDynamicAPILocked();
321        already_initialized = SDL_TRUE;
322    }
323
324    #if !SDL_ATOMIC_DISABLED
325    SDL_AtomicUnlock_REAL(&lock);
326    #endif
327}
328
329#endif  /* SDL_DYNAMIC_API */
330
331/* vi: set ts=4 sw=4 expandtab: */
332
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