Implemented the Dynamic API magic.

src/dynapi/SDL_dynapi.c

@@ -0,0 +1,302 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "SDL_config.h"
+#include "SDL_dynapi.h"
+
+#if SDL_DYNAMIC_API
+
+#include "SDL.h"
+
+/* !!! FIXME: Shouldn't these be included in SDL.h? */
+#include "SDL_shape.h"
+#include "SDL_syswm.h"
+
+/* This is the version of the dynamic API. This doesn't match the SDL version
+   and should not change until there's been a major revamp in API/ABI.
+   So 2.0.5 adds functions over 2.0.4? This number doesn't change;
+   the sizeof (jump_table) changes instead. But 2.1.0 changes how a function
+   works in an incompatible way or removes a function? This number changes,
+   since sizeof (jump_table) isn't sufficient anymore. It's likely
+   we'll forget to bump every time we add a function, so this is the
+   failsafe switch for major API change decisions. Respect it and use it
+   sparingly. */
+#define SDL_DYNAPI_VERSION 1
+
+static void SDL_InitDynamicAPI(void);
+
+
+/* BE CAREFUL CALLING ANY SDL CODE IN HERE, IT WILL BLOW UP.
+   Even self-contained stuff might call SDL_Error and break everything. */
+
+
+/* behold, the macro salsa! */
+
+/* !!! FIXME: ...disabled...until we write it.  :) */
+#define DISABLE_JUMP_MAGIC 1
+
+#if DISABLE_JUMP_MAGIC
+/* Can't use the macro for varargs nonsense. This is atrocious. */
+#define SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, logname, prio) \
+    _static void SDL_Log##logname##name(int category, const char *fmt, ...) { \
+        va_list ap; initcall; va_start(ap, fmt); \
+        jump_table.SDL_LogMessageV(category, SDL_LOG_PRIORITY_##prio, fmt, ap); \
+        va_end(ap); \
+    }
+
+#define SDL_DYNAPI_VARARGS(_static, name, initcall) \
+    _static int SDL_SetError##name(const char *fmt, ...) { \
+        char buf[512]; /* !!! FIXME: dynamic allocation */ \
+        va_list ap; initcall; va_start(ap, fmt); \
+        jump_table.SDL_vsnprintf(buf, sizeof (buf), fmt, ap); \
+        va_end(ap); \
+        return jump_table.SDL_SetError("%s", buf); \
+    } \
+    _static int SDL_sscanf##name(const char *buf, const char *fmt, ...) { \
+        int retval; va_list ap; initcall; va_start(ap, fmt); \
+        retval = jump_table.SDL_vsscanf(buf, fmt, ap); \
+        va_end(ap); \
+        return retval; \
+    } \
+    _static int SDL_snprintf##name(char *buf, size_t buflen, const char *fmt, ...) { \
+        int retval; va_list ap; initcall; va_start(ap, fmt); \
+        retval = jump_table.SDL_vsnprintf(buf, buflen, fmt, ap); \
+        va_end(ap); \
+        return retval; \
+    } \
+    _static void SDL_Log##name(const char *fmt, ...) { \
+        va_list ap; initcall; va_start(ap, fmt); \
+        jump_table.SDL_LogMessageV(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO, fmt, ap); \
+        va_end(ap); \
+    } \
+    _static void SDL_LogMessage##name(int category, SDL_LogPriority priority, const char *fmt, ...) { \
+        va_list ap; initcall; va_start(ap, fmt); \
+        jump_table.SDL_LogMessageV(category, priority, fmt, ap); \
+        va_end(ap); \
+    } \
+    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Verbose, VERBOSE) \
+    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Debug, DEBUG) \
+    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Info, INFO) \
+    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Warn, WARN) \
+    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Error, ERROR) \
+    SDL_DYNAPI_VARARGS_LOGFN(_static, name, initcall, Critical, CRITICAL)
+#endif
+
+
+/* Typedefs for function pointers for jump table, and predeclare funcs */
+/* The DEFAULT funcs will init jump table and then call real function. */
+/* The REAL funcs are the actual functions, name-mangled to not clash. */
+#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
+    typedef rc (*SDL_DYNAPIFN_##fn) params; \
+    static rc fn##_DEFAULT params; \
+    extern rc fn##_REAL params;
+#include "SDL_dynapi_procs.h"
+#undef SDL_DYNAPI_PROC
+
+/* The jump table! */
+typedef struct {
+    #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) SDL_DYNAPIFN_##fn fn;
+    #include "SDL_dynapi_procs.h"
+    #undef SDL_DYNAPI_PROC
+} SDL_DYNAPI_jump_table;
+
+/* Predeclare the default functions for initializing the jump table. */
+#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) static rc fn##_DEFAULT params;
+#include "SDL_dynapi_procs.h"
+#undef SDL_DYNAPI_PROC
+
+/* The actual jump table. */
+static SDL_DYNAPI_jump_table jump_table = {
+    #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) fn##_DEFAULT,
+    #include "SDL_dynapi_procs.h"
+    #undef SDL_DYNAPI_PROC
+};
+
+/* Default functions init the function table then call right thing. */
+#if DISABLE_JUMP_MAGIC
+#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
+    static rc fn##_DEFAULT params { \
+        SDL_InitDynamicAPI(); \
+        ret jump_table.fn args; \
+    }
+#define SDL_DYNAPI_PROC_NO_VARARGS 1
+#include "SDL_dynapi_procs.h"
+#undef SDL_DYNAPI_PROC
+#undef SDL_DYNAPI_PROC_NO_VARARGS
+SDL_DYNAPI_VARARGS(static, _DEFAULT, SDL_InitDynamicAPI())
+#else
+/* !!! FIXME: need the jump magic. */
+#error Write me.
+#endif
+
+/* Public API functions to jump into the jump table. */
+#if DISABLE_JUMP_MAGIC
+#define SDL_DYNAPI_PROC(rc,fn,params,args,ret) \
+    rc fn params { ret jump_table.fn args; }
+#define SDL_DYNAPI_PROC_NO_VARARGS 1
+#include "SDL_dynapi_procs.h"
+#undef SDL_DYNAPI_PROC
+#undef SDL_DYNAPI_PROC_NO_VARARGS
+SDL_DYNAPI_VARARGS(,,)
+#else
+/* !!! FIXME: need the jump magic. */
+#error Write me.
+#endif
+
+
+
+/* Here's the exported entry point that fills in the jump table. */
+/*  Use specific types when an "int" might suffice to keep this sane. */
+typedef Sint32 (SDLCALL *SDL_DYNAPI_ENTRYFN)(Uint32 apiver, void *table, Uint32 tablesize);
+extern DECLSPEC Sint32 SDLCALL SDL_DYNAPI_entry(Uint32, void *, Uint32);
+
+Sint32
+SDL_DYNAPI_entry(Uint32 apiver, void *table, Uint32 tablesize)
+{
+    SDL_DYNAPI_jump_table *output_jump_table = (SDL_DYNAPI_jump_table *) table;
+
+    if (apiver != SDL_DYNAPI_VERSION) {
+        /* !!! FIXME: can maybe handle older versions? */
+        return -1;  /* not compatible. */
+    } else if (tablesize > sizeof (jump_table)) {
+        return -1;  /* newer version of SDL with functions we can't provide. */
+    }
+
+    /* Init our jump table first. */
+    #define SDL_DYNAPI_PROC(rc,fn,params,args,ret) jump_table.fn = fn##_REAL;
+    #include "SDL_dynapi_procs.h"
+    #undef SDL_DYNAPI_PROC
+
+    /* Then the external table... */
+    if (output_jump_table != &jump_table) {
+        jump_table.SDL_memcpy(output_jump_table, &jump_table, tablesize);
+    }
+
+    /* Safe to call SDL functions now; jump table is initialized! */
+
+    return 0;  /* success! */
+}
+
+
+/* Obviously we can't use SDL_LoadObject() to load SDL.  :)  */
+/* Also obviously, we never close the loaded library. */
+#if defined(_WINDOWS)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN 1
+#endif
+#include <windows.h>
+static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
+{
+    HANDLE lib = LoadLibraryA(fname);
+    return lib ? GetProcAddress(lib, sym) : NULL;
+}
+
+#elif defined(__HAIKU__)
+#include <os/kernel/image.h>
+static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
+{
+    image_id lib = load_add_on(fname);
+    void *retval = NULL;
+    if ((lib < 0) || (get_image_symbol(lib, sym, B_SYMBOL_TYPE_TEXT, &retval) != B_NO_ERROR)) {
+        retval = NULL;
+    }
+    return retval;
+}
+#elif defined(unix) || defined(__APPLE__)
+#include <dlfcn.h>
+static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
+{
+    void *lib = dlopen(fname, RTLD_NOW | RTLD_LOCAL);
+    return lib ? dlsym(lib, sym) : NULL;
+}
+#else
+#error Please define your platform.
+#endif
+
+
+static void
+SDL_InitDynamicAPILocked(void)
+{
+    const char *libname = SDL_getenv_REAL("SDL_DYNAMIC_API");
+    SDL_DYNAPI_ENTRYFN entry = SDL_DYNAPI_entry;  /* funcs from here by default. */
+
+    if (libname) {
+        entry = (SDL_DYNAPI_ENTRYFN) get_sdlapi_entry(libname, "SDL_DYNAPI_entry");
+        if (!entry) {
+            /* !!! FIXME: fail to startup here instead? */
+            /* !!! FIXME: definitely warn user. */
+            /* Just fill in the function pointers from this library. */
+            entry = SDL_DYNAPI_entry;
+        }
+    }
+
+    if (entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table)) < 0) {
+        /* !!! FIXME: fail to startup here instead? */
+        /* !!! FIXME: definitely warn user. */
+        /* Just fill in the function pointers from this library. */
+        if (entry != SDL_DYNAPI_entry) {
+            if (!SDL_DYNAPI_entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table))) {
+                /* !!! FIXME: now we're screwed. Should definitely abort now. */
+            }
+        }
+    }
+
+    /* we intentionally never close the newly-loaded lib, of course. */
+}
+
+static void
+SDL_InitDynamicAPI(void)
+{
+    /* So the theory is that every function in the jump table defaults to
+     *  calling this function, and then replaces itself with a version that
+     *  doesn't call this function anymore. But it's possible that, in an
+     *  extreme corner case, you can have a second thread hit this function
+     *  while the jump table is being initialized by the first.
+     * In this case, a spinlock is really painful compared to what spinlocks
+     *  _should_ be used for, but this would only happen once, and should be
+     *  insanely rare, as you would have to spin a thread outside of SDL (as
+     *  SDL_CreateThread() would also call this function before building the
+     *  new thread).
+     */
+    static volatile SDL_bool already_initialized = SDL_FALSE;
+
+    /* SDL_AtomicLock calls SDL mutex functions to emulate if
+       SDL_ATOMIC_DISABLED, which we can't do here, so in such a
+       configuration, you're on your own. */
+    #if !SDL_ATOMIC_DISABLED
+    static SDL_SpinLock lock = 0;
+    SDL_AtomicLock_REAL(&lock);
+    #endif
+
+    if (!already_initialized) {
+        SDL_InitDynamicAPILocked();
+        already_initialized = SDL_TRUE;
+    }
+
+    #if !SDL_ATOMIC_DISABLED
+    SDL_AtomicUnlock_REAL(&lock);
+    #endif
+}
+
+#endif  /* SDL_DYNAMIC_API */
+
+/* vi: set ts=4 sw=4 expandtab: */
+