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Size: 2250
Comment: Changed example to use return value of SDL_SetError(), changed return statements looking like function calls.
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Size: 2255
Comment: Corrected comment in example.
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| /* These functions should not be used except from pointers in a RWops */ | /* These functions should not be used except from pointers in an SDL_RWops */ |
SDL_AllocRW
Use this function to allocate an empty, unpopulated SDL_RWops structure.
Syntax
SDL_RWops* SDL_AllocRW(void)
Return Value
Returns a pointer to the allocated memory on success, or NULL on failure; call SDL_GetError() for more information.
Code Examples
/* These functions should not be used except from pointers in an SDL_RWops */
static int myseekfunc(SDL_RWops *context, int offset, int whence)
{
return SDL_SetError("Can't seek in this kind of RWops");
}
static int myreadfunc(SDL_RWops *context, void *ptr, int size, int maxnum)
{
SDL_memset(ptr,0,size*maxnum);
return maxnum;
}
static int mywritefunc(SDL_RWops *context, const void *ptr, int size, int num)
{
return num;
}
static int myclosefunc(SDL_RWops *context)
{
if(context->type != 0xdeadbeef)
{
return SDL_SetError("Wrong kind of RWops for myclosefunc()");
}
free(context->hidden.unknown.data1);
SDL_FreeRW(context);
return 0;
}
SDL_RWops *MyCustomRWop()
{
SDL_RWops *c=SDL_AllocRW();
if(c==NULL) return NULL;
c->seek =myseekfunc;
c->read =myreadfunc;
c->write=mywritefunc;
c->close=myclosefunc;
c->type =0xdeadbeef;
c->hidden.unknown.data1=malloc(256);
return c;
}
Remarks
Applications do not need to use this function unless they are providing their own RWops implementation. If you just need a RWops to read/write a common data source, you should use the built-in implementations in SDL, like SDL_RWFromFile() or SDL_RWFromMem(), etc.
You must free the returned pointer with SDL_FreeRW(). Depending on your operating system and compiler, there may be a difference between the malloc() and free() your program uses and the versions SDL calls internally. Trying to mix the two can cause crashing such as segmentation faults. Since all RWops must free themselves when their close method is called, all RWops must be allocated through this function, so they can all be freed correctly with SDL_FreeRW().
