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Size: 1998
Comment: Rewritten
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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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| Deletions are marked like this. | Additions are marked like this. |
| Line 22: | Line 22: |
| SDL_SetError("Can't seek in this kind of RWops"); return(-1); |
return SDL_SetError("Can't seek in this kind of RWops"); |
| Line 29: | Line 28: |
| return(maxnum); | return maxnum; |
| Line 34: | Line 33: |
| return(num); | return num; |
| Line 41: | Line 40: |
| SDL_SetError("Wrong kind of RWops for myclosefunc()"); return(-1); |
return SDL_SetError("Wrong kind of RWops for myclosefunc()"); |
| Line 47: | Line 45: |
| return(0); | return 0; |
| Line 53: | Line 51: |
| if(c==NULL) return(NULL); | if(c==NULL) return NULL; |
| Line 61: | Line 59: |
| return(c); | return c; |
| Line 66: | Line 64: |
| 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. |
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 a 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().
