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Size: 2264
Comment: add SDL_GetError to RV
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Size: 2273
Comment: Apps don't usually need this function.
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| ||<tablewidth="100%" style="color: #FF0000;" :> DRAFT|| | |
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| Use this function to *allocate an empty, unpopulated SDL_RWops structure. * | Use this function to allocate an empty, unpopulated SDL_RWops structure. |
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| *Returns a pointer to ,,the allocated memory on success,, ^a data stream^, or NULL on failure*; call [[SDL_GetError]]() for more information. | Returns a pointer to the allocated memory on success, or NULL on failure; call [[SDL_GetError]]() for more information. |
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| *<<BR>> | |
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| #include <string.h> /* for memset */ #include "SDL_error.h" /* for SDL_SetError */ #include "SDL_rwops.h" |
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| memset(ptr,0,size*maxnum); | SDL_memset(ptr,0,size*maxnum); |
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| /* Note that this function is NOT static -- we want it directly callable from other source files */ | |
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| }}}<<BR>>* | }}} |
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| *<<BR>> /!\ You must free any memory allocated ,,with,, ^using^ [[SDL_AllocRW]]() 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. <<BR>>* |
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. |
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| <<Color2(green,Should malloc() and free() be formatted `malloc()` and `free()`?)>> | 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]](). |
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| .[[SDL_FreeRW]] * | .[[SDL_FreeRW]] |
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)
{
SDL_SetError("Can't seek in this kind of RWops");
return(-1);
}
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)
{
SDL_SetError("Wrong kind of RWops for myclosefunc()");
return(-1);
}
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().
