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Size: 625
Comment: create page, add content (Wed Mar 10 ver; changeset 4428)
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Size: 1998
Comment: Rewritten
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| #pragma disable-camelcase ||<tablewidth="100%" style="color: #FF0000;" :> DRAFT|| |
#pragma camelcase off |
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| Use this function to ^allocate a read/write to a specific SDL_RWops structure^. ??? | Use this function to allocate an empty, unpopulated SDL_RWops structure. |
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| ^Reads or writes to the specified SDL_RWops structure.^ ??? | Returns a pointer to the allocated memory on success, or NULL on failure; call [[SDL_GetError]]() for more information. |
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| You can add your code example here | /* 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); } |
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| ''You can add useful comments here'' | 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
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().
