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Simple DirectMedia Layer
Copyright (C) 1997-2020 Sam Lantinga <>
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.
#ifndef SDL_dataqueue_h_
#define SDL_dataqueue_h_
/* this is not (currently) a public API. But maybe it should be! */
struct SDL_DataQueue;
typedef struct SDL_DataQueue SDL_DataQueue;
SDL_DataQueue *SDL_NewDataQueue(const size_t packetlen, const size_t initialslack);
void SDL_FreeDataQueue(SDL_DataQueue *queue);
void SDL_ClearDataQueue(SDL_DataQueue *queue, const size_t slack);
int SDL_WriteToDataQueue(SDL_DataQueue *queue, const void *data, const size_t len);
size_t SDL_ReadFromDataQueue(SDL_DataQueue *queue, void *buf, const size_t len);
size_t SDL_PeekIntoDataQueue(SDL_DataQueue *queue, void *buf, const size_t len);
size_t SDL_CountDataQueue(SDL_DataQueue *queue);
/* this sets a section of the data queue aside (possibly allocating memory for it)
as if it's been written to, but returns a pointer to that space. You may write
to this space until a read would consume it. Writes (and other calls to this
function) will safely append their data after this reserved space and can
be in flight at the same time. There is no thread safety.
If there isn't an existing block of memory that can contain the reserved
space, one will be allocated for it. You can not (currently) allocate
a space larger than the packetlen requested in SDL_NewDataQueue.
Returned buffer is uninitialized.
This lets you avoid an extra copy in some cases, but it's safer to use
SDL_WriteToDataQueue() unless you know what you're doing.
Returns pointer to buffer of at least (len) bytes, NULL on error.
void *SDL_ReserveSpaceInDataQueue(SDL_DataQueue *queue, const size_t len);
#endif /* SDL_dataqueue_h_ */
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