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//
// TPCircularBuffer.h
// Circular/Ring buffer implementation
//
// https://github.com/michaeltyson/TPCircularBuffer
//
// Created by Michael Tyson on 10/12/2011.
//
//
// This implementation makes use of a virtual memory mapping technique that inserts a virtual copy
// of the buffer memory directly after the buffer's end, negating the need for any buffer
// wrap-around logic. Clients can simply use the returned memory address as if it were contiguous
// space.
//
// The implementation is thread-safe in the case of a single producer and single consumer.
//
// Virtual memory technique originally proposed by Philip Howard (http://vrb.slashusr.org/), and
// adapted to Darwin by Kurt Revis (http://www.snoize.com,
// http://www.snoize.com/Code/PlayBufferedSoundFile.tar.gz)
//
//
// Copyright (C) 2012-2013 A Tasty Pixel
//
// 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 TPCircularBuffer_h
#define TPCircularBuffer_h
#include <libkern/OSAtomic.h>
#include <string.h>
#include <winpr/assert.h>
#ifdef __cplusplus
extern "C"
{
#endif
typedef struct
{
void* buffer;
int32_t length;
int32_t tail;
int32_t head;
volatile int32_t fillCount;
} TPCircularBuffer;
/*!
* Initialise buffer
*
* Note that the length is advisory only: Because of the way the
* memory mirroring technique works, the true buffer length will
* be multiples of the device page size (e.g. 4096 bytes)
*
* @param buffer Circular buffer
* @param length Length of buffer
*/
bool TPCircularBufferInit(TPCircularBuffer* buffer, int32_t length);
/*!
* Cleanup buffer
*
* Releases buffer resources.
*/
void TPCircularBufferCleanup(TPCircularBuffer* buffer);
/*!
* Clear buffer
*
* Resets buffer to original, empty state.
*
* This is safe for use by consumer while producer is accessing
* buffer.
*/
void TPCircularBufferClear(TPCircularBuffer* buffer);
// Reading (consuming)
/*!
* Access end of buffer
*
* This gives you a pointer to the end of the buffer, ready
* for reading, and the number of available bytes to read.
*
* @param buffer Circular buffer
* @param availableBytes On output, the number of bytes ready for reading
* @return Pointer to the first bytes ready for reading, or NULL if buffer is empty
*/
static __inline__ __attribute__((always_inline)) void*
TPCircularBufferTail(TPCircularBuffer* buffer, int32_t* availableBytes)
{
*availableBytes = buffer->fillCount;
if (*availableBytes == 0)
return NULL;
return (void*)((char*)buffer->buffer + buffer->tail);
}
/*!
* Consume bytes in buffer
*
* This frees up the just-read bytes, ready for writing again.
*
* @param buffer Circular buffer
* @param amount Number of bytes to consume
*/
static __inline__ __attribute__((always_inline)) void
TPCircularBufferConsume(TPCircularBuffer* buffer, int32_t amount)
{
buffer->tail = (buffer->tail + amount) % buffer->length;
OSAtomicAdd32Barrier(-amount, &buffer->fillCount);
WINPR_ASSERT(buffer->fillCount >= 0);
}
/*!
* Version of TPCircularBufferConsume without the memory barrier, for more optimal use in
* single-threaded contexts
*/
static __inline__ __attribute__((always_inline)) void
TPCircularBufferConsumeNoBarrier(TPCircularBuffer* buffer, int32_t amount)
{
buffer->tail = (buffer->tail + amount) % buffer->length;
buffer->fillCount -= amount;
WINPR_ASSERT(buffer->fillCount >= 0);
}
/*!
* Access front of buffer
*
* This gives you a pointer to the front of the buffer, ready
* for writing, and the number of available bytes to write.
*
* @param buffer Circular buffer
* @param availableBytes On output, the number of bytes ready for writing
* @return Pointer to the first bytes ready for writing, or NULL if buffer is full
*/
static __inline__ __attribute__((always_inline)) void*
TPCircularBufferHead(TPCircularBuffer* buffer, int32_t* availableBytes)
{
*availableBytes = (buffer->length - buffer->fillCount);
if (*availableBytes == 0)
return NULL;
return (void*)((char*)buffer->buffer + buffer->head);
}
// Writing (producing)
/*!
* Produce bytes in buffer
*
* This marks the given section of the buffer ready for reading.
*
* @param buffer Circular buffer
* @param amount Number of bytes to produce
*/
static __inline__ __attribute__((always_inline)) void
TPCircularBufferProduce(TPCircularBuffer* buffer, int amount)
{
buffer->head = (buffer->head + amount) % buffer->length;
OSAtomicAdd32Barrier(amount, &buffer->fillCount);
WINPR_ASSERT(buffer->fillCount <= buffer->length);
}
/*!
* Version of TPCircularBufferProduce without the memory barrier, for more optimal use in
* single-threaded contexts
*/
static __inline__ __attribute__((always_inline)) void
TPCircularBufferProduceNoBarrier(TPCircularBuffer* buffer, int amount)
{
buffer->head = (buffer->head + amount) % buffer->length;
buffer->fillCount += amount;
WINPR_ASSERT(buffer->fillCount <= buffer->length);
}
/*!
* Helper routine to copy bytes to buffer
*
* This copies the given bytes to the buffer, and marks them ready for writing.
*
* @param buffer Circular buffer
* @param src Source buffer
* @param len Number of bytes in source buffer
* @return true if bytes copied, false if there was insufficient space
*/
static __inline__ __attribute__((always_inline)) bool
TPCircularBufferProduceBytes(TPCircularBuffer* buffer, const void* src, int32_t len)
{
int32_t space;
void* ptr = TPCircularBufferHead(buffer, &space);
if (space < len)
return false;
memcpy(ptr, src, len);
TPCircularBufferProduce(buffer, len);
return true;
}
#ifdef __cplusplus
}
#endif
#endif
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