A simple, fast circular buffer implementation for audio processing

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A simple C implementation for a circular (ring) buffer. Thread-safe with a single producer and a single consumer, using OSAtomic.h primitives, and avoids any need for buffer wrapping logic by using a virtual memory map technique to place a virtual copy of the buffer straight after the end of the real buffer.

Usage

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Initialisation and cleanup: `TPCircularBufferInit` and `TPCircularBufferCleanup` to allocate and free resources.

Producing: Use `TPCircularBufferHead` to get a pointer to write to the buffer, followed by `TPCircularBufferProduce` to submit the written data.  `TPCircularBufferProduceBytes` is a convenience routine for writing data straight to the buffer.

Consuming: Use `TPCircularBufferTail` to get a pointer to the next data to read, followed by `TPCircularBufferConsume` to free up the space once processed.

TPCircularBuffer+AudioBufferList.(c,h) contain helper functions to queue and dequeue AudioBufferList

structures. These will automatically adjust the mData fields of each buffer to point to 16-byte aligned

regions within the circular buffer.

Thread safety

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As long as you restrict multithreaded access to just one producer, and just one consumer, this utility should be thread safe. 

Only one shared variable is used (the buffer fill count), and OSAtomic primitives are used to write to this value to ensure atomicity.

License

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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.

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Virtual memory technique originally proposed by [Philip Howard](http://vrb.slashusr.org/), and [adapted to Darwin](http://www.snoize.com/Code/PlayBufferedSoundFile.tar.gz) by [Kurt Revis](http://www.snoize.com)

See more info at [atastypixel.com](http://atastypixel.com/blog/a-simple-fast-circular-buffer-implementation-for-audio-processing/)