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#ifndef RINGBUFFER_H
#define RINGBUFFER_H
#include <stddef.h>
#include <atomic>
#include <memory>
#include <utility>
#include "almalloc.h"
/* NOTE: This lockless ringbuffer implementation is copied from JACK, extended
* to include an element size. Consequently, parameters and return values for a
* size or count is in 'elements', not bytes. Additionally, it only supports
* single-consumer/single-provider operation.
*/
struct ll_ringbuffer_data {
char *buf;
size_t len;
};
using ll_ringbuffer_data_pair = std::pair<ll_ringbuffer_data,ll_ringbuffer_data>;
struct RingBuffer {
std::atomic<size_t> mWritePtr{0u};
std::atomic<size_t> mReadPtr{0u};
size_t mSize{0u};
size_t mSizeMask{0u};
size_t mElemSize{0u};
alignas(16) char mBuffer[];
/** Reset the read and write pointers to zero. This is not thread safe. */
void reset() noexcept;
/**
* The non-copying data reader. Returns two ringbuffer data pointers that
* hold the current readable data. If the readable data is in one segment
* the second segment has zero length.
*/
ll_ringbuffer_data_pair getReadVector() const noexcept;
/**
* The non-copying data writer. Returns two ringbuffer data pointers that
* hold the current writeable data. If the writeable data is in one segment
* the second segment has zero length.
*/
ll_ringbuffer_data_pair getWriteVector() const noexcept;
/**
* Return the number of elements available for reading. This is the number
* of elements in front of the read pointer and behind the write pointer.
*/
size_t readSpace() const noexcept;
/**
* The copying data reader. Copy at most `cnt' elements into `dest'.
* Returns the actual number of elements copied.
*/
size_t read(void *dest, size_t cnt) noexcept;
/**
* The copying data reader w/o read pointer advance. Copy at most `cnt'
* elements into `dest'. Returns the actual number of elements copied.
*/
size_t peek(void *dest, size_t cnt) const noexcept;
/** Advance the read pointer `cnt' places. */
void readAdvance(size_t cnt) noexcept;
/**
* Return the number of elements available for writing. This is the number
* of elements in front of the write pointer and behind the read pointer.
*/
size_t writeSpace() const noexcept;
/**
* The copying data writer. Copy at most `cnt' elements from `src'. Returns
* the actual number of elements copied.
*/
size_t write(const void *src, size_t cnt) noexcept;
/** Advance the write pointer `cnt' places. */
void writeAdvance(size_t cnt) noexcept;
DEF_PLACE_NEWDEL()
};
using RingBufferPtr = std::unique_ptr<RingBuffer>;
/**
* Create a new ringbuffer to hold at least `sz' elements of `elem_sz' bytes.
* The number of elements is rounded up to the next power of two (even if it is
* already a power of two, to ensure the requested amount can be written).
*/
RingBufferPtr CreateRingBuffer(size_t sz, size_t elem_sz, int limit_writes);
#endif /* RINGBUFFER_H */
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