95 lines
3.1 KiB
C++
95 lines
3.1 KiB
C++
#ifndef RINGBUFFER_H
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#define RINGBUFFER_H
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#include <stddef.h>
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#include <atomic>
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#include <memory>
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#include <utility>
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#include "almalloc.h"
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/* NOTE: This lockless ringbuffer implementation is copied from JACK, extended
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* to include an element size. Consequently, parameters and return values for a
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* size or count is in 'elements', not bytes. Additionally, it only supports
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* single-consumer/single-provider operation.
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*/
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struct ll_ringbuffer {
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std::atomic<size_t> write_ptr{0u};
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std::atomic<size_t> read_ptr{0u};
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size_t size{0u};
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size_t size_mask{0u};
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size_t elem_size{0u};
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alignas(16) char buf[];
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DEF_PLACE_NEWDEL()
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};
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struct ll_ringbuffer_data {
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char *buf;
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size_t len;
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};
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using ll_ringbuffer_data_pair = std::pair<ll_ringbuffer_data,ll_ringbuffer_data>;
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/**
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* Create a new ringbuffer to hold at least `sz' elements of `elem_sz' bytes.
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* The number of elements is rounded up to the next power of two (even if it is
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* already a power of two, to ensure the requested amount can be written).
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*/
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ll_ringbuffer *ll_ringbuffer_create(size_t sz, size_t elem_sz, int limit_writes);
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/** Reset the read and write pointers to zero. This is not thread safe. */
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void ll_ringbuffer_reset(ll_ringbuffer *rb);
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/**
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* The non-copying data reader. Returns two ringbuffer data pointers that hold
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* the current readable data at `rb'. If the readable data is in one segment
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* the second segment has zero length.
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*/
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ll_ringbuffer_data_pair ll_ringbuffer_get_read_vector(const ll_ringbuffer *rb);
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/**
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* The non-copying data writer. Returns two ringbuffer data pointers that hold
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* the current writeable data at `rb'. If the writeable data is in one segment
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* the second segment has zero length.
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*/
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ll_ringbuffer_data_pair ll_ringbuffer_get_write_vector(const ll_ringbuffer *rb);
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/**
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* Return the number of elements available for reading. This is the number of
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* elements in front of the read pointer and behind the write pointer.
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*/
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size_t ll_ringbuffer_read_space(const ll_ringbuffer *rb);
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/**
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* The copying data reader. Copy at most `cnt' elements from `rb' to `dest'.
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* Returns the actual number of elements copied.
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*/
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size_t ll_ringbuffer_read(ll_ringbuffer *rb, void *dest, size_t cnt);
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/**
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* The copying data reader w/o read pointer advance. Copy at most `cnt'
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* elements from `rb' to `dest'. Returns the actual number of elements copied.
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*/
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size_t ll_ringbuffer_peek(ll_ringbuffer *rb, void *dest, size_t cnt);
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/** Advance the read pointer `cnt' places. */
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void ll_ringbuffer_read_advance(ll_ringbuffer *rb, size_t cnt);
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/**
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* Return the number of elements available for writing. This is the number of
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* elements in front of the write pointer and behind the read pointer.
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*/
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size_t ll_ringbuffer_write_space(const ll_ringbuffer *rb);
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/**
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* The copying data writer. Copy at most `cnt' elements to `rb' from `src'.
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* Returns the actual number of elements copied.
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*/
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size_t ll_ringbuffer_write(ll_ringbuffer *rb, const void *src, size_t cnt);
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/** Advance the write pointer `cnt' places. */
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void ll_ringbuffer_write_advance(ll_ringbuffer *rb, size_t cnt);
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using RingBufferPtr = std::unique_ptr<ll_ringbuffer>;
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#endif /* RINGBUFFER_H */
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