🛠️🐜 Antkeeper superbuild with dependencies included
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115 lines
3.7 KiB
115 lines
3.7 KiB
#ifndef RINGBUFFER_H
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#define RINGBUFFER_H
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#include <atomic>
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#include <memory>
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#include <stddef.h>
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#include <utility>
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#include "albyte.h"
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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 RingBuffer {
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private:
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std::atomic<size_t> mWritePtr{0u};
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std::atomic<size_t> mReadPtr{0u};
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size_t mWriteSize{0u};
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size_t mSizeMask{0u};
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size_t mElemSize{0u};
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al::FlexArray<al::byte, 16> mBuffer;
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public:
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struct Data {
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al::byte *buf;
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size_t len;
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};
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using DataPair = std::pair<Data,Data>;
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RingBuffer(const size_t count) : mBuffer{count} { }
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/** Reset the read and write pointers to zero. This is not thread safe. */
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void reset() noexcept;
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/**
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* The non-copying data reader. Returns two ringbuffer data pointers that
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* hold the current readable data. 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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DataPair getReadVector() const noexcept;
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/**
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* The non-copying data writer. Returns two ringbuffer data pointers that
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* hold the current writeable data. 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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DataPair getWriteVector() const noexcept;
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/**
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* Return the number of elements available for reading. This is the number
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* of elements in front of the read pointer and behind the write pointer.
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*/
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size_t readSpace() const noexcept
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{
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const size_t w{mWritePtr.load(std::memory_order_acquire)};
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const size_t r{mReadPtr.load(std::memory_order_acquire)};
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return (w-r) & mSizeMask;
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}
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/**
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* The copying data reader. Copy at most `cnt' elements into `dest'.
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* Returns the actual number of elements copied.
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*/
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size_t read(void *dest, size_t cnt) noexcept;
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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 into `dest'. Returns the actual number of elements copied.
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*/
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size_t peek(void *dest, size_t cnt) const noexcept;
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/** Advance the read pointer `cnt' places. */
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void readAdvance(size_t cnt) noexcept
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{ mReadPtr.fetch_add(cnt, std::memory_order_acq_rel); }
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/**
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* Return the number of elements available for writing. This is the number
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* of elements in front of the write pointer and behind the read pointer.
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*/
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size_t writeSpace() const noexcept
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{
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const size_t w{mWritePtr.load(std::memory_order_acquire)};
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const size_t r{mReadPtr.load(std::memory_order_acquire) + mWriteSize - mSizeMask};
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return (r-w-1) & mSizeMask;
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}
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/**
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* The copying data writer. Copy at most `cnt' elements from `src'. Returns
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* the actual number of elements copied.
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*/
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size_t write(const void *src, size_t cnt) noexcept;
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/** Advance the write pointer `cnt' places. */
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void writeAdvance(size_t cnt) noexcept
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{ mWritePtr.fetch_add(cnt, std::memory_order_acq_rel); }
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size_t getElemSize() const noexcept { return mElemSize; }
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/**
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* Create a new ringbuffer to hold at least `sz' elements of `elem_sz'
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* bytes. The number of elements is rounded up to the next power of two
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* (even if it is already a power of two, to ensure the requested amount
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* can be written).
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*/
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static std::unique_ptr<RingBuffer> Create(size_t sz, size_t elem_sz, int limit_writes);
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DEF_FAM_NEWDEL(RingBuffer, mBuffer)
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};
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using RingBufferPtr = std::unique_ptr<RingBuffer>;
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#endif /* RINGBUFFER_H */
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