52 lines
2.3 KiB
C
52 lines
2.3 KiB
C
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/*
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* Created by Ben Allison on 11/10/07.
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* Copyright 2007-2011 Nullsoft, Inc. All rights reserved.
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*
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* Ring Buffer class
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* Thread safety:
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* This class can be used from exactly two simultaneous threads without locking
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* as long as one thread only writes and the other thread only reads
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* the writer thread may call empty(), avail(), size(), write(), fill(
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* the reader thread my call empty(), avail(), size(), read(), peek(), advance()
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*
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* two (or more) readers or two (or more) writers requires external locking
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*
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* Reset(), reserve(), clear(), LockBuffer(), UnlockBuffer() are not thread-safe
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*/
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#pragma once
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#include <stddef.h>
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#include "foundation/types.h"
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class LockFreeRingBuffer
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{
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public:
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LockFreeRingBuffer();
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~LockFreeRingBuffer();
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void Reset();
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int expand(size_t bytes); // like reserve, but only expands upward. non-destructive. returns an NError
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bool reserve(size_t bytes);
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bool empty() const;
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size_t avail() const; // how much available for writing
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size_t size() const; // how much available for reading
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void clear();
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size_t read(void *dest, size_t len); // returns amount actually read
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size_t advance(size_t len); // same as read() but doesn't write the data any where.
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size_t peek(void *dest, size_t len) const; // same as read() but doesn't advance the read pointer
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size_t write(const void *src, size_t len);
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size_t update(size_t len); // same as write() but doesn't write the data, usually used after a get_buffer call
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size_t at(size_t offset, void *dest, size_t len) const; // peeks() from offset. returns bytes read
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size_t write_position() const; // returns an integer representing a write position
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size_t read_position() const; // returns an integer representing the read position
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size_t advance_to(size_t position); // moves the read pointer to a position previously returned from write_position(). returns bytes advanced
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void get_write_buffer(size_t bytes, void **buffer, size_t *bytes_available); /* returns a pointer that you can write data to, you MUST call update() when you are done */
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void get_read_buffer(size_t bytes, const void **buffer, size_t *bytes_available); /* returns a pointer that you can read data from, call advance() when you are done */
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private:
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volatile size_t ringBufferUsed;
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size_t ringBufferSize;
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char *ringBuffer;
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char *ringWritePosition;
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char *ringReadPosition;
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};
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