78 lines
2.6 KiB
C++
78 lines
2.6 KiB
C++
/*
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* RingBuffer.h
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* simple_mp3_playback
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*
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* Created by Ben Allison on 11/10/07.
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* Copyright 2007 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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class Filler
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{
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public:
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virtual size_t Read(void *dest, size_t len)=0;
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};
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class Drainer
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{
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public:
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virtual size_t Write(const void *dest, size_t len)=0;
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};
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class RingBuffer
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{
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public:
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RingBuffer() {}
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~RingBuffer();
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void Reset();
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bool reserve( size_t bytes ); // destructive.
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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 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 fill( Filler *filler, size_t max_bytes );
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size_t drain( Drainer *drainer, size_t max_bytes );
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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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void get_read_buffer( size_t bytes, const void **buffer, size_t *bytes_available ) const; /* returns a pointer that you can read data from, call advance() when you are done */
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/* DO NOT USING THIS UNLESS YOU KNOW WHAT YOU'RE DOING
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you should only use it when the ring buffer is empty
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1) call clear() beforehand - very important!
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2) call LockBuffer(), it'll give you a buffer
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3) call UnlockBufer() with how much you've written
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4) you catch the man
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*/
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void *LockBuffer();
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void UnlockBuffer( size_t written );
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private:
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volatile size_t ringBufferUsed = 0;
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size_t ringBufferSize = 0;
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char *ringBuffer = 0;
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char *ringWritePosition = 0;
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char *ringReadPosition = 0;
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};
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