winamp/Src/nu/RingBuffer.h
2024-09-24 14:54:57 +02:00

78 lines
2.6 KiB
C++

/*
* RingBuffer.h
* simple_mp3_playback
*
* Created by Ben Allison on 11/10/07.
* Copyright 2007 Nullsoft, Inc. All rights reserved.
*
* Ring Buffer class
* Thread safety:
* This class can be used from exactly two simultaneous threads without locking
* as long as one thread only writes and the other thread only reads
* the writer thread may call empty(), avail(), size(), write(), fill(
* the reader thread my call empty(), avail(), size(), read(), peek(), advance()
*
* two (or more) readers or two (or more) writers requires external locking
*
* Reset(), reserve(), clear(), LockBuffer(), UnlockBuffer() are not thread-safe
*/
#pragma once
#include <stddef.h>
class Filler
{
public:
virtual size_t Read(void *dest, size_t len)=0;
};
class Drainer
{
public:
virtual size_t Write(const void *dest, size_t len)=0;
};
class RingBuffer
{
public:
RingBuffer() {}
~RingBuffer();
void Reset();
bool reserve( size_t bytes ); // destructive.
int expand( size_t bytes ); // like reserve, but only expands upward. non-destructive. returns an NError
bool empty() const;
size_t avail() const; // how much available for writing
size_t size() const; // how much available for reading
void clear();
size_t read( void *dest, size_t len ); // returns amount actually read
size_t advance( size_t len ); // same as read() but doesn't write the data any where.
size_t peek( void *dest, size_t len ) const; // same as read() but doesn't advance the read pointer
size_t write( const void *src, size_t len );
size_t fill( Filler *filler, size_t max_bytes );
size_t drain( Drainer *drainer, size_t max_bytes );
size_t at( size_t offset, void *dest, size_t len ) const; // peeks() from offset. returns bytes read
size_t write_position() const; // returns an integer representing a write position
size_t read_position() const; // returns an integer representing the read position
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 */
/* DO NOT USING THIS UNLESS YOU KNOW WHAT YOU'RE DOING
you should only use it when the ring buffer is empty
1) call clear() beforehand - very important!
2) call LockBuffer(), it'll give you a buffer
3) call UnlockBufer() with how much you've written
4) you catch the man
*/
void *LockBuffer();
void UnlockBuffer( size_t written );
private:
volatile size_t ringBufferUsed = 0;
size_t ringBufferSize = 0;
char *ringBuffer = 0;
char *ringWritePosition = 0;
char *ringReadPosition = 0;
};