Initial community commit

Src/nu/RingBuffer.h

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+/*
+ *  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;
+};