//========= Copyright © 1996-2005, Valve Corporation, All rights reserved. ============//
//
// Purpose: Defines an interface for circular buffers. Data can be written to
//			and read from these buffers as though from a file. When it is 
//			write-overflowed (you write more data in than the buffer can hold),
//			the read pointer is advanced to allow the new data to be written.
//			This means old data will be discarded if you write too much data
//			into the buffer.
//
//	MikeD:	Moved all the functions into a class.
//			Changed it so when the buffer overflows, the old data
//			is discarded rather than the new.
//
//=====================================================================================//

#ifndef CIRCULARBUFFER_H
#define CIRCULARBUFFER_H

#pragma once

#include "tier0/dbg.h"

class CCircularBuffer
{
public:
						CCircularBuffer();
						CCircularBuffer( int size );
	void				SetSize( int nSize );

protected:
	inline void			AssertValid()
	{
#ifdef _DEBUG
		Assert( this );
		Assert( m_nSize > 0 );
		Assert( m_nCount >= 0 );
		Assert( m_nCount <= m_nSize );
		Assert( m_nWrite < m_nSize );

		// Verify that m_nCount is correct.
		if( m_nRead == m_nWrite )
		{
			Assert( m_nCount == 0 || m_nCount == m_nSize );
		}
		else
		{
			int testCount=0;
			if ( m_nRead < m_nWrite )
				testCount = m_nWrite - m_nRead;
			else
				testCount = (m_nSize - m_nRead) + m_nWrite;

			Assert( testCount == m_nCount );
		}
#endif
	}

public:

	void				Flush();
	int					GetSize();					// Get the size of the buffer (how much can you write without reading
													// before losing data.
	
	int					GetWriteAvailable();		// Get the amount available to write without overflowing.
													// Note: you can write however much you want, but it may overflow,
													// in which case the newest data is kept and the oldest is discarded.
	
	int					GetReadAvailable();			// Get the amount available to read.
	
	int					Peek(char *pchDest, int nCount);
	int					Advance(int nCount);
	int					Read(void *pchDest, int nCount);
	int					Write(void *pchData, int nCount);

public:
	int		m_nCount;			// Space between the read and write pointers (how much data we can read).
	
	int		m_nRead;			// Read index into circular buffer
	int		m_nWrite;			// Write index into circular buffer
	
	int		m_nSize;			// Size of circular buffer in bytes (how much data it can hold).
	char	m_chData[1];		// Circular buffer holding data
};


// Use this to instantiate a CircularBuffer.
template< int size >
class CSizedCircularBuffer : public CCircularBuffer
{
public:
	CSizedCircularBuffer() : CCircularBuffer(size) {}

private:
	char	myData[size-1];
};

CCircularBuffer *AllocateCircularBuffer( int nSize );
void FreeCircularBuffer( CCircularBuffer *pCircularBuffer );

#endif // CIRCULARBUFFER_H