/* 
 * $Id: GolombBuffer.cpp 726 2008-08-12 20:49:01Z casimir666 $
 *
 * (C) 2006-2007 see AUTHORS
 *
 * This file is part of mplayerc.
 *
 * Mplayerc is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Mplayerc is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */


#include "StdAfx.h"
#include "GolombBuffer.h"

CGolombBuffer::CGolombBuffer(BYTE* pBuffer, int nSize)
{
	m_pBuffer	= pBuffer;
	m_nSize		= nSize;

	m_nBitPos	= 0;

	m_bitbuff	= 0;
	m_bitlen	= 0;
}


UINT64 CGolombBuffer::BitRead(int nBits, bool fPeek)
{
//	ASSERT(nBits >= 0 && nBits <= 64);

	while(m_bitlen < nBits)
	{
		m_bitbuff <<= 8;

		if (m_nBitPos >= m_nSize) return 0;

		*(BYTE*)&m_bitbuff = m_pBuffer[m_nBitPos++];
		m_bitlen += 8;
	}

	int bitlen = m_bitlen - nBits;

	UINT64 ret = (m_bitbuff >> bitlen) & ((1ui64 << nBits) - 1);

	if(!fPeek)
	{
		m_bitbuff &= ((1ui64 << bitlen) - 1);
		m_bitlen = bitlen;
	}

	return ret;
}


UINT64 CGolombBuffer::UExpGolombRead()
{
	int n = -1;
	for(BYTE b = 0; !b; n++) b = (BYTE)BitRead(1);
	return (1ui64 << n) - 1 + BitRead(n);
}

INT64 CGolombBuffer::SExpGolombRead()
{
	UINT64 k = UExpGolombRead();
	return ((k&1) ? 1 : -1) * ((k + 1) >> 1);
}


void CGolombBuffer::BitByteAlign()
{
	m_bitlen &= ~7;
}

__int64 CGolombBuffer::GetPos()
{
	return m_nBitPos - (m_bitlen>>3);
}


void CGolombBuffer::ReadBuffer(BYTE* pDest, int nSize)
{
	ASSERT (m_nBitPos + nSize <= m_nSize);
	ASSERT (m_bitlen == 0);
	nSize = min (nSize, m_nSize - m_nBitPos);
	
	memcpy (pDest, m_pBuffer+m_nBitPos, nSize);
	m_nBitPos += nSize;
}