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/*
* (C) 2008-2012 see Authors.txt
*
* This file is part of MPC-HC.
*
* MPC-HC 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.
*
* MPC-HC 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)
{
Reset();
}
CGolombBuffer::~CGolombBuffer()
{
}
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;
// The shift to 64 bits can give incorrect results.
// "The behavior is undefined if the right operand is negative, or greater than or equal to the length in bits of the promoted left operand."
if (nBits == 64) {
ret = m_bitbuff;
} else {
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;
}
int 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;
}
void CGolombBuffer::Reset()
{
m_nBitPos = 0;
m_bitlen = 0;
m_bitbuff = 0;
}
void CGolombBuffer::Reset(BYTE* pNewBuffer, int nNewSize)
{
m_pBuffer = pNewBuffer;
m_nSize = nNewSize;
Reset();
}
void CGolombBuffer::SkipBytes(int nCount)
{
m_nBitPos += nCount;
m_bitlen = 0;
m_bitbuff = 0;
}
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