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/*
* Copyright (C) 2011 Hendrik Leppkes
* http://www.1f0.de
*
* This Program 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 2, or (at your option)
* any later version.
*
* This Program 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; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* Initial design and concept by Gabest and the MPC-HC Team, copyright under GPLv2
*/
#include "stdafx.h"
#include "ByteParser.h"
CByteParser::CByteParser(const BYTE *pData, uint32_t length)
: m_pData(pData), m_pCurrent(pData), m_pEnd(pData+length), m_dwLen(length), m_bitBuffer(0), m_bitLen(0)
{
}
CByteParser::~CByteParser()
{
}
uint32_t CByteParser::BitRead(uint8_t numBits, bool peek)
{
ASSERT(numBits <= 32);
ASSERT(numBits <= (m_bitLen + (8 * (m_pEnd - m_pCurrent))));
if (numBits == 0) { return 0; }
bool atEnd = false;
// Read more data in the buffer
while(m_bitLen < numBits) {
m_bitBuffer <<= 8;
m_bitBuffer += !atEnd ? *m_pCurrent : 0;
// Just a safety check so we don't cross the array boundary
if (m_pCurrent < m_pEnd) { m_pCurrent++; } else { atEnd = true; }
m_bitLen += 8;
}
// Number of superfluous bits in the buffer
int bitlen = m_bitLen - numBits;
// Compose the return value
// Shift the value so the superfluous bits fall off, and then crop the result with an AND
uint32_t ret = (m_bitBuffer >> bitlen) & ((1ui64 << numBits) - 1);
// If we're not peeking, then update the buffer and remove the data we just read
if(!peek) {
m_bitBuffer &= ((1ui64 << bitlen) - 1);
m_bitLen = bitlen;
}
return ret;
}
// Exponential Golomb Coding (with k = 0)
// As used in H.264/MPEG-4 AVC
// http://en.wikipedia.org/wiki/Exponential-Golomb_coding
uint64_t CByteParser::UExpGolombRead() {
int n = -1;
for(BYTE b = 0; !b; n++) {
b = BitRead(1);
}
return (1ui64 << n) - 1 + BitRead(n);
}
int64_t CByteParser::SExpGolombRead() {
uint64_t k = UExpGolombRead();
// Negative numbers are interleaved in the series
// k: 0, 1, 2, 3, 4, 5, 6, ...
// Actual: 0, 1, -1, 2, -2, 3, -3, ....
// So all even numbers are negative (last bit = 0)
return ((k&1) ? 1 : -1) * ((k + 1) >> 1);
}
void CByteParser::Seek(DWORD pos)
{
m_pCurrent = m_pData + min(m_dwLen, pos);
BitFlush();
}
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