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/*
* Copyright (C) 2004-2012 Geometer Plus <[email protected]>
*
* 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 of the License, 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; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
#ifndef __BITSTREAM_H__
#define __BITSTREAM_H__
#include <string>
class BitStream {
public:
static const int BufferSize;
public:
BitStream();
void setData(const std::string &data);
void reset();
unsigned int peek(unsigned char length);
void remove(unsigned char length);
unsigned int get(unsigned char length);
unsigned int bytesLeft() const;
unsigned int get4BytesDirect();
bool getBytesDirect(unsigned char *buffer, unsigned int length);
private:
bool ensure(unsigned char length);
private:
unsigned int myBuffer;
unsigned char myBitCounter;
const unsigned char *myByteStream;
const unsigned char *myByteStreamEnd;
private:
BitStream(const BitStream&);
const BitStream &operator = (const BitStream&);
};
inline BitStream::BitStream() : myBuffer(0), myBitCounter(0) {
}
inline void BitStream::setData(const std::string &data) {
myByteStream = (const unsigned char*)data.data();
myByteStreamEnd = myByteStream + data.length();
myBuffer = 0;
myBitCounter = 0;
}
inline void BitStream::reset() {
myByteStream -= myBitCounter / 8;
myBuffer = 0;
myBitCounter = 0;
}
inline bool BitStream::ensure(unsigned char length) {
while ((myBitCounter < length) && (bytesLeft() >= 2)) {
myBuffer |= ((myByteStream[1] << 8) | myByteStream[0]) << (BitStream::BufferSize - 16 - myBitCounter);
myBitCounter += 16;
myByteStream += 2;
}
return myBitCounter >= length;
}
inline unsigned int BitStream::peek(unsigned char length) {
ensure(length);
return (length > 0) ? (myBuffer >> (BufferSize - length)) : 0;
}
inline void BitStream::remove(unsigned char length) {
if (ensure(length)) {
myBuffer <<= length;
myBitCounter -= length;
}
}
inline unsigned int BitStream::get(unsigned char length) {
unsigned int bits;
if (length > 16) {
bits = peek(length - 16) << 16;
remove(length - 16);
bits += peek(16);
remove(16);
} else {
bits = peek(length);
remove(length);
}
return bits;
}
inline unsigned int BitStream::bytesLeft() const {
return myByteStreamEnd - myByteStream;
}
#endif /* __BITSTREAM_H__ */
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