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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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.
*
*/
// Based on eos' BitStream implementation
#ifndef COMMON_BITSTREAM_H
#define COMMON_BITSTREAM_H
#include "common/scummsys.h"
namespace Common {
class SeekableReadStream;
/**
* A bit stream, giving access to data one bit at a time.
*
* Used in engines:
* - scumm
*/
class BitStream {
public:
BitStream();
virtual ~BitStream();
/** Read a bit from the bitstream. */
virtual uint32 getBit() = 0;
/** Read a number of bits, creating a multi-bit value. */
virtual uint32 getBits(uint32 n) = 0;
/** Add more bits, creating a multi-bit value in stages. */
virtual void addBit(uint32 &x, uint32 n) = 0;
/** Skip a number of bits. */
void skip(uint32 n);
/** Get the current position, in bits. */
virtual uint32 pos() const = 0;
/** Return the number of bits in the stream. */
virtual uint32 size() const = 0;
};
/**
* A big-endian bit stream.
*
* The input data is read one byte at a time. Their bits are handed out
* in the order of MSB to LSB. When all 8 bits of a byte have been consumed,
* another input data byte is read.
*/
class BitStreamBE : public BitStream {
public:
/**
* Create a big endian bit stream.
*
* Reads and copies bitCount bits from the provided stream.
* Ownership of the stream is not transferred.
*/
BitStreamBE(SeekableReadStream &stream, uint32 bitCount);
/**
* Create a big endian bit stream.
*
* Reads and copies bitCount bits from the provided data.
* Ownership of the data is not transferred.
*/
BitStreamBE(const byte *data, uint32 bitCount);
~BitStreamBE();
uint32 getBit();
/**
* Read a number of bits, creating a multi-bit value.
*
* The bits are read one at a time, in the order MSB to LSB and
* or'd together to create a multi-bit value.
*/
uint32 getBits(uint32 n);
/**
* Add more bits, creating a multi-bit value in stages.
*
* Shifts in n new bits into the value x, in the order of MSB to LSB.
*/
void addBit(uint32 &x, uint32 n);
uint32 pos() const;
uint32 size() const;
private:
SeekableReadStream *_stream;
byte _value; ///< Current byte.
uint8 _inValue; ///< Position within the current byte.
};
/**
* A little-endian bit stream, reading 32bit values at a time.
*
* The input data is read one little-endian uint32 at a time. Their bits are
* handed out in the order of LSB to MSB. When all 8 bits of a byte have been
* consumed, another little-endian input data uint32 is read.
*/
class BitStream32LE : public BitStream {
public:
/**
* Create a little-endian bit stream.
*
* Reads and copies bitCount bits from the provided stream.
* Ownership of the stream is not transferred.
*/
BitStream32LE(SeekableReadStream &stream, uint32 bitCount);
/**
* Create a little-endian bit stream.
*
* Reads and copies bitCount bits from the provided data.
* Ownership of the data is not transferred.
*/
BitStream32LE(const byte *data, uint32 bitCount);
~BitStream32LE();
uint32 getBit();
/**
* Read a number of bits, creating a multi-bit value.
*
* The bits are read one at a time, in the order LSB to MSB and
* or'd together to create a multi-bit value.
*/
uint32 getBits(uint32 n);
/**
* Add more bits, creating a multi-bit value in stages.
*
* Shifts in n new bits into the value x, in the order of LSB to MSB.
*/
void addBit(uint32 &x, uint32 n);
uint32 pos() const;
uint32 size() const;
private:
SeekableReadStream *_stream;
uint32 _value; ///< Current 32bit value.
uint8 _inValue; ///< Position within the current 32bit value.
};
} // End of namespace Common
#endif // COMMON_BITSTREAM_H
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