mirror of
https://github.com/libretro/scummvm.git
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174 lines
4.4 KiB
C++
174 lines
4.4 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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// Based on eos' BitStream implementation
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#ifndef COMMON_BITSTREAM_H
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#define COMMON_BITSTREAM_H
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#include "common/scummsys.h"
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namespace Common {
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class SeekableReadStream;
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/**
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* A bit stream, giving access to data one bit at a time.
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*
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* Used in engines:
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* - scumm
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*/
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class BitStream {
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public:
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BitStream();
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virtual ~BitStream();
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/** Read a bit from the bitstream. */
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virtual uint32 getBit() = 0;
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/** Read a number of bits, creating a multi-bit value. */
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virtual uint32 getBits(uint32 n) = 0;
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/** Add more bits, creating a multi-bit value in stages. */
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virtual void addBit(uint32 &x, uint32 n) = 0;
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/** Skip a number of bits. */
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void skip(uint32 n);
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/** Get the current position, in bits. */
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virtual uint32 pos() const = 0;
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/** Return the number of bits in the stream. */
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virtual uint32 size() const = 0;
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};
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/**
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* A big-endian bit stream.
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*
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* The input data is read one byte at a time. Their bits are handed out
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* in the order of MSB to LSB. When all 8 bits of a byte have been consumed,
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* another input data byte is read.
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*/
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class BitStreamBE : public BitStream {
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public:
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/**
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* Create a big endian bit stream.
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*
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* Reads and copies bitCount bits from the provided stream.
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* Ownership of the stream is not transferred.
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*/
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BitStreamBE(SeekableReadStream &stream, uint32 bitCount);
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/**
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* Create a big endian bit stream.
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*
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* Reads and copies bitCount bits from the provided data.
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* Ownership of the data is not transferred.
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*/
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BitStreamBE(const byte *data, uint32 bitCount);
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~BitStreamBE();
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uint32 getBit();
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/**
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* Read a number of bits, creating a multi-bit value.
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*
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* The bits are read one at a time, in the order MSB to LSB and
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* or'd together to create a multi-bit value.
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*/
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uint32 getBits(uint32 n);
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/**
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* Add more bits, creating a multi-bit value in stages.
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*
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* Shifts in n new bits into the value x, in the order of MSB to LSB.
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*/
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void addBit(uint32 &x, uint32 n);
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uint32 pos() const;
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uint32 size() const;
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private:
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SeekableReadStream *_stream;
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byte _value; ///< Current byte.
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uint8 _inValue; ///< Position within the current byte.
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};
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/**
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* A little-endian bit stream, reading 32bit values at a time.
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*
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* The input data is read one little-endian uint32 at a time. Their bits are
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* handed out in the order of LSB to MSB. When all 8 bits of a byte have been
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* consumed, another little-endian input data uint32 is read.
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*/
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class BitStream32LE : public BitStream {
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public:
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/**
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* Create a little-endian bit stream.
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*
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* Reads and copies bitCount bits from the provided stream.
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* Ownership of the stream is not transferred.
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*/
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BitStream32LE(SeekableReadStream &stream, uint32 bitCount);
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/**
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* Create a little-endian bit stream.
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*
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* Reads and copies bitCount bits from the provided data.
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* Ownership of the data is not transferred.
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*/
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BitStream32LE(const byte *data, uint32 bitCount);
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~BitStream32LE();
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uint32 getBit();
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/**
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* Read a number of bits, creating a multi-bit value.
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*
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* The bits are read one at a time, in the order LSB to MSB and
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* or'd together to create a multi-bit value.
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*/
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uint32 getBits(uint32 n);
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/**
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* Add more bits, creating a multi-bit value in stages.
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*
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* Shifts in n new bits into the value x, in the order of LSB to MSB.
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*/
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void addBit(uint32 &x, uint32 n);
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uint32 pos() const;
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uint32 size() const;
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private:
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SeekableReadStream *_stream;
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uint32 _value; ///< Current 32bit value.
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uint8 _inValue; ///< Position within the current 32bit value.
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};
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} // End of namespace Common
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#endif // COMMON_BITSTREAM_H
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