COMMON: Add a BitStream class
Based on eos' BitStream
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Matthew Hoops
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215
common/bitstream.cpp
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215
common/bitstream.cpp
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/* 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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#include "common/bitstream.h"
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#include "common/memstream.h"
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#include "common/stream.h"
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#include "common/textconsole.h"
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#include "common/util.h"
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namespace Common {
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BitStream::BitStream() {
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}
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BitStream::~BitStream() {
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}
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void BitStream::skip(uint32 n) {
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while (n-- > 0)
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getBit();
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}
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BitStreamBE::BitStreamBE(SeekableReadStream &stream, uint32 bitCount) : _value(0), _inValue(0) {
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if ((bitCount % 8) != 0)
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error("Big-endian bit stream size has to be divisible by 8");
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// Read the number of bytes of the stream
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uint32 byteSize = bitCount / 8;
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byte *data = new byte[byteSize];
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if (stream.read(data, byteSize) != byteSize) {
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delete[] data;
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error("Bad BitStreamBE size");
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}
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}
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BitStreamBE::BitStreamBE(const byte *data, uint32 bitCount) : _value(0), _inValue(0) {
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if ((bitCount % 8) != 0)
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error("Big-endian bit stream size has to be divisible by 8");
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// Copy the number of bytes from the data array
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uint32 byteSize = bitCount / 8;
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byte *dataN = new byte[byteSize];
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memcpy(dataN, data, byteSize);
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_stream = new MemoryReadStream(dataN, byteSize, DisposeAfterUse::YES);
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}
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BitStreamBE::~BitStreamBE() {
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delete _stream;
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}
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uint32 BitStreamBE::getBit() {
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if (_inValue == 0) {
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// Need to get new byte
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if (_stream->eos())
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error("End of bit stream reached");
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_value = _stream->readByte();
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}
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// Get the current bit
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int b = ((_value & 0x80) == 0) ? 0 : 1;
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// Shift to the next bit
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_value <<= 1;
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// Increase the position within the current byte
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_inValue = (_inValue + 1) % 8;
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return b;
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}
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uint32 BitStreamBE::getBits(uint32 n) {
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if (n > 32)
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error("Too many bits requested to be read");
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// Read the number of bits
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uint32 v = 0;
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while (n-- > 0)
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v = (v << 1) | getBit();
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return v;
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}
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void BitStreamBE::addBit(uint32 &x, uint32 n) {
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x = (x << 1) | getBit();
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}
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uint32 BitStreamBE::pos() const {
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if (_stream->pos() == 0)
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return 0;
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uint32 p = (_inValue == 0) ? _stream->pos() : (_stream->pos() - 1);
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return p * 8 + _inValue;
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}
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uint32 BitStreamBE::size() const {
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return _stream->size() * 8;
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}
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BitStream32LE::BitStream32LE(SeekableReadStream &stream, uint32 bitCount) : _value(0), _inValue(0) {
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if ((bitCount % 32) != 0)
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error("32bit little-endian bit stream size has to be divisible by 32");
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// Read the number of bytes of the stream
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uint32 byteSize = bitCount / 8;
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byte *data = new byte[byteSize];
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if (stream.read(data, byteSize) != byteSize) {
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delete[] data;
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error("Bad BitStream32LE size");
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}
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_stream = new MemoryReadStream(data, byteSize, DisposeAfterUse::YES);
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}
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BitStream32LE::BitStream32LE(const byte *data, uint32 bitCount) : _value(0), _inValue(0) {
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if ((bitCount % 32) != 0)
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error("32bit little-endian bit stream size has to be divisible by 32");
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// Copy the number of bytes from the data array
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uint32 byteSize = bitCount / 8;
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byte *dataN = new byte[byteSize];
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memcpy(dataN, data, byteSize);
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_stream = new MemoryReadStream(dataN, byteSize, DisposeAfterUse::YES);
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}
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BitStream32LE::~BitStream32LE() {
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delete _stream;
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}
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uint32 BitStream32LE::getBit() {
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if (_inValue == 0) {
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// Need to get new 32bit value
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if (_stream->eos())
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error("End of bit stream reached");
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_value = _stream->readUint32LE();
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}
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// Get the current bit
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int b = ((_value & 1) == 0) ? 0 : 1;
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// Shift to the next bit
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_value >>= 1;
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// Increase the position within the current byte
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_inValue = (_inValue + 1) % 32;
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return b;
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}
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uint32 BitStream32LE::getBits(uint32 n) {
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if (n > 32)
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error("Too many bits requested to be read");
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// Read the number of bits
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uint32 v = 0;
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for (uint32 i = 0; i < n; i++)
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v = (v >> 1) | (((uint32) getBit()) << 31);
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v >>= (32 - n);
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return v;
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}
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void BitStream32LE::addBit(uint32 &x, uint32 n) {
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x = (x & ~(1 << n)) | (getBit() << n);
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}
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uint32 BitStream32LE::pos() const {
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if (_stream->pos() == 0)
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return 0;
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uint32 p = ((_inValue == 0) ? _stream->pos() : (_stream->pos() - 1)) & 0xFFFFFFFC;
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return p * 8 + _inValue;
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}
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uint32 BitStream32LE::size() const {
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return _stream->size() * 8;
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}
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} // End of namespace Common
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102
common/bitstream.h
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102
common/bitstream.h
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@ -0,0 +1,102 @@
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/* 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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/** A bit stream. */
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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. */
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virtual uint32 getBit() = 0;
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/** Read a number of bits. */
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virtual uint32 getBits(uint32 n) = 0;
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/** Adding another bit. */
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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. */
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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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/** A big endian bit stream. */
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class BitStreamBE : public BitStream {
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public:
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BitStreamBE(SeekableReadStream &stream, uint32 bitCount);
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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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uint32 getBits(uint32 n);
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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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/** A 32bit little endian bit stream. */
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class BitStream32LE : public BitStream {
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public:
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BitStream32LE(SeekableReadStream &stream, uint32 bitCount);
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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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uint32 getBits(uint32 n);
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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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@ -2,6 +2,7 @@ MODULE := common
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MODULE_OBJS := \
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archive.o \
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bitstream.o \
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config-file.o \
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config-manager.o \
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dcl.o \
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