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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 3 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, see <http://www.gnu.org/licenses/>.
*
*/
#include "common/memstream.h"
#include "common/textconsole.h"
#include "engines/nancy/decompress.h"
namespace Nancy {
Decompressor::Decompressor() :
_bufpos(0),
_err(false),
_val(0),
_output(nullptr),
_input(nullptr),
_pos(nullptr),
_end(nullptr) {}
Decompressor::~Decompressor() {
delete[] _input;
}
void Decompressor::init(Common::SeekableReadStream &input, Common::WriteStream &output) {
memset(_buf, ' ', kBufSize);
_bufpos = kBufStart;
_err = false;
_val = 0;
// We store the input data in a raw buffer, since we need to check if we're at the end of the
// stream on _every_ read byte. This way we avoid doing a vtable lookup per byte, which makes
// decompression roughly twice as fast
delete[] _input;
_input = new byte[input.size() + 1];
input.read(_input, input.size());
_pos = _input;
_end = _input + input.size();
_output = &output;
}
bool Decompressor::readByte(byte &b) {
b = *_pos++ - _val++;
return _pos <= _end;
}
bool Decompressor::writeByte(byte b) {
_output->writeByte(b);
_buf[_bufpos++] = b;
_bufpos &= kBufSize - 1;
return true;
}
bool Decompressor::decompress(Common::SeekableReadStream &input, Common::MemoryWriteStream &output) {
init(input, output);
uint16 bits = 0;
if (input.err()) {
warning("Failed to decompress resource");
return false;
}
while (1) {
byte b;
bits >>= 1;
// The highest 8 bits are used to keep track of how many bits are left to process
if (!(bits & 0x100)) {
// Out of bits
if (!readByte(b))
break;
bits = 0xff00 | b;
}
if (bits & 1) {
// Literal byte
if (!readByte(b))
break;
writeByte(b);
} else {
// Copy from buffer
byte b2;
if (!readByte(b) || !readByte(b2))
break;
uint16 offset = b | ((b2 & 0xf0) << 4);
uint16 len = (b2 & 0xf) + 3;
for (uint i = 0; i < len; i++)
writeByte(_buf[(offset + i) & (kBufSize - 1)]);
}
}
if (output.err() || output.pos() != output.size()) {
// Workaround for nancy3 file "SLN RollPanOpn.avf", which outputs 2 bytes less than it should
if (output.size() - output.pos() <= 2) {
return true;
}
warning("Failed to decompress resource");
return false;
}
return true;
}
} // End of namespace Nancy
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