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https://github.com/libretro/scummvm.git
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df10ff8ac3
With the new optimizations, the decompressor will read exactly one byte past the end of its input. This commit makes the input buffer one byte longer to compensate for that.
126 lines
3.0 KiB
C++
126 lines
3.0 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 modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (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, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "common/memstream.h"
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#include "common/textconsole.h"
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#include "engines/nancy/decompress.h"
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namespace Nancy {
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Decompressor::Decompressor() :
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_bufpos(0),
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_err(false),
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_val(0),
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_output(nullptr),
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_input(nullptr),
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_pos(nullptr),
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_end(nullptr) {}
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Decompressor::~Decompressor() {
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delete[] _input;
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}
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void Decompressor::init(Common::SeekableReadStream &input, Common::WriteStream &output) {
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memset(_buf, ' ', kBufSize);
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_bufpos = kBufStart;
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_err = false;
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_val = 0;
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// We store the input data in a raw buffer, since we need to check if we're at the end of the
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// stream on _every_ read byte. This way we avoid doing a vtable lookup per byte, which makes
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// decompression roughly twice as fast
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delete[] _input;
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_input = new byte[input.size() + 1];
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input.read(_input, input.size());
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_pos = _input;
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_end = _input + input.size();
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_output = &output;
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}
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bool Decompressor::readByte(byte &b) {
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b = *_pos++ - _val++;
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return _pos <= _end;
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}
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bool Decompressor::writeByte(byte b) {
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_output->writeByte(b);
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_buf[_bufpos++] = b;
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_bufpos &= kBufSize - 1;
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return true;
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}
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bool Decompressor::decompress(Common::SeekableReadStream &input, Common::MemoryWriteStream &output) {
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init(input, output);
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uint16 bits = 0;
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if (input.err()) {
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warning("Failed to decompress resource");
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return false;
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}
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while (1) {
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byte b;
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bits >>= 1;
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// The highest 8 bits are used to keep track of how many bits are left to process
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if (!(bits & 0x100)) {
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// Out of bits
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if (!readByte(b))
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break;
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bits = 0xff00 | b;
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}
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if (bits & 1) {
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// Literal byte
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if (!readByte(b))
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break;
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writeByte(b);
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} else {
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// Copy from buffer
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byte b2;
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if (!readByte(b) || !readByte(b2))
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break;
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uint16 offset = b | ((b2 & 0xf0) << 4);
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uint16 len = (b2 & 0xf) + 3;
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for (uint i = 0; i < len; i++)
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writeByte(_buf[(offset + i) & (kBufSize - 1)]);
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}
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}
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if (output.err() || output.pos() != output.size()) {
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// Workaround for nancy3 file "SLN RollPanOpn.avf", which outputs 2 bytes less than it should
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if (output.size() - output.pos() <= 2) {
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return true;
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}
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warning("Failed to decompress resource");
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return false;
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}
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return true;
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}
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} // End of namespace Nancy
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