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https://github.com/libretro/scummvm.git
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104 lines
2.4 KiB
C++
104 lines
2.4 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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#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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void Decompressor::init(Common::ReadStream &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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_input = &input;
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_output = &output;
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}
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bool Decompressor::readByte(byte &b) {
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b = _input->readByte();
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if (_input->eos())
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return false;
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if (_input->err())
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error("Read error encountered during decompression");
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b -= _val++;
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return true;
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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::ReadStream &input, Common::MemoryWriteStream &output) {
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init(input, output);
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uint16 bits = 0;
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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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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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