FIFE
2008.0
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00001 /*************************************************************************** 00002 * Copyright (C) 2005-2008 by the FIFE team * 00003 * http://www.fifengine.de * 00004 * This file is part of FIFE. * 00005 * * 00006 * FIFE is free software; you can redistribute it and/or * 00007 * modify it under the terms of the GNU Lesser General Public * 00008 * License as published by the Free Software Foundation; either * 00009 * version 2.1 of the License, or (at your option) any later version. * 00010 * * 00011 * This library is distributed in the hope that it will be useful, * 00012 * but WITHOUT ANY WARRANTY; without even the implied warranty of * 00013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * 00014 * Lesser General Public License for more details. * 00015 * * 00016 * You should have received a copy of the GNU Lesser General Public * 00017 * License along with this library; if not, write to the * 00018 * Free Software Foundation, Inc., * 00019 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * 00020 ***************************************************************************/ 00021 00022 // Standard C++ library includes 00023 #include <algorithm> 00024 00025 // 3rd party library includes 00026 00027 // FIFE includes 00028 #include "vfs/raw/rawdata.h" 00029 #include "util/base/exception.h" 00030 00031 #include "lzssdecoder.h" 00032 00033 // just a quick&dirty wrapper around anchorites implementation - needs to be replaced with our own LZSS implementation 00034 namespace FIFE { 00035 00036 LZSSDecoder::LZSSDecoder() {} 00037 LZSSDecoder::~LZSSDecoder() {} 00038 00039 00040 void LZSSDecoder::decode(RawData* input, uint8_t* output, const uint32_t outputsize) { 00041 00042 m_outindex = 0; 00043 m_outlen = outputsize; 00044 00045 while (m_outindex < outputsize) { 00046 uint16_t blockdesc = input->read16Big(); 00047 uint16_t bytesToRead = blockdesc & 0x7fff; 00048 00049 if (blockdesc & 0x8000) { // uncompressed 00050 input->readInto(output + m_outindex, bytesToRead); 00051 m_outindex += bytesToRead; 00052 } else { 00053 // Allocate +2 bytes so that on corrupt data the LZSS 00054 // decoder won't crash the input buffer. 00055 std::vector<uint8_t> indata(bytesToRead + 2); 00056 input->readInto(&indata[0], bytesToRead); 00057 LZSSDecode(&indata[0], bytesToRead, output); 00058 // Note outindex is advanced inside LZSSDecode. 00059 } 00060 00061 } 00062 } 00063 00064 void LZSSDecoder::LZSSDecode(uint8_t* in , long len, uint8_t* out) { 00065 const long c_nRingBufferSize = 4096; 00066 const long c_nMatchLengthUpperLimit = 18; 00067 const long c_nThreshold = 2; 00068 00069 char buffer[c_nRingBufferSize + c_nMatchLengthUpperLimit - 1]; 00070 int ibuf = 0; 00071 int c; 00072 00073 int i; 00074 int j; 00075 int k; 00076 int r; 00077 00078 unsigned int flags; 00079 00080 for (i = 0; i < c_nRingBufferSize - c_nMatchLengthUpperLimit; i++) { 00081 buffer[i] = ' '; 00082 } 00083 00084 r = c_nRingBufferSize - c_nMatchLengthUpperLimit; 00085 flags = 0; 00086 while ( ibuf < len ) { 00087 if (((flags >>= 1) & 256) == 0) { 00088 c = in[ibuf++]; 00089 flags = c | 0xff00;/* uses higher byte cleverly to count eight */ 00090 } 00091 00092 if (flags & 1) { 00093 c = in[ibuf++]; 00094 out[m_outindex++] = c; 00095 00096 buffer[r++] = c; 00097 r &= (c_nRingBufferSize - 1); 00098 } else { 00099 i = in[ibuf++]; 00100 j = in[ibuf++]; 00101 00102 i |= ((j & 0xf0) << 4); 00103 j = (j & 0x0f) + c_nThreshold; 00104 00105 for (k = 0; k <= j; k++) { 00106 c = buffer[(i + k) & (c_nRingBufferSize - 1)]; 00107 00108 out[m_outindex++] = c; 00109 00110 buffer[r++] = c; 00111 r &= (c_nRingBufferSize - 1); 00112 } 00113 } 00114 } 00115 } 00116 00117 00118 }