112 lines
2.9 KiB
C++
112 lines
2.9 KiB
C++
/* Tarlz - Archiver with multimember lzip compression
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Copyright (C) 2013-2018 Antonio Diaz Diaz.
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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 2 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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#ifndef LZ_API_VERSION
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#define LZ_API_VERSION 1
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#endif
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enum {
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min_dictionary_bits = 12,
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min_dictionary_size = 1 << min_dictionary_bits,
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max_dictionary_bits = 29,
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max_dictionary_size = 1 << max_dictionary_bits,
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min_member_size = 36 };
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class CRC32
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{
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uint32_t data[256]; // Table of CRCs of all 8-bit messages.
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public:
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CRC32()
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{
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for( unsigned n = 0; n < 256; ++n )
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{
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unsigned c = n;
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for( int k = 0; k < 8; ++k )
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{ if( c & 1 ) c = 0xEDB88320U ^ ( c >> 1 ); else c >>= 1; }
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data[n] = c;
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}
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}
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void update_byte( uint32_t & crc, const uint8_t byte ) const
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{ crc = data[(crc^byte)&0xFF] ^ ( crc >> 8 ); }
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};
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inline bool isvalid_ds( const unsigned dictionary_size )
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{ return ( dictionary_size >= min_dictionary_size &&
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dictionary_size <= max_dictionary_size ); }
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const uint8_t lzip_magic[5] = { 0x4C, 0x5A, 0x49, 0x50, 1 }; // "LZIP\1"
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struct Lzip_header
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{
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uint8_t data[6]; // 0-3 magic bytes
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// 4 version
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// 5 coded_dict_size
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enum { size = 6 };
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bool verify_magic() const
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{ return ( std::memcmp( data, lzip_magic, 5 ) == 0 ); }
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bool verify_prefix( const int sz ) const // detect (truncated) header
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{
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for( int i = 0; i < sz && i < 5; ++i )
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if( data[i] != lzip_magic[i] ) return false;
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return ( sz > 0 );
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}
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unsigned dictionary_size() const
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{
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unsigned sz = ( 1 << ( data[5] & 0x1F ) );
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if( sz > min_dictionary_size )
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sz -= ( sz / 16 ) * ( ( data[5] >> 5 ) & 7 );
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return sz;
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}
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};
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struct Lzip_trailer
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{
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uint8_t data[20]; // 0-3 CRC32 of the uncompressed data
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// 4-11 size of the uncompressed data
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// 12-19 member size including header and trailer
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enum { size = 20 };
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unsigned data_crc() const
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{
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unsigned tmp = 0;
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for( int i = 3; i >= 0; --i ) { tmp <<= 8; tmp += data[i]; }
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return tmp;
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}
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unsigned long long data_size() const
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{
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unsigned long long tmp = 0;
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for( int i = 11; i >= 4; --i ) { tmp <<= 8; tmp += data[i]; }
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return tmp;
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}
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unsigned long long member_size() const
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{
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unsigned long long tmp = 0;
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for( int i = 19; i >= 12; --i ) { tmp <<= 8; tmp += data[i]; }
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return tmp;
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}
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};
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