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