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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;
}
};
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