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Diffstat (limited to 'main.cc')
| -rw-r--r-- | main.cc | 114 |
1 files changed, 114 insertions, 0 deletions
@@ -0,0 +1,114 @@ +/* Lzd - Educational decompressor for lzip files + Copyright (C) 2013 Antonio Diaz Diaz. + + This program is free software: you have unlimited permission + to copy, distribute and modify it. + + 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. +*/ +/* + Return values: 0 for a normal exit, 1 for environmental problems + (file not found, invalid flags, I/O errors, etc), 2 to indicate a + corrupt or invalid input file. +*/ + +#include <algorithm> +#include <cerrno> +#include <cstdio> +#include <cstdlib> +#include <cstring> +#include <stdint.h> +#include <unistd.h> +#if defined(__MSVCRT__) || defined(__OS2__) +#include <io.h> +#endif + +#include "decoder.cc" + + +enum { min_dictionary_size = 1 << 12, + max_dictionary_size = 1 << 29 }; + +typedef uint8_t File_header[6]; // 0-3 magic, 4 version, 5 coded_dict_size + +typedef uint8_t File_trailer[20]; + // 0-3 CRC32 of the uncompressed data + // 4-11 size of the uncompressed data + // 12-19 member size including header and trailer + + +int main( const int argc, const char * const argv[] ) + { + if( argc > 1 ) + { + std::printf( "Lzd %s - Educational decompressor for lzip files.\n", + PROGVERSION ); + std::printf( "Study the source to learn how a simple lzip decompressor works.\n" + "It is not safe to use it for any real work.\n" + "\nUsage: %s < file.lz > file\n", argv[0] ); + std::printf( "Lzd decompresses from standard input to standard output.\n" + "\nCopyright (C) 2013 Antonio Diaz Diaz.\n" + "This is free software: you are free to change and redistribute it.\n" + "There is NO WARRANTY, to the extent permitted by law.\n" + "Report bugs to lzip-bug@nongnu.org\n" + "Lzip home page: http://www.nongnu.org/lzip/lzip.html\n" ); + return 0; + } + +#if defined(__MSVCRT__) || defined(__OS2__) + setmode( STDIN_FILENO, O_BINARY ); + setmode( STDOUT_FILENO, O_BINARY ); +#endif + + if( isatty( STDIN_FILENO ) ) + { + std::fprintf( stderr, "I won't read compressed data from a terminal.\n" + "Try '%s --help' for more information.\n", argv[0] ); + return 1; + } + + for( bool first_member = true; ; first_member = false ) + { + File_header header; + for( int i = 0; i < 6; ++i ) + header[i] = std::getc( stdin ); + if( std::feof( stdin ) || std::memcmp( header, "LZIP", 4 ) != 0 ) + { + if( first_member ) + { std::fprintf( stderr, "Bad magic number (file not in lzip format)\n" ); + return 2; } + break; + } + if( header[4] != 1 ) + { + std::fprintf( stderr, "Version %d member format not supported.\n", + header[4] ); + return 2; + } + unsigned dict_size = 1 << ( header[5] & 0x1F ); + dict_size -= ( dict_size / 16 ) * ( ( header[5] >> 5 ) & 7 ); + if( dict_size < min_dictionary_size || dict_size > max_dictionary_size ) + { std::fprintf( stderr, "Invalid dictionary size in member header\n" ); + return 2; } + + LZ_decoder decoder( dict_size ); + if( !decoder.decode_member() ) + { std::fprintf( stderr, "Data error\n" ); return 2; } + + File_trailer trailer; + for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin ); + unsigned crc = 0; + for( int i = 3; i >= 0; --i ) { crc <<= 8; crc += trailer[i]; } + unsigned long long data_size = 0; + for( int i = 11; i >= 4; --i ) { data_size <<= 8; data_size += trailer[i]; } + if( crc != decoder.crc() || data_size != decoder.data_position() ) + { std::fprintf( stderr, "CRC error\n" ); return 2; } + } + + if( std::fclose( stdout ) != 0 ) + { std::fprintf( stderr, "Can't close stdout: %s\n", std::strerror( errno ) ); + return 1; } + return 0; + } |