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diff --git a/lzip_index.cc b/lzip_index.cc
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+/* Lzip - LZMA lossless data compressor
+ Copyright (C) 2008-2024 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/>.
+*/
+
+#define _FILE_OFFSET_BITS 64
+
+#include <algorithm>
+#include <cerrno>
+#include <cstdio>
+#include <cstring>
+#include <string>
+#include <vector>
+#include <stdint.h>
+#include <unistd.h>
+
+#include "lzip.h"
+#include "lzip_index.h"
+
+
+namespace {
+
+int seek_read( const int fd, uint8_t * const buf, const int size,
+ const long long pos )
+ {
+ if( lseek( fd, pos, SEEK_SET ) == pos )
+ return readblock( fd, buf, size );
+ return 0;
+ }
+
+} // end namespace
+
+
+bool Lzip_index::check_header( const Lzip_header & header )
+ {
+ if( !header.check_magic() )
+ { error_ = bad_magic_msg; retval_ = 2; return false; }
+ if( !header.check_version() )
+ { error_ = bad_version( header.version() ); retval_ = 2; return false; }
+ if( !isvalid_ds( header.dictionary_size() ) )
+ { error_ = bad_dict_msg; retval_ = 2; return false; }
+ return true;
+ }
+
+void Lzip_index::set_errno_error( const char * const msg )
+ {
+ error_ = msg; error_ += std::strerror( errno );
+ retval_ = 1;
+ }
+
+void Lzip_index::set_num_error( const char * const msg, unsigned long long num )
+ {
+ char buf[80];
+ snprintf( buf, sizeof buf, "%s%llu", msg, num );
+ error_ = buf;
+ retval_ = 2;
+ }
+
+
+bool Lzip_index::read_header( const int fd, Lzip_header & header,
+ const long long pos, const bool ignore_marking )
+ {
+ if( seek_read( fd, header.data, header.size, pos ) != header.size )
+ { set_errno_error( "Error reading member header: " ); return false; }
+ uint8_t byte;
+ if( !ignore_marking && readblock( fd, &byte, 1 ) == 1 && byte != 0 )
+ { error_ = marking_msg; retval_ = 2; return false; }
+ return true;
+ }
+
+
+// If successful, push last member and set pos to member header.
+bool Lzip_index::skip_trailing_data( const int fd, unsigned long long & pos,
+ const Cl_options & cl_opts )
+ {
+ if( pos < min_member_size ) return false;
+ enum { block_size = 16384,
+ buffer_size = block_size + Lzip_trailer::size - 1 + Lzip_header::size };
+ uint8_t buffer[buffer_size];
+ int bsize = pos % block_size; // total bytes in buffer
+ if( bsize <= buffer_size - block_size ) bsize += block_size;
+ int search_size = bsize; // bytes to search for trailer
+ int rd_size = bsize; // bytes to read from file
+ unsigned long long ipos = pos - rd_size; // aligned to block_size
+
+ while( true )
+ {
+ if( seek_read( fd, buffer, rd_size, ipos ) != rd_size )
+ { set_errno_error( "Error seeking member trailer: " ); return false; }
+ const uint8_t max_msb = ( ipos + search_size ) >> 56;
+ for( int i = search_size; i >= Lzip_trailer::size; --i )
+ if( buffer[i-1] <= max_msb ) // most significant byte of member_size
+ {
+ const Lzip_trailer & trailer =
+ *(const Lzip_trailer *)( buffer + i - trailer.size );
+ const unsigned long long member_size = trailer.member_size();
+ if( member_size == 0 ) // skip trailing zeros
+ { while( i > trailer.size && buffer[i-9] == 0 ) --i; continue; }
+ if( member_size > ipos + i || !trailer.check_consistency() ) continue;
+ Lzip_header header;
+ if( !read_header( fd, header, ipos + i - member_size,
+ cl_opts.ignore_marking ) ) return false;
+ if( !header.check() ) continue;
+ const Lzip_header & header2 = *(const Lzip_header *)( buffer + i );
+ const bool full_h2 = bsize - i >= header.size;
+ if( header2.check_prefix( bsize - i ) ) // last member
+ {
+ if( !full_h2 ) error_ = "Last member in input file is truncated.";
+ else if( check_header( header2 ) )
+ error_ = "Last member in input file is truncated or corrupt.";
+ retval_ = 2; return false;
+ }
+ if( !cl_opts.loose_trailing && full_h2 && header2.check_corrupt() )
+ { error_ = corrupt_mm_msg; retval_ = 2; return false; }
+ if( !cl_opts.ignore_trailing )
+ { error_ = trailing_msg; retval_ = 2; return false; }
+ const unsigned long long data_size = trailer.data_size();
+ if( !cl_opts.ignore_empty && data_size == 0 )
+ { error_ = empty_msg; retval_ = 2; return false; }
+ pos = ipos + i - member_size; // good member
+ const unsigned dictionary_size = header.dictionary_size();
+ if( dictionary_size_ < dictionary_size )
+ dictionary_size_ = dictionary_size;
+ member_vector.push_back( Member( 0, data_size, pos, member_size,
+ dictionary_size ) );
+ return true;
+ }
+ if( ipos == 0 )
+ { set_num_error( "Bad trailer at pos ", pos - Lzip_trailer::size );
+ return false; }
+ bsize = buffer_size;
+ search_size = bsize - Lzip_header::size;
+ rd_size = block_size;
+ ipos -= rd_size;
+ std::memcpy( buffer + rd_size, buffer, buffer_size - rd_size );
+ }
+ }
+
+
+Lzip_index::Lzip_index( const int infd, const Cl_options & cl_opts )
+ : insize( lseek( infd, 0, SEEK_END ) ), retval_( 0 ), dictionary_size_( 0 )
+ {
+ if( insize < 0 )
+ { set_errno_error( "Input file is not seekable: " ); return; }
+ if( insize < min_member_size )
+ { error_ = "Input file is too short."; retval_ = 2; return; }
+ if( insize > INT64_MAX )
+ { error_ = "Input file is too long (2^63 bytes or more).";
+ retval_ = 2; return; }
+
+ Lzip_header header;
+ if( !read_header( infd, header, 0, cl_opts.ignore_marking ) ||
+ !check_header( header ) ) return;
+
+ unsigned long long pos = insize; // always points to a header or to EOF
+ while( pos >= min_member_size )
+ {
+ Lzip_trailer trailer;
+ if( seek_read( infd, trailer.data, trailer.size, pos - trailer.size ) !=
+ trailer.size )
+ { set_errno_error( "Error reading member trailer: " ); break; }
+ const unsigned long long member_size = trailer.member_size();
+ if( member_size > pos || !trailer.check_consistency() ) // bad trailer
+ {
+ if( member_vector.empty() )
+ { if( skip_trailing_data( infd, pos, cl_opts ) ) continue; return; }
+ set_num_error( "Bad trailer at pos ", pos - trailer.size ); break;
+ }
+ if( !read_header( infd, header, pos - member_size, cl_opts.ignore_marking ) )
+ break;
+ if( !header.check() ) // bad header
+ {
+ if( member_vector.empty() )
+ { if( skip_trailing_data( infd, pos, cl_opts ) ) continue; return; }
+ set_num_error( "Bad header at pos ", pos - member_size ); break;
+ }
+ const unsigned long long data_size = trailer.data_size();
+ if( !cl_opts.ignore_empty && data_size == 0 )
+ { error_ = empty_msg; retval_ = 2; break; }
+ pos -= member_size; // good member
+ const unsigned dictionary_size = header.dictionary_size();
+ if( dictionary_size_ < dictionary_size )
+ dictionary_size_ = dictionary_size;
+ member_vector.push_back( Member( 0, data_size, pos, member_size,
+ dictionary_size ) );
+ }
+ if( pos != 0 || member_vector.empty() || retval_ != 0 )
+ {
+ member_vector.clear();
+ if( retval_ == 0 ) { error_ = "Can't create file index."; retval_ = 2; }
+ return;
+ }
+ std::reverse( member_vector.begin(), member_vector.end() );
+ for( unsigned long i = 0; ; ++i )
+ {
+ const long long end = member_vector[i].dblock.end();
+ if( end < 0 || end > INT64_MAX )
+ {
+ member_vector.clear();
+ error_ = "Data in input file is too long (2^63 bytes or more).";
+ retval_ = 2; return;
+ }
+ if( i + 1 >= member_vector.size() ) break;
+ member_vector[i+1].dblock.pos( end );
+ }
+ }