Disk ARchive 2.4.2
escape.hpp
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00001 /*********************************************************************/
00002 // dar - disk archive - a backup/restoration program
00003 // Copyright (C) 2002-2052 Denis Corbin
00004 //
00005 // This program is free software; you can redistribute it and/or
00006 // modify it under the terms of the GNU General Public License
00007 // as published by the Free Software Foundation; either version 2
00008 // of the License, or (at your option) any later version.
00009 //
00010 // This program is distributed in the hope that it will be useful,
00011 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00012 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00013 // GNU General Public License for more details.
00014 //
00015 // You should have received a copy of the GNU General Public License
00016 // along with this program; if not, write to the Free Software
00017 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
00018 //
00019 // to contact the author : http://dar.linux.free.fr/email.html
00020 /*********************************************************************/
00021 // $Id: escape.hpp,v 1.25 2011/04/17 18:43:39 edrusb Rel $
00022 //
00023 /*********************************************************************/
00024 
00040 
00041 
00042 #ifndef ESCAPE_HPP
00043 #define ESCAPE_HPP
00044 
00045 #include "../my_config.h"
00046 
00047 extern "C"
00048 {
00049 #if HAVE_LIMITS_H
00050 #include <limits.h>
00051 #endif
00052 }
00053 
00054 #include <set>
00055 
00056 #include "generic_file.hpp"
00057 
00058 #define ESCAPE_FIXED_SEQUENCE_NORMAL 0xAD
00059 #define ESCAPE_FIXED_SEQUENCE_SPARSE_FILE 0xAE
00060 
00061 #define MAX_BUFFER_SIZE 204800
00062 #ifdef SSIZE_MAX
00063 #if SSIZE_MAX < MAX_BUFFER_SIZE
00064 #undef MAX_BUFFER_SIZE
00065 #define MAX_BUFFER_SIZE SSIZE_MAX
00066 #endif
00067 #endif
00068 
00069 namespace libdar
00070 {
00071 
00074 
00075     class escape : public generic_file
00076     {
00077     public:
00078         enum sequence_type
00079         {
00080             seqt_undefined,       //< not enough data to define the type of the escape sequence
00081             seqt_not_a_sequence,  //< to escape data corresponding to an escape sequence's fixed byte sequence
00082             seqt_file,            //< placed before inode information, eventually followed by file data
00083             seqt_ea,              //< placed before EA data
00084             seqt_catalogue,       //< placed before the archive's internal catalogue
00085             seqt_data_name,       //< placed before the archive data_name (at the beginning of the archive)
00086             seqt_file_crc,        //< placed before the CRC of file's data
00087             seqt_ea_crc,          //< placed before the CRC of file's EA
00088             seqt_changed,         //< placed before new copy of file's data if file's data changed while reading it for backup
00089             seqt_dirty,           //< placed after data CRC if file is dirty
00090             seqt_failed_backup    //< placed after inode information if the file could not be openned at backup time
00091         };
00092 
00093             // the archive layout of marks is :
00094             // ... <seqt_file> <inode> [<file data> [<seqt_changed> <new copy of data> [...] ] <seqt_file_crc> <CRC>[<seqt_dirty>]] [<seqt_ea> <EA> <sqt_ea_crc> <CRC>] ...
00095             // this previous sequence that we will call <SEQ> is repeated for each file, then on the overall archive we have :
00096             // <seqt_data_name> <data_name> <SEQ> ... <SEQ> <seqt_catalogue> <catalogue> <terminator>
00097 
00098             // the provided "below" object must exist during the whole live of the escape object, the escape object does not own this "below" object
00099             // it must be destroyed by the caller/creator of the escape object.
00100 
00101 
00102             // constructors & destructors
00103 
00104         escape(generic_file *below,                           //< "Below" is the generic file that holds the escaped data
00105                const std::set<sequence_type> & x_unjumpable); //< a set of marks that can never been jumped over when skipping for the next mark of a any given type.
00106         escape(const escape & ref) : generic_file(ref) { copy_from(ref); };
00107         const escape & operator = (const escape & ref);
00108         ~escape();
00109 
00110             // escape specific routines
00111 
00112         void add_mark_at_current_position(sequence_type t);
00113 
00115 
00120         bool skip_to_next_mark(sequence_type t, bool jump);
00121         bool next_to_read_is_mark(sequence_type t);
00122         bool next_to_read_is_which_mark(sequence_type & t);
00123 
00124         void add_unjumpable_mark(sequence_type t) { if(is_terminated()) throw SRC_BUG; unjumpable.insert(t); };
00125         void remove_unjumpable_mark(sequence_type t);
00126         bool is_unjumpable_mark(sequence_type t) const { return unjumpable.find(t) != unjumpable.end(); };
00127         void clear_all_unjumpable_marks() { unjumpable.clear(); };
00128 
00129             // generic_file inherited routines
00130             // NOTA: Nothing is done to prevent skip* operation to put the read cursor in the middle of an escape sequence and
00131             // thus incorrectly consider it as normal data. Such event should only occure upon archive corruption and will be detected
00132             // by checksum mechanisms.
00133 
00134         bool skip(const infinint & pos);
00135         bool skip_to_eof();
00136         bool skip_relative(S_I x);
00137         infinint get_position();
00138 
00139         generic_file *get_below() const { return x_below; };
00140 
00141     protected:
00142         U_I inherited_read(char *a, U_I size);
00143         void inherited_write(const char *a, U_I size);
00144         void inherited_sync_write() { flush_write(); };
00145         void inherited_terminate() { flush_or_clean(); };
00146 
00147         void change_fixed_escape_sequence(unsigned char value) { fixed_sequence[0] = value; };
00148         bool has_escaped_data_since_last_skip() const { return escaped_data_count_since_last_skip > 0; };
00149 
00150     private:
00151 
00152             //-- constants
00153 
00155         static const U_I ESCAPE_SEQUENCE_LENGTH = 6;
00156         static const U_I WRITE_BUFFER_SIZE = 2*ESCAPE_SEQUENCE_LENGTH;
00157         static const U_I READ_BUFFER_SIZE = MAX_BUFFER_SIZE;
00158 
00160 
00166         static const unsigned char usual_fixed_sequence[ESCAPE_SEQUENCE_LENGTH];
00167 
00168             //-- variables
00169 
00170         generic_file *x_below;        //< the generic_file in which we read/write escaped data from/to the object is not owned by "this"
00171         U_I write_buffer_size;        //< amount of data in write transit not yet written to "below" (may have to be escaped)
00172         char write_buffer[WRITE_BUFFER_SIZE]; //< data in write transit, all data is unescaped, up to the first real mark, after it, data is raw (may be escaped)
00173                                               //< the first real mark is pointed to by escape_seq_offset_in_buffer
00174         U_I read_buffer_size;         //< amount of data in write transit, read from below, but not yet unescaped and returned to the upper layer
00175         U_I already_read;             //< data in buffer that has already returned to the upper layer
00176         bool read_eof;                //< whether we reached a escape sequence while reading data
00177         U_I escape_seq_offset_in_buffer; //< location of the first escape sequence which is not a data sequence
00178         char read_buffer[READ_BUFFER_SIZE]; //< data in read transit
00179         std::set<sequence_type> unjumpable; //< list of mark that cannot be jumped over when searching for the next mark
00180         unsigned char fixed_sequence[ESCAPE_SEQUENCE_LENGTH]; // the preambule of an escape sequence to use/search for
00181         infinint escaped_data_count_since_last_skip;
00182 
00183             //-- routines
00184 
00185         void set_fixed_sequence_for(sequence_type t) { fixed_sequence[ESCAPE_SEQUENCE_LENGTH - 1] = type2char(t); };
00186         void check_below() { if(x_below == NULL) throw SRC_BUG; };
00187         void clean_data() { read_buffer_size = already_read = escape_seq_offset_in_buffer = 0; }; //< drops all in-transit data
00188         void flush_write();                                                                       //< write down to "below" all in-transit data
00189         void flush_or_clean()
00190         {
00191             switch(get_mode())
00192             {
00193             case gf_read_only:
00194                 clean_data();
00195                 break;
00196             case gf_write_only:
00197                 flush_write();
00198                 break;
00199             default:
00200                 throw SRC_BUG;
00201             }
00202         };
00203         void copy_from(const escape & ref);
00204         bool mini_read_buffer(); //< returns true if it could end having at least ESCAPE_SEQUENCE_LENGTH bytes in read_buffer, false else (EOF reached).
00205 
00206             //-- static routine(s)
00207 
00208             // some convertion routines
00209         static char type2char(sequence_type x);
00210         static sequence_type char2type(char x);
00211 
00213 
00215 
00218         static U_I trouve_amorce(const char *a, U_I size, const unsigned char escape_sequence[ESCAPE_SEQUENCE_LENGTH]);
00219 
00221 
00228         static U_I remove_data_marks_and_stop_at_first_real_mark(char *a, U_I size, U_I & delta, const unsigned char escape_sequence[ESCAPE_SEQUENCE_LENGTH]);
00229     };
00230 
00232 
00233 } // end of namespace
00234 
00235 #endif
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