escape.hpp

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/*********************************************************************/
// dar - disk archive - a backup/restoration program
// Copyright (C) 2002-2024 Denis Corbin
//
// 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, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// to contact the author, see the AUTHOR file
/*********************************************************************/



#ifndef ESCAPE_HPP
#define ESCAPE_HPP

#include "../my_config.h"

extern "C"
{
#if HAVE_LIMITS_H
#include <limits.h>
#endif
}

#include <set>

#include "generic_file.hpp"

#define ESCAPE_FIXED_SEQUENCE_NORMAL 0xAD
#define ESCAPE_FIXED_SEQUENCE_SPARSE_FILE 0xAE

#define MAX_BUFFER_SIZE 102400
#ifdef SSIZE_MAX
#if SSIZE_MAX < MAX_BUFFER_SIZE
#undef MAX_BUFFER_SIZE
#define MAX_BUFFER_SIZE SSIZE_MAX
#endif
#endif

namespace libdar
{


    class escape : public generic_file
    {
    public:
    enum sequence_type
    {
        seqt_undefined,       
        seqt_not_a_sequence,  
        seqt_file,            
        seqt_ea,              
        seqt_catalogue,       
        seqt_data_name,       
        seqt_file_crc,        
        seqt_ea_crc,          
        seqt_changed,         
        seqt_dirty,           
        seqt_failed_backup,   
        seqt_fsa,             
        seqt_fsa_crc,         
        seqt_delta_sig,       
        seqt_in_place         
    };

        // the archive layout of marks is for each entry:
        // #seqt_file# <inode> [<file data> [#seqt_changed# <new copy of data> [...] ] #seqt_file_crc# <CRC>[#seqt_dirty#]] [#seqt_ea# <EA> #seqt_ea_crc# <CRC>]
        // this previous sequence that we will call <SEQ> is repeated for each file, then on the overall archive we have :
        // #seqt_data_name# <data_name> <SEQ> ... <SEQ> #seqt_catalogue# <catalogue> <terminator>

        // the provided "below" object must exist during the whole live of the escape object,
        // the escape object does not own this "below" object
        // it must be destroyed by the caller/creator of the escape object.


        // constructors & destructors

    escape(generic_file *below,                           
           const std::set<sequence_type> & x_unjumpable   
          );
    escape(const escape & ref) : generic_file(ref) { copy_from(ref); };
    escape(escape && ref) noexcept : generic_file(std::move(ref)) { nullifyptr(); move_from(std::move(ref)); };
    escape & operator = (const escape & ref);
    escape & operator = (escape && ref) noexcept { generic_file::operator = (std::move(ref)); move_from(std::move(ref)); return *this; };
    ~escape();

        // escape specific routines

    void add_mark_at_current_position(sequence_type t);


    bool skip_to_next_mark(sequence_type t, bool jump);
    bool next_to_read_is_mark(sequence_type t);
    bool next_to_read_is_which_mark(sequence_type & t);

    void add_unjumpable_mark(sequence_type t) { if(is_terminated()) throw SRC_BUG; unjumpable.insert(t); };
    void remove_unjumpable_mark(sequence_type t);
    bool is_unjumpable_mark(sequence_type t) const { return unjumpable.find(t) != unjumpable.end(); };
    void clear_all_unjumpable_marks() { unjumpable.clear(); };


        // generic_file inherited routines
        // NOTA: Nothing is done to prevent skip* operation to put the read cursor in the middle of an escape sequence and
        // thus incorrectly consider it as normal data. Such event should only occure upon archive corruption and will be detected
        // by checksum mechanisms.

    virtual bool skippable(skippability direction, const infinint & amount) override;
    virtual bool skip(const infinint & pos) override;
    virtual bool skip_to_eof() override;
    virtual bool skip_relative(S_I x) override;
    virtual bool truncatable(const infinint & pos) const override { return x_below->truncatable(pos); };
    virtual infinint get_position() const override;

    protected:
    virtual void inherited_read_ahead(const infinint & amount) override;
    virtual U_I inherited_read(char *a, U_I size) override;
    virtual void inherited_write(const char *a, U_I size) override;
    virtual void inherited_truncate(const infinint & pos) override;
    virtual void inherited_sync_write() override { flush_write(); };
    virtual void inherited_flush_read() override { flush_write(); clean_read(); };
    virtual void inherited_terminate() override { flush_or_clean(); };

    void change_fixed_escape_sequence(unsigned char value) { fixed_sequence[0] = value; };
    bool has_escaped_data_since_last_skip() const { return escaped_data_count_since_last_skip > 0; };

    private:

        //-- constants

    static constexpr U_I ESCAPE_SEQUENCE_LENGTH = 6;
    static constexpr U_I INITIAL_WRITE_BUFFER_SIZE = 2*ESCAPE_SEQUENCE_LENGTH;
    static constexpr U_I INITIAL_READ_BUFFER_SIZE = MAX_BUFFER_SIZE;
    static const infinint READ_BUFFER_SIZE_INFININT;


    static const unsigned char usual_fixed_sequence[ESCAPE_SEQUENCE_LENGTH];

        //-- variables

    generic_file *x_below;                
    U_I write_buffer_size;                
    char write_buffer[INITIAL_WRITE_BUFFER_SIZE]; 
    U_I already_read;                     
    bool read_eof;                        
    U_I escape_seq_offset_in_buffer;      
    char* read_buffer;                    
    U_I read_buffer_size;                 
    U_I read_buffer_alloc;                
    std::set<sequence_type> unjumpable;   
    unsigned char fixed_sequence[ESCAPE_SEQUENCE_LENGTH]; 
    infinint escaped_data_count_since_last_skip;
    infinint below_position;              

        //-- routines

    void set_fixed_sequence_for(sequence_type t) { fixed_sequence[ESCAPE_SEQUENCE_LENGTH - 1] = type2char(t); };
    void check_below() const { if(x_below == nullptr) throw SRC_BUG; };
    void clean_read();  
    void flush_write(); 
    void flush_or_clean()
    {
        switch(get_mode())
        {
        case gf_read_only:
        clean_read();
        break;
        case gf_write_only:
        case gf_read_write:
        flush_write();
        break;
        default:
        throw SRC_BUG;
        }
    };
    void nullifyptr() noexcept { x_below = nullptr; };
    void copy_from(const escape & ref);
    void move_from(escape && ref) noexcept;
    bool mini_read_buffer(); 

        //-- static routine(s)

        // some convertion routines
    static char type2char(sequence_type x);
    static sequence_type char2type(char x);



    static U_I trouve_amorce(const char *a, U_I size, const unsigned char escape_sequence[ESCAPE_SEQUENCE_LENGTH]);


    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]);
    };


} // end of namespace

#endif