generic_file.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 GENERIC_FILE_HPP
#define GENERIC_FILE_HPP

#include "../my_config.h"

extern "C"
{
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
} // end extern "C"

#include "proto_generic_file.hpp"
#include "integers.hpp"
#include "crc.hpp"
#include "infinint.hpp"
#include "gf_mode.hpp"

#include <string>

namespace libdar
{



    class generic_file: public proto_generic_file
    {
    public :
        generic_file(gf_mode m) { rw = m; terminated = no_read_ahead = false; enable_crc(false); checksum = nullptr; };

    generic_file(const generic_file &ref) { copy_from(ref); };

    generic_file(generic_file && ref) noexcept { nullifyptr(); move_from(std::move(ref)); };

    generic_file & operator = (const generic_file & ref) { destroy(); copy_from(ref); return *this; };

    generic_file & operator = (generic_file && ref) noexcept { move_from(std::move(ref)); return *this; };


        ~generic_file() noexcept(false) { destroy(); };

    void terminate();

    bool operator == (generic_file & ref);
    bool operator != (generic_file & ref) { return ! (*this == ref); };

        gf_mode get_mode() const { return rw; };

    void read_ahead(const infinint & amount);

    void ignore_read_ahead(bool mode) { no_read_ahead = mode; };

        virtual U_I read(char *a, U_I size) override;

        virtual void write(const char *a, U_I size) override;


        void write(const std::string & arg);

        S_I read_back(char &a);

    S_I read_forward(char &a) { if(terminated) throw SRC_BUG; return read(&a, 1); };


    enum skippability { skip_backward, skip_forward };


    virtual bool skippable(skippability direction, const infinint & amount) = 0;


        virtual bool skip(const infinint & pos) = 0;

        virtual bool skip_to_eof() = 0;

        virtual bool skip_relative(S_I x) = 0;


    virtual bool truncatable(const infinint & pos) const = 0;


    virtual void truncate(const infinint & pos);

        virtual infinint get_position() const = 0;

        virtual void copy_to(generic_file &ref);


        virtual void copy_to(generic_file &ref, const infinint & crc_size, crc * & value);

        U_32 copy_to(generic_file &ref, U_32 size); // returns the number of byte effectively copied

        infinint copy_to(generic_file &ref, infinint size); // returns the number of byte effectively copied


        bool diff(generic_file & f,
          const infinint & me_read_ahead,
          const infinint & you_read_ahead,
          const infinint & crc_size,
          crc * & value);

    bool diff(generic_file & f,
          const infinint & me_read_ahead,
          const infinint & you_read_ahead,
          const infinint & crc_size,
          crc * & value,
          infinint & err_offset);


        void reset_crc(const infinint & width);

    bool crc_status() const { return active_read == &generic_file::read_crc; };


        crc *get_crc();

    void sync_write();

    void flush_read();


    protected :
        void set_mode(gf_mode x) { rw = x; };


    virtual void inherited_read_ahead(const infinint & amount) = 0;



        virtual U_I inherited_read(char *a, U_I size) = 0;


        virtual void inherited_write(const char *a, U_I size) = 0;


    virtual void inherited_truncate(const infinint & pos) = 0;



    virtual void inherited_sync_write() = 0;


    virtual void inherited_flush_read() = 0;


    virtual void inherited_terminate() = 0;


    bool is_terminated() const { return terminated; };

    private :
        gf_mode rw;
        crc *checksum;
    bool terminated;
    bool no_read_ahead;
        U_I (generic_file::* active_read)(char *a, U_I size);
        void (generic_file::* active_write)(const char *a, U_I size);

        void enable_crc(bool mode);

        U_I read_crc(char *a, U_I size);
        void write_crc(const char *a, U_I size);
    void destroy();
    void nullifyptr() noexcept { checksum = nullptr; };
    void copy_from(const generic_file & ref);
    void move_from(generic_file && ref) noexcept;
    };


} // end of namespace

#endif