fdstream.hpp

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/*
 * This file is part of Algorithms library toolkit.
 * Copyright (C) 2017 Jan Travnicek (jan.travnicek@fit.cvut.cz)
 
 * Algorithms library toolkit 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 3 of the License, or
 * (at your option) any later version.
 
 * Algorithms library toolkit 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 Algorithms library toolkit.  If not, see <http://www.gnu.org/licenses/>.
 */
 
/*
 * \brief
 * ofdstream takes a primary file descriptor (fd) and fallback file descriptor by constructor to use for output
 * if the primary fd is not valid for any reason, ofdstream will try to use fallback fd, if even fallback fd is not valid, ofdstream sets its state to ios::fail
 * if the primary fd (or fallback fd) is valid , it is used for successive buffered output
 *
 * supplied file descriptor has to be already open in order for ofdstream to work
 * ofdstream does not close the file descriptor and does not change internal flags of the file descriptor during the lifetime of ofdstream and during destruction of ofdstream
 *
 * typical use is to use as primary fd some arbitrary fd (5) and for fallback fd some standard fd (2) if we wish to see the output
 */
 
#pragma once
 
#include <unistd.h>
#include <fcntl.h>
#include <ostream>
#include <istream>
#include <array>
#include <ext/ostream>
 
namespace ext {
 
extern const int CERR_FD;
 
extern const int CMEASURE_FD;
 
extern const int CLOG_FD;
 
extern const int FAIL_FD;
 
class fdstreambuf final : public std::streambuf {
    static const size_t buff_sz = 512;
 
    int fd;
 
    std::array < char_type, buff_sz > buff;
 
    bool flush ( );
 
protected:
    int_type pbackfail ( int_type ) override;
 
    int_type underflow ( ) override;
 
    int_type overflow ( int_type ) override;
 
    int sync ( ) override;
 
public:
    explicit fdstreambuf ( int fileDescriptor );
 
    ~fdstreambuf ( ) override;
 
    fdstreambuf ( const fdstreambuf & ) = delete;
 
    fdstreambuf & operator =( const fdstreambuf & ) = delete;
};
 
class fdaccessor {
    int fd;
 
    bool redirected;
 
public:
    explicit fdaccessor ( int, int );
 
    int get_fd ( ) const;
 
    bool is_redirected ( ) const;
};
 
class ofdstream : public ext::ostream {
    fdaccessor fda;
 
    fdstreambuf fdbuf;
 
public:
    explicit ofdstream ( int fd, int fallback_fd = FAIL_FD);
 
    ~ofdstream ( ) override;
 
    bool is_redirected ( ) const;
};
 
class ifdstream : public std::istream {
    fdaccessor fda;
 
    fdstreambuf fdbuf;
 
public:
    explicit ifdstream ( int, int = FAIL_FD);
 
    ~ifdstream ( ) override;
 
    bool is_redirected ( ) const;
};
 
} /* namespace ext */