tee_stdio_filebuf.hh

/* tee_stdio_filebuf.hh - a stdio_filebuf that behaves as tee(1)
 *
 * Copyright (C) Javier Lopez-Gomez, 2016
 *
 * 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.
 */

#include <ext/stdio_filebuf.h>

template <typename _CharT, typename _Traits = std::char_traits<_CharT>>
class tee_stdio_filebuf : public __gnu_cxx::stdio_filebuf<_CharT, _Traits> {
protected:
  typedef __gnu_cxx::stdio_filebuf<_CharT, _Traits> filebuf_type;
  std::ostream _out;

  typename filebuf_type::int_type underflow() {
    auto ret = filebuf_type::underflow();
    _out.write(filebuf_type::gptr(), filebuf_type::egptr() - filebuf_type::gptr());
    return ret;
  }

public:
  /**
   *  @param  _fd  An open file descriptor.
   *  @param  _mode  Same meaning as in a standard filebuf.
   *  @param  _obuf The std::basic_filebuf to write if a read from this
   *      filebuf is attempted
   *
   *  This constructor associates a file stream buffer with an open
   *  POSIX file descriptor; a read from this filebuf will cause the read
   *  buffer to be written to _obuf. The file descriptor will be
   *  automatically closed when the stdio_filebuf is closed/destroyed.
   */
  tee_stdio_filebuf(int _fd, std::ios_base::openmode _mode, std::basic_filebuf<_CharT, _Traits> &_obuf)
      : filebuf_type(_fd, _mode), _out(&_obuf) {}
};