std_sstream.h

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// String based streams -*- C++ -*-

// Copyright (C) 1997, 1998, 1999, 2002, 2003 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
// any later version.

// This library 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 library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

//
// ISO C++ 14882: 27.7  String-based streams
//

/** @file sstream
 *  This is a Standard C++ Library header.  You should @c #include this header
 *  in your programs, rather than any of the "st[dl]_*.h" implementation files.
 */

#ifndef _CPP_SSTREAM
#define _CPP_SSTREAM	1

#pragma GCC system_header

#include <istream>
#include <ostream>

namespace std
{
  // [27.7.1] template class basic_stringbuf
  /**
   *  @brief  The actual work of input and output (for std::string).
   *
   *  This class associates either or both of its input and output sequences
   *  with a sequence of characters, which can be initialized from, or made
   *  available as, a @c std::basic_string.  (Paraphrased from [27.7.1]/1.)
   *
   *  For this class, open modes (of type @c ios_base::openmode) have
   *  @c in set if the input sequence can be read, and @c out set if the
   *  output sequence can be written.
  */
  template<typename _CharT, typename _Traits, typename _Alloc>
    class basic_stringbuf : public basic_streambuf<_CharT, _Traits>
    {
    public:
      // Types:
      typedef _CharT 					char_type;
      typedef _Traits 					traits_type;
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 251. basic_stringbuf missing allocator_type
      typedef _Alloc				       	allocator_type;
#endif
      typedef typename traits_type::int_type 		int_type;
      typedef typename traits_type::pos_type 		pos_type;
      typedef typename traits_type::off_type 		off_type;

      //@{
      /**
       *  @if maint
       *  @doctodo
       *  @endif
      */
      typedef basic_streambuf<char_type, traits_type>  	__streambuf_type;
      typedef basic_string<char_type, _Traits, _Alloc> 	__string_type;
      typedef typename __string_type::size_type		__size_type;
      //@}

    protected:
      // Data Members:
      /**
       *  @if maint
       *  @doctodo
       *  @endif
      */
      __string_type 		_M_string;

    public:
      // Constructors:
      /**
       *  @brief  Starts with an empty string buffer.
       *  @param  mode  Whether the buffer can read, or write, or both.
       *
       *  The default constructor initializes the parent class using its
       *  own default ctor.
      */
      explicit
      basic_stringbuf(ios_base::openmode __mode = ios_base::in | ios_base::out)
      : __streambuf_type(), _M_string()
      { _M_stringbuf_init(__mode); }

      /**
       *  @brief  Starts with an existing string buffer.
       *  @param  str  A string to copy as a starting buffer.
       *  @param  mode  Whether the buffer can read, or write, or both.
       *
       *  This constructor initializes the parent class using its
       *  own default ctor.
      */
      explicit
      basic_stringbuf(const __string_type& __str,
		      ios_base::openmode __mode = ios_base::in | ios_base::out)
      : __streambuf_type(), _M_string(__str.data(), __str.size())
      { _M_stringbuf_init(__mode); }

      // Get and set:
      /**
       *  @brief  Copying out the string buffer.
       *  @return  A copy of one of the underlying sequences.
       *
       *  "If the buffer is only created in input mode, the underlying
       *  character sequence is equal to the input sequence; otherwise, it
       *  is equal to the output sequence." [27.7.1.2]/1
      */
      __string_type
      str() const
      {
	if (_M_mode & ios_base::out)
	  {
	    // This is the deal: _M_string.size() is a value that
	    // represents the size of the initial string that makes
	    // _M_string, and may not be the correct size of the
	    // current stringbuf internal buffer.
	    __size_type __len = _M_string.size();
	    if (_M_out_end > _M_out_beg)
	      __len = max(__size_type(_M_out_end - _M_out_beg), __len);
	    return __string_type(_M_out_beg, _M_out_beg + __len);
	  }
	else
	  return _M_string;
      }

      /**
       *  @brief  Setting a new buffer.
       *  @param  s  The string to use as a new sequence.
       *
       *  Deallocates any previous stored sequence, then copies @a s to
       *  use as a new one.
      */
      void
      str(const __string_type& __s)
      {
	// Cannot use _M_string = __s, since v3 strings are COW.
	_M_string.assign(__s.data(), __s.size());
	_M_stringbuf_init(_M_mode);
      }

    protected:
      // Common initialization code for both ctors goes here.
      /**
       *  @if maint
       *  @doctodo
       *  @endif
      */
      void
      _M_stringbuf_init(ios_base::openmode __mode)
      {
	// _M_buf_size is a convenient alias for "what the streambuf
	// thinks the allocated size of the string really is." This is
	// necessary as ostringstreams are implemented with the
	// streambufs having control of the allocation and
	// re-allocation of the internal string object, _M_string.
	_M_buf_size = _M_string.size();

	// NB: Start ostringstream buffers at 512 bytes. This is an
	// experimental value (pronounced "arbitrary" in some of the
	// hipper english-speaking countries), and can be changed to
	// suit particular needs.
	_M_buf_size_opt = 512;
	_M_mode = __mode;
	if (_M_mode & (ios_base::ate | ios_base::app))
	  _M_really_sync(0, _M_buf_size);
	else
	  _M_really_sync(0, 0);
      }

      // Overridden virtual functions:
      // [documentation is inherited]
      virtual int_type
      underflow()
      {
	if (_M_in_cur && _M_in_cur < _M_in_end)
	  return traits_type::to_int_type(*gptr());
	else
	  return traits_type::eof();
      }

      // [documentation is inherited]
      virtual int_type
      pbackfail(int_type __c = traits_type::eof());

      // [documentation is inherited]
      virtual int_type
      overflow(int_type __c = traits_type::eof());

      /**
       *  @brief  Manipulates the buffer.
       *  @param  s  Pointer to a buffer area.
       *  @param  n  Size of @a s.
       *  @return  @c this
       *
       *  If no buffer has already been created, and both @a s and @a n are
       *  non-zero, then @c s is used as a buffer; see
       *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2
       *  for more.
      */
      virtual __streambuf_type*
      setbuf(char_type* __s, streamsize __n)
      {
	if (__s && __n)
	  {
	    _M_string = __string_type(__s, __n);
	    _M_really_sync(0, 0);
	  }
	return this;
      }

      // [documentation is inherited]
      virtual pos_type
      seekoff(off_type __off, ios_base::seekdir __way,
	      ios_base::openmode __mode = ios_base::in | ios_base::out);

      // [documentation is inherited]
      virtual pos_type
      seekpos(pos_type __sp,
	      ios_base::openmode __mode = ios_base::in | ios_base::out);

      // Internal function for correctly updating the internal buffer
      // for a particular _M_string, due to initialization or
      // re-sizing of an existing _M_string.
      // Assumes: contents of _M_string and internal buffer match exactly.
      // __i == _M_in_cur - _M_in_beg
      // __o == _M_out_cur - _M_out_beg
      /**
       *  @if maint
       *  @doctodo
       *  @endif
      */
      virtual int
      _M_really_sync(__size_type __i, __size_type __o)
      {
	char_type* __base = const_cast<char_type*>(_M_string.data());
	bool __testin = _M_mode & ios_base::in;
	bool __testout = _M_mode & ios_base::out;
	__size_type __len = _M_string.size();

	_M_buf = __base;
	if (__testin)
	    this->setg(__base, __base + __i, __base + __len);
	if (__testout)
	  {
	    this->setp(__base, __base + __len);
	    _M_out_cur += __o;
	  }
	return 0;
      }
    };


  // [27.7.2] Template class basic_istringstream
  /**
   *  @brief  Controlling input for std::string.
   *
   *  This class supports reading from objects of type std::basic_string,
   *  using the inherited functions from std::basic_istream.  To control
   *  the associated sequence, an instance of std::basic_stringbuf is used,
   *  which this page refers to as @c sb.
  */
  template<typename _CharT, typename _Traits, typename _Alloc>
    class basic_istringstream : public basic_istream<_CharT, _Traits>
    {
    public:
      // Types:
      typedef _CharT 					char_type;
      typedef _Traits 					traits_type;
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 251. basic_stringbuf missing allocator_type
      typedef _Alloc				       	allocator_type;
#endif
      typedef typename traits_type::int_type 		int_type;
      typedef typename traits_type::pos_type 		pos_type;
      typedef typename traits_type::off_type 		off_type;

      // Non-standard types:
      typedef basic_string<_CharT, _Traits, _Alloc> 	__string_type;
      typedef basic_stringbuf<_CharT, _Traits, _Alloc> 	__stringbuf_type;
      typedef basic_istream<char_type, traits_type>	__istream_type;

    private:
      /**
       *  @if maint
       *  @doctodo
       *  @endif
      */
      __stringbuf_type	_M_stringbuf;

    public:
      // Constructors:
      /**
       *  @brief  Default constructor starts with an empty string buffer.
       *  @param  mode  Whether the buffer can read, or write, or both.
       *