libstdc++-v3/include/std/ostream

// Output streams -*- C++ -*-

// Copyright (C) 1997-2026 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 3, 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.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file include/ostream
 *  This is a Standard C++ Library header.
 */

//
// ISO C++ 14882: 27.6.2  Output streams
//

#ifndef _GLIBCXX_OSTREAM
#define _GLIBCXX_OSTREAM 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/requires_hosted.h> // iostreams

#include <bits/ostream.h>

#ifdef __glibcxx_print
# include <format> // format_string, make_format_args
#endif

#ifndef _GLIBCXX_NO_INLINE_PRINT
# include <bits/ostream_print.h>
#endif

# define __glibcxx_want_print
#include <bits/version.h> // __cpp_lib_print, __glibcxx_syncbuf

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Standard basic_ostream manipulators

  /**
   *  @brief  Write a newline and flush the stream.
   *
   *  This manipulator is often mistakenly used when a simple newline is
   *  desired, leading to poor buffering performance.  See
   *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
   *  for more on this subject.
  */
  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    endl(basic_ostream<_CharT, _Traits>& __os)
    { return flush(__os.put(__os.widen('\n'))); }

  /**
   *  @brief  Write a null character into the output sequence.
   *
   *  <em>Null character</em> is @c CharT() by definition.  For CharT
   *  of @c char, this correctly writes the ASCII @c NUL character
   *  string terminator.
  */
  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    ends(basic_ostream<_CharT, _Traits>& __os)
    { return __os.put(_CharT()); }

  /**
   *  @brief  Flushes the output stream.
   *
   *  This manipulator simply calls the stream's @c flush() member function.
  */
  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    flush(basic_ostream<_CharT, _Traits>& __os)
    { return __os.flush(); }

#ifdef __glibcxx_syncbuf // C++ >= 20 && HOSTED && CXX11ABI
  template<typename _CharT, typename _Traits>
    class __syncbuf_base : public basic_streambuf<_CharT, _Traits>
    {
    public:
      static bool*
      _S_get(basic_streambuf<_CharT, _Traits>* __buf [[maybe_unused]]) noexcept
      {
#if __cpp_rtti
	if (auto __p = dynamic_cast<__syncbuf_base*>(__buf))
	  return &__p->_M_emit_on_sync;
#endif
	return nullptr;
      }

    protected:
      __syncbuf_base(basic_streambuf<_CharT, _Traits>* __w = nullptr)
      : _M_wrapped(__w)
      { }

      basic_streambuf<_CharT, _Traits>* _M_wrapped = nullptr;
      bool _M_emit_on_sync = false;
      bool _M_needs_sync = false;
    };

  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    emit_on_flush(basic_ostream<_CharT, _Traits>& __os)
    {
      if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
	*__flag = true;
      return __os;
    }

  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    noemit_on_flush(basic_ostream<_CharT, _Traits>& __os)
    {
      if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
	*__flag = false;
      return __os;
    }

  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    flush_emit(basic_ostream<_CharT, _Traits>& __os)
    {
      struct _Restore
      {
	~_Restore() { *_M_flag = _M_prev; }

	bool _M_prev = false;
	bool* _M_flag = &_M_prev;
      } __restore;

      if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
	{
	  __restore._M_prev = *__flag;
	  __restore._M_flag = __flag;
	  *__flag = true;
	}

      __os.flush();
      return __os;
    }
#endif // __glibcxx_syncbuf

#if __cpp_lib_print // C++ >= 23
  void
  vprint_nonunicode(ostream& __os, string_view __fmt, format_args __args);

  void
  vprint_unicode(ostream& __os, string_view __fmt, format_args __args);

  template<typename... _Args>
    inline void
    print(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args)
    {
      auto __fmtargs = std::make_format_args(__args...);
#if defined(_WIN32) && !defined(__CYGWIN__)
      if constexpr (__unicode::__literal_encoding_is_utf8())
	std::vprint_unicode(__os, __fmt.get(), __fmtargs);
      else
#endif
	std::vprint_nonunicode(__os, __fmt.get(), __fmtargs);
    }

  template<typename... _Args>
    inline void
    println(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args)
    {
      auto __fmtargs = std::make_format_args(__args...);
      std::string __fmtn;
      __fmtn.reserve(__fmt.get().size() + 1);
      __fmtn = __fmt.get();
      __fmtn += '\n';
#if defined(_WIN32) && !defined(__CYGWIN__)
      if constexpr (__unicode::__literal_encoding_is_utf8())
	std::vprint_unicode(__os, __fmtn, __fmtargs);
      else
#endif
	std::vprint_nonunicode(__os, __fmtn, __fmtargs);
    }

  // Defined for C++26, supported as an extension to C++23.
  inline void println(ostream& __os)
  {
#if defined(_WIN32) && !defined(__CYGWIN__)
    if constexpr (__unicode::__literal_encoding_is_utf8())
      std::vprint_unicode(__os, "\n", std::make_format_args());
    else
#endif
      __os.put('\n');
  }
#endif // __cpp_lib_print

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#include <bits/ostream.tcc>

#endif	/* _GLIBCXX_OSTREAM */