libstdc++-v3/include/std/ostream

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

// Copyright (C) 1997-2025 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>
#if __cplusplus > 202002L
# include <format>
#endif

# define __glibcxx_want_print
#include <bits/version.h> // __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
  inline void
  vprint_nonunicode(ostream& __os, string_view __fmt, format_args __args)
  {
    ostream::sentry __cerb(__os);
    if (__cerb)
      {
	__format::_Str_sink<char> __buf;
	std::vformat_to(__buf.out(), __os.getloc(), __fmt, __args);
	auto __out = __buf.view();

	__try
	  {
	    std::__ostream_write(__os, __out.data(), __out.size());
	  }
	__catch(const __cxxabiv1::__forced_unwind&)
	  {
	    __os._M_setstate(ios_base::badbit);
	    __throw_exception_again;
	  }
	__catch(...)
	  { __os._M_setstate(ios_base::badbit); }
      }
  }

  inline void
  vprint_unicode(ostream& __os, string_view __fmt, format_args __args)
  {
#if !defined(_WIN32) || defined(__CYGWIN__)
    // For most targets we don't need to do anything special to write
    // Unicode to a terminal.
    std::vprint_nonunicode(__os, __fmt, __args);
#else
    ostream::sentry __cerb(__os);
    if (__cerb)
      {
	__format::_Str_sink<char> __buf;
	std::vformat_to(__buf.out(), __os.getloc(), __fmt, __args);
	auto __out = __buf._M_span();

	void* __open_terminal(streambuf*);
	error_code __write_to_terminal(void*, span<char>);
	// If stream refers to a terminal, write a Unicode string to it.
	if (auto __term = __open_terminal(__os.rdbuf()))
	  {
#if !defined(_WIN32) || defined(__CYGWIN__)
	    // For POSIX, __open_terminal(streambuf*) uses fdopen to open a
	    // new file, so we would need to close it here. This code is not
	    // actually compiled because it's inside an #ifdef _WIN32 group,
	    // but just in case that changes in future ...
	    struct _Guard
	    {
	      _Guard(void* __p) : _M_f((FILE*)__p) { }
	      ~_Guard() { std::fclose(_M_f); }
	      _Guard(_Guard&&) = delete;
	      _Guard& operator=(_Guard&&) = delete;
	      FILE* _M_f;
	    };
	    _Guard __g(__term);
#endif

	    ios_base::iostate __err = ios_base::goodbit;
	    __try
	      {
		if (__os.rdbuf()->pubsync() == -1)
		  __err = ios::badbit;
		else if (auto __e = __write_to_terminal(__term, __out))
		  if (__e != std::make_error_code(errc::illegal_byte_sequence))
		    __err = ios::badbit;
	      }
	    __catch(const __cxxabiv1::__forced_unwind&)
	      {
		__os._M_setstate(ios_base::badbit);
		__throw_exception_again;
	      }
	    __catch(...)
	      { __os._M_setstate(ios_base::badbit); }

	    if (__err)
	      __os.setstate(__err);
	    return;
	  }

	// Otherwise just insert the string as vprint_nonunicode does.
	__try
	  {
	    std::__ostream_write(__os, __out.data(), __out.size());
	  }
	__catch(const __cxxabiv1::__forced_unwind&)
	  {
	    __os._M_setstate(ios_base::badbit);
	    __throw_exception_again;
	  }
	__catch(...)
	  { __os._M_setstate(ios_base::badbit); }
      }
#endif // _WIN32
  }

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

  template<typename... _Args>
    inline void
    println(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args)
    {
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 4088. println ignores the locale imbued in std::ostream
      std::print(__os, "{}\n", std::format(__os.getloc(), __fmt,
					   std::forward<_Args>(__args)...));
    }

  // 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 */