libstdc++-v3/include/std/print

// <print> Print functions -*- C++ -*-

// Copyright The GNU Toolchain Authors.
//
// 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/print
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_PRINT
#define _GLIBCXX_PRINT 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/requires_hosted.h> // for std::format

#define __glibcxx_want_print
#include <bits/version.h>

#ifdef __cpp_lib_print // C++ >= 23

#include <format>
#include <cstdio>
#include <cerrno>
#include <bits/functexcept.h>

#ifdef _WIN32
# include <system_error>
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace __format
{
#if _GLIBCXX_USE_STDIO_LOCKING && _GLIBCXX_USE_GLIBC_STDIO_EXT
  // These are defined in <stdio_ext.h> but we don't want to include that.
  extern "C" int __fwritable(FILE*) noexcept;
  extern "C" int __flbf(FILE*) noexcept;
  extern "C" size_t __fbufsize(FILE*) noexcept;

  // A format sink that writes directly to a Glibc FILE.
  // The file is locked on construction and its buffer is accessed directly.
  class _File_sink final : _Buf_sink<char>
  {
    struct _File
    {
      explicit
      _File(FILE* __f) : _M_file(__f)
      {
	::flockfile(__f);
	// Ensure stream is in write mode
        if (!__fwritable(__f))
	  {
	    ::funlockfile(__f);
	    __throw_system_error(EACCES);
	  }
	// Allocate buffer if needed:
        if (_M_write_buf().empty())
	  if (::__overflow(__f, EOF) == EOF)
	    {
	      const int __err = errno;
	      ::funlockfile(__f);
	      __throw_system_error(__err);
	    }
      }

      ~_File() { ::funlockfile(_M_file); }

      _File(_File&&) = delete;

      // A span viewing the unused portion of the stream's output buffer.
      std::span<char>
      _M_write_buf() noexcept
      {
	return {_M_file->_IO_write_ptr,
		size_t(_M_file->_IO_buf_end - _M_file->_IO_write_ptr)};
      }

      // Flush the output buffer to the file so we can write to it again.
      void
      _M_flush()
      {
	if (::fflush_unlocked(_M_file))
	  __throw_system_error(errno);
      }

      // Update the current position in the output buffer.
      void
      _M_bump(size_t __n) noexcept
      { _M_file->_IO_write_ptr += __n; }

      bool
      _M_line_buffered() const noexcept
      { return __flbf(_M_file); } // Or: _M_file->_flags & 0x200

      bool
      _M_unbuffered() const noexcept
      { return __fbufsize(_M_file) == 1; } // Or: _M_file->_flags & 0x2

      FILE* _M_file;
    } _M_file;

    bool _M_add_newline; // True for std::println, false for std::print.

    // Flush the stream's put area so it can be refilled.
    void
    _M_overflow() override
    {
      auto __s = this->_M_used();
      if (__s.data() == this->_M_buf)
	{
	  // Characters in internal buffer need to be transferred to the FILE.
	  auto __n = ::fwrite_unlocked(__s.data(), 1, __s.size(),
				       _M_file._M_file);
	  if (__n != __s.size())
	    __throw_system_error(errno);
	  this->_M_reset(this->_M_buf);
	}
      else
	{
	  // Characters were written directly to the FILE's output buffer.
	  _M_file._M_bump(__s.size());
	  _M_file._M_flush();
	  this->_M_reset(_M_file._M_write_buf());
	}
    }

  public:
    _File_sink(FILE* __f, bool __add_newline)
    : _M_file(__f), _M_add_newline(__add_newline)
    {
      if (!_M_file._M_unbuffered())
	// Write directly to the FILE's output buffer.
	this->_M_reset(_M_file._M_write_buf());
    }

    ~_File_sink() noexcept(false)
    {
      auto __s = this->_M_used();
      if (__s.data() == this->_M_buf) // Unbuffered stream
	{
	  _File_sink::_M_overflow();
	  if (_M_add_newline)
	    ::putc_unlocked('\n', _M_file._M_file);
	}
      else
	{
	  _M_file._M_bump(__s.size());
	  if (_M_add_newline)
	    ::putc_unlocked('\n', _M_file._M_file);
	  else if (_M_file._M_line_buffered() && __s.size()
		     && (__s.back() == '\n'
			   || __builtin_memchr(__s.data(), '\n', __s.size())))
	    _M_file._M_flush();
	}
    }

    using _Sink<char>::out;
  };
#elif _GLIBCXX_USE_STDIO_LOCKING
  // A format sink that buffers output and then copies it to a stdio FILE.
  // The file is locked on construction and written to using fwrite_unlocked.
  class _File_sink final : _Buf_sink<char>
  {
    FILE* _M_file;
    bool _M_add_newline;

    // Transfer buffer contents to the FILE, so buffer can be refilled.
    void
    _M_overflow() override
    {
      auto __s = this->_M_used();
#if _GLIBCXX_HAVE_FWRITE_UNLOCKED
      auto __n = ::fwrite_unlocked(__s.data(), 1, __s.size(), _M_file);
      if (__n != __s.size())
	__throw_system_error(errno);
#else
      for (char __c : __s)
	::putc_unlocked(__c, _M_file);
      if (::ferror(_M_file))
	__throw_system_error(errno);
#endif
      this->_M_reset(this->_M_buf);
    }

  public:
    _File_sink(FILE* __f, bool __add_newline) noexcept
    : _Buf_sink<char>(), _M_file(__f), _M_add_newline(__add_newline)
    { ::flockfile(__f); }

    ~_File_sink() noexcept(false)
    {
      _File_sink::_M_overflow();
      if (_M_add_newline)
	::putc_unlocked('\n', _M_file);
      ::funlockfile(_M_file);
    }

    using _Sink<char>::out;
  };
#else
  // A wrapper around a format sink that copies the output to a stdio FILE.
  // This is not actually a _Sink itself, but it creates one to hold the
  // formatted characters and then copies them to the file when finished.
  class _File_sink final
  {
    FILE* _M_file;
    _Str_sink<char> _M_sink;
    bool _M_add_newline;

  public:
    _File_sink(FILE* __f, bool __add_newline) noexcept
    : _M_file(__f), _M_add_newline(__add_newline)
    { }

    ~_File_sink() noexcept(false)
    {
      string __s = std::move(_M_sink).get();
      if (_M_add_newline)
	__s += '\n';
      auto __n = std::fwrite(__s.data(), 1, __s.size(), _M_file);
      if (__n < __s.size())
	__throw_system_error(EIO);
    }

    auto out() { return _M_sink.out(); }
  };
#endif
} // namespace __format

  inline void
  vprint_nonunicode(FILE* __stream, string_view __fmt, format_args __args)
  {
    std::vformat_to(__format::_File_sink(__stream, false).out(), __fmt, __args);
  }

  inline void
  vprint_nonunicode_buffered(FILE* __stream, string_view __fmt,
			     format_args __args)
  {
    __format::_Str_sink<char> __buf;
    std::vformat_to(__buf.out(), __fmt, __args);
    auto __out = __buf.view();
    if (std::fwrite(__out.data(), 1, __out.size(), __stream) != __out.size())
      __throw_system_error(EIO);
  }

  inline void
  vprint_unicode(FILE* __stream, 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(__stream, __fmt, __args);
#else
    __format::_Str_sink<char> __buf;
    std::vformat_to(__buf.out(), __fmt, __args);
    auto __out = __buf._M_span();

    void* __open_terminal(FILE*);
    error_code __write_to_terminal(void*, span<char>);
    // If stream refers to a terminal, write a native Unicode string to it.
    if (auto __term = __open_terminal(__stream))
      {
	error_code __e;
	if (!std::fflush(__stream))
	  {
	    __e = __write_to_terminal(__term, __out);
	    if (!__e)
	      return;
	    if (__e == std::make_error_code(errc::illegal_byte_sequence))
	      return;
	  }
	else
	  __e = error_code(errno, generic_category());
	_GLIBCXX_THROW_OR_ABORT(system_error(__e, "std::vprint_unicode"));
      }

    // Otherwise just write the string to the file.
    if (std::fwrite(__out.data(), 1, __out.size(), __stream) != __out.size())
      __throw_system_error(EIO);
#endif
  }

  inline void
  vprint_unicode_buffered(FILE* __stream, 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. Just use the nonunicode function.
    std::vprint_nonunicode_buffered(__stream, __fmt, __args);
#else
    // For Windows the locking function formats everything first anyway,
    // so no formatting happens while a lock is taken. Just use that.
    std::vprint_unicode(__stream, __fmt, __args);
#endif
  }

  template<typename... _Args>
    inline void
    print(FILE* __stream, format_string<_Args...> __fmt, _Args&&... __args)
    {
      constexpr bool __locksafe =
	(enable_nonlocking_formatter_optimization<remove_cvref_t<_Args>> && ...);

      auto __fmtargs = std::make_format_args(__args...);
#if defined(_WIN32) && !defined(__CYGWIN__)
      if constexpr (__unicode::__literal_encoding_is_utf8())
	std::vprint_unicode_buffered(__stream, __fmt.get(), __fmtargs);
      else
#endif

      if constexpr (__locksafe)
	std::vprint_nonunicode(__stream, __fmt.get(), __fmtargs);
      else
	std::vprint_nonunicode_buffered(__stream, __fmt.get(), __fmtargs);
    }

  template<typename... _Args>
    inline void
    print(format_string<_Args...> __fmt, _Args&&... __args)
    { std::print(stdout, __fmt, std::forward<_Args>(__args)...); }

  template<typename... _Args>
    inline void
    println(FILE* __stream, format_string<_Args...> __fmt, _Args&&... __args)
    {
      constexpr bool __locksafe =
	(enable_nonlocking_formatter_optimization<remove_cvref_t<_Args>> && ...);

      // The standard wants us to call
      // print(stream, runtime_format(string(fmt.get()) + '\n'), args...)
      // here, but we can avoid that string concatenation in most cases,
      // and we know what that would call, so we can call that directly.

      auto __fmtargs = std::make_format_args(__args...);
#if defined(_WIN32) && !defined(__CYGWIN__)
      if constexpr (__unicode::__literal_encoding_is_utf8())
	{
	  // We can't avoid the string concatenation here, but we can call
	  // vprint_unicode_buffered directly, since that's what print would do.
	  string __fmtn;
	  __fmtn.reserve(__fmt.get().size() + 1);
	  __fmtn = __fmt.get();
	  __fmtn += '\n';
	  std::vprint_unicode_buffered(__stream, __fmtn, __fmtargs);
	}
      else
#endif

      // For non-Windows and for non-Unicode on Windows, we know that print
      // would call vprint_nonunicode or vprint_nonunicode_buffered with a
      // newline appended to the format-string. Use a _File_sink that adds
      // the newline automatically and write to it directly.
      if constexpr (__locksafe)
	std::vformat_to(__format::_File_sink(__stream, true).out(),
			__fmt.get(), __fmtargs);
      else
	{
	  // Format to a string buffer first, then write the result to a
	  // _File_sink that adds a newline.
	  __format::_Str_sink<char> __buf;
	  std::vformat_to(__buf.out(), __fmt.get(), __fmtargs);
	  string_view __s(__buf.view());
	  __format::_File_sink(__stream, true).out() = __s;
	}
    }

  template<typename... _Args>
    inline void
    println(format_string<_Args...> __fmt, _Args&&... __args)
    { std::println(stdout, __fmt, std::forward<_Args>(__args)...); }

  inline void
  vprint_unicode_buffered(string_view __fmt, format_args __args)
  { std::vprint_unicode_buffered(stdout, __fmt, __args); }

  inline void
  vprint_nonunicode_buffered(string_view __fmt, format_args __args)
  { std::vprint_nonunicode_buffered(stdout, __fmt, __args); }

  // Defined for C++26, supported as an extension to C++23.
  inline void println(FILE* __stream)
  {
#if defined(_WIN32) && !defined(__CYGWIN__)
    if constexpr (__unicode::__literal_encoding_is_utf8())
      std::vprint_unicode_buffered(__stream, "\n", std::make_format_args());
    else
#endif
      if (std::putc('\n', __stream) == EOF)
	__throw_system_error(EIO);
  }

  inline void println() { std::println(stdout); }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // __cpp_lib_print
#endif // _GLIBCXX_PRINT