print.h
Go to the documentation of this file.
// Inline implementation details for std::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/bits/print.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{print}
*
* This file contains the parts of `<print>` which are currently defined
* inline, but should be moved into the library eventually.
*/
#ifndef _GLIBCXX_PRINT_H
#define _GLIBCXX_PRINT_H 1
#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif
#include <bits/requires_hosted.h> // for std::format
#include <bits/version.h>
#ifdef __glibcxx_print // C++ >= 23
#include <format>
#include <cstdio> // FILE, EOF, flockfile, etc.
#include <cerrno> // EACCES, EIO
#include <bits/functexcept.h> // __throw_system_error
#ifdef _WIN32
# include <system_error> // 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.
// __n is the number of characters written to the _M_write_buf() span,
// so will not exceed the size of 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());
}
// This calls I/O functions which are cancellation points, so they
// could exit with a __forced_unwind exception. The noexcept(false)
// allows that to propagate instead of terminating the process.
~_File_sink() noexcept(false)
{
auto __s = this->_M_used();
if (__s.data() == this->_M_buf) // Unbuffered stream
{
_File_sink::_M_overflow(); // Transfer _M_buf to stream.
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); // '\n' triggers a flush
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>
{
struct _File // RAII type to lock/unlock the file.
{
explicit _File(FILE* __f) : _M_file(__f) { ::flockfile(_M_file); }
~_File() { ::funlockfile(_M_file); }
FILE* _M_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._M_file);
if (__n != __s.size())
__throw_system_error(errno);
#else
for (char __c : __s)
::putc_unlocked(__c, _M_file._M_file);
if (::ferror(_M_file._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)
{ }
~_File_sink() noexcept(false) // See above for noexcept(false) rationale.
{
_File_sink::_M_overflow();
if (_M_add_newline)
::putc_unlocked('\n', _M_file._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) // See above for noexcept(false) rationale.
{
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); // Non-POSIX fwrite doesn't set errno.
}
auto out() { return _M_sink.out(); }
};
#endif
} // namespace __format
#ifdef _GLIBCXX_NO_INLINE_PRINT
# define _GLIBCXX_PRINT_INLINE_USED [[__gnu__::__used__]]
#else
# define _GLIBCXX_PRINT_INLINE_USED
#endif
_GLIBCXX_PRINT_INLINE_USED
inline void
vprint_nonunicode(FILE* __stream, string_view __fmt, format_args __args)
{
std::vformat_to(__format::_File_sink(__stream, false).out(), __fmt, __args);
}
_GLIBCXX_PRINT_INLINE_USED
inline void
vprint_nonunicode_buffered(FILE* __stream, string_view __fmt,
format_args __args)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 4549. vprint_nonunicode_buffered ignores its stream parameter
__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);
}
_GLIBCXX_PRINT_INLINE_USED
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
}
_GLIBCXX_PRINT_INLINE_USED
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
}
#undef _GLIBCXX_PRINT_INLINE_USED
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // __glibcxx_print
#endif // _GLIBCXX_PRINT_H
format
system_error
cerrno
cstdio
functexcept.h
version.h
requires_hosted.h
std::generic_category
const error_category & generic_category() noexcept
Error category for errno error codes.
std::make_error_code
error_code make_error_code(future_errc __errc) noexcept
Overload of make_error_code for future_errc.
Definition future:97
std::move
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition move.h:138
std
ISO C++ entities toplevel namespace is std.
std::error_code
Definition system_error:226
std::system_error
An exception type that includes an error_code value.
Definition system_error:559