libcxx/include/print

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_PRINT
#define _LIBCPP_PRINT

/*
namespace std {
  // [print.fun], print functions
  template<class... Args>
    void print(format_string<Args...> fmt, Args&&... args);
  void println();                                                          // Since C++26
  template<class... Args>
    void print(FILE* stream, format_string<Args...> fmt, Args&&... args);
  void println(FILE* stream);                                              // Since C++26

  template<class... Args>
    void println(format_string<Args...> fmt, Args&&... args);
  template<class... Args>
    void println(FILE* stream, format_string<Args...> fmt, Args&&... args);

  void vprint_unicode(string_view fmt, format_args args);
  void vprint_unicode(FILE* stream, string_view fmt, format_args args);

  void vprint_nonunicode(string_view fmt, format_args args);
  void vprint_nonunicode(FILE* stream, string_view fmt, format_args args);
}
*/

#include <__assert>
#include <__concepts/same_as.h>
#include <__config>
#include <__system_error/system_error.h>
#include <__utility/forward.h>
#include <cerrno>
#include <cstdio>
#include <format>
#include <string>
#include <string_view>
#include <version>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#ifdef _LIBCPP_WIN32API
_LIBCPP_EXPORTED_FROM_ABI bool __is_windows_terminal(FILE* __stream);

#  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
// A wrapper for WriteConsoleW which is used to write to the Windows
// console. This function is in the dylib to avoid pulling in windows.h
// in the library headers. The function itself uses some private parts
// of the dylib too.
//
// The function does not depend on the language standard used. Guarding
// it with C++23 would fail since the dylib is currently built using C++20.
//
// Note the function is only implemented on the Windows platform.
_LIBCPP_EXPORTED_FROM_ABI void __write_to_windows_console(FILE* __stream, wstring_view __view);
#  endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
#elif __has_include(<unistd.h>)
_LIBCPP_EXPORTED_FROM_ABI bool __is_posix_terminal(FILE* __stream);
#endif // _LIBCPP_WIN32API

#if _LIBCPP_STD_VER >= 23

#  ifndef _LIBCPP_HAS_NO_UNICODE
// This is the code to transcode UTF-8 to UTF-16. This is used on
// Windows for the native Unicode API. The code is modeled to make it
// easier to extend to
//
//  P2728R0 Unicode in the Library, Part 1: UTF Transcoding
//
// This paper is still under heavy development so it makes no sense yet
// to strictly follow the paper.
namespace __unicode {

// The names of these concepts are modelled after P2728R0, but the
// implementation is not. char16_t may contain 32-bits so depending on the
// number of bits is an issue.
#    ifdef _LIBCPP_SHORT_WCHAR
template <class _Tp>
concept __utf16_code_unit =
    same_as<_Tp, char16_t>
#      ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
    || same_as<_Tp, wchar_t>
#      endif
    ;
template <class _Tp>
concept __utf32_code_unit = same_as<_Tp, char32_t>;
#    else // _LIBCPP_SHORT_WCHAR
template <class _Tp>
concept __utf16_code_unit = same_as<_Tp, char16_t>;
template <class _Tp>
concept __utf32_code_unit =
    same_as<_Tp, char32_t>
#      ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
    || same_as<_Tp, wchar_t>
#      endif
    ;
#    endif // _LIBCPP_SHORT_WCHAR

// Pass by reference since an output_iterator may not be copyable.
template <class _OutIt>
_LIBCPP_HIDE_FROM_ABI constexpr void __encode(_OutIt&, char32_t) = delete;

template <class _OutIt>
  requires __utf16_code_unit<iter_value_t<_OutIt>>
_LIBCPP_HIDE_FROM_ABI constexpr void __encode(_OutIt& __out_it, char32_t __value) {
  // [print.fun]/7 : "if `out` contains invalid code units, the behavior is undefined and implementations are encouraged
  // to diagnose it".
  _LIBCPP_ASSERT_UNCATEGORIZED(__is_scalar_value(__value), "an invalid unicode scalar value results in invalid UTF-16");

  if (__value < 0x10000) {
    *__out_it++ = __value;
    return;
  }

  __value -= 0x10000;
  *__out_it++ = 0xd800 + (__value >> 10);
  *__out_it++ = 0xdc00 + (__value & 0x3FF);
}

template <class _OutIt>
  requires __utf32_code_unit<iter_value_t<_OutIt>>
_LIBCPP_HIDE_FROM_ABI constexpr void __encode(_OutIt& __out_it, char32_t __value) {
  // [print.fun]/7 : "if `out` contains invalid code units, the behavior is undefined and implementations are encouraged
  // to diagnose it".
  _LIBCPP_ASSERT_UNCATEGORIZED(__is_scalar_value(__value), "an invalid unicode scalar value results in invalid UTF-32");
  *__out_it++ = __value;
}

template <class _OutIt, input_iterator _InIt>
  requires output_iterator<_OutIt, const iter_value_t<_OutIt>&> && (!same_as<iter_value_t<_OutIt>, iter_value_t<_InIt>>)
_LIBCPP_HIDE_FROM_ABI constexpr _OutIt __transcode(_InIt __first, _InIt __last, _OutIt __out_it) {
  // The __code_point_view has a basic_string_view interface.
  // When transcoding becomes part of the standard we probably want to
  // look at smarter algorithms.
  // For example, when processing a code point that is encoded in
  // 1 to 3 code units in UTF-8, the result will always be encoded
  // in 1 code unit in UTF-16 (code points that require 4 code
  // units in UTF-8 will require 2 code units in UTF-16).
  //
  // Note if P2728 is accepted types like int may become valid. In that case
  // the __code_point_view should use a span. Libc++ will remove support for
  // char_traits<int>.

  // TODO PRINT Validate with clang-tidy
  // NOLINTNEXTLINE(bugprone-dangling-handle)
  basic_string_view<iter_value_t<_InIt>> __data{__first, __last};
  __code_point_view<iter_value_t<_InIt>> __view{__data.begin(), __data.end()};
  while (!__view.__at_end())
    __unicode::__encode(__out_it, __view.__consume().__code_point);
  return __out_it;
}

} // namespace __unicode

#  endif //  _LIBCPP_HAS_NO_UNICODE

namespace __print {

// [print.fun]/2
//   Effects: If the ordinary literal encoding ([lex.charset]) is UTF-8, equivalent to:
//     vprint_unicode(stream, fmt.str, make_format_args(args...));
//   Otherwise, equivalent to:
//     vprint_nonunicode(stream, fmt.str, make_format_args(args...));
//
// Based on the compiler and its compilation flags this value is or is
// not true. As mentioned in P2093R14 this only affects Windows. The
// test below could also be done for
// - GCC using __GNUC_EXECUTION_CHARSET_NAME
//   https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html
// - Clang using __clang_literal_encoding__
//   https://clang.llvm.org/docs/LanguageExtensions.html#builtin-macros
//   (note at the time of writing Clang is hard-coded to UTF-8.)
//

#  ifdef _LIBCPP_HAS_NO_UNICODE
inline constexpr bool __use_unicode_execution_charset = false;
#  elif defined(_MSVC_EXECUTION_CHARACTER_SET)
// This is the same test MSVC STL uses in their implementation of <print>
// See: https://learn.microsoft.com/en-us/windows/win32/intl/code-page-identifiers
inline constexpr bool __use_unicode_execution_charset = _MSVC_EXECUTION_CHARACTER_SET == 65001;
#  else
inline constexpr bool __use_unicode_execution_charset = true;
#  endif

_LIBCPP_HIDE_FROM_ABI inline bool __is_terminal([[maybe_unused]] FILE* __stream) {
  // The macro _LIBCPP_TESTING_PRINT_IS_TERMINAL is used to change
  // the behavior in the test. This is not part of the public API.
#  ifdef _LIBCPP_TESTING_PRINT_IS_TERMINAL
  return _LIBCPP_TESTING_PRINT_IS_TERMINAL(__stream);
#  elif _LIBCPP_AVAILABILITY_HAS_PRINT == 0 || defined(_LIBCPP_HAS_NO_TERMINAL)
  return false;
#  elif defined(_LIBCPP_WIN32API)
  return std::__is_windows_terminal(__stream);
#  elif __has_include(<unistd.h>)
  return std::__is_posix_terminal(__stream);
#  else
#    error "Provide a way to determine whether a FILE* is a terminal"
#  endif
}

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void
__vprint_nonunicode(FILE* __stream, string_view __fmt, format_args __args, bool __write_nl) {
  _LIBCPP_ASSERT_NON_NULL(__stream, "__stream must be a valid pointer to an output C stream");
  string __str = std::vformat(__fmt, __args);
  if (__write_nl)
    __str.push_back('\n');

  size_t __size = fwrite(__str.data(), 1, __str.size(), __stream);
  if (__size < __str.size()) {
    if (std::feof(__stream))
      std::__throw_system_error(EIO, "EOF while writing the formatted output");
    std::__throw_system_error(std::ferror(__stream), "failed to write formatted output");
  }
}

#  ifndef _LIBCPP_HAS_NO_UNICODE

// Note these helper functions are mainly used to aid testing.
// On POSIX systems and Windows the output is no longer considered a
// terminal when the output is redirected. Typically during testing the
// output is redirected to be able to capture it. This makes it hard to
// test this code path.
template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void
__vprint_unicode_posix(FILE* __stream, string_view __fmt, format_args __args, bool __write_nl, bool __is_terminal) {
  // TODO PRINT Should flush errors throw too?
  if (__is_terminal)
    std::fflush(__stream);

  __print::__vprint_nonunicode(__stream, __fmt, __args, __write_nl);
}

#    ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void
__vprint_unicode_windows(FILE* __stream, string_view __fmt, format_args __args, bool __write_nl, bool __is_terminal) {
  if (!__is_terminal)
    return __print::__vprint_nonunicode(__stream, __fmt, __args, __write_nl);

  // TODO PRINT Should flush errors throw too?
  std::fflush(__stream);

  string __str = std::vformat(__fmt, __args);
  // UTF-16 uses the same number or less code units than UTF-8.
  // However the size of the code unit is 16 bits instead of 8 bits.
  //
  // The buffer uses the worst-case estimate and should never resize.
  // However when the string is large this could lead to OOM. Using a
  // smaller size might work, but since the buffer uses a grow factor
  // the final size might be larger when the estimate is wrong.
  //
  // TODO PRINT profile and improve the speed of this code.
  __format::__retarget_buffer<wchar_t> __buffer{__str.size()};
  __unicode::__transcode(__str.begin(), __str.end(), __buffer.__make_output_iterator());
  if (__write_nl)
    __buffer.push_back(L'\n');

  [[maybe_unused]] wstring_view __view = __buffer.__view();

  // The macro _LIBCPP_TESTING_PRINT_WRITE_TO_WINDOWS_CONSOLE_FUNCTION is used to change
  // the behavior in the test. This is not part of the public API.
#      ifdef _LIBCPP_TESTING_PRINT_WRITE_TO_WINDOWS_CONSOLE_FUNCTION
  _LIBCPP_TESTING_PRINT_WRITE_TO_WINDOWS_CONSOLE_FUNCTION(__stream, __view);
#      elif defined(_LIBCPP_WIN32API)
  std::__write_to_windows_console(__stream, __view);
#      else
  std::__throw_runtime_error("No defintion of _LIBCPP_TESTING_PRINT_WRITE_TO_WINDOWS_CONSOLE_FUNCTION and "
                             "__write_to_windows_console is not available.");
#      endif
}
#    endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void
__vprint_unicode([[maybe_unused]] FILE* __stream,
                 [[maybe_unused]] string_view __fmt,
                 [[maybe_unused]] format_args __args,
                 [[maybe_unused]] bool __write_nl) {
  _LIBCPP_ASSERT_NON_NULL(__stream, "__stream must be a valid pointer to an output C stream");

  // [print.fun]
  //   7 - Effects: If stream refers to a terminal capable of displaying
  //       Unicode, writes out to the terminal using the native Unicode
  //       API; if out contains invalid code units, the behavior is
  //       undefined and implementations are encouraged to diagnose it.
  //       Otherwise writes out to stream unchanged. If the native
  //       Unicode API is used, the function flushes stream before
  //       writing out.
  //   8 - Throws: Any exception thrown by the call to vformat
  //       ([format.err.report]). system_error if writing to the terminal
  //       or stream fails. May throw bad_alloc.
  //   9 - Recommended practice: If invoking the native Unicode API
  //       requires transcoding, implementations should substitute
  //       invalid code units with U+FFFD replacement character per the
  //       Unicode Standard, Chapter 3.9 U+FFFD Substitution in
  //       Conversion.

  // On non-Windows platforms the Unicode API is the normal file I/O API
  // so there the call can be forwarded to the non_unicode API. On
  // Windows there is a different API. This API requires transcoding.

#    ifndef _LIBCPP_WIN32API
  __print::__vprint_unicode_posix(__stream, __fmt, __args, __write_nl, __print::__is_terminal(__stream));
#    elif !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)
  __print::__vprint_unicode_windows(__stream, __fmt, __args, __write_nl, __print::__is_terminal(__stream));
#    else
#      error "Windows builds with wchar_t disabled are not supported."
#    endif
}

#  endif // _LIBCPP_HAS_NO_UNICODE

} // namespace __print

template <class... _Args>
_LIBCPP_HIDE_FROM_ABI void print(FILE* __stream, format_string<_Args...> __fmt, _Args&&... __args) {
#  ifndef _LIBCPP_HAS_NO_UNICODE
  if constexpr (__print::__use_unicode_execution_charset)
    __print::__vprint_unicode(__stream, __fmt.get(), std::make_format_args(__args...), false);
  else
    __print::__vprint_nonunicode(__stream, __fmt.get(), std::make_format_args(__args...), false);
#  else  // _LIBCPP_HAS_NO_UNICODE
  __print::__vprint_nonunicode(__stream, __fmt.get(), std::make_format_args(__args...), false);
#  endif // _LIBCPP_HAS_NO_UNICODE
}

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

template <class... _Args>
_LIBCPP_HIDE_FROM_ABI void println(FILE* __stream, format_string<_Args...> __fmt, _Args&&... __args) {
#  ifndef _LIBCPP_HAS_NO_UNICODE
  // Note the wording in the Standard is inefficient. The output of
  // std::format is a std::string which is then copied. This solution
  // just appends a newline at the end of the output.
  if constexpr (__print::__use_unicode_execution_charset)
    __print::__vprint_unicode(__stream, __fmt.get(), std::make_format_args(__args...), true);
  else
    __print::__vprint_nonunicode(__stream, __fmt.get(), std::make_format_args(__args...), true);
#  else  // _LIBCPP_HAS_NO_UNICODE
  __print::__vprint_nonunicode(__stream, __fmt.get(), std::make_format_args(__args...), true);
#  endif // _LIBCPP_HAS_NO_UNICODE
}

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void println(FILE* __stream) {
  std::print(__stream, "\n");
}

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void println() {
  println(stdout);
}

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

#  ifndef _LIBCPP_HAS_NO_UNICODE
template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void vprint_unicode(FILE* __stream, string_view __fmt, format_args __args) {
  __print::__vprint_unicode(__stream, __fmt, __args, false);
}

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void vprint_unicode(string_view __fmt, format_args __args) {
  std::vprint_unicode(stdout, __fmt, __args);
}

#  endif // _LIBCPP_HAS_NO_UNICODE

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void vprint_nonunicode(FILE* __stream, string_view __fmt, format_args __args) {
  __print::__vprint_nonunicode(__stream, __fmt, __args, false);
}

template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
_LIBCPP_HIDE_FROM_ABI inline void vprint_nonunicode(string_view __fmt, format_args __args) {
  std::vprint_nonunicode(stdout, __fmt, __args);
}

#endif // _LIBCPP_STD_VER >= 23

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_PRINT