v1/__format/formatter_tuple.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___FORMAT_FORMATTER_TUPLE_H
0011 #define _LIBCPP___FORMAT_FORMATTER_TUPLE_H
0012
0013 #include <__algorithm/ranges_copy.h>
0014 #include <__chrono/statically_widen.h>
0015 #include <__config>
0016 #include <__format/buffer.h>
0017 #include <__format/concepts.h>
0018 #include <__format/format_context.h>
0019 #include <__format/format_error.h>
0020 #include <__format/format_parse_context.h>
0021 #include <__format/formatter.h>
0022 #include <__format/formatter_output.h>
0023 #include <__format/parser_std_format_spec.h>
0024 #include <__type_traits/remove_cvref.h>
0025 #include <__utility/integer_sequence.h>
0026 #include <__utility/pair.h>
0027 #include <string_view>
0028 #include <tuple>
0029
0030 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0031 #  pragma GCC system_header
0032 #endif
0033
0034 _LIBCPP_BEGIN_NAMESPACE_STD
0035
0036 #if _LIBCPP_STD_VER >= 23
0037
0038 template <__fmt_char_type _CharT, class _Tuple, formattable<_CharT>... _Args>
0039 struct _LIBCPP_TEMPLATE_VIS __formatter_tuple {
0040   _LIBCPP_HIDE_FROM_ABI constexpr void set_separator(basic_string_view<_CharT> __separator) noexcept {
0041     __separator_ = __separator;
0042   }
0043   _LIBCPP_HIDE_FROM_ABI constexpr void
0044   set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) noexcept {
0045     __opening_bracket_ = __opening_bracket;
0046     __closing_bracket_ = __closing_bracket;
0047   }
0048
0049   template <class _ParseContext>
0050   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
0051     auto __begin = __parser_.__parse(__ctx, __format_spec::__fields_tuple);
0052
0053     auto __end = __ctx.end();
0054     // Note 'n' is part of the type here
0055     if (__parser_.__clear_brackets_)
0056       set_brackets({}, {});
0057     else if (__begin != __end && *__begin == _CharT('m')) {
0058       if constexpr (sizeof...(_Args) == 2) {
0059         set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
0060         set_brackets({}, {});
0061         ++__begin;
0062       } else
0063         std::__throw_format_error("Type m requires a pair or a tuple with two elements");
0064     }
0065
0066     if (__begin != __end && *__begin != _CharT('}'))
0067       std::__throw_format_error("The format specifier should consume the input or end with a '}'");
0068
0069     __ctx.advance_to(__begin);
0070
0071     // [format.tuple]/7
0072     //   ... For each element e in underlying_, if e.set_debug_format()
0073     //   is a valid expression, calls e.set_debug_format().
0074     std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
0075       auto& __formatter = std::get<_Index>(__underlying_);
0076       __formatter.parse(__ctx);
0077       // Unlike the range_formatter we don't guard against evil parsers. Since
0078       // this format-spec never has a format-spec for the underlying type
0079       // adding the test would give additional overhead.
0080       std::__set_debug_format(__formatter);
0081     });
0082
0083     return __begin;
0084   }
0085
0086   template <class _FormatContext>
0087   typename _FormatContext::iterator _LIBCPP_HIDE_FROM_ABI
0088   format(conditional_t<(formattable<const _Args, _CharT> && ...), const _Tuple&, _Tuple&> __tuple,
0089          _FormatContext& __ctx) const {
0090     __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
0091
0092     if (!__specs.__has_width())
0093       return __format_tuple(__tuple, __ctx);
0094
0095     // The size of the buffer needed is:
0096     // - open bracket characters
0097     // - close bracket character
0098     // - n elements where every element may have a different size
0099     // - (n -1) separators
0100     // The size of the element is hard to predict, knowing the type helps but
0101     // it depends on the format-spec. As an initial estimate we guess 6
0102     // characters.
0103     // Typically both brackets are 1 character and the separator is 2
0104     // characters. Which means there will be
0105     //   (n - 1) * 2 + 1 + 1 = n * 2 character
0106     // So estimate 8 times the range size as buffer.
0107     __format::__retarget_buffer<_CharT> __buffer{8 * tuple_size_v<_Tuple>};
0108     basic_format_context<typename __format::__retarget_buffer<_CharT>::__iterator, _CharT> __c{
0109         __buffer.__make_output_iterator(), __ctx};
0110
0111     __format_tuple(__tuple, __c);
0112
0113     return __formatter::__write_string_no_precision(basic_string_view{__buffer.__view()}, __ctx.out(), __specs);
0114   }
0115
0116   template <class _FormatContext>
0117   _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator __format_tuple(auto&& __tuple, _FormatContext& __ctx) const {
0118     __ctx.advance_to(std::ranges::copy(__opening_bracket_, __ctx.out()).out);
0119
0120     std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
0121       if constexpr (_Index)
0122         __ctx.advance_to(std::ranges::copy(__separator_, __ctx.out()).out);
0123       __ctx.advance_to(std::get<_Index>(__underlying_).format(std::get<_Index>(__tuple), __ctx));
0124     });
0125
0126     return std::ranges::copy(__closing_bracket_, __ctx.out()).out;
0127   }
0128
0129   __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__left};
0130
0131 private:
0132   tuple<formatter<remove_cvref_t<_Args>, _CharT>...> __underlying_;
0133   basic_string_view<_CharT> __separator_       = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
0134   basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "(");
0135   basic_string_view<_CharT> __closing_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, ")");
0136 };
0137
0138 template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
0139 struct _LIBCPP_TEMPLATE_VIS formatter<pair<_Args...>, _CharT>
0140     : public __formatter_tuple<_CharT, pair<_Args...>, _Args...> {};
0141
0142 template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
0143 struct _LIBCPP_TEMPLATE_VIS formatter<tuple<_Args...>, _CharT>
0144     : public __formatter_tuple<_CharT, tuple<_Args...>, _Args...> {};
0145
0146 #endif // _LIBCPP_STD_VER >= 23
0147
0148 _LIBCPP_END_NAMESPACE_STD
0149
0150 #endif // _LIBCPP___FORMAT_FORMATTER_TUPLE_H