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1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___FORMAT_FORMATTER_TUPLE_H
11#define _LIBCPP___FORMAT_FORMATTER_TUPLE_H
12
13#include <__algorithm/ranges_copy.h>
14#include <__chrono/statically_widen.h>
15#include <__config>
16#include <__format/buffer.h>
17#include <__format/concepts.h>
18#include <__format/format_context.h>
19#include <__format/format_error.h>
20#include <__format/format_parse_context.h>
21#include <__format/formatter.h>
22#include <__format/formatter_output.h>
23#include <__format/parser_std_format_spec.h>
24#include <__type_traits/remove_cvref.h>
25#include <__utility/integer_sequence.h>
26#include <__utility/pair.h>
27#include <string_view>
28#include <tuple>
29
30#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31# pragma GCC system_header
32#endif
33
34_LIBCPP_BEGIN_NAMESPACE_STD
35
36#if _LIBCPP_STD_VER >= 23
37
38template <__fmt_char_type _CharT, class _Tuple, formattable<_CharT>... _Args>
39struct __formatter_tuple {
40 _LIBCPP_HIDE_FROM_ABI constexpr void set_separator(basic_string_view<_CharT> __separator) noexcept {
41 __separator_ = __separator;
42 }
43 _LIBCPP_HIDE_FROM_ABI constexpr void
44 set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) noexcept {
45 __opening_bracket_ = __opening_bracket;
46 __closing_bracket_ = __closing_bracket;
47 }
48
49 template <class _ParseContext>
50 _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
51 auto __begin = __parser_.__parse(__ctx, __format_spec::__fields_tuple);
52
53 auto __end = __ctx.end();
54 // Note 'n' is part of the type here
55 if (__parser_.__clear_brackets_)
56 set_brackets({}, {});
57 else if (__begin != __end && *__begin == _CharT('m')) {
58 if constexpr (sizeof...(_Args) == 2) {
59 set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
60 set_brackets({}, {});
61 ++__begin;
62 } else
63 std::__throw_format_error("Type m requires a pair or a tuple with two elements");
64 }
65
66 if (__begin != __end && *__begin != _CharT('}'))
67 std::__throw_format_error("The format specifier should consume the input or end with a '}'");
68
69 __ctx.advance_to(__begin);
70
71 // [format.tuple]/7
72 // ... For each element e in underlying_, if e.set_debug_format()
73 // is a valid expression, calls e.set_debug_format().
74 std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
75 auto& __formatter = std::get<_Index>(__underlying_);
76 __formatter.parse(__ctx);
77 // Unlike the range_formatter we don't guard against evil parsers. Since
78 // this format-spec never has a format-spec for the underlying type
79 // adding the test would give additional overhead.
80 std::__set_debug_format(__formatter);
81 });
82
83 return __begin;
84 }
85
86 template <class _FormatContext>
87 typename _FormatContext::iterator _LIBCPP_HIDE_FROM_ABI
88 format(conditional_t<(formattable<const _Args, _CharT> && ...), const _Tuple&, _Tuple&> __tuple,
89 _FormatContext& __ctx) const {
90 __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
91
92 if (!__specs.__has_width())
93 return __format_tuple(__tuple, __ctx);
94
95 // The size of the buffer needed is:
96 // - open bracket characters
97 // - close bracket character
98 // - n elements where every element may have a different size
99 // - (n -1) separators
100 // The size of the element is hard to predict, knowing the type helps but
101 // it depends on the format-spec. As an initial estimate we guess 6
102 // characters.
103 // Typically both brackets are 1 character and the separator is 2
104 // characters. Which means there will be
105 // (n - 1) * 2 + 1 + 1 = n * 2 character
106 // So estimate 8 times the range size as buffer.
107 __format::__retarget_buffer<_CharT> __buffer{8 * tuple_size_v<_Tuple>};
108 basic_format_context<typename __format::__retarget_buffer<_CharT>::__iterator, _CharT> __c{
109 __buffer.__make_output_iterator(), __ctx};
110
111 __format_tuple(__tuple, __c);
112
113 return __formatter::__write_string_no_precision(basic_string_view{__buffer.__view()}, __ctx.out(), __specs);
114 }
115
116 template <class _FormatContext>
117 _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator __format_tuple(auto&& __tuple, _FormatContext& __ctx) const {
118 __ctx.advance_to(std::ranges::copy(__opening_bracket_, __ctx.out()).out);
119
120 std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
121 if constexpr (_Index)
122 __ctx.advance_to(std::ranges::copy(__separator_, __ctx.out()).out);
123 __ctx.advance_to(std::get<_Index>(__underlying_).format(std::get<_Index>(__tuple), __ctx));
124 });
125
126 return std::ranges::copy(__closing_bracket_, __ctx.out()).out;
127 }
128
129 __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__left};
130
131private:
132 tuple<formatter<remove_cvref_t<_Args>, _CharT>...> __underlying_;
133 basic_string_view<_CharT> __separator_ = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
134 basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "(");
135 basic_string_view<_CharT> __closing_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, ")");
136};
137
138template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
139struct formatter<pair<_Args...>, _CharT> : public __formatter_tuple<_CharT, pair<_Args...>, _Args...> {};
140
141template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
142struct formatter<tuple<_Args...>, _CharT> : public __formatter_tuple<_CharT, tuple<_Args...>, _Args...> {};
143
144#endif // _LIBCPP_STD_VER >= 23
145
146_LIBCPP_END_NAMESPACE_STD
147
148#endif // _LIBCPP___FORMAT_FORMATTER_TUPLE_H
149

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source code of libcxx/include/__format/formatter_tuple.h