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 <__availability>
15#include <__chrono/statically_widen.h>
16#include <__config>
17#include <__format/concepts.h>
18#include <__format/format_args.h>
19#include <__format/format_context.h>
20#include <__format/format_error.h>
21#include <__format/format_parse_context.h>
22#include <__format/formatter.h>
23#include <__format/formatter_output.h>
24#include <__format/parser_std_format_spec.h>
25#include <__iterator/back_insert_iterator.h>
26#include <__type_traits/remove_cvref.h>
27#include <__utility/integer_sequence.h>
28#include <__utility/pair.h>
29#include <string_view>
30#include <tuple>
31
32#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
33#  pragma GCC system_header
34#endif
35
36_LIBCPP_BEGIN_NAMESPACE_STD
37
38#if _LIBCPP_STD_VER > 20
39
40template <__fmt_char_type _CharT, class _Tuple, formattable<_CharT>... _Args>
41struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT __formatter_tuple {
42  _LIBCPP_HIDE_FROM_ABI constexpr void set_separator(basic_string_view<_CharT> __separator) {
43    __separator_ = __separator;
44  }
45  _LIBCPP_HIDE_FROM_ABI constexpr void
46  set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) {
47    __opening_bracket_ = __opening_bracket;
48    __closing_bracket_ = __closing_bracket;
49  }
50
51  template <class _ParseContext>
52  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __parse_ctx) {
53    const _CharT* __begin = __parser_.__parse(__parse_ctx, __format_spec::__fields_tuple);
54
55    // [format.tuple]/7
56    //   ... For each element e in underlying_, if e.set_debug_format()
57    //   is a valid expression, calls e.set_debug_format().
58    // TODO FMT this can be removed when P2733 is accepted.
59    std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
60      std::__set_debug_format(std::get<_Index>(__underlying_));
61    });
62
63    const _CharT* __end = __parse_ctx.end();
64    if (__begin == __end)
65      return __begin;
66
67    if (*__begin == _CharT('m')) {
68      if constexpr (sizeof...(_Args) == 2) {
69        set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
70        set_brackets({}, {});
71        ++__begin;
72      } else
73        std::__throw_format_error("The format specifier m requires a pair or a two-element tuple");
74    } else if (*__begin == _CharT('n')) {
75      set_brackets({}, {});
76      ++__begin;
77    }
78
79    if (__begin != __end && *__begin != _CharT('}'))
80      std::__throw_format_error("The format-spec should consume the input or end with a '}'");
81
82    return __begin;
83  }
84
85  template <class _FormatContext>
86  typename _FormatContext::iterator _LIBCPP_HIDE_FROM_ABI
87  format(conditional_t<(formattable<const _Args, _CharT> && ...), const _Tuple&, _Tuple&> __tuple,
88         _FormatContext& __ctx) const {
89    __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
90
91    if (!__specs.__has_width())
92      return __format_tuple(__tuple, __ctx);
93
94    basic_string<_CharT> __str;
95
96    // Since the output is written to a different iterator a new context is
97    // created. Since the underlying formatter uses the default formatting it
98    // doesn't need a locale or the formatting arguments. So creating a new
99    // context works.
100    //
101    // This solution works for this formatter, but it will not work for the
102    // range_formatter. In that patch a generic solution is work in progress.
103    // Once that is finished it can be used here. (The range_formatter will use
104    // these features so it's easier to add it there and then port it.)
105    //
106    // TODO FMT Use formatting wrapping used in the range_formatter.
107    basic_format_context __c = std::__format_context_create(
108        back_insert_iterator{__str},
109        basic_format_args<basic_format_context<back_insert_iterator<basic_string<_CharT>>, _CharT>>{});
110
111    __format_tuple(__tuple, __c);
112
113    return __formatter::__write_string_no_precision(basic_string_view{__str}, __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
124        // During review Victor suggested to make the exposition only
125        // __underlying_ member a local variable. Currently the Standard
126        // requires nested debug-enabled formatter specializations not to
127        // output escaped output. P2733 fixes that bug, once accepted the
128        // code below can be used.
129        // (Note when a paper allows parsing a tuple-underlying-spec the
130        // exposition only member needs to be a class member. Earlier
131        // revisions of P2286 proposed that, but this was not pursued,
132        // due to time constrains and complexity of the matter.)
133        // TODO FMT This can be updated after P2733 is accepted.
134#  if 0
135      // P2286 uses an exposition only member in the formatter
136      //   tuple<formatter<remove_cvref_t<_Args>, _CharT>...> __underlying_;
137      // This was used in earlier versions of the paper since
138      // __underlying_.parse(...) was called. This is no longer the case
139      // so we can reduce the scope of the formatter.
140      //
141      // It does require the underlying's parse effect to be moved here too.
142      using _Arg = tuple_element<_Index, decltype(__tuple)>;
143      formatter<remove_cvref_t<_Args>, _CharT> __underlying;
144
145      // [format.tuple]/7
146      //   ... For each element e in underlying_, if e.set_debug_format()
147      //   is a valid expression, calls e.set_debug_format().
148      std::__set_debug_format(__underlying);
149#  else
150      __ctx.advance_to(std::get<_Index>(__underlying_).format(std::get<_Index>(__tuple), __ctx));
151#  endif
152    });
153
154    return std::ranges::copy(__closing_bracket_, __ctx.out()).out;
155  }
156
157  __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__left};
158
159private:
160  tuple<formatter<remove_cvref_t<_Args>, _CharT>...> __underlying_;
161  basic_string_view<_CharT> __separator_       = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
162  basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "(");
163  basic_string_view<_CharT> __closing_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, ")");
164};
165
166template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
167struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<pair<_Args...>, _CharT>
168    : public __formatter_tuple<_CharT, pair<_Args...>, _Args...> {};
169
170template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
171struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<tuple<_Args...>, _CharT>
172    : public __formatter_tuple<_CharT, tuple<_Args...>, _Args...> {};
173
174#endif //_LIBCPP_STD_VER > 20
175
176_LIBCPP_END_NAMESPACE_STD
177
178#endif // _LIBCPP___FORMAT_FORMATTER_TUPLE_H
179