libcxx/include/__format/range_formatter.h

   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_RANGE_FORMATTER_H
  11 #define _LIBCPP___FORMAT_RANGE_FORMATTER_H
  12
  13 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  14 #  pragma GCC system_header
  15 #endif
  16
  17 #include <__algorithm/ranges_copy.h>
  18 #include <__chrono/statically_widen.h>
  19 #include <__concepts/same_as.h>
  20 #include <__config>
  21 #include <__format/buffer.h>
  22 #include <__format/concepts.h>
  23 #include <__format/format_context.h>
  24 #include <__format/format_error.h>
  25 #include <__format/formatter.h>
  26 #include <__format/formatter_output.h>
  27 #include <__format/parser_std_format_spec.h>
  28 #include <__iterator/back_insert_iterator.h>
  29 #include <__ranges/concepts.h>
  30 #include <__ranges/data.h>
  31 #include <__ranges/from_range.h>
  32 #include <__ranges/size.h>
  33 #include <__type_traits/remove_cvref.h>
  34 #include <string_view>
  35
  36 _LIBCPP_BEGIN_NAMESPACE_STD
  37
  38 #if _LIBCPP_STD_VER >= 23
  39
  40 template <class _Tp, class _CharT = char>
  41   requires same_as<remove_cvref_t<_Tp>, _Tp> && formattable<_Tp, _CharT>
  42 struct _LIBCPP_TEMPLATE_VIS range_formatter {
  43   _LIBCPP_HIDE_FROM_ABI constexpr void set_separator(basic_string_view<_CharT> __separator) noexcept {
  44     __separator_ = __separator;
  45   }
  46   _LIBCPP_HIDE_FROM_ABI constexpr void
  47   set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) noexcept {
  48     __opening_bracket_ = __opening_bracket;
  49     __closing_bracket_ = __closing_bracket;
  50   }
  51
  52   _LIBCPP_HIDE_FROM_ABI constexpr formatter<_Tp, _CharT>& underlying() noexcept { return __underlying_; }
  53   _LIBCPP_HIDE_FROM_ABI constexpr const formatter<_Tp, _CharT>& underlying() const noexcept { return __underlying_; }
  54
  55   template <class _ParseContext>
  56   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
  57     auto __begin = __parser_.__parse(__ctx, __format_spec::__fields_range);
  58     auto __end   = __ctx.end();
  59     // Note the cases where __begin == __end in this code only happens when the
  60     // replacement-field has no terminating }, or when the parse is manually
  61     // called with a format-spec. The former is an error and the latter means
  62     // using a formatter without the format functions or print.
  63     if (__begin == __end) [[unlikely]]
  64       return __parse_empty_range_underlying_spec(__ctx, __begin);
  65
  66     // The n field overrides a possible m type, therefore delay applying the
  67     // effect of n until the type has been procesed.
  68     __parse_type(__begin, __end);
  69     if (__parser_.__clear_brackets_)
  70       set_brackets({}, {});
  71     if (__begin == __end) [[unlikely]]
  72       return __parse_empty_range_underlying_spec(__ctx, __begin);
  73
  74     bool __has_range_underlying_spec = *__begin == _CharT(':');
  75     if (__has_range_underlying_spec) {
  76       // range-underlying-spec:
  77       //   :  format-spec
  78       ++__begin;
  79     } else if (__begin != __end && *__begin != _CharT('}'))
  80       // When there is no underlaying range the current parse should have
  81       // consumed the format-spec. If not, the not consumed input will be
  82       // processed by the underlying. For example {:-} for a range in invalid,
  83       // the sign field is not present. Without this check the underlying_ will
  84       // get -} as input which my be valid.
  85       std::__throw_format_error("The format specifier should consume the input or end with a '}'");
  86
  87     __ctx.advance_to(__begin);
  88     __begin = __underlying_.parse(__ctx);
  89
  90     // This test should not be required if __has_range_underlying_spec is false.
  91     // However this test makes sure the underlying formatter left the parser in
  92     // a valid state. (Note this is not a full protection against evil parsers.
  93     // For example
  94     //   } this is test for the next argument {}
  95     //   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
  96     // could consume more than it should.
  97     if (__begin != __end && *__begin != _CharT('}'))
  98       std::__throw_format_error("The format specifier should consume the input or end with a '}'");
  99
 100     if (__parser_.__type_ != __format_spec::__type::__default) {
 101       // [format.range.formatter]/6
 102       //   If the range-type is s or ?s, then there shall be no n option and no
 103       //   range-underlying-spec.
 104       if (__parser_.__clear_brackets_) {
 105         if (__parser_.__type_ == __format_spec::__type::__string)
 106           std::__throw_format_error("The n option and type s can't be used together");
 107         std::__throw_format_error("The n option and type ?s can't be used together");
 108       }
 109       if (__has_range_underlying_spec) {
 110         if (__parser_.__type_ == __format_spec::__type::__string)
 111           std::__throw_format_error("Type s and an underlying format specification can't be used together");
 112         std::__throw_format_error("Type ?s and an underlying format specification can't be used together");
 113       }
 114     } else if (!__has_range_underlying_spec)
 115       std::__set_debug_format(__underlying_);
 116
 117     return __begin;
 118   }
 119
 120   template <ranges::input_range _Rp, class _FormatContext>
 121     requires formattable<ranges::range_reference_t<_Rp>, _CharT> &&
 122              same_as<remove_cvref_t<ranges::range_reference_t<_Rp>>, _Tp>
 123   _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_Rp&& __range, _FormatContext& __ctx) const {
 124     __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
 125
 126     if (!__specs.__has_width())
 127       return __format_range(__range, __ctx, __specs);
 128
 129     // The size of the buffer needed is:
 130     // - open bracket characters
 131     // - close bracket character
 132     // - n elements where every element may have a different size
 133     // - (n -1) separators
 134     // The size of the element is hard to predict, knowing the type helps but
 135     // it depends on the format-spec. As an initial estimate we guess 6
 136     // characters.
 137     // Typically both brackets are 1 character and the separator is 2
 138     // characters. Which means there will be
 139     //   (n - 1) * 2 + 1 + 1 = n * 2 character
 140     // So estimate 8 times the range size as buffer.
 141     std::size_t __capacity_hint = 0;
 142     if constexpr (std::ranges::sized_range<_Rp>)
 143       __capacity_hint = 8 * ranges::size(__range);
 144     __format::__retarget_buffer<_CharT> __buffer{__capacity_hint};
 145     basic_format_context<typename __format::__retarget_buffer<_CharT>::__iterator, _CharT> __c{
 146         __buffer.__make_output_iterator(), __ctx};
 147
 148     __format_range(__range, __c, __specs);
 149
 150     return __formatter::__write_string_no_precision(__buffer.__view(), __ctx.out(), __specs);
 151   }
 152
 153   template <ranges::input_range _Rp, class _FormatContext>
 154   typename _FormatContext::iterator _LIBCPP_HIDE_FROM_ABI
 155   __format_range(_Rp&& __range, _FormatContext& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) const {
 156     if constexpr (same_as<_Tp, _CharT>) {
 157       switch (__specs.__std_.__type_) {
 158       case __format_spec::__type::__string:
 159       case __format_spec::__type::__debug:
 160         return __format_as_string(__range, __ctx, __specs.__std_.__type_ == __format_spec::__type::__debug);
 161       default:
 162         return __format_as_sequence(__range, __ctx);
 163       }
 164     } else
 165       return __format_as_sequence(__range, __ctx);
 166   }
 167
 168   template <ranges::input_range _Rp, class _FormatContext>
 169   _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
 170   __format_as_string(_Rp&& __range, _FormatContext& __ctx, bool __debug_format) const {
 171     // When the range is contiguous use a basic_string_view instead to avoid a
 172     // copy of the underlying data. The basic_string_view formatter
 173     // specialization is the "basic" string formatter in libc++.
 174     if constexpr (ranges::contiguous_range<_Rp> && std::ranges::sized_range<_Rp>) {
 175       std::formatter<basic_string_view<_CharT>, _CharT> __formatter;
 176       if (__debug_format)
 177         __formatter.set_debug_format();
 178       return __formatter.format(
 179           basic_string_view<_CharT>{
 180               ranges::data(__range),
 181               ranges::size(__range),
 182           },
 183           __ctx);
 184     } else {
 185       std::formatter<basic_string<_CharT>, _CharT> __formatter;
 186       if (__debug_format)
 187         __formatter.set_debug_format();
 188       return __formatter.format(basic_string<_CharT>{from_range, __range}, __ctx);
 189     }
 190   }
 191
 192   template <ranges::input_range _Rp, class _FormatContext>
 193   _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
 194   __format_as_sequence(_Rp&& __range, _FormatContext& __ctx) const {
 195     __ctx.advance_to(ranges::copy(__opening_bracket_, __ctx.out()).out);
 196     bool __use_separator = false;
 197     for (auto&& __e : __range) {
 198       if (__use_separator)
 199         __ctx.advance_to(ranges::copy(__separator_, __ctx.out()).out);
 200       else
 201         __use_separator = true;
 202
 203       __ctx.advance_to(__underlying_.format(__e, __ctx));
 204     }
 205
 206     return ranges::copy(__closing_bracket_, __ctx.out()).out;
 207   }
 208
 209   __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__left};
 210
 211 private:
 212   template <contiguous_iterator _Iterator>
 213   _LIBCPP_HIDE_FROM_ABI constexpr void __parse_type(_Iterator& __begin, _Iterator __end) {
 214     switch (*__begin) {
 215     case _CharT('m'):
 216       if constexpr (__fmt_pair_like<_Tp>) {
 217         set_brackets(_LIBCPP_STATICALLY_WIDEN(_CharT, "{"), _LIBCPP_STATICALLY_WIDEN(_CharT, "}"));
 218         set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ", "));
 219         ++__begin;
 220       } else
 221         std::__throw_format_error("Type m requires a pair or a tuple with two elements");
 222       break;
 223
 224     case _CharT('s'):
 225       if constexpr (same_as<_Tp, _CharT>) {
 226         __parser_.__type_ = __format_spec::__type::__string;
 227         ++__begin;
 228       } else
 229         std::__throw_format_error("Type s requires character type as formatting argument");
 230       break;
 231
 232     case _CharT('?'):
 233       ++__begin;
 234       if (__begin == __end || *__begin != _CharT('s'))
 235         std::__throw_format_error("The format specifier should consume the input or end with a '}'");
 236       if constexpr (same_as<_Tp, _CharT>) {
 237         __parser_.__type_ = __format_spec::__type::__debug;
 238         ++__begin;
 239       } else
 240         std::__throw_format_error("Type ?s requires character type as formatting argument");
 241     }
 242   }
 243
 244   template <class _ParseContext>
 245   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator
 246   __parse_empty_range_underlying_spec(_ParseContext& __ctx, typename _ParseContext::iterator __begin) {
 247     __ctx.advance_to(__begin);
 248     [[maybe_unused]] typename _ParseContext::iterator __result = __underlying_.parse(__ctx);
 249     _LIBCPP_ASSERT_UNCATEGORIZED(
 250         __result == __begin,
 251         "the underlying's parse function should not advance the input beyond the end of the input");
 252     return __begin;
 253   }
 254
 255   formatter<_Tp, _CharT> __underlying_;
 256   basic_string_view<_CharT> __separator_       = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
 257   basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "[");
 258   basic_string_view<_CharT> __closing_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "]");
 259 };
 260
 261 #endif //_LIBCPP_STD_VER >= 23
 262
 263 _LIBCPP_END_NAMESPACE_STD
 264
 265 #endif // _LIBCPP___FORMAT_RANGE_FORMATTER_H