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_FORMAT_STRING_H 11 #define _LIBCPP___FORMAT_FORMAT_STRING_H 12 13 #include <__assert> 14 #include <__config> 15 #include <__format/format_error.h> 16 #include <__iterator/concepts.h> 17 #include <__iterator/iterator_traits.h> // iter_value_t 18 #include <cstddef> 19 #include <cstdint> 20 21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 22 # pragma GCC system_header 23 #endif 24 25 _LIBCPP_BEGIN_NAMESPACE_STD 26 27 #if _LIBCPP_STD_VER >= 20 28 29 namespace __format { 30 31 template <contiguous_iterator _Iterator> 32 struct _LIBCPP_TEMPLATE_VIS __parse_number_result { 33 _Iterator __last; 34 uint32_t __value; 35 }; 36 37 template <contiguous_iterator _Iterator> 38 __parse_number_result(_Iterator, uint32_t) -> __parse_number_result<_Iterator>; 39 40 template <contiguous_iterator _Iterator> 41 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_Iterator> __parse_number(_Iterator __begin, _Iterator __end); 42 43 /** 44 * The maximum value of a numeric argument. 45 * 46 * This is used for: 47 * * arg-id 48 * * width as value or arg-id. 49 * * precision as value or arg-id. 50 * 51 * The value is compatible with the maximum formatting width and precision 52 * using the `%*` syntax on a 32-bit system. 53 */ 54 inline constexpr uint32_t __number_max = INT32_MAX; 55 56 namespace __detail { 57 template <contiguous_iterator _Iterator> 58 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_Iterator> 59 __parse_zero(_Iterator __begin, _Iterator, auto& __parse_ctx) { 60 __parse_ctx.check_arg_id(0); 61 return {++__begin, 0}; // can never be larger than the maximum. 62 } 63 64 template <contiguous_iterator _Iterator> 65 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_Iterator> 66 __parse_automatic(_Iterator __begin, _Iterator, auto& __parse_ctx) { 67 size_t __value = __parse_ctx.next_arg_id(); 68 _LIBCPP_ASSERT_UNCATEGORIZED(__value <= __number_max, "Compilers don't support this number of arguments"); 69 70 return {__begin, uint32_t(__value)}; 71 } 72 73 template <contiguous_iterator _Iterator> 74 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_Iterator> 75 __parse_manual(_Iterator __begin, _Iterator __end, auto& __parse_ctx) { 76 __parse_number_result<_Iterator> __r = __format::__parse_number(__begin, __end); 77 __parse_ctx.check_arg_id(__r.__value); 78 return __r; 79 } 80 81 } // namespace __detail 82 83 /** 84 * Parses a number. 85 * 86 * The number is used for the 31-bit values @em width and @em precision. This 87 * allows a maximum value of 2147483647. 88 */ 89 template <contiguous_iterator _Iterator> 90 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_Iterator> 91 __parse_number(_Iterator __begin, _Iterator __end_input) { 92 using _CharT = iter_value_t<_Iterator>; 93 static_assert(__format::__number_max == INT32_MAX, "The algorithm is implemented based on this value."); 94 /* 95 * Limit the input to 9 digits, otherwise we need two checks during every 96 * iteration: 97 * - Are we at the end of the input? 98 * - Does the value exceed width of an uint32_t? (Switching to uint64_t would 99 * have the same issue, but with a higher maximum.) 100 */ 101 _Iterator __end = __end_input - __begin > 9 ? __begin + 9 : __end_input; 102 uint32_t __value = *__begin - _CharT('0'); 103 while (++__begin != __end) { 104 if (*__begin < _CharT('0') || *__begin > _CharT('9')) 105 return {__begin, __value}; 106 107 __value = __value * 10 + *__begin - _CharT('0'); 108 } 109 110 if (__begin != __end_input && *__begin >= _CharT('0') && *__begin <= _CharT('9')) { 111 /* 112 * There are more than 9 digits, do additional validations: 113 * - Does the 10th digit exceed the maximum allowed value? 114 * - Are there more than 10 digits? 115 * (More than 10 digits always overflows the maximum.) 116 */ 117 uint64_t __v = uint64_t(__value) * 10 + *__begin++ - _CharT('0'); 118 if (__v > __number_max || (__begin != __end_input && *__begin >= _CharT('0') && *__begin <= _CharT('9'))) 119 std::__throw_format_error("The numeric value of the format specifier is too large"); 120 121 __value = __v; 122 } 123 124 return {__begin, __value}; 125 } 126 127 /** 128 * Multiplexer for all parse functions. 129 * 130 * The parser will return a pointer beyond the last consumed character. This 131 * should be the closing '}' of the arg-id. 132 */ 133 template <contiguous_iterator _Iterator> 134 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_Iterator> 135 __parse_arg_id(_Iterator __begin, _Iterator __end, auto& __parse_ctx) { 136 using _CharT = iter_value_t<_Iterator>; 137 switch (*__begin) { 138 case _CharT('0'): 139 return __detail::__parse_zero(__begin, __end, __parse_ctx); 140 141 case _CharT(':'): 142 // This case is conditionally valid. It's allowed in an arg-id in the 143 // replacement-field, but not in the std-format-spec. The caller can 144 // provide a better diagnostic, so accept it here unconditionally. 145 case _CharT('}'): 146 return __detail::__parse_automatic(__begin, __end, __parse_ctx); 147 } 148 if (*__begin < _CharT('0') || *__begin > _CharT('9')) 149 std::__throw_format_error("The argument index starts with an invalid character"); 150 151 return __detail::__parse_manual(__begin, __end, __parse_ctx); 152 } 153 154 } // namespace __format 155 156 #endif //_LIBCPP_STD_VER >= 20 157 158 _LIBCPP_END_NAMESPACE_STD 159 160 #endif // _LIBCPP___FORMAT_FORMAT_STRING_H 161