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 <__config> 14 #include <__debug> 15 #include <__format/format_error.h> 16 #include <cstddef> 17 #include <cstdint> 18 19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20 #pragma GCC system_header 21 #endif 22 23 _LIBCPP_BEGIN_NAMESPACE_STD 24 25 #if _LIBCPP_STD_VER > 17 26 27 // TODO FMT Remove this once we require compilers with proper C++20 support. 28 // If the compiler has no concepts support, the format header will be disabled. 29 // Without concepts support enable_if needs to be used and that too much effort 30 // to support compilers with partial C++20 support. 31 #if !defined(_LIBCPP_HAS_NO_CONCEPTS) 32 33 namespace __format { 34 35 template <class _CharT> 36 struct _LIBCPP_TEMPLATE_VIS __parse_number_result { 37 const _CharT* __ptr; 38 uint32_t __value; 39 }; 40 41 template <class _CharT> 42 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 43 __parse_number(const _CharT* __begin, const _CharT* __end); 44 45 /** 46 * The maximum value of a numeric argument. 47 * 48 * This is used for: 49 * * arg-id 50 * * width as value or arg-id. 51 * * precision as value or arg-id. 52 * 53 * The value is compatible with the maximum formatting width and precision 54 * using the `%*` syntax on a 32-bit system. 55 */ 56 inline constexpr uint32_t __number_max = INT32_MAX; 57 58 namespace __detail { 59 template <class _CharT> 60 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 61 __parse_zero(const _CharT* __begin, const _CharT*, auto& __parse_ctx) { 62 __parse_ctx.check_arg_id(0); 63 return {++__begin, 0}; // can never be larger than the maximum. 64 } 65 66 template <class _CharT> 67 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 68 __parse_automatic(const _CharT* __begin, const _CharT*, auto& __parse_ctx) { 69 size_t __value = __parse_ctx.next_arg_id(); 70 _LIBCPP_ASSERT(__value <= __number_max, 71 "Compilers don't support this number of arguments"); 72 73 return {__begin, uint32_t(__value)}; 74 } 75 76 template <class _CharT> 77 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 78 __parse_manual(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) { 79 __parse_number_result<_CharT> __r = __parse_number(__begin, __end); 80 __parse_ctx.check_arg_id(__r.__value); 81 return __r; 82 } 83 84 } // namespace __detail 85 86 /** 87 * Parses a number. 88 * 89 * The number is used for the 31-bit values @em width and @em precision. This 90 * allows a maximum value of 2147483647. 91 */ 92 template <class _CharT> 93 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 94 __parse_number(const _CharT* __begin, const _CharT* __end_input) { 95 static_assert(__format::__number_max == INT32_MAX, 96 "The algorithm is implemented based on this value."); 97 /* 98 * Limit the input to 9 digits, otherwise we need two checks during every 99 * iteration: 100 * - Are we at the end of the input? 101 * - Does the value exceed width of an uint32_t? (Switching to uint64_t would 102 * have the same issue, but with a higher maximum.) 103 */ 104 const _CharT* __end = __end_input - __begin > 9 ? __begin + 9 : __end_input; 105 uint32_t __value = *__begin - _CharT('0'); 106 while (++__begin != __end) { 107 if (*__begin < _CharT('0') || *__begin > _CharT('9')) 108 return {__begin, __value}; 109 110 __value = __value * 10 + *__begin - _CharT('0'); 111 } 112 113 if (__begin != __end_input && *__begin >= _CharT('0') && 114 *__begin <= _CharT('9')) { 115 116 /* 117 * There are more than 9 digits, do additional validations: 118 * - Does the 10th digit exceed the maximum allowed value? 119 * - Are there more than 10 digits? 120 * (More than 10 digits always overflows the maximum.) 121 */ 122 uint64_t __v = uint64_t(__value) * 10 + *__begin++ - _CharT('0'); 123 if (__v > __number_max || 124 (__begin != __end_input && *__begin >= _CharT('0') && 125 *__begin <= _CharT('9'))) 126 __throw_format_error("The numeric value of the format-spec is too large"); 127 128 __value = __v; 129 } 130 131 return {__begin, __value}; 132 } 133 134 /** 135 * Multiplexer for all parse functions. 136 * 137 * The parser will return a pointer beyond the last consumed character. This 138 * should be the closing '}' of the arg-id. 139 */ 140 template <class _CharT> 141 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 142 __parse_arg_id(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) { 143 switch (*__begin) { 144 case _CharT('0'): 145 return __detail::__parse_zero(__begin, __end, __parse_ctx); 146 147 case _CharT(':'): 148 // This case is conditionally valid. It's allowed in an arg-id in the 149 // replacement-field, but not in the std-format-spec. The caller can 150 // provide a better diagnostic, so accept it here unconditionally. 151 case _CharT('}'): 152 return __detail::__parse_automatic(__begin, __end, __parse_ctx); 153 } 154 if (*__begin < _CharT('0') || *__begin > _CharT('9')) 155 __throw_format_error( 156 "The arg-id of the format-spec starts with an invalid character"); 157 158 return __detail::__parse_manual(__begin, __end, __parse_ctx); 159 } 160 161 } // namespace __format 162 163 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) 164 165 #endif //_LIBCPP_STD_VER > 17 166 167 _LIBCPP_END_NAMESPACE_STD 168 169 #endif // _LIBCPP___FORMAT_FORMAT_STRING_H 170