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 <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 namespace __format { 28 29 template <class _CharT> 30 struct _LIBCPP_TEMPLATE_VIS __parse_number_result { 31 const _CharT* __ptr; 32 uint32_t __value; 33 }; 34 35 template <class _CharT> 36 __parse_number_result(const _CharT*, uint32_t) -> __parse_number_result<_CharT>; 37 38 template <class _CharT> 39 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 40 __parse_number(const _CharT* __begin, const _CharT* __end); 41 42 /** 43 * The maximum value of a numeric argument. 44 * 45 * This is used for: 46 * * arg-id 47 * * width as value or arg-id. 48 * * precision as value or arg-id. 49 * 50 * The value is compatible with the maximum formatting width and precision 51 * using the `%*` syntax on a 32-bit system. 52 */ 53 inline constexpr uint32_t __number_max = INT32_MAX; 54 55 namespace __detail { 56 template <class _CharT> 57 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 58 __parse_zero(const _CharT* __begin, const _CharT*, auto& __parse_ctx) { 59 __parse_ctx.check_arg_id(0); 60 return {++__begin, 0}; // can never be larger than the maximum. 61 } 62 63 template <class _CharT> 64 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 65 __parse_automatic(const _CharT* __begin, const _CharT*, auto& __parse_ctx) { 66 size_t __value = __parse_ctx.next_arg_id(); 67 _LIBCPP_ASSERT(__value <= __number_max, 68 "Compilers don't support this number of arguments"); 69 70 return {__begin, uint32_t(__value)}; 71 } 72 73 template <class _CharT> 74 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 75 __parse_manual(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) { 76 __parse_number_result<_CharT> __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 <class _CharT> 90 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 91 __parse_number(const _CharT* __begin, const _CharT* __end_input) { 92 static_assert(__format::__number_max == INT32_MAX, 93 "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 const _CharT* __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') && 111 *__begin <= _CharT('9')) { 112 113 /* 114 * There are more than 9 digits, do additional validations: 115 * - Does the 10th digit exceed the maximum allowed value? 116 * - Are there more than 10 digits? 117 * (More than 10 digits always overflows the maximum.) 118 */ 119 uint64_t __v = uint64_t(__value) * 10 + *__begin++ - _CharT('0'); 120 if (__v > __number_max || 121 (__begin != __end_input && *__begin >= _CharT('0') && 122 *__begin <= _CharT('9'))) 123 std::__throw_format_error("The numeric value of the format-spec is too large"); 124 125 __value = __v; 126 } 127 128 return {__begin, __value}; 129 } 130 131 /** 132 * Multiplexer for all parse functions. 133 * 134 * The parser will return a pointer beyond the last consumed character. This 135 * should be the closing '}' of the arg-id. 136 */ 137 template <class _CharT> 138 _LIBCPP_HIDE_FROM_ABI constexpr __parse_number_result<_CharT> 139 __parse_arg_id(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) { 140 switch (*__begin) { 141 case _CharT('0'): 142 return __detail::__parse_zero(__begin, __end, __parse_ctx); 143 144 case _CharT(':'): 145 // This case is conditionally valid. It's allowed in an arg-id in the 146 // replacement-field, but not in the std-format-spec. The caller can 147 // provide a better diagnostic, so accept it here unconditionally. 148 case _CharT('}'): 149 return __detail::__parse_automatic(__begin, __end, __parse_ctx); 150 } 151 if (*__begin < _CharT('0') || *__begin > _CharT('9')) 152 std::__throw_format_error("The arg-id of the format-spec starts with an invalid character"); 153 154 return __detail::__parse_manual(__begin, __end, __parse_ctx); 155 } 156 157 } // namespace __format 158 159 #endif //_LIBCPP_STD_VER > 17 160 161 _LIBCPP_END_NAMESPACE_STD 162 163 #endif // _LIBCPP___FORMAT_FORMAT_STRING_H 164