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>
__parse_zero(const _CharT * __begin,const _CharT *,auto & __parse_ctx)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>
__parse_automatic(const _CharT * __begin,const _CharT *,auto & __parse_ctx)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>
__parse_manual(const _CharT * __begin,const _CharT * __end,auto & __parse_ctx)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>
__parse_number(const _CharT * __begin,const _CharT * __end_input)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>
__parse_arg_id(const _CharT * __begin,const _CharT * __end,auto & __parse_ctx)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