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___CHARCONV_TRAITS
11#define _LIBCPP___CHARCONV_TRAITS
12
13#include <__assert>
14#include <__bit/countl.h>
15#include <__charconv/tables.h>
16#include <__charconv/to_chars_base_10.h>
17#include <__config>
18#include <__type_traits/enable_if.h>
19#include <__type_traits/is_unsigned.h>
20#include <cstdint>
21#include <limits>
22
23#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24# pragma GCC system_header
25#endif
26
27_LIBCPP_PUSH_MACROS
28#include <__undef_macros>
29
30_LIBCPP_BEGIN_NAMESPACE_STD
31
32#if _LIBCPP_STD_VER >= 17
33
34namespace __itoa {
35
36template <typename _Tp, typename = void>
37struct _LIBCPP_HIDDEN __traits_base;
38
39template <typename _Tp>
40struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) <= sizeof(uint32_t)>> {
41 using type = uint32_t;
42
43 /// The width estimation using a log10 algorithm.
44 ///
45 /// The algorithm is based on
46 /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
47 /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
48 /// function requires its input to have at least one bit set the value of
49 /// zero is set to one. This means the first element of the lookup table is
50 /// zero.
51 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
52 auto __t = (32 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
53 return __t - (__v < __itoa::__pow10_32[__t]) + 1;
54 }
55
56 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) {
57 return __itoa::__base_10_u32(__p, __v);
58 }
59
60 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_32)& __pow() {
61 return __itoa::__pow10_32;
62 }
63};
64
65template <typename _Tp>
66struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uint64_t)>> {
67 using type = uint64_t;
68
69 /// The width estimation using a log10 algorithm.
70 ///
71 /// The algorithm is based on
72 /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
73 /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
74 /// function requires its input to have at least one bit set the value of
75 /// zero is set to one. This means the first element of the lookup table is
76 /// zero.
77 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
78 auto __t = (64 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
79 return __t - (__v < __itoa::__pow10_64[__t]) + 1;
80 }
81
82 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) {
83 return __itoa::__base_10_u64(__p, __v);
84 }
85
86 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_64)& __pow() {
87 return __itoa::__pow10_64;
88 }
89};
90
91# ifndef _LIBCPP_HAS_NO_INT128
92template <typename _Tp>
93struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(__uint128_t)> > {
94 using type = __uint128_t;
95
96 /// The width estimation using a log10 algorithm.
97 ///
98 /// The algorithm is based on
99 /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
100 /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
101 /// function requires its input to have at least one bit set the value of
102 /// zero is set to one. This means the first element of the lookup table is
103 /// zero.
104 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
105 _LIBCPP_ASSERT_INTERNAL(
106 __v > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fail when this isn't true.");
107 // There's always a bit set in the upper 64-bits.
108 auto __t = (128 - std::__libcpp_clz(static_cast<uint64_t>(__v >> 64))) * 1233 >> 12;
109 _LIBCPP_ASSERT_INTERNAL(__t >= __itoa::__pow10_128_offset, "Index out of bounds");
110 // __t is adjusted since the lookup table misses the lower entries.
111 return __t - (__v < __itoa::__pow10_128[__t - __itoa::__pow10_128_offset]) + 1;
112 }
113
114 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) {
115 return __itoa::__base_10_u128(__p, __v);
116 }
117
118 // TODO FMT This pow function should get an index.
119 // By moving this to its own header it can be reused by the pow function in to_chars_base_10.
120 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_128)& __pow() {
121 return __itoa::__pow10_128;
122 }
123};
124# endif
125
126template <typename _Tp>
127inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
128__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r) {
129 auto __c = __a * __b;
130 __r = __c;
131 return __c > numeric_limits<unsigned char>::max();
132}
133
134template <typename _Tp>
135inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
136__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r) {
137 auto __c = __a * __b;
138 __r = __c;
139 return __c > numeric_limits<unsigned short>::max();
140}
141
142template <typename _Tp>
143inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool __mul_overflowed(_Tp __a, _Tp __b, _Tp& __r) {
144 static_assert(is_unsigned<_Tp>::value, "");
145 return __builtin_mul_overflow(__a, __b, &__r);
146}
147
148template <typename _Tp, typename _Up>
149inline _LIBCPP_HIDE_FROM_ABI bool _LIBCPP_CONSTEXPR_SINCE_CXX23 __mul_overflowed(_Tp __a, _Up __b, _Tp& __r) {
150 return __itoa::__mul_overflowed(__a, static_cast<_Tp>(__b), __r);
151}
152
153template <typename _Tp>
154struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp> {
155 static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
156 using __traits_base<_Tp>::__pow;
157 using typename __traits_base<_Tp>::type;
158
159 // precondition: at least one non-zero character available
160 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char const*
161 __read(char const* __p, char const* __ep, type& __a, type& __b) {
162 type __cprod[digits];
163 int __j = digits - 1;
164 int __i = digits;
165 do {
166 if (*__p < '0' || *__p > '9')
167 break;
168 __cprod[--__i] = *__p++ - '0';
169 } while (__p != __ep && __i != 0);
170
171 __a = __inner_product(__cprod + __i + 1, __cprod + __j, __pow() + 1, __cprod[__i]);
172 if (__itoa::__mul_overflowed(__cprod[__j], __pow()[__j - __i], __b))
173 --__p;
174 return __p;
175 }
176
177 template <typename _It1, typename _It2, class _Up>
178 static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Up
179 __inner_product(_It1 __first1, _It1 __last1, _It2 __first2, _Up __init) {
180 for (; __first1 < __last1; ++__first1, ++__first2)
181 __init = __init + *__first1 * *__first2;
182 return __init;
183 }
184};
185
186} // namespace __itoa
187
188template <typename _Tp>
189inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Tp __complement(_Tp __x) {
190 static_assert(is_unsigned<_Tp>::value, "cast to unsigned first");
191 return _Tp(~__x + 1);
192}
193
194#endif // _LIBCPP_STD_VER >= 17
195
196_LIBCPP_END_NAMESPACE_STD
197
198_LIBCPP_POP_MACROS
199
200#endif // _LIBCPP___CHARCONV_TRAITS
201