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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-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _CONSTEXPR_CHAR_TRAITS11#define _CONSTEXPR_CHAR_TRAITS12 13#include <string>14#include <cassert>15#include <cstddef>16 17#include "test_macros.h"18 19// Tests whether the pointer p is in the range [first, last).20//21// Precondition: The range [first, last) is a valid range.22//23// Typically the pointers are compared with less than. This is not allowed when24// the pointers belong to different ranges, which is UB. Typically, this is25// benign at run-time, however since UB is not allowed during constant26// evaluation this does not compile. This function does the validation without27// UB.28//29// When p is in the range [first, last) the data can be copied from the30// beginning to the end. Otherwise it needs to be copied from the end to the31// beginning.32template <class CharT>33TEST_CONSTEXPR_CXX14 bool is_pointer_in_range(const CharT* first, const CharT* last, const CharT* p) {34 if (first == p) // Needed when n == 035 return true;36 37 for (; first != last; ++first)38 if (first == p)39 return true;40 41 return false;42}43 44template <class CharT>45struct constexpr_char_traits46{47 typedef CharT char_type;48 typedef int int_type;49 typedef std::streamoff off_type;50 typedef std::streampos pos_type;51 typedef std::mbstate_t state_type;52 // The comparison_category is omitted so the class will have weak_ordering53 // in C++20. This is intentional.54 55 static TEST_CONSTEXPR_CXX14 void assign(char_type& c1, const char_type& c2) TEST_NOEXCEPT56 {c1 = c2;}57 58 static TEST_CONSTEXPR bool eq(char_type c1, char_type c2) TEST_NOEXCEPT59 {return c1 == c2;}60 61 static TEST_CONSTEXPR bool lt(char_type c1, char_type c2) TEST_NOEXCEPT62 {return c1 < c2;}63 64 static TEST_CONSTEXPR_CXX14 int compare(const char_type* s1, const char_type* s2, std::size_t n);65 static TEST_CONSTEXPR_CXX14 std::size_t length(const char_type* s);66 static TEST_CONSTEXPR_CXX14 const char_type* find(const char_type* s, std::size_t n, const char_type& a);67 static TEST_CONSTEXPR_CXX14 char_type* move(char_type* s1, const char_type* s2, std::size_t n);68 static TEST_CONSTEXPR_CXX14 char_type* copy(char_type* s1, const char_type* s2, std::size_t n);69 static TEST_CONSTEXPR_CXX14 char_type* assign(char_type* s, std::size_t n, char_type a);70 71 static TEST_CONSTEXPR int_type not_eof(int_type c) TEST_NOEXCEPT72 {return eq_int_type(c, eof()) ? ~eof() : c;}73 74 static TEST_CONSTEXPR char_type to_char_type(int_type c) TEST_NOEXCEPT75 {return char_type(c);}76 77 static TEST_CONSTEXPR int_type to_int_type(char_type c) TEST_NOEXCEPT78 {return int_type(c);}79 80 static TEST_CONSTEXPR bool eq_int_type(int_type c1, int_type c2) TEST_NOEXCEPT81 {return c1 == c2;}82 83 static TEST_CONSTEXPR int_type eof() TEST_NOEXCEPT84 {return int_type(EOF);}85};86 87 88template <class CharT>89TEST_CONSTEXPR_CXX14 int90constexpr_char_traits<CharT>::compare(const char_type* s1, const char_type* s2, std::size_t n)91{92 for (; n; --n, ++s1, ++s2)93 {94 if (lt(*s1, *s2))95 return -1;96 if (lt(*s2, *s1))97 return 1;98 }99 return 0;100}101 102template <class CharT>103TEST_CONSTEXPR_CXX14 std::size_t104constexpr_char_traits<CharT>::length(const char_type* s)105{106 std::size_t len = 0;107 for (; !eq(*s, char_type(0)); ++s)108 ++len;109 return len;110}111 112template <class CharT>113TEST_CONSTEXPR_CXX14 const CharT*114constexpr_char_traits<CharT>::find(const char_type* s, std::size_t n, const char_type& a)115{116 for (; n; --n)117 {118 if (eq(*s, a))119 return s;120 ++s;121 }122 return 0;123}124 125template <class CharT>126TEST_CONSTEXPR_CXX14 CharT* constexpr_char_traits<CharT>::move(char_type* s1, const char_type* s2, std::size_t n) {127 if (s1 == s2)128 return s1;129 130 char_type* r = s1;131 if (is_pointer_in_range(s1, s1 + n, s2)) {132 for (; n; --n)133 assign(*s1++, *s2++);134 } else {135 s1 += n;136 s2 += n;137 for (; n; --n)138 assign(*--s1, *--s2);139 }140 return r;141}142 143template <class CharT>144TEST_CONSTEXPR_CXX14 CharT*145constexpr_char_traits<CharT>::copy(char_type* s1, const char_type* s2, std::size_t n)146{147 if (!TEST_IS_CONSTANT_EVALUATED) // fails in constexpr because we might be comparing unrelated pointers148 assert(s2 < s1 || s2 >= s1+n);149 char_type* r = s1;150 for (; n; --n, ++s1, ++s2)151 assign(*s1, *s2);152 return r;153}154 155template <class CharT>156TEST_CONSTEXPR_CXX14 CharT*157constexpr_char_traits<CharT>::assign(char_type* s, std::size_t n, char_type a)158{159 char_type* r = s;160 for (; n; --n, ++s)161 assign(*s, a);162 return r;163}164 165#endif // _CONSTEXPR_CHAR_TRAITS166