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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _CONSTEXPR_CHAR_TRAITS
#define _CONSTEXPR_CHAR_TRAITS
#include <string>
#include <cassert>
#include <cstddef>
#include "test_macros.h"
// Tests whether the pointer p is in the range [first, last).
//
// Precondition: The range [first, last) is a valid range.
//
// Typically the pointers are compared with less than. This is not allowed when
// the pointers belong to different ranges, which is UB. Typically, this is
// benign at run-time, however since UB is not allowed during constant
// evaluation this does not compile. This function does the validation without
// UB.
//
// When p is in the range [first, last) the data can be copied from the
// beginning to the end. Otherwise it needs to be copied from the end to the
// beginning.
template <class CharT>
TEST_CONSTEXPR_CXX14 bool is_pointer_in_range(const CharT* first, const CharT* last, const CharT* p) {
if (first == p) // Needed when n == 0
return true;
for (; first != last; ++first)
if (first == p)
return true;
return false;
}
template <class CharT>
struct constexpr_char_traits
{
typedef CharT char_type;
typedef int int_type;
typedef std::streamoff off_type;
typedef std::streampos pos_type;
typedef std::mbstate_t state_type;
// The comparison_category is omitted so the class will have weak_ordering
// in C++20. This is intentional.
static TEST_CONSTEXPR_CXX14 void assign(char_type& c1, const char_type& c2) TEST_NOEXCEPT
{c1 = c2;}
static TEST_CONSTEXPR bool eq(char_type c1, char_type c2) TEST_NOEXCEPT
{return c1 == c2;}
static TEST_CONSTEXPR bool lt(char_type c1, char_type c2) TEST_NOEXCEPT
{return c1 < c2;}
static TEST_CONSTEXPR_CXX14 int compare(const char_type* s1, const char_type* s2, std::size_t n);
static TEST_CONSTEXPR_CXX14 std::size_t length(const char_type* s);
static TEST_CONSTEXPR_CXX14 const char_type* find(const char_type* s, std::size_t n, const char_type& a);
static TEST_CONSTEXPR_CXX14 char_type* move(char_type* s1, const char_type* s2, std::size_t n);
static TEST_CONSTEXPR_CXX14 char_type* copy(char_type* s1, const char_type* s2, std::size_t n);
static TEST_CONSTEXPR_CXX14 char_type* assign(char_type* s, std::size_t n, char_type a);
static TEST_CONSTEXPR int_type not_eof(int_type c) TEST_NOEXCEPT
{return eq_int_type(c, eof()) ? ~eof() : c;}
static TEST_CONSTEXPR char_type to_char_type(int_type c) TEST_NOEXCEPT
{return char_type(c);}
static TEST_CONSTEXPR int_type to_int_type(char_type c) TEST_NOEXCEPT
{return int_type(c);}
static TEST_CONSTEXPR bool eq_int_type(int_type c1, int_type c2) TEST_NOEXCEPT
{return c1 == c2;}
static TEST_CONSTEXPR int_type eof() TEST_NOEXCEPT
{return int_type(EOF);}
};
template <class CharT>
TEST_CONSTEXPR_CXX14 int
constexpr_char_traits<CharT>::compare(const char_type* s1, const char_type* s2, std::size_t n)
{
for (; n; --n, ++s1, ++s2)
{
if (lt(*s1, *s2))
return -1;
if (lt(*s2, *s1))
return 1;
}
return 0;
}
template <class CharT>
TEST_CONSTEXPR_CXX14 std::size_t
constexpr_char_traits<CharT>::length(const char_type* s)
{
std::size_t len = 0;
for (; !eq(*s, char_type(0)); ++s)
++len;
return len;
}
template <class CharT>
TEST_CONSTEXPR_CXX14 const CharT*
constexpr_char_traits<CharT>::find(const char_type* s, std::size_t n, const char_type& a)
{
for (; n; --n)
{
if (eq(*s, a))
return s;
++s;
}
return 0;
}
template <class CharT>
TEST_CONSTEXPR_CXX14 CharT* constexpr_char_traits<CharT>::move(char_type* s1, const char_type* s2, std::size_t n) {
if (s1 == s2)
return s1;
char_type* r = s1;
if (is_pointer_in_range(s1, s1 + n, s2)) {
for (; n; --n)
assign(*s1++, *s2++);
} else {
s1 += n;
s2 += n;
for (; n; --n)
assign(*--s1, *--s2);
}
return r;
}
template <class CharT>
TEST_CONSTEXPR_CXX14 CharT*
constexpr_char_traits<CharT>::copy(char_type* s1, const char_type* s2, std::size_t n)
{
if (!TEST_IS_CONSTANT_EVALUATED) // fails in constexpr because we might be comparing unrelated pointers
assert(s2 < s1 || s2 >= s1+n);
char_type* r = s1;
for (; n; --n, ++s1, ++s2)
assign(*s1, *s2);
return r;
}
template <class CharT>
TEST_CONSTEXPR_CXX14 CharT*
constexpr_char_traits<CharT>::assign(char_type* s, std::size_t n, char_type a)
{
char_type* r = s;
for (; n; --n, ++s)
assign(*s, a);
return r;
}
#endif // _CONSTEXPR_CHAR_TRAITS
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