92 lines
2.7 KiB
C++
92 lines
2.7 KiB
C++
/*
|
|
* Copyright (c) Facebook, Inc. and its affiliates.
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <folly/CPortability.h>
|
|
|
|
#include <cstdint>
|
|
#include <cstring>
|
|
#include <type_traits>
|
|
|
|
namespace folly {
|
|
|
|
namespace detail {
|
|
|
|
template <typename Char>
|
|
constexpr size_t constexpr_strlen_internal(const Char* s, size_t len) {
|
|
// clang-format off
|
|
return
|
|
*(s + 0) == Char(0) ? len + 0 :
|
|
*(s + 1) == Char(0) ? len + 1 :
|
|
*(s + 2) == Char(0) ? len + 2 :
|
|
*(s + 3) == Char(0) ? len + 3 :
|
|
*(s + 4) == Char(0) ? len + 4 :
|
|
*(s + 5) == Char(0) ? len + 5 :
|
|
*(s + 6) == Char(0) ? len + 6 :
|
|
*(s + 7) == Char(0) ? len + 7 :
|
|
constexpr_strlen_internal(s + 8, len + 8);
|
|
// clang-format on
|
|
}
|
|
static_assert(
|
|
constexpr_strlen_internal("123456789", 0) == 9,
|
|
"Someone appears to have broken constexpr_strlen...");
|
|
|
|
template <typename Char>
|
|
constexpr int constexpr_strcmp_internal(const Char* s1, const Char* s2) {
|
|
return (*s1 == '\0' || *s1 != *s2)
|
|
? (static_cast<int>(*s1 - *s2))
|
|
: constexpr_strcmp_internal(s1 + 1, s2 + 1);
|
|
}
|
|
} // namespace detail
|
|
|
|
template <typename Char>
|
|
constexpr size_t constexpr_strlen(const Char* s) {
|
|
return detail::constexpr_strlen_internal(s, 0);
|
|
}
|
|
|
|
template <>
|
|
constexpr size_t constexpr_strlen(const char* s) {
|
|
#if FOLLY_HAS_FEATURE(cxx_constexpr_string_builtins)
|
|
// clang provides a constexpr builtin
|
|
return __builtin_strlen(s);
|
|
#elif defined(__GLIBCXX__) && !defined(__clang__)
|
|
// strlen() happens to already be constexpr under gcc
|
|
return std::strlen(s);
|
|
#else
|
|
return detail::constexpr_strlen_internal(s, 0);
|
|
#endif
|
|
}
|
|
|
|
template <typename Char>
|
|
constexpr int constexpr_strcmp(const Char* s1, const Char* s2) {
|
|
return detail::constexpr_strcmp_internal(s1, s2);
|
|
}
|
|
|
|
template <>
|
|
constexpr int constexpr_strcmp(const char* s1, const char* s2) {
|
|
#if FOLLY_HAS_FEATURE(cxx_constexpr_string_builtins)
|
|
// clang provides a constexpr builtin
|
|
return __builtin_strcmp(s1, s2);
|
|
#elif defined(__GLIBCXX__) && !defined(__clang__)
|
|
// strcmp() happens to already be constexpr under gcc
|
|
return std::strcmp(s1, s2);
|
|
#else
|
|
return detail::constexpr_strcmp_internal(s1, s2);
|
|
#endif
|
|
}
|
|
} // namespace folly
|