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96 lines
2.4 KiB
C++
Executable File
96 lines
2.4 KiB
C++
Executable File
/*
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* Copyright 2016 Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <cstdint>
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#include <cstring>
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#include <type_traits>
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namespace folly {
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template <typename T>
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constexpr T constexpr_max(T a, T b) {
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return a > b ? a : b;
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}
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template <typename T>
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constexpr T constexpr_min(T a, T b) {
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return a < b ? a : b;
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}
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namespace detail {
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template <typename T, typename = void>
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struct constexpr_abs_helper {};
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template <typename T>
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struct constexpr_abs_helper<
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T,
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typename std::enable_if<std::is_floating_point<T>::value>::type> {
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static constexpr T go(T t) {
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return t < static_cast<T>(0) ? -t : t;
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}
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};
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template <typename T>
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struct constexpr_abs_helper<
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T,
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typename std::enable_if<
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std::is_integral<T>::value && !std::is_same<T, bool>::value &&
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std::is_unsigned<T>::value>::type> {
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static constexpr T go(T t) {
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return t;
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}
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};
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template <typename T>
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struct constexpr_abs_helper<
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T,
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typename std::enable_if<
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std::is_integral<T>::value && !std::is_same<T, bool>::value &&
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std::is_signed<T>::value>::type> {
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static constexpr typename std::make_unsigned<T>::type go(T t) {
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return t < static_cast<T>(0) ? -t : t;
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}
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};
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}
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template <typename T>
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constexpr auto constexpr_abs(T t)
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-> decltype(detail::constexpr_abs_helper<T>::go(t)) {
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return detail::constexpr_abs_helper<T>::go(t);
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}
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#ifdef _MSC_VER
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constexpr size_t constexpr_strlen_internal(const char* s, size_t len) {
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return *s == '\0' ? len : constexpr_strlen_internal(s + 1, len + 1);
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}
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static_assert(constexpr_strlen_internal("123456789", 0) == 9,
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"Someone appears to have broken constexpr_strlen...");
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#endif
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constexpr size_t constexpr_strlen(const char* s) {
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#if defined(__clang__)
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return __builtin_strlen(s);
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#elif defined(_MSC_VER)
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return s == nullptr ? 0 : constexpr_strlen_internal(s, 0);
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#else
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return std::strlen(s);
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#endif
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}
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}
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