/*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#ifndef FOLLY_OPTIONAL_H_
-#define FOLLY_OPTIONAL_H_
+#pragma once
/*
* Optional - For conditional initialization of values, like boost::optional,
* cout << *v << endl;
* }
*/
+
#include <cstddef>
+#include <functional>
+#include <new>
#include <stdexcept>
#include <type_traits>
#include <utility>
+#include <folly/Launder.h>
+#include <folly/Portability.h>
+#include <folly/Utility.h>
+
namespace folly {
-namespace detail { struct NoneHelper {}; }
+namespace detail {
+struct NoneHelper {};
+
+// Allow each translation unit to control its own -fexceptions setting.
+// If exceptions are disabled, std::terminate() will be called instead of
+// throwing OptionalEmptyException when the condition fails.
+[[noreturn]] void throw_optional_empty_exception();
+}
typedef int detail::NoneHelper::*None;
const None none = nullptr;
-/**
- * gcc-4.7 warns about use of uninitialized memory around the use of storage_
- * even though this is explicitly initialized at each point.
- */
-#if defined(__GNUC__) && !defined(__clang__)
-# pragma GCC diagnostic push
-# pragma GCC diagnostic ignored "-Wuninitialized"
-# pragma GCC diagnostic ignored "-Wpragmas"
-# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
-#endif // __GNUC__
-
class OptionalEmptyException : public std::runtime_error {
public:
OptionalEmptyException()
: std::runtime_error("Empty Optional cannot be unwrapped") {}
};
-template<class Value>
+template <class Value>
class Optional {
public:
typedef Value value_type;
- static_assert(!std::is_reference<Value>::value,
- "Optional may not be used with reference types");
- static_assert(!std::is_abstract<Value>::value,
- "Optional may not be used with abstract types");
-
- Optional() noexcept
- : hasValue_(false) {
- }
+ static_assert(
+ !std::is_reference<Value>::value,
+ "Optional may not be used with reference types");
+ static_assert(
+ !std::is_abstract<Value>::value,
+ "Optional may not be used with abstract types");
- Optional(const Optional& src)
- noexcept(std::is_nothrow_copy_constructible<Value>::value) {
+ Optional() noexcept {}
+ Optional(const Optional& src) noexcept(
+ std::is_nothrow_copy_constructible<Value>::value) {
if (src.hasValue()) {
- construct(src.value());
- } else {
- hasValue_ = false;
+ storage_.construct(src.value());
}
}
- Optional(Optional&& src)
- noexcept(std::is_nothrow_move_constructible<Value>::value) {
-
+ Optional(Optional&& src) noexcept(
+ std::is_nothrow_move_constructible<Value>::value) {
if (src.hasValue()) {
- construct(std::move(src.value()));
+ storage_.construct(std::move(src.value()));
src.clear();
- } else {
- hasValue_ = false;
}
}
- /* implicit */ Optional(const None&) noexcept
- : hasValue_(false) {
- }
+ /* implicit */ Optional(const None&) noexcept {}
- /* implicit */ Optional(Value&& newValue)
- noexcept(std::is_nothrow_move_constructible<Value>::value) {
- construct(std::move(newValue));
+ /* implicit */ Optional(Value&& newValue) noexcept(
+ std::is_nothrow_move_constructible<Value>::value) {
+ storage_.construct(std::move(newValue));
}
- /* implicit */ Optional(const Value& newValue)
- noexcept(std::is_nothrow_copy_constructible<Value>::value) {
- construct(newValue);
+ /* implicit */ Optional(const Value& newValue) noexcept(
+ std::is_nothrow_copy_constructible<Value>::value) {
+ storage_.construct(newValue);
}
- ~Optional() noexcept {
- clear();
+ template <typename... Args>
+ explicit Optional(in_place_t, Args&&... args) noexcept(
+ std::is_nothrow_constructible<Value, Args...>::value) {
+ storage_.construct(std::forward<Args>(args)...);
}
void assign(const None&) {
void assign(Value&& newValue) {
if (hasValue()) {
- value_ = std::move(newValue);
+ *storage_.value_pointer() = std::move(newValue);
} else {
- construct(std::move(newValue));
+ storage_.construct(std::move(newValue));
}
}
void assign(const Value& newValue) {
if (hasValue()) {
- value_ = newValue;
+ *storage_.value_pointer() = newValue;
} else {
- construct(newValue);
+ storage_.construct(newValue);
}
}
- template<class Arg>
+ template <class Arg>
Optional& operator=(Arg&& arg) {
assign(std::forward<Arg>(arg));
return *this;
}
- Optional& operator=(Optional &&other)
- noexcept (std::is_nothrow_move_assignable<Value>::value) {
-
+ Optional& operator=(Optional&& other) noexcept(
+ std::is_nothrow_move_assignable<Value>::value) {
assign(std::move(other));
return *this;
}
- Optional& operator=(const Optional &other)
- noexcept (std::is_nothrow_copy_assignable<Value>::value) {
-
+ Optional& operator=(const Optional& other) noexcept(
+ std::is_nothrow_copy_assignable<Value>::value) {
assign(other);
return *this;
}
- template<class... Args>
+ template <class... Args>
void emplace(Args&&... args) {
clear();
- construct(std::forward<Args>(args)...);
+
storage_.construct(std::forward<Args>(args)...);
}
void clear() {
- if (hasValue()) {
- hasValue_ = false;
- value_.~Value();
- }
+ storage_.clear();
}
- const Value& value() const& {
+ const Value& value() const & {
require_value();
- return value_;
+ return *storage_.value_pointer();
}
Value& value() & {
require_value();
- return value_;
+ return *storage_.value_pointer();
+ }
+
+ Value&& value() && {
+ require_value();
+ return std::move(*storage_.value_pointer());
}
- Value value() && {
+ const Value&& value() const && {
require_value();
- return std::move(value_);
+ return std::move(*storage_.value_pointer());
}
- const Value* get_pointer() const& { return hasValue_ ? &value_ : nullptr; }
- Value* get_pointer() & { return hasValue_ ? &value_ : nullptr; }
- Value* get_pointer() && = delete;
+ const Value* get_pointer() const & {
+ return storage_.value_pointer();
+ }
+ Value* get_pointer() & {
+ return storage_.value_pointer();
+ }
+ Value* get_pointer() && = delete;
- bool hasValue() const { return hasValue_; }
+ bool hasValue() const {
+ return storage_.hasValue();
+ }
explicit operator bool() const {
return hasValue();
}
- const Value& operator*() const& { return value(); }
- Value& operator*() & { return value(); }
- Value operator*() && { return std::move(value()); }
+ const Value& operator*() const & {
+ return value();
+ }
+ Value& operator*() & {
+ return value();
+ }
+ const Value&& operator*() const && {
+ return std::move(value());
+ }
+ Value&& operator*() && {
+ return std::move(value());
+ }
- const Value* operator->() const { return &value(); }
- Value* operator->() { return &value(); }
+ const Value* operator->() const {
+ return &value();
+ }
+ Value* operator->() {
+ return &value();
+ }
// Return a copy of the value if set, or a given default if not.
template <class U>
- Value value_or(U&& dflt) const& {
- return hasValue_ ? value_ : std::forward<U>(dflt);
+ Value value_or(U&& dflt) const & {
+ if (storage_.hasValue()) {
+ return *storage_.value_pointer();
+ }
+
+ return std::forward<U>(dflt);
}
template <class U>
Value value_or(U&& dflt) && {
- return hasValue_ ? std::move(value_) : std::forward<U>(dflt);
+ if (storage_.hasValue()) {
+ return std::move(*storage_.value_pointer());
+ }
+
+ return std::forward<U>(dflt);
}
private:
void require_value() const {
- if (!hasValue_) {
- throw OptionalEmptyException();
+ if (!storage_.hasValue()) {
+ detail::throw_optional_empty_exception();
}
}
- template<class... Args>
- void construct(Args&&... args) {
- const void* ptr = &value_;
- // for supporting const types
- new(const_cast<void*>(ptr)) Value(std::forward<Args>(args)...);
- hasValue_ = true;
- }
+ struct StorageTriviallyDestructible {
+ protected:
+ bool hasValue_;
+ typename std::aligned_storage<sizeof(Value), alignof(Value)>::type
+ value_[1];
- // uninitialized
- union { Value value_; };
- bool hasValue_;
-};
+ public:
+ StorageTriviallyDestructible() : hasValue_{false} {}
+ void clear() {
+ hasValue_ = false;
+ }
+ };
-#if defined(__GNUC__) && !defined(__clang__)
-#pragma GCC diagnostic pop
-#endif
+ struct StorageNonTriviallyDestructible {
+ protected:
+ bool hasValue_;
+ typename std::aligned_storage<sizeof(Value), alignof(Value)>::type
+ value_[1];
+
+ public:
+ StorageNonTriviallyDestructible() : hasValue_{false} {}
+ ~StorageNonTriviallyDestructible() {
+ clear();
+ }
+
+ void clear() {
+ if (hasValue_) {
+ hasValue_ = false;
+ launder(reinterpret_cast<Value*>(value_))->~Value();
+ }
+ }
+ };
+
+ struct Storage : std::conditional<
+ std::is_trivially_destructible<Value>::value,
+ StorageTriviallyDestructible,
+ StorageNonTriviallyDestructible>::type {
+ bool hasValue() const {
+ return this->hasValue_;
+ }
+
+ Value* value_pointer() {
+ if (this->hasValue_) {
+ return launder(reinterpret_cast<Value*>(this->value_));
+ }
+ return nullptr;
+ }
-template<class T>
+ Value const* value_pointer() const {
+ if (this->hasValue_) {
+ return launder(reinterpret_cast<Value const*>(this->value_));
+ }
+ return nullptr;
+ }
+
+ template <class... Args>
+ void construct(Args&&... args) {
+ new (raw_pointer()) Value(std::forward<Args>(args)...);
+ this->hasValue_ = true;
+ }
+
+ private:
+ void* raw_pointer() {
+ return static_cast<void*>(this->value_);
+ }
+ };
+
+ Storage storage_;
+};
+
+template <class T>
const T* get_pointer(const Optional<T>& opt) {
return opt.get_pointer();
}
-template<class T>
+template <class T>
T* get_pointer(Optional<T>& opt) {
return opt.get_pointer();
}
-template<class T>
+template <class T>
void swap(Optional<T>& a, Optional<T>& b) {
if (a.hasValue() && b.hasValue()) {
// both full
}
}
-template<class T,
- class Opt = Optional<typename std::decay<T>::type>>
+template <class T, class Opt = Optional<typename std::decay<T>::type>>
Opt make_optional(T&& v) {
return Opt(std::forward<T>(v));
}
///////////////////////////////////////////////////////////////////////////////
// Comparisons.
-template<class V>
-bool operator==(const Optional<V>& a, const V& b) {
+template <class U, class V>
+bool operator==(const Optional<U>& a, const V& b) {
return a.hasValue() && a.value() == b;
}
-template<class V>
-bool operator!=(const Optional<V>& a, const V& b) {
+template <class U, class V>
+bool operator!=(const Optional<U>& a, const V& b) {
return !(a == b);
}
-template<class V>
-bool operator==(const V& a, const Optional<V>& b) {
+template <class U, class V>
+bool operator==(const U& a, const Optional<V>& b) {
return b.hasValue() && b.value() == a;
}
-template<class V>
-bool operator!=(const V& a, const Optional<V>& b) {
+template <class U, class V>
+bool operator!=(const U& a, const Optional<V>& b) {
return !(a == b);
}
-template<class V>
-bool operator==(const Optional<V>& a, const Optional<V>& b) {
- if (a.hasValue() != b.hasValue()) { return false; }
- if (a.hasValue()) { return a.value() == b.value(); }
+template <class U, class V>
+bool operator==(const Optional<U>& a, const Optional<V>& b) {
+ if (a.hasValue() != b.hasValue()) {
+ return false;
+ }
+ if (a.hasValue()) {
+ return a.value() == b.value();
+ }
return true;
}
-template<class V>
-bool operator!=(const Optional<V>& a, const Optional<V>& b) {
+template <class U, class V>
+bool operator!=(const Optional<U>& a, const Optional<V>& b) {
return !(a == b);
}
-template<class V>
-bool operator< (const Optional<V>& a, const Optional<V>& b) {
- if (a.hasValue() != b.hasValue()) { return a.hasValue() < b.hasValue(); }
- if (a.hasValue()) { return a.value() < b.value(); }
+template <class U, class V>
+bool operator<(const Optional<U>& a, const Optional<V>& b) {
+ if (a.hasValue() != b.hasValue()) {
+ return a.hasValue() < b.hasValue();
+ }
+ if (a.hasValue()) {
+ return a.value() < b.value();
+ }
return false;
}
-template<class V>
-bool operator> (const Optional<V>& a, const Optional<V>& b) {
+template <class U, class V>
+bool operator>(const Optional<U>& a, const Optional<V>& b) {
return b < a;
}
-template<class V>
-bool operator<=(const Optional<V>& a, const Optional<V>& b) {
+template <class U, class V>
+bool operator<=(const Optional<U>& a, const Optional<V>& b) {
return !(b < a);
}
-template<class V>
-bool operator>=(const Optional<V>& a, const Optional<V>& b) {
+template <class U, class V>
+bool operator>=(const Optional<U>& a, const Optional<V>& b) {
return !(a < b);
}
// Suppress comparability of Optional<T> with T, despite implicit conversion.
-template<class V> bool operator< (const Optional<V>&, const V& other) = delete;
-template<class V> bool operator<=(const Optional<V>&, const V& other) = delete;
-template<class V> bool operator>=(const Optional<V>&, const V& other) = delete;
-template<class V> bool operator> (const Optional<V>&, const V& other) = delete;
-template<class V> bool operator< (const V& other, const Optional<V>&) = delete;
-template<class V> bool operator<=(const V& other, const Optional<V>&) = delete;
-template<class V> bool operator>=(const V& other, const Optional<V>&) = delete;
-template<class V> bool operator> (const V& other, const Optional<V>&) = delete;
+template <class V>
+bool operator<(const Optional<V>&, const V& other) = delete;
+template <class V>
+bool operator<=(const Optional<V>&, const V& other) = delete;
+template <class V>
+bool operator>=(const Optional<V>&, const V& other) = delete;
+template <class V>
+bool operator>(const Optional<V>&, const V& other) = delete;
+template <class V>
+bool operator<(const V& other, const Optional<V>&) = delete;
+template <class V>
+bool operator<=(const V& other, const Optional<V>&) = delete;
+template <class V>
+bool operator>=(const V& other, const Optional<V>&) = delete;
+template <class V>
+bool operator>(const V& other, const Optional<V>&) = delete;
///////////////////////////////////////////////////////////////////////////////
} // namespace folly
-#endif // FOLLY_OPTIONAL_H_
+// Allow usage of Optional<T> in std::unordered_map and std::unordered_set
+FOLLY_NAMESPACE_STD_BEGIN
+template <class T>
+struct hash<folly::Optional<T>> {
+ size_t operator()(folly::Optional<T> const& obj) const {
+ if (!obj.hasValue()) {
+ return 0;
+ }
+ return hash<typename remove_const<T>::type>()(*obj);
+ }
+};
+FOLLY_NAMESPACE_STD_END
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