--- /dev/null
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * 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.
+ */
+
+#ifndef FOLLY_OPTIONAL_H_
+#define FOLLY_OPTIONAL_H_
+
+/*
+ * Optional - For conditional initialization of values, like boost::optional,
+ * but with support for move semantics and emplacement. Reference type support
+ * has not been included due to limited use cases and potential confusion with
+ * semantics of assignment: Assigning to an optional reference could quite
+ * reasonably copy its value or redirect the reference.
+ *
+ * Optional can be useful when a variable might or might not be needed:
+ *
+ * Optional<Logger> maybeLogger = ...;
+ * if (maybeLogger) {
+ * maybeLogger->log("hello");
+ * }
+ *
+ * Optional enables a 'null' value for types which do not otherwise have
+ * nullability, especially useful for parameter passing:
+ *
+ * void testIterator(const unique_ptr<Iterator>& it,
+ * initializer_list<int> idsExpected,
+ * Optional<initializer_list<int>> ranksExpected = none) {
+ * for (int i = 0; it->next(); ++i) {
+ * EXPECT_EQ(it->doc().id(), idsExpected[i]);
+ * if (ranksExpected) {
+ * EXPECT_EQ(it->doc().rank(), (*ranksExpected)[i]);
+ * }
+ * }
+ * }
+ *
+ * Optional models OptionalPointee, so calling 'get_pointer(opt)' will return a
+ * pointer to nullptr if the 'opt' is empty, and a pointer to the value if it is
+ * not:
+ *
+ * Optional<int> maybeInt = ...;
+ * if (int* v = get_pointer(maybeInt)) {
+ * cout << *v << endl;
+ * }
+ */
+#include <utility>
+#include <cassert>
+#include <cstddef>
+#include <type_traits>
+
+#include <boost/operators.hpp>
+
+namespace folly {
+
+namespace detail { struct NoneHelper {}; }
+
+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.
+ */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wuninitialized"
+
+template<class Value>
+class Optional : boost::totally_ordered<Optional<Value>,
+ boost::totally_ordered<Optional<Value>, Value>> {
+ typedef void (Optional::*bool_type)() const;
+ void truthy() const {};
+ public:
+ static_assert(!std::is_reference<Value>::value,
+ "Optional may not be used with reference types");
+
+ Optional()
+ : hasValue_(false) {
+ }
+
+ Optional(const Optional& src) {
+ construct(src.value());
+ }
+
+ Optional(Optional&& src) {
+ construct(std::move(src.value()));
+ src.clear();
+ }
+
+ /* implicit */ Optional(const None& empty)
+ : hasValue_(false) {
+ }
+
+ /* implicit */ Optional(Value&& newValue) {
+ construct(std::move(newValue));
+ }
+
+ /* implicit */ Optional(const Value& newValue) {
+ construct(newValue);
+ }
+
+ ~Optional() {
+ clear();
+ }
+
+ void assign(const None&) {
+ clear();
+ }
+
+ void assign(Optional&& src) {
+ if (src.hasValue()) {
+ assign(std::move(src.value()));
+ src.clear();
+ } else {
+ clear();
+ }
+ }
+
+ void assign(const Optional& src) {
+ if (src.hasValue()) {
+ assign(src.value());
+ } else {
+ clear();
+ }
+ }
+
+ void assign(Value&& newValue) {
+ if (hasValue()) {
+ value_ = std::move(newValue);
+ } else {
+ construct(std::move(newValue));
+ }
+ }
+
+ void assign(const Value& newValue) {
+ if (hasValue()) {
+ value_ = newValue;
+ } else {
+ construct(newValue);
+ }
+ }
+
+ template<class Arg>
+ Optional& operator=(Arg&& arg) {
+ assign(std::forward<Arg>(arg));
+ return *this;
+ }
+
+ bool operator<(const Optional& other) const {
+ if (hasValue() != other.hasValue()) {
+ return hasValue() < other.hasValue();
+ }
+ if (hasValue()) {
+ return value() < other.value();
+ }
+ return false; // both empty
+ }
+
+ bool operator<(const Value& other) const {
+ return !hasValue() || value() < other;
+ }
+
+ bool operator==(const Optional& other) const {
+ if (hasValue()) {
+ return other.hasValue() && value() == other.value();
+ } else {
+ return !other.hasValue();
+ }
+ }
+
+ bool operator==(const Value& other) const {
+ return hasValue() && value() == other;
+ }
+
+ template<class... Args>
+ void emplace(Args&&... args) {
+ clear();
+ construct(std::forward<Args>(args)...);
+ }
+
+ void clear() {
+ if (hasValue()) {
+ hasValue_ = false;
+ value().~Value();
+ }
+ }
+
+ const Value& value() const {
+ assert(hasValue());
+ return value_;
+ }
+
+ Value& value() {
+ assert(hasValue());
+ return value_;
+ }
+
+ bool hasValue() const { return hasValue_; }
+
+ /* safe bool idiom */
+ operator bool_type() const {
+ return hasValue() ? &Optional::truthy : nullptr;
+ }
+
+ const Value& operator*() const { return value(); }
+ Value& operator*() { return value(); }
+
+ const Value* operator->() const { return &value(); }
+ Value* operator->() { return &value(); }
+
+ private:
+ 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;
+ }
+
+ // uninitialized
+ union { Value value_; };
+ bool hasValue_;
+};
+
+#pragma GCC diagnostic pop
+
+template<class T>
+const T* get_pointer(const Optional<T>& opt) {
+ return opt ? &opt.value() : nullptr;
+}
+
+template<class T>
+T* get_pointer(Optional<T>& opt) {
+ return opt ? &opt.value() : nullptr;
+}
+
+template<class T>
+void swap(Optional<T>& a, Optional<T>& b) {
+ if (a.hasValue() && b.hasValue()) {
+ // both full
+ using std::swap;
+ swap(a.value(), b.value());
+ } else if (a.hasValue() || b.hasValue()) {
+ std::swap(a, b); // fall back to default implementation if they're mixed.
+ }
+}
+
+}// namespace folly
+
+#endif//FOLLY_OPTIONAL_H_
--- /dev/null
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * 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.
+ */
+
+#include "folly/Optional.h"
+
+#include <memory>
+#include <vector>
+#include <algorithm>
+#include <iomanip>
+#include <string>
+
+#include <glog/logging.h>
+#include <gtest/gtest.h>
+#include <boost/optional.hpp>
+
+using namespace folly;
+using std::unique_ptr;
+using std::shared_ptr;
+
+struct NoDefault {
+ NoDefault(int, int) {}
+ char a, b, c;
+};
+
+static_assert(sizeof(Optional<char>) == 2, "");
+static_assert(sizeof(Optional<int>) == 8, "");
+static_assert(sizeof(Optional<NoDefault>) == 4, "");
+static_assert(sizeof(Optional<char>) == sizeof(boost::optional<char>), "");
+static_assert(sizeof(Optional<short>) == sizeof(boost::optional<short>), "");
+static_assert(sizeof(Optional<int>) == sizeof(boost::optional<int>), "");
+static_assert(sizeof(Optional<double>) == sizeof(boost::optional<double>), "");
+
+TEST(Optional, NoDefault) {
+ Optional<NoDefault> x;
+ EXPECT_FALSE(x);
+ x.emplace(4, 5);
+ EXPECT_TRUE(x);
+ x.clear();
+ EXPECT_FALSE(x);
+}
+
+TEST(Optional, String) {
+ Optional<std::string> maybeString;
+ EXPECT_FALSE(maybeString);
+ maybeString = "hello";
+ EXPECT_TRUE(maybeString);
+}
+
+TEST(Optional, Const) {
+ { // default construct
+ Optional<const int> opt;
+ EXPECT_FALSE(opt);
+ opt.emplace(4);
+ EXPECT_EQ(opt, 4);
+ opt.emplace(5);
+ EXPECT_EQ(opt, 5);
+ opt.clear();
+ EXPECT_FALSE(opt);
+ }
+ { // copy-constructed
+ const int x = 6;
+ Optional<const int> opt(x);
+ EXPECT_EQ(opt, 6);
+ }
+ { // move-constructed
+ const int x = 7;
+ Optional<const int> opt(std::move(x));
+ EXPECT_EQ(opt, 7);
+ }
+ // no assignment allowed
+}
+
+TEST(Optional, Simple) {
+ Optional<int> opt;
+ EXPECT_FALSE(opt);
+ opt = 4;
+ EXPECT_TRUE(opt);
+ EXPECT_EQ(4, *opt);
+ opt = 5;
+ EXPECT_EQ(5, *opt);
+ opt.clear();
+ EXPECT_FALSE(opt);
+}
+
+TEST(Optional, Unique) {
+ Optional<unique_ptr<int>> opt;
+
+ opt.clear();
+ EXPECT_FALSE(opt);
+ // empty->emplaced
+ opt.emplace(new int(5));
+ EXPECT_TRUE(opt);
+ EXPECT_EQ(5, **opt);
+
+ opt.clear();
+ // empty->moved
+ opt = unique_ptr<int>(new int(6));
+ EXPECT_EQ(6, **opt);
+ // full->moved
+ opt = unique_ptr<int>(new int(7));
+ EXPECT_EQ(7, **opt);
+
+ // move it out by move construct
+ Optional<unique_ptr<int>> moved(std::move(opt));
+ EXPECT_TRUE(moved);
+ EXPECT_FALSE(opt);
+ EXPECT_EQ(7, **moved);
+
+ EXPECT_TRUE(moved);
+ opt = std::move(moved); // move it back by move assign
+ EXPECT_FALSE(moved);
+ EXPECT_TRUE(opt);
+ EXPECT_EQ(7, **opt);
+}
+
+TEST(Optional, Shared) {
+ shared_ptr<int> ptr;
+ Optional<shared_ptr<int>> opt;
+ EXPECT_FALSE(opt);
+ // empty->emplaced
+ opt.emplace(new int(5));
+ EXPECT_TRUE(opt);
+ ptr = opt.value();
+ EXPECT_EQ(ptr.get(), opt->get());
+ EXPECT_EQ(2, ptr.use_count());
+ opt.clear();
+ EXPECT_EQ(1, ptr.use_count());
+ // full->copied
+ opt = ptr;
+ EXPECT_EQ(2, ptr.use_count());
+ EXPECT_EQ(ptr.get(), opt->get());
+ opt.clear();
+ EXPECT_EQ(1, ptr.use_count());
+ // full->moved
+ opt = std::move(ptr);
+ EXPECT_EQ(1, opt->use_count());
+ EXPECT_EQ(nullptr, ptr.get());
+ {
+ Optional<shared_ptr<int>> copied(opt);
+ EXPECT_EQ(2, opt->use_count());
+ Optional<shared_ptr<int>> moved(std::move(opt));
+ EXPECT_EQ(2, moved->use_count());
+ moved.emplace(new int(6));
+ EXPECT_EQ(1, moved->use_count());
+ copied = moved;
+ EXPECT_EQ(2, moved->use_count());
+ }
+}
+
+TEST(Optional, Order) {
+ std::vector<Optional<int>> vect{
+ { none },
+ { 3 },
+ { 1 },
+ { none },
+ { 2 },
+ };
+ std::vector<Optional<int>> expected {
+ { none },
+ { none },
+ { 1 },
+ { 2 },
+ { 3 },
+ };
+ std::sort(vect.begin(), vect.end());
+ EXPECT_TRUE(vect == expected);
+}
+
+TEST(Optional, Swap) {
+ Optional<std::string> a;
+ Optional<std::string> b;
+
+ swap(a, b);
+ EXPECT_FALSE(a.hasValue());
+ EXPECT_FALSE(b.hasValue());
+
+ a = "hello";
+ EXPECT_TRUE(a.hasValue());
+ EXPECT_FALSE(b.hasValue());
+ EXPECT_EQ("hello", a.value());
+
+ swap(a, b);
+ EXPECT_FALSE(a.hasValue());
+ EXPECT_TRUE(b.hasValue());
+ EXPECT_EQ("hello", b.value());
+
+ a = "bye";
+ EXPECT_TRUE(a.hasValue());
+ EXPECT_EQ("bye", a.value());
+
+ swap(a, b);
+}
+
+TEST(Optional, Comparisons) {
+ Optional<int> o_;
+ Optional<int> o1(1);
+ Optional<int> o2(2);
+
+ EXPECT_TRUE(o_ < 1);
+ EXPECT_TRUE(o_ <= 1);
+ EXPECT_TRUE(o_ <= o_);
+ EXPECT_TRUE(o_ == o_);
+ EXPECT_TRUE(o_ != 1);
+ EXPECT_TRUE(o_ >= o_);
+ EXPECT_TRUE(1 >= o_);
+ EXPECT_TRUE(1 > o_);
+
+ EXPECT_TRUE(o1 < o2);
+ EXPECT_TRUE(o1 <= o2);
+ EXPECT_TRUE(o1 <= o1);
+ EXPECT_TRUE(o1 == o1);
+ EXPECT_TRUE(o1 != o2);
+ EXPECT_TRUE(o1 >= o1);
+ EXPECT_TRUE(o2 >= o1);
+ EXPECT_TRUE(o2 > o1);
+
+ EXPECT_FALSE(o2 < o1);
+ EXPECT_FALSE(o2 <= o1);
+ EXPECT_FALSE(o2 <= o1);
+ EXPECT_FALSE(o2 == o1);
+ EXPECT_FALSE(o1 != o1);
+ EXPECT_FALSE(o1 >= o2);
+ EXPECT_FALSE(o1 >= o2);
+ EXPECT_FALSE(o1 > o2);
+
+ EXPECT_TRUE(1 < o2);
+ EXPECT_TRUE(1 <= o2);
+ EXPECT_TRUE(1 <= o1);
+ EXPECT_TRUE(1 == o1);
+ EXPECT_TRUE(2 != o1);
+ EXPECT_TRUE(1 >= o1);
+ EXPECT_TRUE(2 >= o1);
+ EXPECT_TRUE(2 > o1);
+
+ EXPECT_FALSE(o2 < 1);
+ EXPECT_FALSE(o2 <= 1);
+ EXPECT_FALSE(o2 <= 1);
+ EXPECT_FALSE(o2 == 1);
+ EXPECT_FALSE(o2 != 2);
+ EXPECT_FALSE(o1 >= 2);
+ EXPECT_FALSE(o1 >= 2);
+ EXPECT_FALSE(o1 > 2);
+}
+
+TEST(Optional, Pointee) {
+ Optional<int> x;
+ EXPECT_FALSE(get_pointer(x));
+ x = 1;
+ EXPECT_TRUE(get_pointer(x));
+ *get_pointer(x) = 2;
+ EXPECT_TRUE(x == 2);
+ x = none;
+ EXPECT_FALSE(get_pointer(x));
+}
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