Optional.h - mozsearch

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//

// Copyright 2015 The ANGLE Project Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

//

// Optional.h:

//   Represents a type that may be invalid, similar to std::optional.

//

#ifndef COMMON_OPTIONAL_H_

#define COMMON_OPTIONAL_H_

#include <utility>

template <class T>

struct Optional

    Optional() : mValid(false), mValue(T()) {}

    Optional(const T &valueIn) : mValid(true), mValue(valueIn) {}

    Optional(const Optional &other) : mValid(other.mValid), mValue(other.mValue) {}

    Optional &operator=(const Optional &other)

        this->mValid = other.mValid;

        this->mValue = other.mValue;

        return *this;

    Optional &operator=(const T &value)

        mValue = value;

        mValid = true;

        return *this;

    Optional &operator=(T &&value)

        mValue = std::move(value);

        mValid = true;

        return *this;

    void reset() { mValid = false; }

    T &&release()

        mValid = false;

        return std::move(mValue);

    static Optional Invalid() { return Optional(); }

    bool valid() const { return mValid; }

    T &value() { return mValue; }

    const T &value() const { return mValue; }

    bool operator==(const Optional &other) const

        return ((mValid == other.mValid) && (!mValid || (mValue == other.mValue)));

    bool operator!=(const Optional &other) const { return !(*this == other); }

    bool operator==(const T &value) const { return mValid && (mValue == value); }

    bool operator!=(const T &value) const { return !(*this == value); }

  private:

    bool mValid;

    T mValue;

};

#endif  // COMMON_OPTIONAL_H_