Source/WebCore/platform/PODInterval.h

/*
 * Copyright (C) 2010 Google Inc. All rights reserved.
 * Copyright (C) 2020 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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#pragma once

#ifndef NDEBUG
#include <wtf/text/TextStream.h>
#endif

namespace WebCore {

// Class template representing a closed interval which can hold arbitrary
// endpoints and a piece of user data. Ordering and equality are defined
// including the UserData, except in the special case of WeakPtr.
//
// Both the T and UserData types must support a copy constructor, operator<,
// operator==, and operator=, except that this does not depend on operator<
// or operator== for WeakPtr.
//
// In debug mode, printing of intervals and the data they contain is
// enabled. This uses WTF::TextStream.
//
// Note that this class supplies a copy constructor and assignment
// operator in order so it can be stored in the red-black tree.

// FIXME: The prefix "POD" here isn't correct; this works with non-POD types.

template<class T, class UserData> class PODIntervalBase {
public:
    const T& low() const { return m_low; }
    const T& high() const { return m_high; }
    const UserData& data() const { return m_data; }

    bool overlaps(const T& low, const T& high) const
    {
        return !(m_high < low || high < m_low);
    }

    bool overlaps(const PODIntervalBase& other) const
    {
        return overlaps(other.m_low, other.m_high);
    }

    const T& maxHigh() const { return m_maxHigh; }
    void setMaxHigh(const T& maxHigh) { m_maxHigh = maxHigh; }

protected:
    PODIntervalBase(const T& low, const T& high, UserData&& data)
        : m_low(low)
        , m_high(high)
        , m_data(WTFMove(data))
        , m_maxHigh(high)
    {
    }

#if COMPILER(MSVC)
    // Work around an MSVC bug.
    PODIntervalBase(const T& low, const T& high, const UserData& data)
        : m_low(low)
        , m_high(high)
        , m_data(data)
        , m_maxHigh(high)
    {
    }
#endif

private:
    T m_low;
    T m_high;
    UserData m_data { };
    T m_maxHigh;
};

template<class T, class UserData> class PODInterval : public PODIntervalBase<T, UserData> {
public:
    PODInterval(const T& low, const T& high, UserData&& data = { })
        : PODIntervalBase<T, UserData>(low, high, WTFMove(data))
    {
    }

    PODInterval(const T& low, const T& high, const UserData& data)
        : PODIntervalBase<T, UserData>(low, high, UserData { data })
    {
    }

    bool operator<(const PODInterval& other) const
    {
        if (Base::low() < other.Base::low())
            return true;
        if (other.Base::low() < Base::low())
            return false;
        if (Base::high() < other.Base::high())
            return true;
        if (other.Base::high() < Base::high())
            return false;
        return Base::data() < other.Base::data();
    }

    bool operator==(const PODInterval& other) const
    {
        return Base::low() == other.Base::low()
            && Base::high() == other.Base::high()
            && Base::data() == other.Base::data();
    }

private:
    using Base = PODIntervalBase<T, UserData>;
};

template<class T, class U> class PODInterval<T, WTF::WeakPtr<U>> : public PODIntervalBase<T, WTF::WeakPtr<U>> {
public:
    PODInterval(const T& low, const T& high, WTF::WeakPtr<U>&& data)
        : PODIntervalBase<T, WTF::WeakPtr<U>>(low, high, WTFMove(data))
    {
    }

    bool operator<(const PODInterval& other) const
    {
        if (Base::low() < other.Base::low())
            return true;
        if (other.Base::low() < Base::low())
            return false;
        return Base::high() < other.Base::high();
    }

private:
    using Base = PODIntervalBase<T, WTF::WeakPtr<U>>;
};

#ifndef NDEBUG

template<class T, class UserData>
TextStream& operator<<(TextStream& stream, const PODInterval<T, UserData>& interval)
{
    return stream << "[PODInterval (" << interval.low() << ", " << interval.high() << "), data=" << *interval.data() << ", maxHigh=" << interval.maxHigh() << ']';
}

#endif

} // namespace WebCore