o3de/Code/Legacy/CryCommon/MiniQueue.h

/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */


// Description : a small memory overhead, fixed size, efficient, iterable
//               queue class  used for CContextView  SObjectClone


#ifndef CRYINCLUDE_CRYCOMMON_MINIQUEUE_H
#define CRYINCLUDE_CRYCOMMON_MINIQUEUE_H
#pragma once


// this class implements a very small queue of plain-old-data
template <typename T, uint8 N>
struct MiniQueue
{
public:
    MiniQueue()
        : m_nValues(0)
        , m_nOffset(0) {}

    MiniQueue(const MiniQueue& mq)
    {
        m_nValues = mq.m_nValues;
        m_nOffset = 0;
        for (int i = 0; i < m_nValues; i++)
        {
            m_vValues[i] = mq[i];
        }
    }

    bool Empty() const
    {
        return m_nValues == 0;
    }
    bool Full() const
    {
        return m_nValues == N;
    }
    uint8 Size() const
    {
        return m_nValues;
    }
    uint8 Capacity() const
    {
        return N;
    }
    ILINE void Push(T nValue)
    {
        assert(!Full());
        m_vValues[(m_nOffset + m_nValues) % N] = nValue;
        m_nValues++;
    }
    // push, but if the queue is full, then pop first
    void CyclePush(T nValue)
    {
        if (Full())
        {
            Pop();
        }
        Push(nValue);
    }
    void PushFront(T nValue)
    {
        assert(!Full());
        m_nOffset = (m_nOffset + (N - 1)) % N;
        m_vValues[m_nOffset] = nValue;
        m_nValues++;
    }
    T Front() const
    {
        assert(!Empty());
        return m_vValues[m_nOffset];
    }
    T& Front()
    {
        assert(!Empty());
        return m_vValues[m_nOffset];
    }
    T& operator[](int i)
    {
        return m_vValues[(m_nOffset + i) % N];
    }
    T operator[](int i) const
    {
        return m_vValues[(m_nOffset + i) % N];
    }
    T Back() const
    {
        assert(!Empty());
        return m_vValues[(m_nOffset + m_nValues - 1) % N];
    }
    T& Back()
    {
        assert(!Empty());
        return m_vValues[(m_nOffset + m_nValues - 1) % N];
    }
    void Pop()
    {
        assert(!Empty());
        m_nOffset = (m_nOffset + 1) % N;
        m_nValues--;
    }
    void PopBack()
    {
        assert(!Empty());
        m_nValues--;
    }
    void Clear()
    {
        m_nOffset = m_nValues = 0;
    }

    struct SIterator
    {
    public:
        SIterator() {}
        SIterator(T* pValues, uint8 nOffset)
            : m_pValues(pValues)
            , m_nOffset(nOffset) {}
        T& operator*()
        {
            return m_pValues[m_nOffset % N];
        }
        T* operator->()
        {
            return &m_pValues[m_nOffset % N];
        }
        SIterator& operator++()
        {
            m_nOffset++;
            return *this;
        }
        SIterator operator++(int)
        {
            SIterator itor = *this;
            ++m_nOffset;
            return itor;
        }
        SIterator& operator--()
        {
            m_nOffset--;
            return *this;
        }
        SIterator& operator+=(uint8 delta)
        {
            m_nOffset += delta;
            return *this;
        }
        SIterator& operator-=(uint8 delta)
        {
            m_nOffset -= delta;
            return *this;
        }

        friend bool operator!=(const SIterator& a, const SIterator& b)
        {
            assert(a.m_pValues == b.m_pValues);
            return a.m_nOffset != b.m_nOffset;
        }
        friend bool operator==(const SIterator& a, const SIterator& b)
        {
            assert(a.m_pValues == b.m_pValues);
            return a.m_nOffset == b.m_nOffset;
        }

        friend int operator-(const SIterator& a, const SIterator& b)
        {
            assert(a.m_pValues == b.m_pValues);
            int diff = int(a.m_nOffset) - int(b.m_nOffset);
            return diff;
        }

        uint8 Offset() { return m_nOffset; }

    private:
        T* m_pValues;
        uint8 m_nOffset;
    };

    SIterator Begin() { return SIterator(m_vValues, m_nOffset); }
    SIterator End() { return SIterator(m_vValues, m_nOffset + m_nValues); }

    SIterator RBegin() { return SIterator(m_vValues, m_nOffset + m_nValues - 1); }
    SIterator REnd() { return SIterator(m_vValues, m_nOffset - 1); }

    struct SConstIterator
    {
    public:
        SConstIterator() {}
        SConstIterator(const T* pValues, uint8 nOffset)
            : m_pValues(pValues)
            , m_nOffset(nOffset) {}
        const T& operator*()
        {
            return m_pValues[m_nOffset % N];
        }
        const T* operator->()
        {
            return &m_pValues[m_nOffset % N];
        }
        SConstIterator& operator++()
        {
            m_nOffset++;
            return *this;
        }
        SConstIterator& operator--()
        {
            m_nOffset--;
            return *this;
        }
        SConstIterator& operator+=(uint8 delta)
        {
            m_nOffset += delta;
            return *this;
        }
        SConstIterator& operator-=(uint8 delta)
        {
            m_nOffset -= delta;
            return *this;
        }
        friend bool operator!=(const SConstIterator& a, const SConstIterator& b)
        {
            assert(a.m_pValues == b.m_pValues);
            return a.m_nOffset != b.m_nOffset;
        }
        friend bool operator==(const SConstIterator& a, const SConstIterator& b)
        {
            assert(a.m_pValues == b.m_pValues);
            return a.m_nOffset == b.m_nOffset;
        }

        friend int operator-(const SConstIterator& a, const SConstIterator& b)
        {
            assert(a.m_pValues == b.m_pValues);
            int diff = int(a.m_nOffset) - int(b.m_nOffset);
            return diff;
        }

        uint8 Offset() { return m_nOffset; }

    private:
        const T* m_pValues;
        uint8 m_nOffset;
    };

    SConstIterator Begin() const { return SConstIterator(m_vValues, m_nOffset); }
    SConstIterator End() const { return SConstIterator(m_vValues, m_nOffset + m_nValues); }

    SConstIterator RBegin() const { return SConstIterator(m_vValues, m_nOffset + m_nValues - 1); }
    SConstIterator REnd() const { return SConstIterator(m_vValues, m_nOffset - 1); }

    void Erase(SIterator where)
    {
        assert(where.Offset() >= m_nOffset);
        assert(where.Offset() < m_nOffset + m_nValues);
        for (size_t offset = where.Offset(); offset < (size_t)(m_nOffset + m_nValues - 1); offset++)
        {
            m_vValues[offset % N] = m_vValues[(offset + 1) % N];
        }
        m_nValues--;
    }

    void Erase(SIterator first, SIterator last)
    {
        int num = last - first;
        if (num == 0)
        {
            return;
        }
        assert(num > 0);
        assert(num <= Size());
        assert(first.Offset() >= m_nOffset);
        assert(first.Offset() < m_nOffset + m_nValues);
        assert(last.Offset() >= m_nOffset);
        assert(last.Offset() <= m_nOffset + m_nValues);
        for (int offset = (int)first.Offset(); offset < m_nOffset + m_nValues - 1; offset++)
        {
            m_vValues[offset % N] = m_vValues[(offset + num) % N];
        }
        m_nValues -= num;
    }

private:
    uint8 m_nValues;
    uint8 m_nOffset;
    T m_vValues[N];
};

#endif // CRYINCLUDE_CRYCOMMON_MINIQUEUE_H