Grid.h

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/* Copyright (C) 2013 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef INCLUDED_GRID
#define INCLUDED_GRID

#include <cstring>

#ifdef NDEBUG
#define GRID_BOUNDS_DEBUG 0
#else
#define GRID_BOUNDS_DEBUG 1
#endif

/**
 * Basic 2D array, intended for storing tile data, plus support for lazy updates
 * by ICmpObstructionManager.
 * @c T must be a POD type that can be initialised with 0s.
 */
template<typename T>
class Grid
{
public:
    Grid() : m_W(0), m_H(0), m_Data(NULL), m_DirtyID(0)
    {
    }

    Grid(u16 w, u16 h) : m_W(w), m_H(h), m_Data(NULL), m_DirtyID(0)
    {
        if (m_W || m_H)
            m_Data = new T[m_W * m_H];
        reset();
    }

    Grid(const Grid& g)
    {
        m_Data = NULL;
        *this = g;
    }

    Grid& operator=(const Grid& g)
    {
        if (this != &g)
        {
            m_W = g.m_W;
            m_H = g.m_H;
            m_DirtyID = g.m_DirtyID;
            delete[] m_Data;
            if (g.m_Data)
            {
                m_Data = new T[m_W * m_H];
                memcpy(m_Data, g.m_Data, m_W*m_H*sizeof(T));
            }
            else
                m_Data = NULL;
        }
        return *this;
    }

    ~Grid()
    {
        delete[] m_Data;
    }

    void reset()
    {
        if (m_Data)
            memset(m_Data, 0, m_W*m_H*sizeof(T));
    }

    void set(int i, int j, const T& value)
    {
#if GRID_BOUNDS_DEBUG
        ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
#endif
        m_Data[j*m_W + i] = value;
    }

    T& get(int i, int j) const
    {
#if GRID_BOUNDS_DEBUG
        ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
#endif
        return m_Data[j*m_W + i];
    }

    u16 m_W, m_H;
    T* m_Data;

    size_t m_DirtyID; // if this is < the id maintained by ICmpObstructionManager then it needs to be updated
};

/**
 * Similar to Grid, except optimised for sparse usage (the grid is subdivided into
 * buckets whose contents are only initialised on demand, to save on memset cost).
 */
template<typename T>
class SparseGrid
{
    NONCOPYABLE(SparseGrid);

    enum { BucketBits = 4, BucketSize = 1 << BucketBits };

    T* GetBucket(int i, int j)
    {
        size_t b = (j >> BucketBits) * m_BW + (i >> BucketBits);
        if (!m_Data[b])
        {
            m_Data[b] = new T[BucketSize*BucketSize];
            memset(m_Data[b], 0, BucketSize*BucketSize*sizeof(T));
        }
        return m_Data[b];
    }

public:
    SparseGrid(u16 w, u16 h) : m_W(w), m_H(h), m_DirtyID(0)
    {
        ENSURE(m_W && m_H);

        m_BW = (u16)((m_W + BucketSize-1) >> BucketBits);
        m_BH = (u16)((m_H + BucketSize-1) >> BucketBits);

        m_Data = new T*[m_BW*m_BH];
        memset(m_Data, 0, m_BW*m_BH*sizeof(T*));
    }

    ~SparseGrid()
    {
        reset();
        delete[] m_Data;
    }

    void reset()
    {
        for (size_t i = 0; i < (size_t)(m_BW*m_BH); ++i)
            delete[] m_Data[i];

        memset(m_Data, 0, m_BW*m_BH*sizeof(T*));
    }

    void set(int i, int j, const T& value)
    {
#if GRID_BOUNDS_DEBUG
        ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
#endif
        GetBucket(i, j)[(j % BucketSize)*BucketSize + (i % BucketSize)] = value;
    }

    T& get(int i, int j)
    {
#if GRID_BOUNDS_DEBUG
        ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
#endif
        return GetBucket(i, j)[(j % BucketSize)*BucketSize + (i % BucketSize)];
    }

    u16 m_W, m_H;
    u16 m_BW, m_BH;
    T** m_Data;

    size_t m_DirtyID; // if this is < the id maintained by ICmpObstructionManager then it needs to be updated
};

#endif // INCLUDED_GRID