Grid.h

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/* Copyright (C) 2020 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 "simulation2/serialization/SerializeTemplates.h"

#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
{
    friend struct SerializeHelper<Grid<T>>;
protected:
    // Tag-dispatching internal utilities for convenience.
    struct default_type{};
    struct is_pod { operator default_type() { return default_type{}; }};
    struct is_container { operator default_type() { return default_type{}; }};

    // helper to detect value_type
    template <typename U, typename = int> struct has_value_type : std::false_type { };
    template <typename U> struct has_value_type <U, decltype(std::declval<typename U::value_type>(), 0)> : std::true_type { };

    template <typename U, typename A, typename B> using if_ = typename std::conditional<U::value, A, B>::type;

    template<typename U>
    using dispatch = if_< std::is_pod<U>, is_pod,
                          if_<has_value_type<U>, is_container,
                        default_type>>;

public:
    Grid() : m_W(0), m_H(0), m_Data(NULL)
    {
    }

    Grid(u16 w, u16 h) : m_W(w), m_H(h), m_Data(NULL)
    {
        resize(w, h);
    }

    Grid(const Grid& g) : m_W(0), m_H(0), m_Data(NULL)
    {
        *this = g;
    }

    using value_type = T;
public:

    // Ensure that o and this are the same size before calling.
    void copy_data(T* o, default_type) { std::copy(o, o + m_H*m_W, &m_Data[0]); }
    void copy_data(T* o, is_pod) { memcpy(m_Data, o, m_W*m_H*sizeof(T)); }

    Grid& operator=(const Grid& g)
    {
        if (this == &g)
            return *this;

        if (m_W == g.m_W && m_H == g.m_H)
        {
            copy_data(g.m_Data, dispatch<T>{});
            return *this;
        }

        m_W = g.m_W;
        m_H = g.m_H;
        SAFE_ARRAY_DELETE(m_Data);
        if (g.m_Data)
        {
            m_Data = new T[m_W * m_H];
            copy_data(g.m_Data, dispatch<T>{});
        }
        return *this;
    }

    void swap(Grid& g)
    {
        std::swap(m_Data, g.m_Data);
        std::swap(m_H, g.m_H);
        std::swap(m_W, g.m_W);
    }

    ~Grid()
    {
        SAFE_ARRAY_DELETE(m_Data);
    }

    // Ensure that o and this are the same size before calling.
    bool compare_data(T* o, default_type) const { return std::equal(&m_Data[0], &m_Data[m_W*m_H], o); }
    bool compare_data(T* o, is_pod) const { return memcmp(m_Data, o, m_W*m_H*sizeof(T)) == 0; }

    bool operator==(const Grid& g) const
    {
        if (!compare_sizes(&g))
            return false;

        return compare_data(g.m_Data, dispatch<T>{});
    }
    bool operator!=(const Grid& g) const { return !(*this==g); }

    bool blank() const
    {
        return m_W == 0 && m_H == 0;
    }

    u16 width() const { return m_W; };
    u16 height() const { return m_H; };


    bool _any_set_in_square(int, int, int, int, default_type) const
    {
        static_assert(!std::is_same<T, T>::value, "Not implemented.");
        return false; // Fix warnings.
    }
    bool _any_set_in_square(int i0, int j0, int i1, int j1, is_pod) const
    {
#if GRID_BOUNDS_DEBUG
        ENSURE(i0 >= 0 && j0 >= 0 && i1 <= m_W && j1 <= m_H);
#endif
        for (int j = j0; j < j1; ++j)
        {
            int sum = 0;
            for (int i = i0; i < i1; ++i)
                sum += m_Data[j*m_W + i];
            if (sum > 0)
                return true;
        }
        return false;
    }

    bool any_set_in_square(int i0, int j0, int i1, int j1) const
    {
        return _any_set_in_square(i0, j0, i1, j1, dispatch<T>{});
    }

    void reset_data(default_type) { std::fill(&m_Data[0], &m_Data[m_H*m_W], T{}); }
    void reset_data(is_pod) { memset(m_Data, 0, m_W*m_H*sizeof(T)); }

    // Reset the data to its default-constructed value (usually 0), not changing size.
    void reset()
    {
        if (m_Data)
            reset_data(dispatch<T>{});
    }

    // Clear the grid setting the size to 0 and freeing any data.
    void clear()
    {
        resize(0, 0);
    }

    void resize(u16 w, u16 h)
    {
        SAFE_ARRAY_DELETE(m_Data);
        m_W = w;
        m_H = h;

        if (!m_W && !m_H)
            return;

        m_Data = new T[m_W * m_H];
        ENSURE(m_Data);
        reset();
    }

    // Add two grids of the same size
    void add(const Grid& g)
    {
#if GRID_BOUNDS_DEBUG
        ENSURE(g.m_W == m_W && g.m_H == m_H);
#endif
        for (int i=0; i < m_H*m_W; ++i)
            m_Data[i] += g.m_Data[i];
    }

    void bitwise_or(const Grid& g)
    {
        if (this == &g)
            return;

#if GRID_BOUNDS_DEBUG
        ENSURE(g.m_W == m_W && g.m_H == m_H);
#endif
        for (int i = 0; i < m_H*m_W; ++i)
            m_Data[i] |= g.m_Data[i];
    }

    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& operator[](std::pair<u16, u16> coords) { return get(coords.first, coords.second); }
    T& get(std::pair<u16, u16> coords) { return get(coords.first, coords.second); }

    T& operator[](std::pair<u16, u16> coords) const { return get(coords.first, coords.second); }
    T& get(std::pair<u16, u16> coords) const { return get(coords.first, coords.second); }

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

    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];
    }

    template<typename U>
    bool compare_sizes(const Grid<U>* g) const
    {
        return g && m_W == g->m_W && m_H == g->m_H;
    }

    u16 m_W, m_H;
    T* m_Data;
};


/**
 * Serialize a grid, applying a simple RLE compression that is assumed efficient.
 */
template<typename T>
struct SerializeHelper<Grid<T>>
{
    void operator()(ISerializer& serialize, const char* name, Grid<T>& value)
    {
        size_t len = value.m_H * value.m_W;
        serialize.NumberU16_Unbounded("width", value.m_W);
        serialize.NumberU16_Unbounded("height", value.m_H);
        if (len == 0)
            return;
        u32 count = 1;
        T prevVal = value.m_Data[0];
        for (size_t i = 1; i < len; ++i)
        {
            if (prevVal == value.m_Data[i])
            {
                count++;
                continue;
            }
            serialize.NumberU32_Unbounded("#", count);
            Serializer(serialize, name, prevVal);
            count = 1;
            prevVal = value.m_Data[i];
        }
        serialize.NumberU32_Unbounded("#", count);
        Serializer(serialize, name, prevVal);
    }

    void operator()(IDeserializer& deserialize, const char* name, Grid<T>& value)
    {
        u16 w, h;
        deserialize.NumberU16_Unbounded("width", w);
        deserialize.NumberU16_Unbounded("height", h);
        u32 len = h * w;
        value.resize(w, h);
        for (size_t i = 0; i < len;)
        {
            u32 count;
            deserialize.NumberU32_Unbounded("#", count);
            T el;
            Serializer(deserialize, name, el);
            std::fill(&value.m_Data[i], &value.m_Data[i+count], el);
            i += count;
        }
    }
};


/**
 * 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]();
        }
        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]();
    }

    ~SparseGrid()
    {
        reset();
        SAFE_ARRAY_DELETE(m_Data);
    }

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

        // Reset m_Data by value-constructing in place with placement new.
        m_Data = new (m_Data) T*[m_BW*m_BH]();
    }

    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
};

/**
 * Structure holding grid dirtiness informations, for clever updates.
 */
struct GridUpdateInformation
{
    bool dirty;
    bool globallyDirty;
    Grid<u8> dirtinessGrid;

    /**
     * Update the information with additionnal needed updates, then erase the source of additions.
     * This can usually be optimized through a careful memory management.
     */
    void MergeAndClear(GridUpdateInformation& b)
    {
        ENSURE(dirtinessGrid.compare_sizes(&b.dirtinessGrid));

        bool wasDirty = dirty;

        dirty |= b.dirty;
        globallyDirty |= b.globallyDirty;

        // If the current grid is useless, swap it
        if (!wasDirty)
            dirtinessGrid.swap(b.dirtinessGrid);
        // If the new grid isn't used, don't bother updating it
        else if (dirty && !globallyDirty)
            dirtinessGrid.bitwise_or(b.dirtinessGrid);

        b.Clean();
    }

    /**
     * Mark everything as clean
     */
    void Clean()
    {
        dirty = false;
        globallyDirty = false;
        dirtinessGrid.reset();
    }
};

#endif // INCLUDED_GRID