gistfile1.cs

using System;
using Unity.Collections;
using Unity.Collections.LowLevel.Unsafe;
using Unity.Entities;
using UnityEngine;


public struct TerrainSprite
{
    public int TerrainId;
    public int VariantId;
    public int BitMaskId;

    public override int GetHashCode()
    {
        int hash = 13;
        hash = (hash * 7) + TerrainId;
        hash = (hash * 7) + VariantId;
        hash = (hash * 7) + BitMaskId;
        return hash;
    }
}

public struct DataLocation
{
    public int FirstValueIndex;
    public int TotalValues;
}

public class MyAmazingSystem : SystemBase
{
    public NativeHashMap<int, DataLocation> _map;
    public NativeList<Color32> _colors;

    // Test Data
    public const int ColorsPerSprite = 64;
    public const int SpriteCount = 100;
    private NativeList<TerrainSprite> _terrainSprites;

    protected override void OnCreate()
    {
        _map = new NativeHashMap<int, DataLocation>(1, Allocator.Persistent);
        _colors = new NativeList<Color32>(ColorsPerSprite, Allocator.Persistent);

        CreateSomeTestData();

        var startIndex = 0;
        for (int i = 0; i < _terrainSprites.Length; i++)
        {
            var sprite = _terrainSprites[i];

            for (int j = 0; j < ColorsPerSprite; j++)
                _colors.Add(new Color32());

            _map.Add(sprite.GetHashCode(), new DataLocation
            {
                FirstValueIndex = startIndex,

                // not nessecary if the color count is always the same.
                TotalValues = ColorsPerSprite
            });

            startIndex += ColorsPerSprite;
        }
    }

    private void CreateSomeTestData()
    {
        _terrainSprites = new NativeList<TerrainSprite>(SpriteCount, Allocator.Temp);
        for (int i = 0; i < SpriteCount; i++)
        {
            _terrainSprites[i] = new TerrainSprite
            {
                BitMaskId = UnityEngine.Random.Range(0, int.MaxValue),
                TerrainId = UnityEngine.Random.Range(0, int.MaxValue),
                VariantId = UnityEngine.Random.Range(0, int.MaxValue),
            };
        }
    }

    protected unsafe override void OnUpdate()
    {
        var randomSpriteIndex = UnityEngine.Random.Range(0, _terrainSprites.Length - 1);
        var spriteToFindColorsFor = _terrainSprites[randomSpriteIndex];

        var results = new NativeArray<Color>(ColorsPerSprite, Allocator.Temp);
        if (_map.TryGetValue(spriteToFindColorsFor.GetHashCode(), out var location))
        {
            var sourcePtr = (byte*)_colors.GetUnsafePtr() + location.FirstValueIndex * sizeof(Color32);
            var size = location.TotalValues * sizeof(Color32);
            UnsafeUtility.MemCpy(results.GetUnsafePtr(), sourcePtr, size);
        }

        // do something with results;
    }

    protected override void OnDestroy()
    {
        _terrainSprites.Dispose();
        _map.Dispose();
        _colors.Dispose();
    }
}