source: binary-improvements/7dtd-server-fixes/src/FileCache/MapTileCache.cs@ 326

using System;
using System.IO;
using UnityEngine;
using Object = UnityEngine.Object;

namespace AllocsFixes.FileCache {
        // Special "cache" for map tile folder as both map rendering and webserver access files in there.
        // Only map rendering tiles are cached. Writing is done by WriteThrough.
        public class MapTileCache : AbstractCache {
                private readonly byte[] transparentTile;
                private CurrentZoomFile[] cache;

                public MapTileCache (int _tileSize) {
                        Texture2D tex = new Texture2D (_tileSize, _tileSize);
                        Color nullColor = new Color (0, 0, 0, 0);
                        for (int x = 0; x < _tileSize; x++) {
                                for (int y = 0; y < _tileSize; y++) {
                                        tex.SetPixel (x, y, nullColor);
                                }
                        }

                        transparentTile = tex.EncodeToPNG ();
                        Object.Destroy (tex);
                }

                public void SetZoomCount (int count) {
                        cache = new CurrentZoomFile[count];
                }

                public byte[] LoadTile (int zoomlevel, string filename) {
                        try {
                                lock (cache) {
                                        if (cache [zoomlevel].filename == null || !cache [zoomlevel].filename.Equals (filename)) {
                                                cache [zoomlevel].filename = filename;

                                                if (!File.Exists (filename)) {
                                                        cache [zoomlevel].data = null;
                                                        return null;
                                                }

                                                cache [zoomlevel].data = File.ReadAllBytes (filename);
                                        }

                                        return cache [zoomlevel].data;
                                }
                        } catch (Exception e) {
                                Log.Out ("Error in MapTileCache.LoadTile: " + e);
                        }

                        return null;
                }

                public void SaveTile (int zoomlevel, byte[] content) {
                        try {
                                lock (cache) {
                                        if (cache [zoomlevel].filename == null) {
                                                return;
                                        }

                                        cache [zoomlevel].data = content;
                                        File.WriteAllBytes (cache [zoomlevel].filename, content);
                                }
                        } catch (Exception e) {
                                Log.Out ("Error in MapTileCache.SaveTile: " + e);
                        }
                }

                public override byte[] GetFileContent (string filename) {
                        try {
                                lock (cache) {
                                        foreach (CurrentZoomFile czf in cache) {
                                                if (czf.filename != null && czf.filename.Equals (filename)) {
                                                        return czf.data;
                                                }
                                        }

                                        if (!File.Exists (filename)) {
                                                return transparentTile;
                                        }

                                        return File.ReadAllBytes (filename);
                                }
                        } catch (Exception e) {
                                Log.Out ("Error in MapTileCache.GetFileContent: " + e);
                        }

                        return null;
                }

                private struct CurrentZoomFile {
                        public string filename;
                        public byte[] data;
                }
        }
}