source: binary-improvements/7dtd-server-fixes/src/FileCache/MapTileCache.cs@ 224

using System;
using System.Collections.Generic;
using System.IO;

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

                private CurrentZoomFile[] cache;

                public MapTileCache ()
                {
                }

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

        }
}