From 85287118a5964ee35357bdeba35d627a882cf388 Mon Sep 17 00:00:00 2001
From: ClemensF <fischer.clemens@gmail.com>
Date: Thu, 18 Jul 2019 21:09:54 +0200
Subject: [PATCH] Version 4.12.2  Improved TileImageLoader.Cache

---
 FileDbCache/WPF/FileDbCache.WPF.csproj |  6 +++
 FileDbCache/WPF/FileDbCache.cs         | 49 +++++++++--------------
 MBTiles/Shared/MBTileData.cs           | 25 ++++++++----
 MBTiles/Shared/MBTileLayer.cs          |  4 +-
 MBTiles/Shared/MBTileSource.cs         | 51 ++++++++++++------------
 MapControl/UWP/ImageFileCache.UWP.cs   | 18 ++++++---
 MapControl/WPF/ImageFileCache.WPF.cs   | 47 ++++++++++++++++------
 MapControl/WPF/TileImageLoader.WPF.cs  | 55 ++++++++++++--------------
 8 files changed, 139 insertions(+), 116 deletions(-)

diff --git a/FileDbCache/WPF/FileDbCache.WPF.csproj b/FileDbCache/WPF/FileDbCache.WPF.csproj
index b722e9de..599a64a6 100644
--- a/FileDbCache/WPF/FileDbCache.WPF.csproj
+++ b/FileDbCache/WPF/FileDbCache.WPF.csproj
@@ -53,6 +53,12 @@
     </None>
     <None Include="packages.config" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\MapControl\WPF\MapControl.WPF.csproj">
+      <Project>{a204a102-c745-4d65-aec8-7b96faedef2d}</Project>
+      <Name>MapControl.WPF</Name>
+    </ProjectReference>
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
diff --git a/FileDbCache/WPF/FileDbCache.cs b/FileDbCache/WPF/FileDbCache.cs
index d3de540a..117b44af 100644
--- a/FileDbCache/WPF/FileDbCache.cs
+++ b/FileDbCache/WPF/FileDbCache.cs
@@ -149,11 +149,15 @@ namespace MapControl.Caching
             {
                 try
                 {
-                    var record = fileDb.GetRecordByKey(key, new string[] { valueField }, false);
+                    var record = fileDb.GetRecordByKey(key, new string[] { valueField, expiresField }, false);
 
                     if (record != null)
                     {
-                        return record[0];
+                        return new ImageCacheItem
+                        {
+                            Buffer = (byte[])record[0],
+                            Expiration = (DateTime)record[1]
+                        };
                     }
                 }
                 catch (Exception ex)
@@ -184,38 +188,21 @@ namespace MapControl.Caching
                 throw new ArgumentNullException("The parameter key must not be null.");
             }
 
-            if (value == null)
-            {
-                throw new ArgumentNullException("The parameter value must not be null.");
-            }
-
-            if (policy == null)
-            {
-                throw new ArgumentNullException("The parameter policy must not be null.");
-            }
-
             if (regionName != null)
             {
                 throw new NotSupportedException("The parameter regionName must be null.");
             }
 
-            if (fileDb.IsOpen)
+            var imageCacheItem = value as ImageCacheItem;
+
+            if (imageCacheItem == null || imageCacheItem.Buffer == null || imageCacheItem.Buffer.Length == 0)
             {
-                var expiration = DateTime.MaxValue;
+                throw new NotSupportedException("The parameter value must be an ImageCacheItem with a non-empty Buffer.");
+            }
 
-                if (policy.AbsoluteExpiration != InfiniteAbsoluteExpiration)
-                {
-                    expiration = policy.AbsoluteExpiration.DateTime;
-                }
-                else if (policy.SlidingExpiration != NoSlidingExpiration)
-                {
-                    expiration = DateTime.UtcNow + policy.SlidingExpiration;
-                }
-
-                if (!AddOrUpdateRecord(key, value, expiration) && RepairDatabase())
-                {
-                    AddOrUpdateRecord(key, value, expiration);
-                }
+            if (fileDb.IsOpen && !AddOrUpdateRecord(key, imageCacheItem) && RepairDatabase())
+            {
+                AddOrUpdateRecord(key, imageCacheItem);
             }
         }
 
@@ -354,11 +341,11 @@ namespace MapControl.Caching
             return false;
         }
 
-        private bool AddOrUpdateRecord(string key, object value, DateTime expiration)
+        private bool AddOrUpdateRecord(string key, ImageCacheItem imageCacheItem)
         {
             var fieldValues = new FieldValues(3);
-            fieldValues.Add(valueField, value);
-            fieldValues.Add(expiresField, expiration);
+            fieldValues.Add(valueField, imageCacheItem.Buffer);
+            fieldValues.Add(expiresField, imageCacheItem.Expiration);
 
             bool recordExists;
 
@@ -398,7 +385,7 @@ namespace MapControl.Caching
                 }
             }
 
-            //Debug.WriteLine("FileDbCache: Writing \"{0}\", Expires {1}", key, expiration.ToLocalTime());
+            //Debug.WriteLine("FileDbCache: Writing \"{0}\", Expires {1}", key, imageCacheItem.Expiration.ToLocalTime());
             return true;
         }
     }
diff --git a/MBTiles/Shared/MBTileData.cs b/MBTiles/Shared/MBTileData.cs
index c079345a..5693706e 100644
--- a/MBTiles/Shared/MBTileData.cs
+++ b/MBTiles/Shared/MBTileData.cs
@@ -20,12 +20,12 @@ namespace MapControl.MBTiles
     {
         private readonly SQLiteConnection connection;
 
-        public MBTileData(string file)
+        private MBTileData(string file)
         {
             connection = new SQLiteConnection("Data Source=" + Path.GetFullPath(file));
         }
 
-        public async Task OpenAsync()
+        private async Task OpenAsync()
         {
             await connection.OpenAsync();
 
@@ -40,6 +40,15 @@ namespace MapControl.MBTiles
             }
         }
 
+        public static async Task<MBTileData> CreateAsync(string file)
+        {
+            var tileData = new MBTileData(file);
+
+            await tileData.OpenAsync();
+
+            return tileData;
+        }
+
         public void Close()
         {
             connection.Close();
@@ -50,9 +59,9 @@ namespace MapControl.MBTiles
             connection.Dispose();
         }
 
-        public async Task<IDictionary<string, string>> ReadMetadataAsync()
+        public async Task<IDictionary<string, string>> ReadMetaDataAsync()
         {
-            var metadata = new Dictionary<string, string>();
+            var metaData = new Dictionary<string, string>();
 
             try
             {
@@ -62,7 +71,7 @@ namespace MapControl.MBTiles
 
                     while (await reader.ReadAsync())
                     {
-                        metadata[(string)reader["name"]] = (string)reader["value"];
+                        metaData[(string)reader["name"]] = (string)reader["value"];
                     }
                 }
             }
@@ -71,16 +80,16 @@ namespace MapControl.MBTiles
                 Debug.WriteLine("MBTileData: " + ex.Message);
             }
 
-            return metadata;
+            return metaData;
         }
 
-        public async Task WriteMetadataAsync(IDictionary<string, string> metadata)
+        public async Task WriteMetaDataAsync(IDictionary<string, string> metaData)
         {
             try
             {
                 using (var command = new SQLiteCommand("insert or replace into metadata (name, value) values (@n, @v)", connection))
                 {
-                    foreach (var keyValue in metadata)
+                    foreach (var keyValue in metaData)
                     {
                         command.Parameters.AddWithValue("@n", keyValue.Key);
                         command.Parameters.AddWithValue("@v", keyValue.Value);
diff --git a/MBTiles/Shared/MBTileLayer.cs b/MBTiles/Shared/MBTileLayer.cs
index d21819d8..e0745dbe 100644
--- a/MBTiles/Shared/MBTileLayer.cs
+++ b/MBTiles/Shared/MBTileLayer.cs
@@ -72,9 +72,7 @@ namespace MapControl.MBTiles
 
             if (file != null)
             {
-                mbTileSource = new MBTileSource(file);
-
-                await mbTileSource.Initialize();
+                mbTileSource = await MBTileSource.CreateAsync(file);
 
                 if (mbTileSource.Name != null)
                 {
diff --git a/MBTiles/Shared/MBTileSource.cs b/MBTiles/Shared/MBTileSource.cs
index 5db7d4a7..779551a7 100644
--- a/MBTiles/Shared/MBTileSource.cs
+++ b/MBTiles/Shared/MBTileSource.cs
@@ -3,6 +3,7 @@
 // Licensed under the Microsoft Public License (Ms-PL)
 
 using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 #if WINDOWS_UWP
 using Windows.UI.Xaml.Media;
@@ -16,47 +17,45 @@ namespace MapControl.MBTiles
     {
         private readonly MBTileData tileData;
 
-        public MBTileSource(string file)
+        public string Name { get; }
+        public string Description { get; }
+        public int? MinZoom { get; }
+        public int? MaxZoom { get; }
+
+        private MBTileSource(MBTileData tileData, IDictionary<string, string> metaData)
         {
-            tileData = new MBTileData(file);
-        }
-
-        public string Name { get; private set; }
-        public string Description { get; private set; }
-        public int? MinZoom { get; private set; }
-        public int? MaxZoom { get; private set; }
-
-        public async Task Initialize()
-        {
-            await tileData.OpenAsync();
-
-            var metadata = await tileData.ReadMetadataAsync();
+            this.tileData = tileData;
 
             string s;
             int minZoom;
             int maxZoom;
 
-            Name = (metadata.TryGetValue("name", out s)) ? s : null;
+            if (metaData.TryGetValue("name", out s))
+            {
+                Name = s;
+            }
 
-            Description = (metadata.TryGetValue("description", out s)) ? s : null;
+            if (metaData.TryGetValue("description", out s))
+            {
+                Description = s;
+            }
 
-            if (metadata.TryGetValue("minzoom", out s) && int.TryParse(s, out minZoom))
+            if (metaData.TryGetValue("minzoom", out s) && int.TryParse(s, out minZoom))
             {
                 MinZoom = minZoom;
             }
-            else
-            {
-                MinZoom = null;
-            }
 
-            if (metadata.TryGetValue("maxzoom", out s) && int.TryParse(s, out maxZoom))
+            if (metaData.TryGetValue("maxzoom", out s) && int.TryParse(s, out maxZoom))
             {
                 MaxZoom = maxZoom;
             }
-            else
-            {
-                MaxZoom = null;
-            }
+        }
+
+        public static async Task<MBTileSource> CreateAsync(string file)
+        {
+            var tileData = await MBTileData.CreateAsync(file);
+
+            return new MBTileSource(tileData, await tileData.ReadMetaDataAsync());
         }
 
         public void Dispose()
diff --git a/MapControl/UWP/ImageFileCache.UWP.cs b/MapControl/UWP/ImageFileCache.UWP.cs
index 090a162b..73459857 100644
--- a/MapControl/UWP/ImageFileCache.UWP.cs
+++ b/MapControl/UWP/ImageFileCache.UWP.cs
@@ -33,7 +33,7 @@ namespace MapControl.Caching
 
             try
             {
-                path = Path.Combine(key.Split('\\', '/', ':', ';'));
+                path = Path.Combine(GetPathElements(key));
             }
             catch (Exception ex)
             {
@@ -69,18 +69,18 @@ namespace MapControl.Caching
 
         public async Task SetAsync(string key, IBuffer buffer, DateTime expiration)
         {
-            var paths = key.Split('\\', '/', ',', ':', ';');
+            var folders = GetPathElements(key);
 
             try
             {
                 var folder = rootFolder;
 
-                for (int i = 0; i < paths.Length - 1; i++)
+                for (int i = 0; i < folders.Length - 1; i++)
                 {
-                    folder = await folder.CreateFolderAsync(paths[i], CreationCollisionOption.OpenIfExists);
+                    folder = await folder.CreateFolderAsync(folders[i], CreationCollisionOption.OpenIfExists);
                 }
 
-                var file = await folder.CreateFileAsync(paths[paths.Length - 1], CreationCollisionOption.ReplaceExisting);
+                var file = await folder.CreateFileAsync(folders[folders.Length - 1], CreationCollisionOption.ReplaceExisting);
                 //Debug.WriteLine("ImageFileCache: Writing {0}, Expires {1}", file.Path, expiration.ToLocalTime());
 
                 await FileIO.WriteBufferAsync(file, buffer);
@@ -88,12 +88,18 @@ namespace MapControl.Caching
                 // Store expiration date in ImageProperties.DateTaken
                 var properties = await file.Properties.GetImagePropertiesAsync();
                 properties.DateTaken = expiration;
+
                 await properties.SavePropertiesAsync();
             }
             catch (Exception ex)
             {
-                Debug.WriteLine("ImageFileCache: Writing {0}\\{1}: {2}", rootFolder.Path, string.Join("\\", paths), ex.Message);
+                Debug.WriteLine("ImageFileCache: Writing {0}: {1}", Path.Combine(rootFolder.Path, Path.Combine(folders)), ex.Message);
             }
         }
+
+        private string[] GetPathElements(string key)
+        {
+            return key.Split('\\', '/', ',', ':', ';');
+        }
     }
 }
diff --git a/MapControl/WPF/ImageFileCache.WPF.cs b/MapControl/WPF/ImageFileCache.WPF.cs
index 9263d114..c860b7b2 100644
--- a/MapControl/WPF/ImageFileCache.WPF.cs
+++ b/MapControl/WPF/ImageFileCache.WPF.cs
@@ -10,12 +10,13 @@ using System.Linq;
 using System.Runtime.Caching;
 using System.Security.AccessControl;
 using System.Security.Principal;
+using System.Text;
 
 namespace MapControl.Caching
 {
     /// <summary>
     /// ObjectCache implementation based on local image files.
-    /// The only valid data type for cached values is byte[].
+    /// The only valid data type for cached values is MapControl.ImageCacheItem.
     /// </summary>
     public class ImageFileCache : ObjectCache
     {
@@ -96,9 +97,9 @@ namespace MapControl.Caching
                 throw new NotSupportedException("The parameter regionName must be null.");
             }
 
-            var buffer = memoryCache.Get(key) as byte[];
+            var imageCacheItem = memoryCache.Get(key) as ImageCacheItem;
 
-            if (buffer == null)
+            if (imageCacheItem == null)
             {
                 var path = FindFile(key);
 
@@ -106,10 +107,24 @@ namespace MapControl.Caching
                 {
                     try
                     {
-                        //Debug.WriteLine("ImageFileCache: Reading " + path);
+                        var buffer = File.ReadAllBytes(path);
+                        var expiration = DateTime.MinValue;
 
-                        buffer = File.ReadAllBytes(path);
-                        memoryCache.Set(key, buffer, new CacheItemPolicy());
+                        if (buffer.Length > 16 && Encoding.ASCII.GetString(buffer, buffer.Length - 16, 8) == "EXPIRES:")
+                        {
+                            expiration = new DateTime(BitConverter.ToInt64(buffer, buffer.Length - 8), DateTimeKind.Utc);
+                            Array.Resize(ref buffer, buffer.Length - 16);
+                        }
+
+                        imageCacheItem = new ImageCacheItem
+                        {
+                            Buffer = buffer,
+                            Expiration = expiration
+                        };
+
+                        memoryCache.Set(key, imageCacheItem, new CacheItemPolicy { AbsoluteExpiration = expiration });
+
+                        //Debug.WriteLine("ImageFileCache: Reading {0}, Expires {1}", path, imageCacheItem.Expiration.ToLocalTime());
                     }
                     catch (Exception ex)
                     {
@@ -118,7 +133,7 @@ namespace MapControl.Caching
                 }
             }
 
-            return buffer;
+            return imageCacheItem;
         }
 
         public override CacheItem GetCacheItem(string key, string regionName = null)
@@ -145,14 +160,14 @@ namespace MapControl.Caching
                 throw new NotSupportedException("The parameter regionName must be null.");
             }
 
-            var buffer = value as byte[];
+            var imageCacheItem = value as ImageCacheItem;
 
-            if (buffer == null || buffer.Length == 0)
+            if (imageCacheItem == null || imageCacheItem.Buffer == null || imageCacheItem.Buffer.Length == 0)
             {
-                throw new NotSupportedException("The parameter value must be a non-empty byte array.");
+                throw new NotSupportedException("The parameter value must be an ImageCacheItem with a non-empty Buffer.");
             }
 
-            memoryCache.Set(key, buffer, policy);
+            memoryCache.Set(key, imageCacheItem, policy);
 
             var path = GetPath(key);
 
@@ -160,10 +175,16 @@ namespace MapControl.Caching
             {
                 try
                 {
-                    //Debug.WriteLine("ImageFileCache: Writing {0}, Expires {1}", path, policy.AbsoluteExpiration.DateTime.ToLocalTime());
+                    //Debug.WriteLine("ImageFileCache: Writing {0}, Expires {1}", path, imageCacheItem.Expiration.ToLocalTime());
 
                     Directory.CreateDirectory(Path.GetDirectoryName(path));
-                    File.WriteAllBytes(path, buffer);
+
+                    using (var stream = File.Create(path))
+                    {
+                        stream.Write(imageCacheItem.Buffer, 0, imageCacheItem.Buffer.Length);
+                        stream.Write(Encoding.ASCII.GetBytes("EXPIRES:"), 0, 8);
+                        stream.Write(BitConverter.GetBytes(imageCacheItem.Expiration.Ticks), 0, 8);
+                    }
 
                     var fileSecurity = File.GetAccessControl(path);
                     fileSecurity.AddAccessRule(fullControlRule);
diff --git a/MapControl/WPF/TileImageLoader.WPF.cs b/MapControl/WPF/TileImageLoader.WPF.cs
index d1e6e64d..c34cb290 100644
--- a/MapControl/WPF/TileImageLoader.WPF.cs
+++ b/MapControl/WPF/TileImageLoader.WPF.cs
@@ -5,17 +5,21 @@
 using System;
 using System.IO;
 using System.Runtime.Caching;
-using System.Text;
 using System.Threading.Tasks;
 using System.Windows.Media;
 
 namespace MapControl
 {
+    public class ImageCacheItem
+    {
+        public byte[] Buffer { get; set; }
+        public DateTime Expiration { get; set; }
+    }
+
     public partial class TileImageLoader
     {
         /// <summary>
-        /// Default folder path where an ObjectCache instance may save cached data,
-        /// i.e. C:\ProgramData\MapControl\TileCache
+        /// Default folder path where an ObjectCache instance may save cached data, i.e. C:\ProgramData\MapControl\TileCache
         /// </summary>
         public static string DefaultCacheFolder
         {
@@ -23,17 +27,18 @@ namespace MapControl
         }
 
         /// <summary>
-        /// The ObjectCache used to cache tile images. The default is MemoryCache.Default.
+        /// An ObjectCache instance used to cache tile image data (i.e. ImageCacheItem objects).
+        /// The default ObjectCache value is MemoryCache.Default.
         /// </summary>
         public static ObjectCache Cache { get; set; } = MemoryCache.Default;
 
 
         private static async Task LoadCachedTileImageAsync(Tile tile, Uri uri, string cacheKey)
         {
-            DateTime expiration;
-            var buffer = GetCachedImage(cacheKey, out expiration);
+            var cacheItem = await GetCacheAsync(cacheKey).ConfigureAwait(false);
+            var buffer = cacheItem?.Buffer;
 
-            if (buffer == null || expiration < DateTime.UtcNow)
+            if (buffer == null || cacheItem.Expiration < DateTime.UtcNow)
             {
                 var response = await ImageLoader.GetHttpResponseAsync(uri, false).ConfigureAwait(false);
 
@@ -43,7 +48,7 @@ namespace MapControl
 
                     if (buffer != null) // tile image available
                     {
-                        await SetCachedImage(cacheKey, buffer, GetExpiration(response.MaxAge)).ConfigureAwait(false);
+                        await SetCacheAsync(cacheKey, buffer, GetExpiration(response.MaxAge)).ConfigureAwait(false);
                     }
                 }
             }
@@ -69,33 +74,25 @@ namespace MapControl
             tile.Image.Dispatcher.InvokeAsync(() => tile.SetImage(image));
         }
 
-        private static byte[] GetCachedImage(string cacheKey, out DateTime expiration)
+        private static Task<ImageCacheItem> GetCacheAsync(string cacheKey)
         {
-            var buffer = Cache.Get(cacheKey) as byte[];
-
-            if (buffer != null && buffer.Length >= 16 &&
-                Encoding.ASCII.GetString(buffer, buffer.Length - 16, 8) == "EXPIRES:")
-            {
-                expiration = new DateTime(BitConverter.ToInt64(buffer, buffer.Length - 8), DateTimeKind.Utc);
-            }
-            else
-            {
-                expiration = DateTime.MinValue;
-            }
-
-            return buffer;
+            return Task.Run(() => Cache.Get(cacheKey) as ImageCacheItem);
         }
 
-        private static async Task SetCachedImage(string cacheKey, byte[] buffer, DateTime expiration)
+        private static Task SetCacheAsync(string cacheKey, byte[] buffer, DateTime expiration)
         {
-            using (var stream = new MemoryStream(buffer.Length + 16))
+            var imageCacheItem = new ImageCacheItem
             {
-                await stream.WriteAsync(buffer, 0, buffer.Length).ConfigureAwait(false);
-                await stream.WriteAsync(Encoding.ASCII.GetBytes("EXPIRES:"), 0, 8).ConfigureAwait(false);
-                await stream.WriteAsync(BitConverter.GetBytes(expiration.Ticks), 0, 8).ConfigureAwait(false);
+                Buffer = buffer,
+                Expiration = expiration
+            };
 
-                Cache.Set(cacheKey, stream.ToArray(), new CacheItemPolicy { AbsoluteExpiration = expiration });
-            }
+            var cacheItemPolicy = new CacheItemPolicy
+            {
+                AbsoluteExpiration = expiration
+            };
+
+            return Task.Run(() => Cache.Set(cacheKey, imageCacheItem, cacheItemPolicy));
         }
     }
 }