项目结构调整

Others/WpfAnimatedGif/Decoding/GifApplicationExtension.cs

@@ -0,0 +1,50 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace WpfAnimatedGif.Decoding
+{
+    // label 0xFF
+    internal class GifApplicationExtension : GifExtension
+    {
+        internal const int ExtensionLabel = 0xFF;
+
+        public int BlockSize { get; private set; }
+        public string ApplicationIdentifier { get; private set; }
+        public byte[] AuthenticationCode { get; private set; }
+        public byte[] Data { get; private set; }
+
+        private GifApplicationExtension()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.SpecialPurpose; }
+        }
+
+        internal static GifApplicationExtension ReadApplication(Stream stream)
+        {
+            var ext = new GifApplicationExtension();
+            ext.Read(stream);
+            return ext;
+        }
+
+        private void Read(Stream stream)
+        {
+            // Note: at this point, the label (0xFF) has already been read
+
+            byte[] bytes = new byte[12];
+            stream.ReadAll(bytes, 0, bytes.Length);
+            BlockSize = bytes[0]; // should always be 11
+            if (BlockSize != 11)
+                throw GifHelpers.InvalidBlockSizeException("Application Extension", 11, BlockSize);
+
+            ApplicationIdentifier = Encoding.ASCII.GetString(bytes, 1, 8);
+            byte[] authCode = new byte[3];
+            Array.Copy(bytes, 9, authCode, 0, 3);
+            AuthenticationCode = authCode;
+            Data = GifHelpers.ReadDataBlocks(stream, false);
+        }
+    }
+}