Changed GetDimensions to handle a stream at the end and one exit

Metadata/Models/Stateless/Dimensions.cs

@@ -8,16 +8,16 @@ internal static class Dimensions
 #pragma warning disable IDE0230
     private static readonly Dictionary<byte[], Func<BinaryReader, Size?>> _ImageFormatDecoders = new()
     {
+        { new byte[] { 0xff, 0xd8 }, DecodeJfif },
         { new byte[] { 0x42, 0x4D }, DecodeBitmap },
+        { new byte[] { 0x52, 0x49, 0x46, 0x46 }, DecodeWebP },
         { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x37, 0x61 }, DecodeGif },
         { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61 }, DecodeGif },
         { new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }, DecodePng },
-        { new byte[] { 0xff, 0xd8 }, DecodeJfif },
-        { new byte[] { 0x52, 0x49, 0x46, 0x46 }, DecodeWebP },
     };
 #pragma warning restore IDE0230
 
-    private static bool StartsWith(byte[] thisBytes, byte[] thatBytes)
+    private static bool StartsWith(List<byte> thisBytes, byte[] thatBytes)
     {
         for (int i = 0; i < thatBytes.Length; i += 1)
         {
@@ -103,30 +103,49 @@ internal static class Dimensions
 
     internal static Size? GetDimensions(BinaryReader binaryReader)
     {
-        int maxMagicBytesLength = _ImageFormatDecoders.Keys.OrderByDescending(x => x.Length).First().Length;
+        Size? result;
-        byte[] magicBytes = new byte[maxMagicBytesLength];
+        List<byte> magicBytes = [];
-        for (int i = 0; i < maxMagicBytesLength; i += 1)
+        int[] magicBytesLengths = (from l in _ImageFormatDecoders.Keys where l.Length <= binaryReader.BaseStream.Length orderby l.Length descending select l.Length).ToArray();
+        if (magicBytesLengths.Length == 0)
+            result = null;
+        else
         {
-            magicBytes[i] = binaryReader.ReadByte();
+            result = null;
+            if (binaryReader.BaseStream.Length == binaryReader.BaseStream.Position)
+                _ = binaryReader.BaseStream.Seek(0, SeekOrigin.Begin);
+            for (int i = 0; i < magicBytesLengths[0]; i++)
+            {
+                magicBytes.Add(binaryReader.ReadByte());
                 foreach (KeyValuePair<byte[], Func<BinaryReader, Size?>> kvPair in _ImageFormatDecoders)
                 {
                     if (StartsWith(magicBytes, kvPair.Key))
-                    return kvPair.Value(binaryReader);
+                    {
+                        result = kvPair.Value(binaryReader);
+                        break;
                     }
                 }
-        return null;
+                if (result is not null)
+                    break;
+            }
+        }
+        return result;
     }
 
     internal static Size? GetDimensions(string path)
     {
-        using BinaryReader binaryReader = new(File.OpenRead(path));
+        Size? result;
-        return GetDimensions(binaryReader);
+        using FileStream fileStream = File.OpenRead(path);
+        using BinaryReader binaryReader = new(fileStream);
+        result = GetDimensions(binaryReader);
+        return result;
     }
 
     internal static Size? GetDimensions(Stream stream)
     {
+        Size? result;
         using BinaryReader binaryReader = new(stream);
-        return GetDimensions(binaryReader);
+        result = GetDimensions(binaryReader);
+        return result;
     }
 
 }