Fix header finder

src/ImageSharp/Formats/Jpeg/Port/JpegDecoderCore.cs

@@ -10,6 +10,7 @@ namespace ImageSharp.Formats.Jpeg.Port
     using System.IO;
 
     using ImageSharp.Formats.Jpeg.Port.Components;
+    using ImageSharp.Memory;
     using ImageSharp.PixelFormats;
 
     /// <summary>
@@ -99,6 +100,8 @@ namespace ImageSharp.Formats.Jpeg.Port
             fileMarker = this.ReadUint16();
 
             this.quantizationTables = new QuantizationTables();
+            this.dcHuffmanTables = new HuffmanTables();
+            this.acHuffmanTables = new HuffmanTables();
 
             while (fileMarker != JpegConstants.Markers.EOI)
             {
@@ -342,9 +345,9 @@ namespace ImageSharp.Formats.Jpeg.Port
                 throw new ImageFormatException("DHT has wrong length");
             }
 
-            // TODO: Pool this
+            using (var huffmanData = new Buffer<byte>(remaining))
-            byte[] huffmanData = new byte[remaining];
+            {
-            this.InputStream.Read(huffmanData, 0, remaining);
+                this.InputStream.Read(huffmanData.Array, 1, remaining);
 
                 int o = 0;
                 for (int i = 0; i < remaining;)
@@ -388,9 +391,16 @@ namespace ImageSharp.Formats.Jpeg.Port
                         huffmanValues);
                 }
             }
+        }
 
         private void BuildHuffmanTable(HuffmanTables tables, int index, byte[] codeLengths, short[] values)
         {
+            int length = 16;
+            while (length > 0 && codeLengths[length - 1] == 0)
+            {
+                length--;
+            }
+
             Span<short> tableSpan = tables.Tables.GetRowSpan(index);
         }
 
@@ -432,7 +442,7 @@ namespace ImageSharp.Formats.Jpeg.Port
             {
                 int value = this.InputStream.Read(this.uint16Buffer, 0, 2);
 
-                if (value <= 0)
+                if (value == 0)
                 {
                     return JpegConstants.Markers.EOI;
                 }
@@ -459,7 +469,7 @@ namespace ImageSharp.Formats.Jpeg.Port
                     this.uint16Buffer[0] = this.uint16Buffer[1];
 
                     value = this.InputStream.ReadByte();
-                    if (value <= 0)
+                    if (value == -1)
                     {
                         return JpegConstants.Markers.EOI;
                     }