From 48b45a4791847c090f4c7e423fbcbf80a1944846 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Tue, 15 Nov 2016 23:19:21 +1100
Subject: [PATCH] Reuse Crc

---
 src/ImageSharp/Formats/Png/PngDecoderCore.cs | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index f31af2b49d..4d581b2b6e 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -44,6 +44,11 @@ namespace ImageSharp.Formats
         /// </summary>
         private readonly char[] chars = new char[4];
 
+        /// <summary>
+        /// Reusable crc for validating chunks.
+        /// </summary>
+        private readonly Crc32 crc = new Crc32();
+
         /// <summary>
         /// The stream to decode from.
         /// </summary>
@@ -594,11 +599,11 @@ namespace ImageSharp.Formats
 
             chunk.Crc = BitConverter.ToUInt32(this.crcBuffer, 0);
 
-            Crc32 crc = new Crc32();
-            crc.Update(this.chunkTypeBuffer);
-            crc.Update(chunk.Data, 0, chunk.Length);
+            this.crc.Reset();
+            this.crc.Update(this.chunkTypeBuffer);
+            this.crc.Update(chunk.Data, 0, chunk.Length);
 
-            if (crc.Value != chunk.Crc)
+            if (this.crc.Value != chunk.Crc)
             {
                 throw new ImageFormatException("CRC Error. PNG Image chunk is corrupt!");
             }