From 14f7ff8fb74a7cd20eb799e70328439fac3c075d Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 21 Mar 2018 08:41:47 -0700
Subject: [PATCH] Remove ReverseBytes (replacing with faster BinaryPrimitives
 calls)

---
 .../Common/Extensions/ByteExtensions.cs       | 33 -------------------
 src/ImageSharp/Formats/Png/PngDecoderCore.cs  | 12 +++----
 src/ImageSharp/Formats/Png/PngEncoderCore.cs  | 11 ++++---
 3 files changed, 12 insertions(+), 44 deletions(-)

diff --git a/src/ImageSharp/Common/Extensions/ByteExtensions.cs b/src/ImageSharp/Common/Extensions/ByteExtensions.cs
index f6c720795..b5b868dea 100644
--- a/src/ImageSharp/Common/Extensions/ByteExtensions.cs
+++ b/src/ImageSharp/Common/Extensions/ByteExtensions.cs
@@ -12,39 +12,6 @@ namespace SixLabors.ImageSharp
     /// </summary>
     internal static class ByteExtensions
     {
-        /// <summary>
-        /// Optimized <see cref="T:byte[]"/> reversal algorithm.
-        /// </summary>
-        /// <param name="source">The byte array.</param>
-        public static void ReverseBytes(this byte[] source)
-        {
-            ReverseBytes(source, 0, source.Length);
-        }
-
-        /// <summary>
-        /// Optimized <see cref="T:byte[]"/> reversal algorithm.
-        /// </summary>
-        /// <param name="source">The byte array.</param>
-        /// <param name="index">The index.</param>
-        /// <param name="length">The length.</param>
-        /// <exception cref="System.ArgumentNullException"><paramref name="source"/> is null.</exception>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReverseBytes(this byte[] source, int index, int length)
-        {
-            Guard.NotNull(source, nameof(source));
-
-            int i = index;
-            int j = index + length - 1;
-            while (i < j)
-            {
-                byte temp = source[i];
-                source[i] = source[j];
-                source[j] = temp;
-                i++;
-                j--;
-            }
-        }
-
         /// <summary>
         /// Returns a reference to the given position of the array unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
         /// </summary>
diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index fbb5c29a4..349fa7745 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -1251,14 +1251,13 @@ namespace SixLabors.ImageSharp.Formats.Png
         private void ReadChunkCrc(PngChunk chunk)
         {
             int numBytes = this.currentStream.Read(this.crcBuffer, 0, 4);
+
             if (numBytes >= 1 && numBytes <= 3)
             {
                 throw new ImageFormatException("Image stream is not valid!");
             }
-
-            this.crcBuffer.ReverseBytes();
-
-            chunk.Crc = BitConverter.ToUInt32(this.crcBuffer, 0);
+            
+            chunk.Crc = BinaryPrimitives.ReadUInt32BigEndian(this.crcBuffer);
 
             this.crc.Reset();
             this.crc.Update(this.chunkTypeBuffer);
@@ -1323,15 +1322,14 @@ namespace SixLabors.ImageSharp.Formats.Png
         private void ReadChunkLength(PngChunk chunk)
         {
             int numBytes = this.currentStream.Read(this.chunkLengthBuffer, 0, 4);
+
             if (numBytes < 4)
             {
                 chunk.Length = -1;
                 return;
             }
 
-            this.chunkLengthBuffer.ReverseBytes();
-
-            chunk.Length = BitConverter.ToInt32(this.chunkLengthBuffer, 0);
+            chunk.Length = BinaryPrimitives.ReadInt32BigEndian(this.chunkLengthBuffer);
         }
 
         /// <summary>
diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
index 7ae075569..55bf1bbec 100644
--- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
@@ -5,6 +5,7 @@ using System;
 using System.Buffers.Binary;
 using System.IO;
 using System.Linq;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Formats.Png.Filters;
 using SixLabors.ImageSharp.Formats.Png.Zlib;
@@ -251,9 +252,10 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <param name="value">The value to write.</param>
         private static void WriteInteger(Stream stream, int value)
         {
-            byte[] buffer = BitConverter.GetBytes(value);
+            byte[] buffer = new byte[4];
+
+            BinaryPrimitives.WriteInt32BigEndian(buffer, value);
 
-            buffer.ReverseBytes();
             stream.Write(buffer, 0, 4);
         }
 
@@ -264,9 +266,10 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <param name="value">The value to write.</param>
         private static void WriteInteger(Stream stream, uint value)
         {
-            byte[] buffer = BitConverter.GetBytes(value);
+            byte[] buffer = new byte[4];
+
+            BinaryPrimitives.WriteUInt32BigEndian(buffer, value);
 
-            buffer.ReverseBytes();
             stream.Write(buffer, 0, 4);
         }