From 5679c42dcaa130aec19defba5ffa821071e88f8e Mon Sep 17 00:00:00 2001
From: Dirk Lemstra <dirk@git.imagemagick.org>
Date: Sat, 3 Feb 2018 17:57:14 +0100
Subject: [PATCH] Move swap to classes to avoid odd issues on Mono.

---
 .../Common/Extensions/ComparableExtensions.cs      | 14 --------------
 src/ImageSharp/Formats/Png/PngDecoderCore.cs       | 12 +++++++++---
 src/ImageSharp/Formats/Png/PngEncoderCore.cs       |  5 +++--
 src/ImageSharp/Image/ImageFrame{TPixel}.cs         |  4 +++-
 4 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/src/ImageSharp/Common/Extensions/ComparableExtensions.cs b/src/ImageSharp/Common/Extensions/ComparableExtensions.cs
index 8bebb3de7..d6dade770 100644
--- a/src/ImageSharp/Common/Extensions/ComparableExtensions.cs
+++ b/src/ImageSharp/Common/Extensions/ComparableExtensions.cs
@@ -169,19 +169,5 @@ namespace SixLabors.ImageSharp
         {
             return (byte)value.Clamp(0, 255);
         }
-
-        /// <summary>
-        /// Swaps the references to two objects in memory.
-        /// </summary>
-        /// <param name="first">The first reference.</param>
-        /// <param name="second">The second reference.</param>
-        /// <typeparam name="T">The type of object.</typeparam>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void Swap<T>(ref T first, ref T second)
-        {
-            T temp = second;
-            second = first;
-            first = temp;
-        }
     }
 }
diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index 5cdf80289..e39187e08 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -14,7 +14,6 @@ using SixLabors.ImageSharp.Formats.Png.Zlib;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.MetaData;
 using SixLabors.ImageSharp.PixelFormats;
-using static SixLabors.ImageSharp.ComparableExtensions;
 
 namespace SixLabors.ImageSharp.Formats.Png
 {
@@ -589,7 +588,7 @@ namespace SixLabors.ImageSharp.Formats.Png
 
                 this.ProcessDefilteredScanline(this.scanline.Array, image);
 
-                Swap(ref this.scanline, ref this.previousScanline);
+                this.SwapBuffers();
                 this.currentRow++;
             }
         }
@@ -665,7 +664,7 @@ namespace SixLabors.ImageSharp.Formats.Png
                     Span<TPixel> rowSpan = image.GetPixelRowSpan(this.currentRow);
                     this.ProcessInterlacedDefilteredScanline(this.scanline.Array, rowSpan, Adam7FirstColumn[this.pass], Adam7ColumnIncrement[this.pass]);
 
-                    Swap(ref this.scanline, ref this.previousScanline);
+                    this.SwapBuffers();
 
                     this.currentRow += Adam7RowIncrement[this.pass];
                 }
@@ -1348,5 +1347,12 @@ namespace SixLabors.ImageSharp.Formats.Png
                 default: throw new ArgumentException($"Not a valid pass index: {passIndex}");
             }
         }
+
+        private void SwapBuffers()
+        {
+            Buffer<byte> temp = this.previousScanline;
+            this.previousScanline = this.scanline;
+            this.scanline = temp;
+        }
     }
 }
diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
index 6dbf2eeb8..385d40b6b 100644
--- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
@@ -11,7 +11,6 @@ using SixLabors.ImageSharp.Formats.Png.Zlib;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Quantizers;
-using static SixLabors.ImageSharp.ComparableExtensions;
 
 namespace SixLabors.ImageSharp.Formats.Png
 {
@@ -645,7 +644,9 @@ namespace SixLabors.ImageSharp.Formats.Png
                         Buffer<byte> r = this.EncodePixelRow(pixels.GetPixelRowSpan(y), y);
                         deflateStream.Write(r.Array, 0, resultLength);
 
-                        Swap(ref this.rawScanline, ref this.previousScanline);
+                        Buffer<byte> temp = this.rawScanline;
+                        this.rawScanline = this.previousScanline;
+                        this.previousScanline = temp;
                     }
                 }
 
diff --git a/src/ImageSharp/Image/ImageFrame{TPixel}.cs b/src/ImageSharp/Image/ImageFrame{TPixel}.cs
index e39cc1ab2..ba475f9cf 100644
--- a/src/ImageSharp/Image/ImageFrame{TPixel}.cs
+++ b/src/ImageSharp/Image/ImageFrame{TPixel}.cs
@@ -168,7 +168,9 @@ namespace SixLabors.ImageSharp
         {
             Guard.NotNull(pixelSource, nameof(pixelSource));
 
-            ComparableExtensions.Swap(ref this.pixelBuffer, ref pixelSource.pixelBuffer);
+            Buffer2D<TPixel> temp = this.pixelBuffer;
+            this.pixelBuffer = pixelSource.pixelBuffer;
+            pixelSource.pixelBuffer = temp;
         }
 
         /// <summary>