From 22449d642ad91fe5da6fc785cc5f5adfd01a38e7 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Wed, 29 Jul 2020 16:28:50 +0100
Subject: [PATCH] Use MemoryMarshal.CreateSpan

---
 Directory.Build.props                         | 26 +++++++++++--------
 .../Jpeg/Components/GenericBlock8x8.cs        | 10 ++++++-
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/Directory.Build.props b/Directory.Build.props
index 14c9da79d..0f9c5bdde 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -30,17 +30,17 @@
 
   <!--
     https://apisof.net/
-    +===================+=======+==========+=====================+=============+=================+====================+==============+=========+
-    | SUPPORTS          | MATHF | HASHCODE | EXTENDED_INTRINSICS | SPAN_STREAM | ENCODING_STRING | RUNTIME_INTRINSICS | CODECOVERAGE | HOTPATH |
-    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|
-    | netcoreapp3.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        Y           |      Y       |    Y    |
-    | netcoreapp2.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        N           |      Y       |    N    |
-    | netcoreapp2.0     |   Y   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |
-    | netstandard2.1    |   Y   |    Y     |         N           |      Y      |        Y        |        N           |      Y       |    N    |
-    | netstandard2.0    |   N   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |
-    | netstandard1.3    |   N   |    N     |         N           |      N      |        N        |        N           |      N       |    N    |
-    | net472            |   N   |    N     |         Y           |      N      |        N        |        N           |      Y       |    N    |
-    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|
+    +===================+=======+==========+=====================+=============+=================+====================+==============+=========+============|
+    | SUPPORTS          | MATHF | HASHCODE | EXTENDED_INTRINSICS | SPAN_STREAM | ENCODING_STRING | RUNTIME_INTRINSICS | CODECOVERAGE | HOTPATH | CREATESPAN |
+    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|============|
+    | netcoreapp3.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        Y           |      Y       |    Y    |      Y     |
+    | netcoreapp2.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        N           |      Y       |    N    |      Y     |
+    | netcoreapp2.0     |   Y   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |      Y     |
+    | netstandard2.1    |   Y   |    Y     |         N           |      Y      |        Y        |        N           |      Y       |    N    |      Y     |
+    | netstandard2.0    |   N   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |      N     |
+    | netstandard1.3    |   N   |    N     |         N           |      N      |        N        |        N           |      N       |    N    |      N     |
+    | net472            |   N   |    N     |         Y           |      N      |        N        |        N           |      Y       |    N    |      N     |
+    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|============|
     -->
 
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
@@ -52,6 +52,7 @@
     <DefineConstants>$(DefineConstants);SUPPORTS_RUNTIME_INTRINSICS</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_HOTPATH</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp2.1'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MATHF</DefineConstants>
@@ -60,10 +61,12 @@
     <DefineConstants>$(DefineConstants);SUPPORTS_SPAN_STREAM</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_ENCODING_STRING</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp2.0'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MATHF</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.1'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MATHF</DefineConstants>
@@ -71,6 +74,7 @@
     <DefineConstants>$(DefineConstants);SUPPORTS_SPAN_STREAM</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_ENCODING_STRING</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
diff --git a/src/ImageSharp/Formats/Jpeg/Components/GenericBlock8x8.cs b/src/ImageSharp/Formats/Jpeg/Components/GenericBlock8x8.cs
index 38b902b88..92ba1afd3 100644
--- a/src/ImageSharp/Formats/Jpeg/Components/GenericBlock8x8.cs
+++ b/src/ImageSharp/Formats/Jpeg/Components/GenericBlock8x8.cs
@@ -109,6 +109,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
         /// <summary>
         /// Only for on-stack instances!
         /// </summary>
-        public Span<T> AsSpanUnsafe() => new Span<T>(Unsafe.AsPointer(ref this), Size);
+        public Span<T> AsSpanUnsafe()
+        {
+#if SUPPORTS_CREATESPAN
+            Span<GenericBlock8x8<T>> s = MemoryMarshal.CreateSpan(ref this, 1);
+            return MemoryMarshal.Cast<GenericBlock8x8<T>, T>(s);
+#else
+            return new Span<T>(Unsafe.AsPointer(ref this), Size);
+#endif
+        }
     }
 }