From bb641e13a24c1d76ed5b80bf41ab693daa4d4c5c Mon Sep 17 00:00:00 2001
From: Sam Harwell <Sam.Harwell@microsoft.com>
Date: Thu, 27 Apr 2023 11:13:46 -0500
Subject: [PATCH] Use optimized hash creation methods on .NET 5+

---
 .../Workspace/Solution/Checksum_Factory.cs    | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/Checksum_Factory.cs b/src/Workspaces/Core/Portable/Workspace/Solution/Checksum_Factory.cs
index 5dcf4f0a2367e..bfc1b283da99c 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/Checksum_Factory.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/Checksum_Factory.cs
@@ -34,6 +34,19 @@ internal partial class Checksum
 
         public static Checksum Create(IEnumerable<string> values)
         {
+#if NET5_0_OR_GREATER
+            using var pooledHash = s_incrementalHashPool.GetPooledObject();
+
+            foreach (var value in values)
+            {
+                pooledHash.Object.AppendData(MemoryMarshal.AsBytes(value.AsSpan()));
+                pooledHash.Object.AppendData(MemoryMarshal.AsBytes("\0".AsSpan()));
+            }
+
+            Span<byte> hash = stackalloc byte[SHA256HashSizeBytes];
+            pooledHash.Object.GetHashAndReset(hash);
+            return From(hash);
+#else
             using var pooledHash = s_incrementalHashPool.GetPooledObject();
             using var pooledBuffer = SharedPools.ByteArray.GetPooledObject();
             var hash = pooledHash.Object;
@@ -45,10 +58,16 @@ public static Checksum Create(IEnumerable<string> values)
             }
 
             return From(hash.GetHashAndReset());
+#endif
         }
 
         public static Checksum Create(string value)
         {
+#if NET5_0_OR_GREATER
+            Span<byte> hash = stackalloc byte[SHA256HashSizeBytes];
+            SHA256.HashData(MemoryMarshal.AsBytes(value.AsSpan()), hash);
+            return From(hash);
+#else
             using var pooledHash = s_incrementalHashPool.GetPooledObject();
             using var pooledBuffer = SharedPools.ByteArray.GetPooledObject();
             var hash = pooledHash.Object;
@@ -56,10 +75,34 @@ public static Checksum Create(string value)
             AppendData(hash, pooledBuffer.Object, value);
 
             return From(hash.GetHashAndReset());
+#endif
         }
 
         public static Checksum Create(Stream stream)
         {
+#if NET7_0_OR_GREATER
+            Span<byte> hash = stackalloc byte[SHA256HashSizeBytes];
+            SHA256.HashData(stream, hash);
+            return From(hash);
+#elif NET5_0_OR_GREATER
+            using var pooledHash = s_incrementalHashPool.GetPooledObject();
+            Span<byte> buffer = stackalloc byte[SharedPools.ByteBufferSize];
+
+            int bytesRead;
+            do
+            {
+                bytesRead = stream.Read(buffer);
+                if (bytesRead > 0)
+                {
+                    pooledHash.Object.AppendData(buffer[..bytesRead]);
+                }
+            }
+            while (bytesRead > 0);
+
+            Span<byte> hash = stackalloc byte[SHA256HashSizeBytes];
+            pooledHash.Object.GetHashAndReset(hash);
+            return From(hash);
+#else
             using var pooledHash = s_incrementalHashPool.GetPooledObject();
             using var pooledBuffer = SharedPools.ByteArray.GetPooledObject();
 
@@ -91,6 +134,7 @@ public static Checksum Create(Stream stream)
             // hash algorithm used here should remain functionally correct even
             // after the truncation
             return From(bytes);
+#endif
         }
 
         public static Checksum Create(IObjectWritable @object)