Support cancellation in GetFileHash and VerifyFileHash

src/Tasks/FileIO/GetFileHash.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Security.Cryptography;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Shared;
@@ -17,7 +18,7 @@ namespace Microsoft.Build.Tasks
     /// <summary>
     /// Computes the checksum for a single file.
     /// </summary>
-    public sealed class GetFileHash : TaskExtension
+    public sealed class GetFileHash : TaskExtension, ICancelableTask
     {
         internal const string _defaultFileHashAlgorithm = "SHA256";
         internal const string _hashEncodingHex = "hex";
@@ -77,8 +78,10 @@ public override bool Execute()
                 return false;
             }
 
+            var parallelOptions = new ParallelOptions() { CancellationToken = _cancellationTokenSource.Token };
+
             var writeLock = new object();
-            Parallel.For(0, Files.Length, index =>
+            Parallel.For(0, Files.Length, parallelOptions, index =>
             {
                 var file = Files[index];
 
@@ -88,7 +91,7 @@ public override bool Execute()
                     return;
                 }
 
-                var hash = ComputeHash(algorithmFactory, file.ItemSpec);
+                var hash = ComputeHash(algorithmFactory, file.ItemSpec, _cancellationTokenSource.Token);
                 var encodedHash = EncodeHash(encoding, hash);
 
                 lock (writeLock)
@@ -115,6 +118,13 @@ public override bool Execute()
             return !Log.HasLoggedErrors;
         }
 
+        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
+
+        public void Cancel()
+        {
+            _cancellationTokenSource.Cancel();
+        }
+
         internal static string EncodeHash(HashEncoding encoding, byte[] hash)
         {
             return encoding switch
@@ -128,12 +138,16 @@ internal static string EncodeHash(HashEncoding encoding, byte[] hash)
         internal static bool TryParseHashEncoding(string value, out HashEncoding encoding)
             => Enum.TryParse<HashEncoding>(value, /*ignoreCase:*/ true, out encoding);
 
-        internal static byte[] ComputeHash(Func<HashAlgorithm> algorithmFactory, string filePath)
+        internal static byte[] ComputeHash(Func<HashAlgorithm> algorithmFactory, string filePath, CancellationToken ct)
         {
             using (var stream = File.OpenRead(filePath))
             using (var algorithm = algorithmFactory())
             {
+#if NET5_0_OR_GREATER
+                return algorithm.ComputeHashAsync(stream, ct).Result;
+#else
                 return algorithm.ComputeHash(stream);
+#endif
             }
         }
     }

src/Tasks/FileIO/VerifyFileHash.cs

@@ -4,6 +4,7 @@
 using System;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Shared.FileSystem;
+using System.Threading;
 
 #nullable disable
 
@@ -12,7 +13,7 @@ namespace Microsoft.Build.Tasks
     /// <summary>
     /// Verifies that a file matches the expected file hash.
     /// </summary>
-    public sealed class VerifyFileHash : TaskExtension
+    public sealed class VerifyFileHash : TaskExtension, ICancelableTask
     {
         /// <summary>
         /// The file path.
@@ -56,7 +57,7 @@ public override bool Execute()
                 return false;
             }
 
-            byte[] hash = GetFileHash.ComputeHash(algorithmFactory, File);
+            byte[] hash = GetFileHash.ComputeHash(algorithmFactory, File, _cancellationTokenSource.Token);
             string actualHash = GetFileHash.EncodeHash(encoding, hash);
             var comparison = encoding == Tasks.HashEncoding.Hex
                 ? StringComparison.OrdinalIgnoreCase
@@ -69,5 +70,12 @@ public override bool Execute()
 
             return !Log.HasLoggedErrors;
         }
+
+        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
+
+        public void Cancel()
+        {
+            _cancellationTokenSource.Cancel();
+        }
     }
 }