Rewrite Get-FileHash to use static HashData methods (PowerShell#18471)

Author: turbedi

src/Microsoft.PowerShell.Commands.Utility/commands/utility/GetHash.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Diagnostics;
 using System.IO;
 using System.Management.Automation;
 using System.Security.Cryptography;
@@ -68,15 +69,6 @@ public string[] LiteralPath
         [Parameter(Mandatory = true, ParameterSetName = StreamParameterSet, Position = 0)]
         public Stream InputStream { get; set; }
 
-        /// <summary>
-        /// BeginProcessing() override.
-        /// This is for hash function init.
-        /// </summary>
-        protected override void BeginProcessing()
-        {
-            InitHasher(Algorithm);
-        }
-
         /// <summary>
         /// ProcessRecord() override.
         /// This is for paths collecting from pipe.
@@ -133,6 +125,26 @@ protected override void ProcessRecord()
             }
         }
 
+        private byte[] ComputeHash(Stream stream)
+        {
+            switch (Algorithm)
+            {
+                case HashAlgorithmNames.SHA1:
+                    return SHA1.HashData(stream);
+                case HashAlgorithmNames.SHA256:
+                    return SHA256.HashData(stream);
+                case HashAlgorithmNames.SHA384:
+                    return SHA384.HashData(stream);
+                case HashAlgorithmNames.SHA512:
+                    return SHA512.HashData(stream);
+                case HashAlgorithmNames.MD5:
+                    return MD5.HashData(stream);
+            }
+
+            Debug.Assert(false, "invalid hash algorithm");
+            return SHA256.HashData(stream);
+        }
+
         /// <summary>
         /// Perform common error checks.
         /// Populate source code.
@@ -141,12 +153,9 @@ protected override void EndProcessing()
         {
             if (ParameterSetName == StreamParameterSet)
             {
-                byte[] bytehash = null;
-                string hash = null;
+                byte[] bytehash = ComputeHash(InputStream);
 
-                bytehash = hasher.ComputeHash(InputStream);
-
-                hash = BitConverter.ToString(bytehash).Replace("-", string.Empty);
+                string hash = BitConverter.ToString(bytehash).Replace("-", string.Empty);
                 WriteHashResult(Algorithm, hash, string.Empty);
             }
         }
@@ -159,16 +168,15 @@ protected override void EndProcessing()
         /// <returns>Boolean value indicating whether the hash calculation succeeded or failed.</returns>
         private bool ComputeFileHash(string path, out string hash)
         {
-            byte[] bytehash = null;
             Stream openfilestream = null;
 
             hash = null;
 
             try
             {
                 openfilestream = File.OpenRead(path);
+                byte[] bytehash = ComputeHash(openfilestream);
 
-                bytehash = hasher.ComputeHash(openfilestream);
                 hash = BitConverter.ToString(bytehash).Replace("-", string.Empty);
             }
             catch (FileNotFoundException ex)
@@ -259,11 +267,6 @@ public string Algorithm
 
         private string _Algorithm = HashAlgorithmNames.SHA256;
 
-        /// <summary>
-        /// Hash algorithm is used.
-        /// </summary>
-        protected HashAlgorithm hasher;
-
         /// <summary>
         /// Hash algorithm names.
         /// </summary>
@@ -275,40 +278,6 @@ internal static class HashAlgorithmNames
             public const string SHA384 = "SHA384";
             public const string SHA512 = "SHA512";
         }
-
-        /// <summary>
-        /// Init a hash algorithm.
-        /// </summary>
-        protected void InitHasher(string Algorithm)
-        {
-            try
-            {
-                switch (Algorithm)
-                {
-                    case HashAlgorithmNames.SHA1:
-                        hasher = SHA1.Create();
-                        break;
-                    case HashAlgorithmNames.SHA256:
-                        hasher = SHA256.Create();
-                        break;
-                    case HashAlgorithmNames.SHA384:
-                        hasher = SHA384.Create();
-                        break;
-                    case HashAlgorithmNames.SHA512:
-                        hasher = SHA512.Create();
-                        break;
-                    case HashAlgorithmNames.MD5:
-                        hasher = MD5.Create();
-                        break;
-                }
-            }
-            catch
-            {
-                // Seems it will never throw! Remove?
-                Exception exc = new NotSupportedException(UtilityCommonStrings.AlgorithmTypeNotSupported);
-                ThrowTerminatingError(new ErrorRecord(exc, "AlgorithmTypeNotSupported", ErrorCategory.NotImplemented, null));
-            }
-        }
     }
 
     /// <summary>

src/Microsoft.PowerShell.Commands.Utility/commands/utility/UtilityCommon.cs

@@ -82,11 +82,6 @@ public static class UtilityResources
         /// </summary>
         public static string FormatHexPathPrefix { get { return UtilityCommonStrings.FormatHexPathPrefix; } }
 
-        /// <summary>
-        /// Error message to indicate that requested algorithm is not supported on the target platform.
-        /// </summary>
-        public static string AlgorithmTypeNotSupported { get { return UtilityCommonStrings.AlgorithmTypeNotSupported; } }
-
         /// <summary>
         /// The file '{0}' could not be parsed as a PowerShell Data File.
         /// </summary>

src/Microsoft.PowerShell.Commands.Utility/resources/UtilityCommonStrings.resx

@@ -162,9 +162,6 @@
   <data name="PSPrefixReservedInInformationTag" xml:space="preserve">
     <value>Cannot use tag '{0}'. The 'PS' prefix is reserved.</value>
   </data>
-  <data name="AlgorithmTypeNotSupported" xml:space="preserve">
-    <value>Algorithm '{0}' is not supported in this system.</value>
-  </data>
   <data name="CouldNotParseAsPowerShellDataFile" xml:space="preserve">
     <value>The file '{0}' could not be parsed as a PowerShell Data File.</value>
   </data>