Improve performance of Utils.ArrayEquals

NBitcoin.Bench/README.md

@@ -2,11 +2,12 @@
 
 This project use BenchmarkDotnet to measure performance of parts of NBitcoin implementation.
 
-You can generate flamegraph to view with Perfview on Windows with the following command:
+You can generate flamegraph to view with [PerfView](https://github.com/microsoft/perfview) on Windows with the following command:
+
 ```powershell
 dotnet run -c Release -- --runtimes net8.0 --filter *GolombRiceFilters* --profiler ETW
 ```
 
-Where `GolombRiceFilters` is the name of the benchmark class you are insterested in.
+Where `GolombRiceFilters` is the name of the benchmark class you are interested in.
 
 For generating flamegraph on linux, see [this comment](https://github.com/MetacoSA/NBitcoin/pull/656#issuecomment-462927805).

NBitcoin.Bench/UtilsBench.cs

@@ -0,0 +1,35 @@
+using BenchmarkDotNet.Attributes;
+using NBitcoin.DataEncoders;
+using System.Collections.Generic;
+
+namespace NBitcoin.Bench;
+
+[MemoryDiagnoser]
+public class UtilsBench
+{
+	private static readonly byte[] taprootPubKeyA = Encoders.Hex.DecodeData("54c9e50dde41d5fc0b3dc0ff1ed4f6603a493d0a50dcc1badc3a5d959da7e750");
+	private static readonly byte[] taprootPubKeyB = Encoders.Hex.DecodeData("7ca556cf2fc5ba848c5ede3c8f0605dc78c005244915ad42b4b15076eb4b2c43");
+
+	public static IEnumerable<object[]> ArrayEqualArgs
+	{
+		get
+		{
+			yield return new byte[][] { [], [] }; // No bytes.
+			yield return new byte[][] { [], [0x01] }; // Empty array against non-empty array.
+			yield return new byte[][] { [0x01], [0x02] }; // 1-byte arrays which are not equal.
+			yield return new byte[][] { [0x01, 0x02], [0x01, 0x03] }; // 2-byte arrays which are not equal.
+			yield return new byte[][] { [0x01, 0x02, 0x03], [0x02, 0x03, 0x04] }; // 3-byte arrays which are not equal.
+			yield return new byte[][] { [0x01, 0x02, 0x03, 0x04, 0x05], [0x01, 0x02, 0x03, 0x04, 0x05] }; // 5-byte arrays which are equal.
+			yield return new byte[][] { [0x01, 0x02, 0x03, 0x04, 0x06, 0x05], [0x01, 0x02, 0x03, 0x04, 0x05, 0x06] }; // 6-byte arrays which are not equal.
+			yield return new byte[][] { [.. taprootPubKeyA], [.. taprootPubKeyA] }; // Create a copy to avoid reference equality
+			yield return new byte[][] { [.. taprootPubKeyA], [.. taprootPubKeyB] };
+		}
+	}
+
+	[Benchmark]
+	[ArgumentsSource(nameof(ArrayEqualArgs))]
+	public bool ArrayEqual(byte[] a, byte[] b)
+	{
+		return Utils.ArrayEqual(a, b);
+	}
+}

NBitcoin.Tests/util_tests.cs

@@ -938,7 +938,7 @@ public void CanEncryptAndDecryptMessages()
 				Assert.True(Utils.ArrayEqual(text1, plainText));
 				Assert.Equal(text2, Encoders.ASCII.EncodeData(plainText));
 
-				// Encrypt twice, should not give twice same cypher
+				// Encrypt twice, should not give twice same cipher
 				var cipherText3 = key.PubKey.Encrypt(plainText);
 				Assert.True(!Utils.ArrayEqual(cipherText1, cipherText3));
 			}

NBitcoin/Utils.cs

@@ -471,24 +471,26 @@ internal static void SafeSet(ManualResetEvent ar)
 			}
 			catch { }
 		}
-		public static bool ArrayEqual(byte[] a, byte[] b)
+		public static bool ArrayEqual(byte[]? a, byte[]? b)
 		{
 			if (a == null && b == null)
 				return true;
-			if (a == null)
+			if (a == null || b == null)
 				return false;
-			if (b == null)
+
+			if (a.Length != b.Length)
 				return false;
-			return ArrayEqual(a, 0, b, 0, Math.Max(a.Length, b.Length));
+
+			return ArrayEqual(a, 0, b, 0, a.Length);
 		}
-		public static bool ArrayEqual(byte[] a, int startA, byte[] b, int startB, int length)
+
+		public static bool ArrayEqual(byte[]? a, int startA, byte[]? b, int startB, int length)
 		{
 			if (a == null && b == null)
 				return true;
-			if (a == null)
-				return false;
-			if (b == null)
+			if (a == null || b == null)
 				return false;
+
 			var alen = a.Length - startA;
 			var blen = b.Length - startB;