Optimize HexEncoder.DecodeData methods for .NET 8+

NBitcoin.Bench/HexBench.cs

@@ -1,32 +1,56 @@
 using BenchmarkDotNet.Attributes;
 using NBitcoin.DataEncoders;
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
-namespace NBitcoin.Bench
+namespace NBitcoin.Bench;
+
+[MemoryDiagnoser]
+public class HexBench
 {
-	public class HexBench
+	const string str = "d54994ece1d11b19785c7248868696250ab195605b469632b7bd68130e880c9a";
+	const string uint256_str = "00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
+	string random_str_10kb;
+
+	private byte[] bytes;
+
+	[GlobalSetup]
+	public void Setup()
+	{
+		bytes = Encoders.Hex.DecodeData(str);
+
+		var randomBytes = new byte[10 * 1024];
+		Random.Shared.NextBytes(randomBytes);
+		random_str_10kb = Encoders.Hex.EncodeData(randomBytes);
+	}
+
+	[Benchmark]
+	public void DecodeData()
+	{
+		Encoders.Hex.DecodeData(str);
+	}
+
+	[Benchmark]
+	[Arguments(uint256_str)] // 32 bytes
+	[Arguments(uint256_str + uint256_str)] // 64 bytes
+	[Arguments(uint256_str + uint256_str + uint256_str)] // 96 bytes
+	public void DecodeDataSpan(string hexString)
+	{
+		Span<byte> tmp = stackalloc byte[hexString.Length / 2];
+		HexEncoder hex = (HexEncoder)Encoders.Hex;
+		hex.DecodeData(hexString, tmp);
+	}
+
+	[Benchmark]
+	public void DecodeDataLongSpan()
+	{
+		Span<byte> tmp = stackalloc byte[random_str_10kb.Length / 2];
+		HexEncoder hex = (HexEncoder)Encoders.Hex;
+		hex.DecodeData(random_str_10kb, tmp);
+	}
+
+	[Benchmark]
+	public void EncodeData()
 	{
-		string str = "d54994ece1d11b19785c7248868696250ab195605b469632b7bd68130e880c9a";
-		private byte[] bytes;
-
-		[GlobalSetup]
-		public void Setup()
-		{
-			bytes = Encoders.Hex.DecodeData(str);
-		}
-		[Benchmark]
-		public void Decode()
-		{
-			Encoders.Hex.DecodeData(str);
-		}
-		[Benchmark]
-		public void Encode()
-		{
-			Encoders.Hex.EncodeData(bytes);
-		}
+		Encoders.Hex.EncodeData(bytes);
 	}
 }

NBitcoin.Tests/uint256_tests.cs

@@ -1,11 +1,7 @@
-using NBitcoin.Protocol;
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Reflection;
-using System.Text;
-using System.Threading.Tasks;
 using Xunit;
 
 namespace NBitcoin.Tests

NBitcoin/DataEncoders/HexEncoder.cs

@@ -57,7 +57,8 @@ public override string EncodeData(byte[] data, int offset, int count)
 			if (data == null)
 				throw new ArgumentNullException(nameof(data));
 
-#if NET6_0_OR_GREATER
+#if NET8_0_OR_GREATER
+			// TODO: Convert.ToHexStringLower (.NET 9+) once available.
 			return Convert.ToHexString(data, offset, count).ToLowerInvariant();
 #elif !HAS_SPAN
 			int pos = 0;
@@ -98,6 +99,10 @@ public override byte[] DecodeData(string encoded)
 		{
 			if (encoded == null)
 				throw new ArgumentNullException(nameof(encoded));
+
+#if NET8_0_OR_GREATER
+			return Convert.FromHexString(encoded);
+#else
 			if (encoded.Length % 2 == 1)
 				throw new FormatException("Invalid Hex String");
 
@@ -111,6 +116,7 @@ public override byte[] DecodeData(string encoded)
 				result[j] = (byte)((hi << 4) | lo);
 			}
 			return result;
+#endif
 		}
 #if HAS_SPAN
 		public void DecodeData(string encoded, Span<byte> output)
@@ -121,6 +127,12 @@ public void DecodeData(string encoded, Span<byte> output)
 				throw new FormatException("Invalid Hex String");
 			if (output.Length < (encoded.Length >> 1))
 				throw new ArgumentException("output should be bigger", nameof(output));
+
+#if NET8_0_OR_GREATER
+			var decoded = Convert.FromHexString(encoded);
+			decoded.CopyTo(output);
+#else
+			// TODO: Convert.FromHexString(string source, Span<byte> destination) (.NET 10+) once available.
 			try
 			{
 				for (int i = 0, j = 0; i < encoded.Length; i += 2, j++)
@@ -133,6 +145,7 @@ public void DecodeData(string encoded, Span<byte> output)
 				}
 			}
 			catch(IndexOutOfRangeException) { throw new FormatException("Invalid Hex String"); }
+#endif
 		}
 #endif
 		public bool IsValid(string str)