WIP

NBitcoin.Bench/UInt256Bench.cs

@@ -25,6 +25,25 @@ public void WriteToString()
 		{
 			Value.ToString();
 		}
+
+#if HAS_SPAN
+		[Benchmark]
+		[Arguments(new char[] {
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0',
+			'0','0','0','0','0','0','0','0'
+		})]
+		public void WriteToSpanString(Span<char> destinationSpan)
+		{
+			Value.ToSpanString(destinationSpan);
+		}
+#endif
+
 		[Benchmark]
 		public void Read()
 		{

NBitcoin.Tests/NBitcoin.Tests.csproj

@@ -41,8 +41,8 @@
 		<ProjectReference Include="..\NBitcoin.Altcoins\NBitcoin.Altcoins.csproj" />
 		<ProjectReference Include="..\NBitcoin.TestFramework\NBitcoin.TestFramework.csproj" />
 		<PackageReference Include="Microsoft.CSharp" Version="4.6.0" />
-		<PackageReference Include="xunit" Version="2.4.1" />
-		<PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">
+		<PackageReference Include="xunit" Version="2.6.5" />
+		<PackageReference Include="xunit.runner.visualstudio" Version="2.5.6">
 		  <PrivateAssets>all</PrivateAssets>
 		  <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
 		</PackageReference>

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
@@ -147,7 +143,7 @@ public void uitnSerializationTests2()
 
 		[Fact]
 		[Trait("UnitTest", "UnitTest")]
-		public void uitnSerializationTests()
+		public void uintSerializationTests()
 		{
 			MemoryStream ms = new MemoryStream();
 			BitcoinStream stream = new BitcoinStream(ms, true);
@@ -193,6 +189,16 @@ public void uitnSerializationTests()
 			Assert.True(vs2.SequenceEqual(vs));
 		}
 
+		[Fact]
+		[Trait("UnitTest", "UnitTest")]
+		public void uintSpanSerializationTests()
+		{
+			var v1 = new uint256("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
+
+			Assert.Equal("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff", v1.ToString());
+			Assert.Equal("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff".AsSpan(), v1.ToSpanString());
+		}
+
 		private void AssertEquals(uint256 a, uint256 b)
 		{
 			Assert.Equal(a, b);

NBitcoin/UInt256.cs

@@ -1,9 +1,8 @@
 
+using NBitcoin.DataEncoders;
 using System;
-using System.Collections;
 using System.Linq;
 using System.Runtime.InteropServices;
-using NBitcoin.DataEncoders;
 
 namespace NBitcoin
 {
@@ -161,6 +160,43 @@ public override string ToString()
 			return Encoder.EncodeData(bytes);
 		}
 
+#if HAS_SPAN
+		/// <remarks>The method allocates a new 64 char array.</remarks>
+		public Span<char> ToSpanString()
+		{
+			Span<char> result = new char[64];
+
+			ToSpanString(result);
+			return result;
+		}
+
+		/// <remarks>The method does not allocate.</remarks>
+		public void ToSpanString(Span<char> destination)
+		{
+			Span<ulong> ulongs = stackalloc ulong[4];
+			ulongs[0] = pn0;
+			ulongs[1] = pn1;
+			ulongs[2] = pn2;
+			ulongs[3] = pn3;
+			Span<byte> bytes = MemoryMarshal.Cast<ulong, byte>(ulongs);
+
+			if (BitConverter.IsLittleEndian)
+			{
+				for (int i = 31, j = 0; i >= 0; i--, j += 2)
+				{
+					HexEncoder.ToCharsBuffer(bytes[i], destination, startingIndex: j);
+				}
+			}
+			else
+			{
+				for (int i = 0; i < 32; i++)
+				{
+					HexEncoder.ToCharsBuffer(bytes[i], destination, startingIndex: i);
+				}
+			}
+		}
+#endif
+
 		public uint256(ulong b)
 		{
 			pn0 = (uint)b;