Use 'bigEndian' Guid method argument in .NET 8.

src/NGuid/GuidHelpers.cs

@@ -106,9 +106,14 @@ public static Guid CreateFromName(Guid namespaceId, ReadOnlySpan<byte> name, int
 
 		// convert the namespace UUID to network order (step 3)
 		Span<byte> buffer = name.Length < 500 ? stackalloc byte[16 + name.Length + 20] : new byte[16 + name.Length + 20];
+#if NET8_0_OR_GREATER
+		if (!namespaceId.TryWriteBytes(buffer, bigEndian: true, out _))
+			throw new InvalidOperationException("Failed to write namespace ID bytes to buffer");
+#else
 		if (!namespaceId.TryWriteBytes(buffer))
 			throw new InvalidOperationException("Failed to write Guid bytes to buffer");
 		SwapByteOrder(buffer);
+#endif
 
 		// compute the hash of the namespace ID concatenated with the name (step 4)
 #pragma warning disable CA5350 // Do Not Use Weak Cryptographic Algorithms
@@ -131,9 +136,13 @@ public static Guid CreateFromName(Guid namespaceId, ReadOnlySpan<byte> name, int
 		// set the two most significant bits (bits 6 and 7) of the clock_seq_hi_and_reserved to zero and one, respectively (step 10)
 		newGuid[8] = (byte) ((newGuid[8] & 0x3F) | 0x80);
 
+#if NET8_0_OR_GREATER
+		return new Guid(newGuid, bigEndian: true);
+#else
 		// convert the resulting UUID to local byte order (step 13)
 		SwapByteOrder(newGuid);
 		return new Guid(newGuid);
+#endif
 	}
 #endif
 
@@ -354,14 +363,17 @@ public static Guid CreateVersion8(ReadOnlySpan<byte> bytes)
 		Span<byte> guidBytes = stackalloc byte[16];
 		bytes[..16].CopyTo(guidBytes);
 
-		// convert the bytes to network order (so that bytes[0] is the first byte in the serialized GUID output)
-		SwapByteOrder(guidBytes);
-
 		// set the version and variant fields
-		guidBytes[7] = (byte) (0x80 | (guidBytes[7] & 0xF));
+		guidBytes[6] = (byte) (0x80 | (guidBytes[6] & 0xF));
 		guidBytes[8] = (byte) (0x80 | (guidBytes[8] & 0x3F));
 
+#if NET8_0_OR_GREATER
+		return new Guid(guidBytes, bigEndian: true);
+#else
+		// convert the bytes to network order (so that bytes[0] is the first byte in the serialized GUID output)
+		SwapByteOrder(guidBytes);
 		return new Guid(guidBytes);
+#endif
 	}
 #endif
 
@@ -422,10 +434,15 @@ public static Guid CreateVersion8FromName(HashAlgorithmName hashAlgorithmName, G
 #endif
 		Span<byte> buffer = name.Length < 500 ? stackalloc byte[16 + name.Length] : new byte[16 + name.Length];
 
+#if NET8_0_OR_GREATER
+		if (!namespaceId.TryWriteBytes(buffer, bigEndian: true, out _))
+			throw new InvalidOperationException("Failed to write namespace ID bytes to buffer");
+#else
 		// convert the hash space and namespace UUIDs to network order
 		if (!namespaceId.TryWriteBytes(buffer))
 			throw new InvalidOperationException("Failed to write namespace ID bytes to buffer");
 		SwapByteOrder(buffer);
+#endif
 
 		// compute the hash of [ namespace ID, name ]
 		name.CopyTo(buffer[16..]);
@@ -447,9 +464,13 @@ public static Guid CreateVersion8FromName(HashAlgorithmName hashAlgorithmName, G
 		newGuid[6] = (byte) ((newGuid[6] & 0x0F) | 0x80);
 		newGuid[8] = (byte) ((newGuid[8] & 0x3F) | 0x80);
 
+#if NET8_0_OR_GREATER
+		return new Guid(newGuid, bigEndian: true);
+#else
 		// convert the resulting UUID to local byte order
 		SwapByteOrder(newGuid);
 		return new Guid(newGuid);
+#endif
 	}
 #endif
 
@@ -479,6 +500,7 @@ private static HashAlgorithm GetHashAlgorithm(HashAlgorithmName hashAlgorithmNam
 	/// </summary>
 	public static readonly Guid IsoOidNamespace = new("6ba7b812-9dad-11d1-80b4-00c04fd430c8");
 
+#if !NET8_0_OR_GREATER
 	// Converts a GUID (expressed as a byte array) to/from network order (MSB-first).
 	internal static void SwapByteOrder(Span<byte> guid)
 	{
@@ -487,6 +509,7 @@ internal static void SwapByteOrder(Span<byte> guid)
 		SwapBytes(guid, 4, 5);
 		SwapBytes(guid, 6, 7);
 	}
+#endif
 
 	private static void SwapBytes(Span<byte> guid, int left, int right)
 	{

tests/NGuid.Tests/GuidHelpersTests.cs

@@ -1,5 +1,4 @@
 using System.Buffers.Binary;
-using System.Globalization;
 using System.Text;
 
 namespace NGuid.Tests;
@@ -13,8 +12,10 @@ public void SwapByteOrder()
 		var bytes = guid.ToByteArray();
 		Assert.Equal([4, 3, 2, 1, 6, 5, 8, 7, 9, 10, 11, 12, 13, 14, 15, 16], bytes);
 
+#if !NET8_0_OR_GREATER
 		GuidHelpers.SwapByteOrder(bytes);
 		Assert.Equal([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16], bytes);
+#endif
 	}
 
 	[Theory]
@@ -83,7 +84,7 @@ public void CreateV6()
 	[InlineData("2022-02-22T14:22:22-05:00", "1ec9414c-232a-6b00")] // https://datatracker.ietf.org/doc/html/draft-ietf-uuidrev-rfc4122bis-14#name-example-of-a-uuidv6-value
 	public void CreateV6FromTimeProvider(string timestamp, string expectedPrefix)
 	{
-		var timeProvider = new FixedTimeProvider(DateTimeOffset.Parse(timestamp, CultureInfo.InvariantCulture));
+		var timeProvider = new FixedTimeProvider(DateTimeOffset.Parse(timestamp, System.Globalization.CultureInfo.InvariantCulture));
 		var guid = GuidHelpers.CreateVersion6(timeProvider);
 		Assert.StartsWith(expectedPrefix, guid.ToString("d"), StringComparison.Ordinal);
 	}
@@ -108,7 +109,7 @@ public void CreateV7()
 	[InlineData("2022-02-22T14:22:22-05:00", "017f22e2-79b0-7")] // https://datatracker.ietf.org/doc/html/draft-ietf-uuidrev-rfc4122bis-14#name-example-of-a-uuidv7-value
 	public void CreateV7FromTimeProvider(string timestamp, string expectedPrefix)
 	{
-		var timeProvider = new FixedTimeProvider(DateTimeOffset.Parse(timestamp, CultureInfo.InvariantCulture));
+		var timeProvider = new FixedTimeProvider(DateTimeOffset.Parse(timestamp, System.Globalization.CultureInfo.InvariantCulture));
 		var guid = GuidHelpers.CreateVersion7(timeProvider);
 		Assert.StartsWith(expectedPrefix, guid.ToString("d"), StringComparison.Ordinal);
 	}
@@ -129,12 +130,12 @@ public void ConvertV4ToV6() =>
 	[InlineData("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", "ffffffff-ffff-8fff-bfff-ffffffffffff")]
 	public void CreateV8(string input, string expected)
 	{
-#if NET8_0_OR_GREATER
+#if NET5_0_OR_GREATER
 		var bytes = Convert.FromHexString(input);
 #else
 		var bytes = new byte[input.Length / 2];
 		for (var i = 0; i < bytes.Length; i++)
-			bytes[i] = byte.Parse(input.Substring(i * 2, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture);
+			bytes[i] = byte.Parse(input.Substring(i * 2, 2), System.Globalization.NumberStyles.HexNumber, System.Globalization.CultureInfo.InvariantCulture);
 #endif
 		var guid = GuidHelpers.CreateVersion8(bytes);
 		Assert.Equal(new Guid(expected), guid);

tests/NGuid.Tests/NGuid.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net481;net8.0;net9.0</TargetFrameworks>
+    <TargetFrameworks>net481;net6.0;net8.0;net9.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <IsTestProject>true</IsTestProject>
     <NoWarn>$(NoWarn);CA1515;CS1591</NoWarn>