41 lines
1.0 KiB
C#
41 lines
1.0 KiB
C#
using System.Runtime.InteropServices;
|
|
using System.Security.Cryptography;
|
|
|
|
namespace Just.Core;
|
|
|
|
public enum GuidV8Entropy { Strong, Weak }
|
|
|
|
public static class GuidV8
|
|
{
|
|
[Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
public static Guid NewGuid(GuidV8Entropy entropy = GuidV8Entropy.Strong) => NewGuid(DateTime.UtcNow, entropy);
|
|
|
|
[Pure]
|
|
public static Guid NewGuid(DateTime dateTime, GuidV8Entropy entropy = GuidV8Entropy.Strong)
|
|
{
|
|
var timestamp = dateTime.ToBinary() & 0x3FFF_FFFF_FFFF_FFFF;
|
|
|
|
Span<byte> ts = stackalloc byte[8];
|
|
MemoryMarshal.Write(ts, timestamp);
|
|
|
|
Span<byte> bytes = stackalloc byte[16];
|
|
|
|
ts[4..].CopyTo(bytes[..4]);
|
|
ts[2..4].CopyTo(bytes[4..6]);
|
|
ts[..2].CopyTo(bytes[6..8]);
|
|
|
|
bytes[7] = (byte)((bytes[7] & 0x0f) | 0x80);
|
|
|
|
if (entropy == GuidV8Entropy.Strong)
|
|
{
|
|
RandomNumberGenerator.Fill(bytes[8..]);
|
|
}
|
|
else
|
|
{
|
|
Random.Shared.NextBytes(bytes[8..]);
|
|
}
|
|
|
|
return new Guid(bytes);
|
|
}
|
|
}
|