43 lines
1.3 KiB
C#
43 lines
1.3 KiB
C#
using System.Security.Cryptography;
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namespace Just.Core;
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public static class GuidV8
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{
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private const long TicksPrecision = TimeSpan.TicksPerMillisecond / 10;
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static Guid NewGuid(RngEntropy entropy = RngEntropy.Strong) => NewGuid(DateTime.UtcNow, entropy);
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public static Guid NewGuid(DateTime dateTime, RngEntropy entropy = RngEntropy.Strong)
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{
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var epoch = dateTime.Subtract(DateTime.UnixEpoch);
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var timestamp = epoch.Ticks / TicksPrecision;
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uint tsHigh = (uint)((timestamp >> 16) & 0xFFFFFFFF);
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ushort tsLow = (ushort)(timestamp & 0x0000FFFF);
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Span<byte> bytes = stackalloc byte[10];
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if (entropy == RngEntropy.Strong)
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{
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RandomNumberGenerator.Fill(bytes);
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}
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else
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{
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Random.Shared.NextBytes(bytes);
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}
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bytes[0] = (byte)((bytes[0] & 0x0F) | 0x80); // Version 8
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bytes[2] = (byte)((bytes[2] & 0x1F) | 0x80); // Variant 0b1000
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ushort version = (ushort)((bytes[0] << 8) | bytes[1]);
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return new Guid(
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tsHigh,
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tsLow,
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version,
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bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7], bytes[8], bytes[9]);
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}
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}
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