42 lines
1.2 KiB
C#
42 lines
1.2 KiB
C#
using System.Security.Cryptography;
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namespace Fleet.Core;
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/// <summary>26 个字符的 ULID（Crockford base32，前 48 位为毫秒时间戳），按时间可排序。</summary>
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public static class Ulid
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{
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private const string Alphabet = "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
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public static string New(TimeProvider time)
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{
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long ms = time.GetUtcNow().ToUnixTimeMilliseconds();
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Span<byte> random = stackalloc byte[10];
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RandomNumberGenerator.Fill(random);
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Span<char> chars = stackalloc char[26];
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for (int i = 9; i >= 0; i--)
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{
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chars[i] = Alphabet[(int)(ms & 31)];
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ms >>= 5;
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}
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// 80 位随机数 → 16 个 base32 字符
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UInt128 r = 0;
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foreach (byte b in random)
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{
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r = (r << 8) | b;
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}
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for (int i = 25; i >= 10; i--)
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{
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chars[i] = Alphabet[(int)(r & 31)];
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r >>= 5;
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}
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return new string(chars);
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}
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/// <summary>带类型前缀的 ID，例如 <c>agt_01J…</c>。</summary>
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public static string NewPrefixed(string prefix, TimeProvider time) => prefix + "_" + New(time);
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}
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