48 lines
1.6 KiB
C#
48 lines
1.6 KiB
C#
using NodaTime;
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namespace Foxnouns.Backend.Database;
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public class SnowflakeGenerator : ISnowflakeGenerator
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{
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/// <summary>
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/// Singleton instance of SnowflakeGenerator. Where possible, use an injected ISnowflakeGenerator instead
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/// (see IServiceCollection.AddSnowflakeGenerator).
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/// </summary>
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public static SnowflakeGenerator Instance { get; } = new();
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private readonly byte _processId;
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private long _increment;
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public SnowflakeGenerator(int? processId = null)
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{
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processId ??= Environment.ProcessId;
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_processId = (byte)(processId % 32);
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_increment = Random.Shared.NextInt64() % 4096;
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}
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/// <summary>
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/// Generate a snowflake ID for the given timestamp.
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/// </summary>
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/// <param name="time">An optional timestamp. If null, use the current timestamp.</param>
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/// <returns>A new snowflake ID.</returns>
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public Snowflake GenerateSnowflake(Instant? time = null)
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{
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time ??= SystemClock.Instance.GetCurrentInstant();
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long increment = Interlocked.Increment(ref _increment);
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int threadId = Environment.CurrentManagedThreadId % 32;
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long timestamp = time.Value.ToUnixTimeMilliseconds() - Snowflake.Epoch;
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return (timestamp << 22)
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| (uint)(_processId << 17)
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| (uint)(threadId << 12)
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| (increment % 4096);
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}
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}
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public static class SnowflakeGeneratorServiceExtensions
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{
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public static IServiceCollection AddSnowflakeGenerator(
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this IServiceCollection services,
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int? processId = null
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) => services.AddSingleton<ISnowflakeGenerator>(new SnowflakeGenerator(processId));
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}
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