129 lines
4.8 KiB
C#
129 lines
4.8 KiB
C#
using System;
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using System.Threading;
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namespace StandardScene.CommonTools
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{
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public sealed class SnowflakeIdGenerator
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{
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// 默认起始时间戳：2026-01-01T00:00:00.000Z（Unix 毫秒）
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// 如果你希望生成的数字更短，可以在构造函数里传入更“近”的 _epochMs（建议全系统统一）。
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private const long DefaultEpochMs = 1767225600000L;
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private const int WorkerIdBits = 5; // 机器ID所占的位数
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private const int DatacenterIdBits = 5; // 数据中心ID所占的位数
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private const int MaxWorkerId = -1 ^ (-1 << WorkerIdBits); // 最大机器ID
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private const int MaxDatacenterId = -1 ^ (-1 << DatacenterIdBits); // 最大数据中心ID
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private const int SequenceBits = 12; // 序列号所占的位数
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private const int WorkerIdShift = SequenceBits; // 机器ID左移的位数
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private const int DatacenterIdShift = SequenceBits + WorkerIdBits; // 数据中心ID左移的位数
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private const int TimestampLeftShift = SequenceBits + WorkerIdBits + DatacenterIdBits; // 时间戳左移的位数
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private const long SequenceMask = -1L ^ (-1L << SequenceBits); // 序列号的最大值
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private const string Base62Alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
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private readonly object _syncRoot = new object();
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private readonly long _epochMs;
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private readonly long _workerId; // 机器ID
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private readonly long _datacenterId; // 数据中心ID
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private long _sequence; // 序列号
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private long _lastTimestamp = -1L; // 上次生成ID的时间戳
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public SnowflakeIdGenerator(long workerId, long datacenterId, long? epochMs = null)
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{
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this._epochMs = epochMs ?? DefaultEpochMs;
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if (this._epochMs > TimeGen())
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{
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throw new ArgumentException("_epochMs cannot be in the future.");
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}
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if (workerId is > MaxWorkerId or < 0)
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{
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throw new ArgumentException($"worker Id can't be greater than {MaxWorkerId} or less than 0");
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}
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if (datacenterId is > MaxDatacenterId or < 0)
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{
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throw new ArgumentException($"{datacenterId} can't be greater than {MaxDatacenterId} or less than 0");
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}
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this._workerId = workerId;
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this._datacenterId = datacenterId;
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}
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public long NextId()
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{
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lock (_syncRoot)
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{
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long timestamp = TimeGen();
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if (timestamp < _lastTimestamp)
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{
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// 容忍系统时钟回拨：等待到追上 _lastTimestamp，避免直接抛异常把业务打崩。
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timestamp = TilNextMillis(_lastTimestamp);
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}
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if (_lastTimestamp == timestamp)
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{
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_sequence = (_sequence + 1) & SequenceMask;
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if (_sequence == 0)
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{
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timestamp = TilNextMillis(_lastTimestamp);
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}
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}
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else
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{
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_sequence = 0;
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}
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_lastTimestamp = timestamp;
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long id = ((timestamp - _epochMs) << TimestampLeftShift)
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| (_datacenterId << DatacenterIdShift)
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| (_workerId << WorkerIdShift)
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| _sequence;
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return id;
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}
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}
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/// <summary>
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/// 生成更短的字符串形式 ID（Base62 编码），便于显示/存储。
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/// </summary>
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public string NextIdBase62()
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{
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ulong value = unchecked((ulong)NextId());
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return ToBase62(value);
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}
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private static long TilNextMillis(long lastTimestamp)
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{
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var spin = new SpinWait();
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long timestamp;
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do
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{
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spin.SpinOnce();
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timestamp = TimeGen();
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}
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while (timestamp <= lastTimestamp);
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return timestamp;
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}
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private static long TimeGen()
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{
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return DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
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}
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private static string ToBase62(ulong value)
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{
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if (value == 0)
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{
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return "0";
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}
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// 2^64-1 的 base62 最大长度为 11（因为 62^11 > 2^64）。
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char[] buffer = new char[11];
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int pos = buffer.Length;
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while (value > 0)
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{
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ulong rem = value % 62;
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value /= 62;
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buffer[--pos] = Base62Alphabet[(int)rem];
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}
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return new string(buffer, pos, buffer.Length - pos);
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}
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}
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}
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