C# 雪花演算法Snowflake

阿新 • • 發佈：2021-12-08

生成唯一long型別自增Id：

using System;

namespace ConsoleApp1
{
    public static class Snowflake
    {
        static SnowflakeTool idworker = new SnowflakeTool(1);
        public static long Next()
        {
            return idworker.nextId();
        }
    }

    public class SnowflakeTool
    {
         
//機器ID
        private static long nodeId;
        private static long twepoch = 687888001020L; //唯一時間，這是一個避免重複的隨機量，自行設定不要大於當前時間戳
        private static long sequence = 0L;
        private static int workerIdBits = 4; //機器碼位元組數。4個位元組用來儲存機器碼(定義為Long型別會出現，最大偏移64位，所以左移64位沒有意義)
        public static long maxWorkerId = -1L 
 ^ -1L << workerIdBits; //最大機器ID
        private static int sequenceBits = 10; //計數器位元組數，10個位元組用來儲存計數碼
        private static int workerIdShift = sequenceBits; //機器碼資料左移位數，就是後面計數器佔用的位數
        private static int timestampLeftShift = sequenceBits + workerIdBits; //時間戳左移動位數就是機器碼和計數器總位元組數
        public static 
 long sequenceMask = -1L ^ -1L << sequenceBits; //一微秒內可以產生計數，如果達到該值則等到下一微妙在進行生成
        private long lastTimestamp = -1L;

        /// <summary>
        /// 機器碼
        /// </summary>
        /// <param name="workerId"></param>
        public SnowflakeTool(long workerId)
        {
            if (workerId > maxWorkerId || workerId < 0)
                throw new Exception(string.Format("節點id 不能大於 {0} 或者 小於 0 ", workerId));
            SnowflakeTool.nodeId = workerId;

        }

        public long nextId()
        {
            lock (this)
            {
                long timestamp = timeGen();
                if (this.lastTimestamp == timestamp)
                { //同一微妙中生成ID
                    SnowflakeTool.sequence = (SnowflakeTool.sequence + 1) & SnowflakeTool.sequenceMask; //用&運算計算該微秒內產生的計數是否已經到達上限
                    if (SnowflakeTool.sequence == 0)
                    {
                        //一微妙內產生的ID計數已達上限，等待下一微妙
                        timestamp = tillNextMillis(this.lastTimestamp);
                    }
                }
                else
                { //不同微秒生成ID
                    SnowflakeTool.sequence = 0; //計數清0
                }
                if (timestamp < lastTimestamp)
                { //如果當前時間戳比上一次生成ID時時間戳還小，丟擲異常，因為不能保證現在生成的ID之前沒有生成過
                    throw new Exception(string.Format("Clock moved backwards.  Refusing to generate id for {0} milliseconds",
                        this.lastTimestamp - timestamp));
                }
                this.lastTimestamp = timestamp; //把當前時間戳儲存為最後生成ID的時間戳
                long nextId = (timestamp - twepoch << timestampLeftShift) | SnowflakeTool.nodeId << SnowflakeTool.workerIdShift | SnowflakeTool.sequence;
                return nextId;
            }
        }

        /// <summary>
        /// 獲取下一微秒時間戳
        /// </summary>
        /// <param name="lastTimestamp"></param>
        /// <returns></returns>
        private long tillNextMillis(long lastTimestamp)
        {
            long timestamp = timeGen();
            while (timestamp <= lastTimestamp)
            {
                timestamp = timeGen();
            }
            return timestamp;
        }

        /// <summary>
        /// 生成當前時間戳
        /// </summary>
        /// <returns></returns>
        private long timeGen()
        {
            return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
        }
    }
}

View Code

呼叫校驗重複：

var list = new List<long>();
            for (int i = 0; i < 100000; i++)
            {
                var id = Snowflake.Next();// 通過雪花演算法
              
               Console.WriteLine(id);
          
            }
//校驗重複
 Console.WriteLine("--------------------------------------");
            Console.WriteLine(list.Distinct().Count());

            Console.WriteLine("--------------------------------------");

            var list2 = list.GroupBy(x => x).Where(x => x.Count() > 1);
            foreach (var item in list2)
            {
                Console.WriteLine(item.Key);
            }
 Console.ReadKey();

View Code

long型別序列化精度丟失的處理：

 [JsonConverter(typeof(MyNumberConverter), NumberConverterShip.Int64)]
        public long GoodsId { set; get; }

MyNumberConverter，NumberConverterShip：

using Newtonsoft.Json;
using System;
using System.ComponentModel;
using System.Linq;

namespace Seckill.EntityFrameworkCore.Converter
{
    /// <inheritdoc />
    /// <summary>
    /// 大資料json序列化重寫
    /// </summary>
    public sealed class MyNumberConverter : JsonConverter
    {
        /// <summary>
        /// 轉換成字串的型別
        /// </summary>
        private readonly NumberConverterShip _ship;

        /// <summary>
        /// 大資料json序列化重寫例項化
        /// </summary>
        public MyNumberConverter()
        {
            _ship = (NumberConverterShip)0xFF;
        }

        /// <summary>
        /// 大資料json序列化重寫例項化
        /// </summary>
        /// <param name="ship">轉換成字串的型別</param>
        public MyNumberConverter(NumberConverterShip ship)
        {
            _ship = ship;
        }

        /// <inheritdoc />
        /// <summary>
        /// 確定此例項是否可以轉換指定的物件型別。
        /// </summary>
        /// <param name="objectType">物件的型別。</param>
        /// <returns>如果此例項可以轉換指定的物件型別，則為：<c>true</c>，否則為：<c>false</c></returns>
        public override bool CanConvert(Type objectType)
        {
            var typecode = Type.GetTypeCode(objectType.Name.Equals("Nullable`1") ? objectType.GetGenericArguments().First() : objectType);
            switch (typecode)
            {
                case TypeCode.Decimal:
                    return (_ship & NumberConverterShip.Decimal) == NumberConverterShip.Decimal;
                case TypeCode.Double:
                    return (_ship & NumberConverterShip.Double) == NumberConverterShip.Double;
                case TypeCode.Int64:
                    return (_ship & NumberConverterShip.Int64) == NumberConverterShip.Int64;
                case TypeCode.UInt64:
                    return (_ship & NumberConverterShip.UInt64) == NumberConverterShip.UInt64;
                case TypeCode.Single:
                    return (_ship & NumberConverterShip.Single) == NumberConverterShip.Single;
                default: return false;
            }
        }

        /// <inheritdoc />
        /// <summary>
        /// 讀取物件的JSON表示。
        /// </summary>
        /// <param name="reader">從 <see cref="T:Newtonsoft.Json.JsonReader" /> 中讀取。</param>
        /// <param name="objectType">物件的型別。</param>
        /// <param name="existingValue">正在讀取的物件的現有值。</param>
        /// <param name="serializer">呼叫的序列化器例項。</param>
        /// <returns>物件值。</returns>
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            return AsType(reader.Value.ToString(), objectType);
        }

        /// <summary>
        /// 字串格式資料轉其他型別資料
        /// </summary>
        /// <param name="input">輸入的字串</param>
        /// <param name="destinationType">目標格式</param>
        /// <returns>轉換結果</returns>
        public static object AsType(string input, Type destinationType)
        {
            try
            {
                var converter = TypeDescriptor.GetConverter(destinationType);
                if (converter.CanConvertFrom(typeof(string)))
                {
                    return converter.ConvertFrom(null, null, input);
                }

                converter = TypeDescriptor.GetConverter(typeof(string));
                if (converter.CanConvertTo(destinationType))
                {
                    return converter.ConvertTo(null, null, input, destinationType);
                }
            }
            catch
            {
                return null;
            }
            return null;
        }

        /// <inheritdoc />
        /// <summary>
        /// 寫入物件的JSON表示形式。
        /// </summary>
        /// <param name="writer">要寫入的 <see cref="T:Newtonsoft.Json.JsonWriter" /> 。</param>
        /// <param name="value">要寫入物件值</param>
        /// <param name="serializer">呼叫的序列化器例項。</param>
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            if (value == null)
            {
                writer.WriteNull();
            }
            else
            {
                var objectType = value.GetType();
                var typeCode = Type.GetTypeCode(objectType.Name.Equals("Nullable`1") ? objectType.GetGenericArguments().First() : objectType);
                switch (typeCode)
                {
                    case TypeCode.Decimal:
                        writer.WriteValue(((decimal)value).ToString("f6"));
                        break;
                    case TypeCode.Double:
                        writer.WriteValue(((double)value).ToString("f4"));
                        break;
                    case TypeCode.Single:
                        writer.WriteValue(((float)value).ToString("f2"));
                        break;
                    default:
                        writer.WriteValue(value.ToString());
                        break;
                }
            }
        }
    }

    /// <summary>
    /// 轉換成字串的型別
    /// </summary>
    [Flags]
    public enum NumberConverterShip
    {
        /// <summary>
        /// 長整數
        /// </summary>
        Int64 = 1,

        /// <summary>
        /// 無符號長整數
        /// </summary>
        UInt64 = 2,

        /// <summary>
        /// 浮點數
        /// </summary>
        Single = 4,

        /// <summary>
        /// 雙精度浮點數
        /// </summary>
        Double = 8,

        /// <summary>
        /// 大數字
        /// </summary>
        Decimal = 16
    }
}