Introduction

This is written based on Twitter's snowflake. Here is the Chinese introduction.

As shown in the picture above, a 64-bit ID, except for the leftmost sign bit (fixed to 0, To ensure that the generated IDs are all positive), there are still 63 bits available.

The following code is slightly different from the digit allocation in the picture, except that the 10-bit working machine ID in the middle part remains unchanged, and the number of digits in the timestamp and serial number It can be changed according to your own needs, that is to say, you can move the working machine ID in the middle to the left or to the right.

Code

/// <summary>
    /// 64位ID生成器,最高位為符號(hào)位,始終為0,可用位數(shù)63.
    /// 實(shí)例編號(hào)占10位,范圍為0-1023
    /// 時(shí)間戳和索引共占53位
    /// </summary>
    public sealed class IdCreator
    {        long timestamp = 0;//當(dāng)前時(shí)間戳
        long index = 0;//索引/計(jì)數(shù)器
        long instanceID;//實(shí)例編號(hào)
        int indexBitLength;//索引可用位數(shù)
        long tsMax = 0;//時(shí)間戳最大值
        long indexMax = 0;        static IdCreator _default = new IdCreator();        /// <summary>
        /// 
        /// </summary>
        /// <param name="instanceID">實(shí)例編號(hào)(0-1023)</param>
        /// <param name="indexBitLength">索引可用位數(shù)(1-32).每秒可生成ID數(shù)等于2的indexBitLength次方.大并發(fā)情況下,當(dāng)前秒內(nèi)ID數(shù)達(dá)到最大值時(shí),將使用下一秒的時(shí)間戳,不影響獲取ID.</param>
        /// <param name="initTimestamp">初始化時(shí)間戳,精確到秒.當(dāng)之前同一實(shí)例生成ID的timestamp值大于當(dāng)前時(shí)間的時(shí)間戳?xí)r,
        /// 有可能會(huì)產(chǎn)生重復(fù)ID(如持續(xù)一段時(shí)間的大并發(fā)請(qǐng)求).設(shè)置initTimestamp比最后的時(shí)間戳大一些,可避免這種問題</param>
        public IdCreator(int instanceID, int indexBitLength, long? initTimestamp = null)        {            if (instanceID < 0)
            {                //這里給每個(gè)實(shí)例隨機(jī)生成個(gè)實(shí)例編號(hào)
                Random r = new Random();                this.instanceID = r.Next(0, 1024);
            }            else
            {                this.instanceID = instanceID % 1024;
            }            if (indexBitLength < 1)
            {                this.indexBitLength = 1;
            }            else if (indexBitLength > 32)            {                this.indexBitLength = 32;
            }            else
            {                this.indexBitLength = indexBitLength;
            }
            tsMax = Convert.ToInt64(new string(&#39;1&#39;, 53 - indexBitLength), 2);
            indexMax = Convert.ToInt64(new string(&#39;1&#39;, indexBitLength), 2);            if (initTimestamp != null)
            {                this.timestamp = initTimestamp.Value;
            }
        }        /// <summary>
        /// 默認(rèn)每實(shí)例每秒生成65536個(gè)ID,從1970年1月1日起,累計(jì)可使用4358年
        /// </summary>
        /// <param name="instanceID">實(shí)例編號(hào)(0-1023)</param>
        public IdCreator(int instanceID) : this(instanceID, 16)        {

        }        /// <summary>
        /// 默認(rèn)每秒生成65536個(gè)ID,從1970年1月1日起,累計(jì)可使用4358年
        /// </summary>
        public IdCreator() : this(-1)        {

        }        /// <summary>
        /// 生成64位ID
        /// </summary>
        /// <returns></returns>
        public long Create()        {            long id = 0;            lock (this)
            {                //增加時(shí)間戳部分
                long ts = Harry.Common.Utils.GetTimeStamp() / 1000;

                ts = ts % tsMax;  //如果超過時(shí)間戳允許的最大值,從0開始
                id = ts << (10 + indexBitLength);//騰出后面部分,給實(shí)例編號(hào)和縮引編號(hào)使用

                //增加實(shí)例部分
                id = id | (instanceID << indexBitLength);                //獲取計(jì)數(shù)
                if (timestamp < ts)
                {
                    timestamp = ts;
                    index = 0;
                }                else
                {                    if (index > indexMax)
                    {
                        timestamp++;
                        index = 0;
                    }
                }

                id = id | index;

                index++;
            }            return id;
        }        /// <summary>
        /// 獲取當(dāng)前實(shí)例的時(shí)間戳
        /// </summary>
        public long CurrentTimestamp
        {            get
            {                return this.timestamp;
            }
        }        /// <summary>
        /// 默認(rèn)每實(shí)例每秒生成65536個(gè)ID,從1970年1月1日起,累計(jì)可使用4358年
        /// </summary>
        public static IdCreator Default
        {            get
            {                return _default;
            }
        }
    }

Code description

When using it, you need a new IdCreator instance, and then call the Create() method to generate an ID number. The instance of IdCreator needs to be assigned to a static variable to ensure the uniqueness of the ID number. If it is a distributed deployment, the instanceID parameter needs to be passed to the constructor of IdCreator , each deployment must have a different value, ranging from 0-1023. The indexBitLength parameter in the constructor represents the length of the 'serial number' on the far right in the figure, which is no longer fixed to 12bit, and ranges from 1- 32. The remaining available bits are left for the timestamp.

Note: The timestamp of the IdCreator class is measured in seconds. If you want to change it to milliseconds, you only need to change the code long ts = Harry.Common.Utils.GetTimeStamp () / 1000; change to long ts = Harry.Common.Utils.GetTimeStamp(); and that’s it.

Sample code

 IdCreator c=new IdCreator(0,16); 
  var id=c.Create();