初始化

Common/SnowIdGenerate/IdWorker.cs

@@ -0,0 +1,118 @@
+/** Copyright 2010-2012 Twitter, Inc.*/
+
+/**
+ * An object that generates IDs.
+ * This is broken into a separate class in case
+ * we ever want to support multiple worker threads
+ * per process
+ */
+
+using System;
+
+namespace Snowflake
+{
+    public class IdWorker
+    {
+        public const long Twepoch = 1288834974657L;
+
+        const int WorkerIdBits = 5;
+        const int DatacenterIdBits = 5;
+        const int SequenceBits = 12;
+        const long MaxWorkerId = -1L ^ (-1L << WorkerIdBits);
+        const long MaxDatacenterId = -1L ^ (-1L << DatacenterIdBits);
+
+        private const int WorkerIdShift = SequenceBits;
+        private const int DatacenterIdShift = SequenceBits + WorkerIdBits;
+        public const int TimestampLeftShift = SequenceBits + WorkerIdBits + DatacenterIdBits;
+        private const long SequenceMask = -1L ^ (-1L << SequenceBits);
+
+        private long _sequence = 0L;
+        private long _lastTimestamp = -1L;
+	
+	
+        public IdWorker(long workerId, long datacenterId, long sequence = 0L) 
+        {
+            WorkerId = workerId;
+            DatacenterId = datacenterId;
+            _sequence = sequence;
+		
+            // sanity check for workerId
+            if (workerId > MaxWorkerId || workerId < 0) 
+            {
+                throw new ArgumentException( String.Format("worker Id can't be greater than {0} or less than 0", MaxWorkerId) );
+            }
+
+            if (datacenterId > MaxDatacenterId || datacenterId < 0)
+            {
+                throw new ArgumentException( String.Format("datacenter Id can't be greater than {0} or less than 0", MaxDatacenterId));
+            }
+
+            //log.info(
+            //    String.Format("worker starting. timestamp left shift {0}, datacenter id bits {1}, worker id bits {2}, sequence bits {3}, workerid {4}",
+            //                  TimestampLeftShift, DatacenterIdBits, WorkerIdBits, SequenceBits, workerId)
+            //    );	
+        }
+	
+        public long WorkerId {get; protected set;}
+        public long DatacenterId {get; protected set;}
+
+        public long Sequence
+        {
+            get { return _sequence; }
+            internal set { _sequence = value; }
+        }
+
+        // def get_timestamp() = System.currentTimeMillis
+
+        readonly object _lock = new Object();
+	
+        public virtual long NextId() 
+        {
+            lock(_lock) 
+            {
+                var timestamp = TimeGen();
+
+                if (timestamp < _lastTimestamp) 
+                {
+                    //exceptionCounter.incr(1);
+                    //log.Error("clock is moving backwards.  Rejecting requests until %d.", _lastTimestamp);
+                    throw new InvalidSystemClock(String.Format(
+                        "Clock moved backwards.  Refusing to generate id for {0} milliseconds", _lastTimestamp - timestamp));
+                }
+
+                if (_lastTimestamp == timestamp) 
+                {
+                    _sequence = (_sequence + 1) & SequenceMask;
+                    if (_sequence == 0) 
+                    {
+                        timestamp = TilNextMillis(_lastTimestamp);
+                    }
+                } else {
+                    _sequence = 0;
+                }
+
+                _lastTimestamp = timestamp;
+                var id = ((timestamp - Twepoch) << TimestampLeftShift) |
+                         (DatacenterId << DatacenterIdShift) |
+                         (WorkerId << WorkerIdShift) | _sequence;
+					
+                return id;
+            }
+        }
+
+        protected virtual long TilNextMillis(long lastTimestamp)
+        {
+            var timestamp = TimeGen();
+            while (timestamp <= lastTimestamp) 
+            {
+                timestamp = TimeGen();
+            }
+            return timestamp;
+        }
+
+        protected virtual long TimeGen()
+        {
+            return System.CurrentTimeMillis();
+        }      
+    }
+}