92 lines
1.8 KiB
Go
Executable File
92 lines
1.8 KiB
Go
Executable File
package snowflake
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import (
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"fmt"
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"hash/fnv"
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"math"
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"net"
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"sync"
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"time"
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)
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const (
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totalBits = 64
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epochBits = 32
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nodeIDBits = 10
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sequenceBits = 12
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// Custom Epoch (January 1, 2015 Midnight UTC = 2015-01-01T00:00:00Z)
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customEpoch uint64 = 1420070400000
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)
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var maxNodeID uint64
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var maxSequence uint64
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var nodeID uint64
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var lastTimestamp uint64 = 0
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var sequence uint64
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func init() {
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maxNodeID = uint64(math.Pow(2, nodeIDBits) - 1)
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maxSequence = uint64(math.Pow(2, sequenceBits) - 1)
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nodeID = generateNodeID()
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}
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func generateNodeID() uint64 {
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var nodeID uint64
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if interfaces, err := net.Interfaces(); err == nil {
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h := fnv.New32a()
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for _, i := range interfaces {
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h.Write(i.HardwareAddr)
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}
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nodeID = uint64(h.Sum32())
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} else {
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panic("interfaces not available")
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}
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nodeID = nodeID & maxNodeID
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return nodeID
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}
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var timestampMutex sync.Mutex
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var sequenceMutex sync.Mutex
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// Next returns the next logical snowflake
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func Next() uint64 {
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timestampMutex.Lock()
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currentTimestamp := ts()
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timestampMutex.Unlock()
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sequenceMutex.Lock()
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if currentTimestamp == lastTimestamp {
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sequence = (sequence + 1) & maxSequence
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if sequence == 0 {
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// Sequence Exhausted, wait till next millisecond.
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currentTimestamp = waitNextMillis(currentTimestamp)
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}
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} else {
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sequence = 0
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}
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sequenceMutex.Unlock()
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lastTimestamp = currentTimestamp
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id := currentTimestamp << (totalBits - epochBits)
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fmt.Printf("%b\n", id)
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id |= (nodeID << (totalBits - epochBits - nodeIDBits))
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fmt.Printf("%b\n", id)
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id |= sequence
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fmt.Printf("%b\n", id)
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return id
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}
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func ts() uint64 {
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return uint64(time.Now().UnixNano()/1000000) - customEpoch
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}
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func waitNextMillis(currentTimestamp uint64) uint64 {
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for currentTimestamp == lastTimestamp {
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currentTimestamp = ts()
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}
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return currentTimestamp
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}
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