mirror of
https://github.com/buger/goreplay.git
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95 lines
2.0 KiB
Go
95 lines
2.0 KiB
Go
package gou
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import (
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"crypto/md5"
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"crypto/rand"
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"encoding/binary"
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"fmt"
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"io"
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"os"
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"strconv"
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"sync/atomic"
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"time"
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)
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const (
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//2013-2-3
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ourEpoch = uint32(1359931242)
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)
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func init() {
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initHostPidId()
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}
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/*
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Special thanks to ideas from Mgo, and Noeqd, this is somewhat inbetween them
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https://github.com/bmizerany/noeqd
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It is a roughly sortable UID, but uses machine specific info (host, processid)
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as part of the uid so each machine *will* have unique id's
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The host+processid is 3 bytes
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*/
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// uidCounter is an atomically incremented each time we created
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// a new uid within given ms time window
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var uidCounter uint32 = 0
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// hostPidId stores the generated hostPid
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var hostPidId []byte
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// initHostPidId generates a machine-process specific id by using hostname
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// and processid
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func initHostPidId() {
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var sum [4]byte
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hostB := sum[:]
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host, err := os.Hostname()
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if err != nil {
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// if we cannot get hostname, just use a random set of bytes
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_, err2 := io.ReadFull(rand.Reader, hostB)
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if err2 != nil {
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panic(fmt.Errorf("cannot get hostname: %v; %v", err, err2))
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}
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} else {
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hw := md5.New()
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hw.Write([]byte(host))
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copy(hostB, hw.Sum(nil))
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}
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pid := os.Getpid()
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hostI := binary.BigEndian.Uint32(hostB)
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uid := uint32(pid) + uint32(hostI)
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binary.BigEndian.PutUint32(hostB, uid)
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b := make([]byte, 4)
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binary.BigEndian.PutUint32(b, uid)
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hostPidId = b[:]
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}
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// uid is a 64 bit int uid
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type Uid uint64
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// Create a new uint64 unique id
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func NewUid() uint64 {
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b := make([]byte, 8)
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ts := uint32(time.Now().Unix()) - ourEpoch
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// Timestamp, 4 bytes, big endian
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binary.BigEndian.PutUint32(b, ts)
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//Debugf("ts=%v b=%v", ts, b)
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// first 3 bytes of host/pid
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b[4] = hostPidId[2]
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b[5] = hostPidId[3]
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b[6] = hostPidId[3]
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// Increment, 2 bytes, big endian
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i := atomic.AddUint32(&uidCounter, 1)
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//b[6] = byte(i >> 8)
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b[7] = byte(i)
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ui := binary.BigEndian.Uint64(b)
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//Debugf("ui=%d b=%v ", ui, b)
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return ui
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}
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func (u *Uid) String() string {
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return strconv.FormatUint(uint64(*u), 10)
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}
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