Initial commit.

idgen.go

@@ -0,0 +1,66 @@
+package idgen
+
+import (
+	"crypto/rand"
+	"encoding/base32"
+	"sync"
+	"time"
+)
+
+var encoding = base32.StdEncoding.WithPadding(base32.NoPadding)
+
+// Creates a new, random token from 20 random bytes, encoded as base32.
+func NewToken() string {
+	buf := make([]byte, 20)
+	rand.Read(buf) // Guaranteed not to return an error.
+	return encoding.EncodeToString(buf)
+}
+
+var (
+	lock   sync.Mutex
+	ts     int64 = time.Now().Unix()
+	seq    int64 = 0
+	seqMax int64 = 1 << 20
+)
+
+// NextID can generate ~1M int64s per second.
+//
+// nodeID must be in [0, 63]. The counter is shared across all nodeIDs within a
+// process, so IDs are not guaranteed to be sequential.
+func NextID(nodeID int64) int64 {
+	if nodeID < 0 || nodeID >= 64 {
+		panic("nodeID out of range [0, 63]")
+	}
+
+	for {
+		if id := nextID(nodeID); id != 0 {
+			return id
+		}
+		time.Sleep(100 * time.Millisecond)
+	}
+}
+
+func nextID(nodeID int64) int64 {
+	lock.Lock()
+	defer lock.Unlock()
+
+	tt := time.Now().Unix()
+	if tt > ts {
+		ts = tt
+		seq = 1
+	} else {
+		seq++
+		if seq >= seqMax {
+			return 0
+		}
+	}
+
+	return (ts << 26) + (nodeID << 20) + seq
+}
+
+func SplitID(id int64) (unixTime, nodeID, counter int64) {
+	counter = id & (0x00000000000FFFFF)
+	nodeID = (id >> 20) & (0x000000000000003F)
+	unixTime = id >> 26
+	return
+}