migrate code for github

providers/bind/serial.go

@@ -0,0 +1,71 @@
+package bind
+
+import (
+	"log"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var nowFunc func() time.Time = time.Now
+
+// generate_serial takes an old SOA serial number and increments it.
+func generate_serial(old_serial uint32) uint32 {
+	// Serial numbers are in the format yyyymmddvv
+	// where vv is a version count that starts at 01 each day.
+	// Multiple serial numbers generated on the same day increase vv.
+	// If the old serial number is not in this format, it gets replaced
+	// with the new format. However if that would mean a new serial number
+	// that is smaller than the old one, we punt and increment the old number.
+	// At no time will a serial number == 0 be returned.
+
+	original := old_serial
+	old_serialStr := strconv.FormatUint(uint64(old_serial), 10)
+	var new_serial uint32
+
+	// Make draft new serial number:
+	today := nowFunc().UTC()
+	todayStr := today.Format("20060102")
+	version := uint32(1)
+	todayNum, err := strconv.ParseUint(todayStr, 10, 32)
+	if err != nil {
+		log.Fatalf("new serial won't fit in 32 bits: %v", err)
+	}
+	draft := uint32(todayNum)*100 + version
+
+	method := "none" // Used only in debugging.
+	if old_serial > draft {
+		// If old_serial was really slow, upgrade to new yyyymmddvv standard:
+		method = "o>d"
+		new_serial = old_serial + 1
+		new_serial = old_serial + 1
+	} else if old_serial == draft {
+		// Edge case: increment old serial:
+		method = "o=d"
+		new_serial = draft + 1
+	} else if len(old_serialStr) != 10 {
+		// If old_serial is wrong number of digits, upgrade to yyyymmddvv standard:
+		method = "len!=10"
+		new_serial = draft
+	} else if strings.HasPrefix(old_serialStr, todayStr) {
+		// If old_serial just needs to be incremented:
+		method = "prefix"
+		new_serial = old_serial + 1
+	} else {
+		// First serial number to be requested today:
+		method = "default"
+		new_serial = draft
+	}
+
+	if new_serial == 0 {
+		// We never return 0 as the serial number.
+		new_serial = 1
+	}
+	if old_serial == new_serial {
+		log.Fatalf("%v: old_serial == new_serial (%v == %v) draft=%v method=%v", original, old_serial, new_serial, draft, method)
+	}
+	if old_serial > new_serial {
+		log.Fatalf("%v: old_serial > new_serial (%v > %v) draft=%v method=%v", original, old_serial, new_serial, draft, method)
+	}
+	return new_serial
+}