write code frame

state.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	bolt "go.etcd.io/bbolt"
+)
+
+var bucketName = []byte("migrator_state")
+
+// openStateDB opens (or creates) a BoltDB at given path.
+func openStateDB(path string) (*bolt.DB, error) {
+	return bolt.Open(path, 0600, nil)
+}
+
+// getLastUID returns last migrated UID for given key.
+func getLastUID(db *bolt.DB, key string) (uint32, error) {
+	var uid uint32
+	err := db.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket(bucketName)
+		if b == nil {
+			return nil
+		}
+		v := b.Get([]byte(key))
+		if v == nil {
+			return nil
+		}
+		uid = binary.BigEndian.Uint32(v)
+		return nil
+	})
+	return uid, err
+}
+
+// setLastUID updates last migrated UID for given key.
+func setLastUID(db *bolt.DB, key string, uid uint32) error {
+	return db.Update(func(tx *bolt.Tx) error {
+		b, err := tx.CreateBucketIfNotExists(bucketName)
+		if err != nil {
+			return err
+		}
+		buf := make([]byte, 4)
+		binary.BigEndian.PutUint32(buf, uid)
+		return b.Put([]byte(key), buf)
+	})
+}
+
+// formatStateKey creates state key from src, dst and mailbox.
+func formatStateKey(src, dst, mbox string) string {
+	return fmt.Sprintf("%s|%s|%s", src, dst, mbox)
+}