Release v0.3.0

vendor/github.com/lightningnetwork/lnd/channeldb/meta.go

@@ -0,0 +1,80 @@
+package channeldb
+
+import (
+	"github.com/lightningnetwork/lnd/channeldb/kvdb"
+)
+
+var (
+	// metaBucket stores all the meta information concerning the state of
+	// the database.
+	metaBucket = []byte("metadata")
+
+	// dbVersionKey is a boltdb key and it's used for storing/retrieving
+	// current database version.
+	dbVersionKey = []byte("dbp")
+)
+
+// Meta structure holds the database meta information.
+type Meta struct {
+	// DbVersionNumber is the current schema version of the database.
+	DbVersionNumber uint32
+}
+
+// FetchMeta fetches the meta data from boltdb and returns filled meta
+// structure.
+func (d *DB) FetchMeta(tx kvdb.ReadTx) (*Meta, error) {
+	meta := &Meta{}
+
+	err := kvdb.View(d, func(tx kvdb.ReadTx) error {
+		return fetchMeta(meta, tx)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return meta, nil
+}
+
+// fetchMeta is an internal helper function used in order to allow callers to
+// re-use a database transaction. See the publicly exported FetchMeta method
+// for more information.
+func fetchMeta(meta *Meta, tx kvdb.ReadTx) error {
+	metaBucket := tx.ReadBucket(metaBucket)
+	if metaBucket == nil {
+		return ErrMetaNotFound
+	}
+
+	data := metaBucket.Get(dbVersionKey)
+	if data == nil {
+		meta.DbVersionNumber = getLatestDBVersion(dbVersions)
+	} else {
+		meta.DbVersionNumber = byteOrder.Uint32(data)
+	}
+
+	return nil
+}
+
+// PutMeta writes the passed instance of the database met-data struct to disk.
+func (d *DB) PutMeta(meta *Meta) error {
+	return kvdb.Update(d, func(tx kvdb.RwTx) error {
+		return putMeta(meta, tx)
+	})
+}
+
+// putMeta is an internal helper function used in order to allow callers to
+// re-use a database transaction. See the publicly exported PutMeta method for
+// more information.
+func putMeta(meta *Meta, tx kvdb.RwTx) error {
+	metaBucket, err := tx.CreateTopLevelBucket(metaBucket)
+	if err != nil {
+		return err
+	}
+
+	return putDbVersion(metaBucket, meta)
+}
+
+func putDbVersion(metaBucket kvdb.RwBucket, meta *Meta) error {
+	scratch := make([]byte, 4)
+	byteOrder.PutUint32(scratch, meta.DbVersionNumber)
+	return metaBucket.Put(dbVersionKey, scratch)
+}