lnd.xprv/watchtower/wtdb/version.go

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package wtdb
import "github.com/coreos/bbolt"
// migration is a function which takes a prior outdated version of the database
// instances and mutates the key/bucket structure to arrive at a more
// up-to-date version of the database.
type migration func(tx *bbolt.Tx) error
// version pairs a version number with the migration that would need to be
// applied from the prior version to upgrade.
type version struct {
number uint32
migration migration
}
// dbVersions stores all versions and migrations of the database. This list will
// be used when opening the database to determine if any migrations must be
// applied.
var dbVersions = []version{
{
// Initial version requires no migration.
number: 0,
migration: nil,
},
}
// getLatestDBVersion returns the last known database version.
func getLatestDBVersion(versions []version) uint32 {
return versions[len(versions)-1].number
}
// getMigrations returns a slice of all updates with a greater number that
// curVersion that need to be applied to sync up with the latest version.
func getMigrations(versions []version, curVersion uint32) []version {
var updates []version
for _, v := range versions {
if v.number > curVersion {
updates = append(updates, v)
}
}
return updates
}
// getDBVersion retrieves the current database version from the metadata bucket
// using the dbVersionKey.
func getDBVersion(tx *bbolt.Tx) (uint32, error) {
metadata := tx.Bucket(metadataBkt)
if metadata == nil {
return 0, ErrUninitializedDB
}
versionBytes := metadata.Get(dbVersionKey)
if len(versionBytes) != 4 {
return 0, ErrNoDBVersion
}
return byteOrder.Uint32(versionBytes), nil
}
// initDBVersion initializes the top-level metadata bucket and writes the passed
// version number as the current version.
func initDBVersion(tx *bbolt.Tx, version uint32) error {
_, err := tx.CreateBucketIfNotExists(metadataBkt)
if err != nil {
return err
}
return putDBVersion(tx, version)
}
// putDBVersion stores the passed database version in the metadata bucket under
// the dbVersionKey.
func putDBVersion(tx *bbolt.Tx, version uint32) error {
metadata := tx.Bucket(metadataBkt)
if metadata == nil {
return ErrUninitializedDB
}
versionBytes := make([]byte, 4)
byteOrder.PutUint32(versionBytes, version)
return metadata.Put(dbVersionKey, versionBytes)
}