7454b7df95
This commit performs a slight refactoring of the internals (and API) of the [Fetch|Put]Meta methods. The changes are rather minor and simply eliminate the conditional branching structure with usage of an internal function. This new form is much easier to follow.
84 lines
2.0 KiB
Go
84 lines
2.0 KiB
Go
package channeldb
|
|
|
|
import (
|
|
"github.com/boltdb/bolt"
|
|
)
|
|
|
|
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 *bolt.Tx) (*Meta, error) {
|
|
meta := &Meta{}
|
|
|
|
err := d.View(func(tx *bolt.Tx) 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 *bolt.Tx) error {
|
|
metaBucket := tx.Bucket(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 d.Update(func(tx *bolt.Tx) 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 *bolt.Tx) error {
|
|
metaBucket, err := tx.CreateBucketIfNotExists(metaBucket)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
return putDbVersion(metaBucket, meta)
|
|
}
|
|
|
|
func putDbVersion(metaBucket *bolt.Bucket, meta *Meta) error {
|
|
scratch := make([]byte, 4)
|
|
byteOrder.PutUint32(scratch, meta.DbVersionNumber)
|
|
if err := metaBucket.Put(dbVersionKey, scratch); err != nil {
|
|
return err
|
|
}
|
|
return nil
|
|
}
|