// PrefixTransform constructs a KeyTransform with a pair of functions that
// add or remove the given prefix key.
//
// Warning: will panic if prefix not found when it should be there. This is
// to avoid insidious data inconsistency errors.
func PrefixTransform(prefix ds.Key) ktds.KeyTransform {
return &ktds.Pair{
// Convert adds the prefix
Convert: func(k ds.Key) ds.Key {
return prefix.Child(k)
},
// Invert removes the prefix. panics if prefix not found.
Invert: func(k ds.Key) ds.Key {
if !prefix.IsAncestorOf(k) {
fmt.Errorf("Expected prefix (%s) in key (%s)", prefix, k)
panic("expected prefix not found")
}
s := strings.TrimPrefix(k.String(), prefix.String())
return ds.NewKey(s)
},
}
}
// KeyFilename returns the filename associated with `key`
func (d *Datastore) KeyFilename(key ds.Key) string {
return filepath.Join(d.path, key.String(), ".dsobject")
}