ObjectSizesHistogram:    flat.ObjSizes.toMap(),
			ObjectVersionsHistogram: flat.ObjVersions.toMap(),
		}
		dst[bucket.Name] = bui
	}
	return dst
}

// sizeRecursive returns the path as a flattened entry.
func (d *dataUsageCache) sizeRecursive(path string) *dataUsageEntry {
	root := d.find(path)
	if root == nil || len(root.Children) == 0 {
		return root
	}
	flat := d.flatten(*root)
	return &flat
}

func (f *folderScanner) sendUpdate() {
	// Send at most an update every minute.
	if f.updates == nil || time.Since(f.lastUpdate) < time.Minute {
		return
	}
	if flat := f.updateCache.sizeRecursive(f.newCache.Info.Name); flat != nil {
		select {
		case f.updates <- flat.clone():
		default:
		}
		f.lastUpdate = time.Now()
	}
}

// scanFolder will scan the provided folder.