[libvirt-users] who is the end user of libvirt-iohelper?

Hello everybody! I'm trying to make some experiments with writing/reading stream to/from volume. I've realized that libvirt-iohelper are ran to make this operations: 1) reading stream from stdin and writng to a file 2) reading stream from a file and writing to stdout I've also realized that virsh uses libvirt-iohelper via virStorageVolUpload/virStorageVolDownload. But i can't find the place where virsh works with stdin/stdout (reading/writing full data to this I/O).