This change replaces the current 64 bit sequential GID with 64 bits
random bytes GID in an attempt to support persistent GID. Internally,
the GID is stored as uint64_t. For human representation and RPC
interface, GID is represented as 16 bytes hex string. For console
readout, 16 bytes are too long, so it is abbreviated to first 6 bytes.
When querying GID in RPC calls, user can speicfy the prefix of GID as
long as the prefix is shared by more than 1 GID entries.
If true is given, which is default, save the uploaded torrent or
metalink metadata in the directory specified by --dir option. The
filename consists of SHA1-hash hex string of metadata plus
extension. For torrent, the extension is '.torrent'. For metalink, it
is '.meta4'. If false is given to this option, the downloads added by
aria2.addTorrent or aria2.addMetalink will not be saved by
--save-session option.
This option sets a piece length for HTTP/FTP downloads. This is the
boundary when aria2 splits a file. All splits occur at multiple of
this length. This option will be ignored in BitTorrent downloads. It
will be also ignored if Metalink file contains piece hashes.
Tatsuhiro Tsujikawa