ZLIB
ZLIB - Compressed communication
There are two variants of zlib support, FULL and GET, and only one should be used on a each communications channel set up.
ZLIB-FULL
If, during SUP negotiation, a peer sends "ZLIF" in its support string, it must accept two additional commands, ZON and ZOF. Upon reception of ZON the peer must start decompressing the incoming stream of data with zlib before interpreting it, and stop doing so after ZOF is received (in the compressed stream). The compressing end must partially flush the zlib buffer after each chunk of data to allow for decompression by the peer.
ZLIB-GET
The alternative is to send "ZLIG" to indicate that zlib is supported for binary transfers using the GET command, but not otherwise. A flag "ZL1" is added to the to the SND command to indicate that the data will come compressed, and the client receiving requests it by adding the same flag to GET (the sending client may ignore a request for a compressed transfer, but may also use it even when not requested by the receiver). The <bytes> parameter of the GET and SND commands is to be interpreted as the number of uncompressed bytes to be transferred.
