Syncs up flushing to the next byte boundary.
Used when more data is to be compressed later on.
Z_FULL_FLUSH
Syncs up flushing to the next byte boundary.
Used when more data is to be compressed later on,
and the decompressor needs to be restartable at this
point.
Z_FINISH
(default) Used when finished compressing the data.
Compress and return any remaining data. The returned data should be appended to that returned by compress().