:   '''zlib push''' ''mode channel'' ?''options ...''?
This command, part of [zlib], adds a compressing or decompressing transformation to ''channel''. The type of transformation is given by the ''mode'', which must be one of '''compress''', '''decompress''', '''deflate''', '''inflate''', '''gzip''', '''gunzip'''.

The following options may be used:
   '''-header''' ''dict'':   Define gzip header fields, using same rules as [zlib gzip]. Only used for the '''gzip''' transformation.
   '''-level''' ''level'':   Define the compression level, using same rules as [zlib compress], [zlib deflate] and [zlib gzip]. Only used for compressing transformations.

The following [fconfigure]/[chan configure] options are added:
   '''-flush''' ''type'':   This write-only option causes an immediate operation: it flushes the internal buffers of the transformation. Two types of flush are currently defined: '''sync''' flushes empty the buffers but do not make the state restartable, and '''full''' flushes empty the buffers and also make the state restartable (at greater performance penalty). For decompressing transformations, there's no difference.
   '''-checksum''' ''number'':   This read-only option returns the checksum of the uncompressed data seen so far. The algorithm used is format-dependent.
   '''-header''' ''dict'':   This read-only option returns the header dictionary (according to [zlib gunzip] rules) from a '''gunzip''' transformation.

To reverse the '''zlib push''', use [chan pop].
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%| [Category Command] | [Category Compression] | [Category Channel] |%
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