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.TH FILTER-DEFLATE 2
.SH NAME
deflate, inflate \- data compression filters
.SH SYNOPSIS
.EX
include "filter.m";
deflate := load Filter Filter->DEFLATEPATH;
inflate := load Filter Filter->INFLATEPATH;
init: fn();
start: fn(param: string): chan of ref Rq;
.EE
.SH DESCRIPTION
These implementation modules conform to the
.B Filter
module interface for data-processing filters.
For details of the interface, see
.IR filter (2).
.PP
.I Deflate
implements gzip-compatible stream compression.
The
.I param
string argument to
.B start
can contain one or more of the following option characters:
.RS 10
.TP
.RB ` d '
Enable debugging output. Each line of debugging output
is provided in an
.B Rq.Info
message.
.TP
.RB ` v '
Enable verbose mode. Each line of verbose output
is provided in an
.B Rq.Info
message.
.TP
.RB ` h '
Add a gzip header and footer to the data. With this flag,
the data after filtering will be in exactly the same
format as a gzip file, with accompanying checksum.
.TP
.RB ` 0 '\ to\ ` 9 '
Specifies the level of compression to be used (9 highest). See
.IR gzip (1).
.RE
.PP
.I Inflate
performs the inverse operation to
.BR deflate .
If the
.I param
argument to
.B start
begins with the character
.RB ` h '
then the input to the filter is assumed to be in the
standard gzip file format; the output will be checked
for integrity. While processing, the
.B Rq.Info
message is used to transmit some information; the type
of information is determined by the first word of
.IR msg ,
as follows:
.RS
.TP
.B file
The rest of
.I msg
(after a following space) is the name of the original filename
before compression.
.TP
.B mtime
The rest of
.I msg
(after a following space) is the modification time of the
original file before compression.
.RE
.SH SOURCE
.B /appl/lib/deflate.b
.br
.B /appl/lib/inflate.b
.SH SEE ALSO
.IR gzip (1),
.IR filter (2)
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