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     FILTER-DEFLATE(2)                               FILTER-DEFLATE(2)

     NAME
          deflate, inflate - data compression filters

     SYNOPSIS
          include "filter.m";

          deflate := load Filter Filter->DEFLATEPATH;
          inflate := load Filter Filter->INFLATEPATH;

          init:  fn();
          start: fn(param: string): chan of ref Rq;

     DESCRIPTION
          These implementation modules conform to the Filter module
          interface for data-processing filters.  For details of the
          interface, see filter(2).

          Deflate implements gzip-compatible stream compression.  The
          param string argument to start can contain one or more of
          the following option characters:

                    `d'  Enable debugging output. Each line of debug-
                         ging output is provided in an Rq.Info mes-
                         sage.

                    `v'  Enable verbose mode. Each line of verbose
                         output is provided in an Rq.Info message.

                    `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.

                    `z'  Add a zlib header and footer to the data.
                         The footer contains a checksum.

                    `0' to `9'
                         Specifies the level of compression to be used
                         (9 highest). See gzip(1).

          Inflate performs the inverse operation to deflate.  If the
          param argument to start begins with the character `h' then
          the input to the filter is assumed to be in the standard
          gzip file format; if it starts with the character `z' it is
          assumed to be in zlib format; the output will be checked for
          integrity in both cases. While processing a gzip stream, the
          Rq.Info message is used to transmit some information; the
          type of information is determined by the first word of msg,
          as follows:

     FILTER-DEFLATE(2)                               FILTER-DEFLATE(2)

               file The rest of msg (after a following space) is the
                    name of the original filename before compression.

               mtime
                    The rest of msg (after a following space) is the
                    modification time of the original file before com-
                    pression.

     SOURCE
          /appl/lib/deflate.b
          /appl/lib/inflate.b

     SEE ALSO
          gzip(1), filter(2)
          Internet RFCs RFC1950, RFC1951, and RFC1952.