Editing mirc/identifiers/$compress

{{mirc title|$compress Identifier}}
The '''$compress''' identifier performs compression of a disk file or binary variable.


== Synopsis ==
<pre>$compress( <filename | BinaryVariable> ,[b][lN] )</pre>

== Parameters ==
<span style="display: inline-block; width: 50px;">'''Data'''</span>First parameter can be either a disk file (default) or a Binary Variable<br />
<span style="display: inline-block; width: 50px;">'''b'''</span>Informs that first parameter should be treated as a Binary Variable instead of filename.<br />
<span style="display: inline-block; width: 50px;">'''lN'''</span>Default compression level is 6 (slower, smallest output). lN overrides to use compression level N, where N is integer 1-6.

== Example ==

There are patterns that often appear near the beginning, but there's no guaranteed signature to be found at the beginning of a compressed file, except the 1st character is $chr(120) small-x.

Returns 1 if it compressed the file, or 0 if it did not. It will repeatedly process the same file and return 1, even if the attempt to compress an already compressed file slightly increases the file. 0 can indicate there's no-such-file, the file wasn't already compressed, or a failure to decompress corrupted data.

<pre>
//noop | $compress(versions.txt) | echo -a test
//bset -t &snip 1 $read($mircini,ntw,*16777215*) | echo 4 -a / $bvar(&snip,1-) |      $compress(&snip,b) | echo 5 -a \ $bvar(&snip,1-)
//bset -t &snip 1 $read($mircini,ntw,*16777215*) | echo 4 -a / $bvar(&snip,1-) | noop $compress(&snip,b) | echo 5 -a \ $bvar(&snip,1-)
</pre>

In the above example, the first 2 lines are incorrect usage, and fail to alter the filename or binary variable, nor do they display the following echo. You must use $compress an argument to something else, which should be done in order to determine success or failure.

<source lang="mIRC">
alias compress-then-send {
  if (!$comchan($1,1)) { echo 5 -a no shared channels with nick $1 | return }
  if (!$isfile($2-)) { echo 5 -a filename does not exist: $2- | return }
  bread $qt($2-) 0 1 &snip
  if ($bvar(&snip,1) != 120) { var %i $compress($2-) | if (%i == 0) echo 5 -a warning failure to compress $1- }
  dcc send $1 $2-
}
</source>

'''Note:''' Before making a script which automatically compresses all files before sending them and decompressing them when they finish, you should take several issues into account.
# You shouldn't automatically decompress or compress files without making certain that the same file isn't also being transferred to/from someone else.
# Besides {{mIRC|on events/on filesent|ON FILESENT}}, Transfers can also terminate with {{mIRC|on events/on sendfail|ON SENDFAIL}}, clicking to close the send window, using the {{mIRC|/close}} command with the -s switch, mIRC crashing, etc.
# To make certain all files get safely decompressed, the script should probably work from a file listing that doesn't remove lines until the file has been determined to be decompressed.

== Compatibility ==
{{mIRC compatibility|6.1}}

== See also ==
* {{mIRC|$decompress}}

[[Category:mIRC identifiers|compress]]