POE::Filter::Map(3) User Contributed Perl Documentation POE::Filter::Map(3)NAMEPOE::Filter::Map - transform input and/or output within a filter stack
SYNOPSIS
#!perl
use POE qw(
Wheel::FollowTail
Filter::Line Filter::Map Filter::Stackable
);
POE::Session->create(
inline_states => {
_start => sub {
my $parse_input_as_lines = POE::Filter::Line->new();
my $redact_some_lines = POE::Filter::Map->new(
Code => sub {
my $input = shift;
$input = "[REDACTED]" unless $input =~ /sudo\[\d+\]/i;
return $input;
},
);
my $filter_stack = POE::Filter::Stackable->new(
Filters => [
$parse_input_as_lines, # first on get, last on put
$redact_some_lines, # first on put, last on get
]
);
$_[HEAP]{tailor} = POE::Wheel::FollowTail->new(
Filename => "/var/log/system.log",
InputEvent => "got_log_line",
Filter => $filter_stack,
);
},
got_log_line => sub {
print "Log: $_[ARG0]\n";
}
}
);
POE::Kernel->run();
exit;
DESCRIPTIONPOE::Filter::Map transforms data inside the filter stack. It may be
used to transform input, output, or both depending on how it is
constructed. This filter is named and modeled after Perl's built-in
map() function.
POE::Filter::Map is designed to be combined with other filters through
POE::Filter::Stackable. In the "SYNOPSIS" example, a filter stack is
created to parse logs as lines and redact all entries that don't
pertain to a sudo process.
PUBLIC FILTER METHODS
In addition to the usual POE::Filter methods, POE::Filter::Map also
supports the following.
new
new() constructs a new POE::Filter::Map object. It must either be
called with a single Code parameter, or both a Put and a Get parameter.
The values for Code, Put and Get are code references that, when
invoked, return transformed versions of their sole parameters. A Code
function will be used for both input and output, while Get and Put
functions allow input and output to be filtered in different ways.
# Decrypt rot13.
sub decrypt_rot13 {
my $encrypted = shift;
$encrypted =~ tr[a-zA-Z][n-za-mN-ZA-M];
return $encrypted;
}
# Encrypt rot13.
sub encrypt_rot13 {
my $plaintext = shift;
$plaintext =~ tr[a-zA-Z][n-za-mN-ZA-M];
return $plaintext;
}
# Decrypt rot13 on input, and encrypt it on output.
my $rot13_transcrypter = POE::Filter::Map->new(
Get => \&decrypt_rot13,
Put => \&encrypt_rot13,
);
Rot13 is symmetric, so the above example can be simplified to use a
single Code function.
my $rot13_transcrypter = POE::Filter::Map->new(
Code => sub {
local $_ = shift;
tr[a-zA-Z][n-za-mN-ZA-M];
return $_;
}
);
modify
modify() changes a POE::Filter::Map object's behavior at run-time. It
accepts the same parameters as new(), and it replaces the existing
transforms with new ones.
# Switch to "reverse" encryption for testing.
$rot13_transcrypter->modify(
Code => sub { return scalar reverse shift }
);
SEE ALSO
POE::Filter for more information about filters in general.
POE::Filter::Stackable for more details on stacking filters.
BUGS
None known.
AUTHORS & COPYRIGHTS
The Map filter was contributed by Dieter Pearcey. Documentation is
provided by Rocco Caputo.
Please see the POE manpage for more information about authors and
contributors.
perl v5.14.2 2011-12-15 POE::Filter::Map(3)
