poe::filter::map(3pm) [debian man page]

POE::Filter::Map(3pm)					User Contributed Perl Documentation				     POE::Filter::Map(3pm)

NAME

       POE::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]
";
	     }
	   }
	 );

	 POE::Kernel->run();
	 exit;

DESCRIPTION

       POE::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							    2012-05-15						     POE::Filter::Map(3pm)

POE::Filter::Line(3pm)					User Contributed Perl Documentation				    POE::Filter::Line(3pm)

NAME

       POE::Filter::Line - serialize and parse terminated records (lines)

SYNOPSIS

	 #!perl

	 use POE qw(Wheel::FollowTail Filter::Line);

	 POE::Session->create(
	   inline_states => {
	     _start => sub {
	       $_[HEAP]{tailor} = POE::Wheel::FollowTail->new(
		 Filename => "/var/log/system.log",
		 InputEvent => "got_log_line",
		 Filter => POE::Filter::Line->new(),
	       );
	     },
	     got_log_line => sub {
	       print "Log: $_[ARG0]
";
	     }
	   }
	 );

	 POE::Kernel->run();
	 exit;

DESCRIPTION

       POE::Filter::Line parses stream data into terminated records.  The default parser interprets newlines as the record terminator, and the
       default serializer appends network newlines (CR/LF, or "x0Dx0A") to outbound records.

       Record terminators are removed from the data POE::Filter::Line returns.

       POE::Filter::Line supports a number of other ways to parse lines.  Constructor parameters may specify literal newlines, regular
       expressions, or that the filter should detect newlines on its own.

PUBLIC FILTER METHODS

       POE::Filter::Line's new() method has some interesting parameters.

   new
       new() accepts a list of named parameters.

       In all cases, the data interpreted as the record terminator is stripped from the data POE::Filter::Line returns.

       "InputLiteral" may be used to parse records that are terminated by some literal string.	For example, POE::Filter::Line may be used to
       parse and emit C-style lines, which are terminated with an ASCII NUL:

	 my $c_line_filter = POE::Filter::Line->new(
	   InputLiteral => chr(0),
	   OutputLiteral => chr(0),
	 );

       "OutputLiteral" allows a filter to put() records with a different record terminator than it parses.  This can be useful in applications
       that must translate record terminators.

       "Literal" is a shorthand for the common case where the input and output literals are identical.	The previous example may be written as:

	 my $c_line_filter = POE::Filter::Line->new(
	   Literal => chr(0),
	 );

       An application can also allow POE::Filter::Line to figure out which newline to use.  This is done by specifying "InputLiteral" to be undef:

	 my $whichever_line_filter = POE::Filter::Line->new(
	   InputLiteral => undef,
	   OutputLiteral => "
",
	 );

       "InputRegexp" may be used in place of "InputLiteral" to recognize line terminators based on a regular expression.  In this example, input
       is terminated by two or more consecutive newlines.  On output, the paragraph separator is "---" on a line by itself.

	 my $paragraph_filter = POE::Filter::Line->new(
	   InputRegexp => "([x0Dx0A]{2,})",
	   OutputLiteral => "
---
",
	 );

PUBLIC FILTER METHODS

       POE::Filter::Line has no additional public methods.

SEE ALSO

       Please see POE::Filter for documentation regarding the base interface.

       The SEE ALSO section in POE contains a table of contents covering the entire POE distribution.

BUGS

       The default input newline parser is a regexp that has an unfortunate race condition.  First the regular expression:

	 /(x0Dx0A?|x0Ax0D?)/

       While it quickly recognizes most forms of newline, it can sometimes detect an extra blank line.	This happens when a two-byte newline
       character is broken between two reads.  Consider this situation:

	 some stream dataCR
	 LFother stream data

       The regular expression will see the first CR without its corresponding LF.  The filter will properly return "some stream data" as a line.
       When the next packet arrives, the leading "LF" will be treated as the terminator for a 0-byte line.  The filter will faithfully return this
       empty line.

       It is advised to specify literal newlines or use the autodetect feature in applications where blank lines are significant.

AUTHORS &; COPYRIGHTS
       Please see POE for more information about authors and contributors.

perl v5.14.2							    2012-05-15						    POE::Filter::Line(3pm)