1POE::Filter::Map(3)   User Contributed Perl Documentation  POE::Filter::Map(3)
2
3
4

NAME

6       POE::Filter::Map - transform input and/or output within a filter stack
7

SYNOPSIS

9         #!perl
10
11         use POE qw(
12           Wheel::FollowTail
13           Filter::Line Filter::Map Filter::Stackable
14         );
15
16         POE::Session->create(
17           inline_states => {
18             _start => sub {
19               my $parse_input_as_lines = POE::Filter::Line->new();
20
21               my $redact_some_lines = POE::Filter::Map->new(
22                 Code => sub {
23                   my $input = shift;
24                   $input = "[REDACTED]" unless $input =~ /sudo\[\d+\]/i;
25                   return $input;
26                 },
27               );
28
29               my $filter_stack = POE::Filter::Stackable->new(
30                 Filters => [
31                   $parse_input_as_lines, # first on get, last on put
32                   $redact_some_lines, # first on put, last on get
33                 ]
34               );
35
36               $_[HEAP]{tailor} = POE::Wheel::FollowTail->new(
37                 Filename => "/var/log/system.log",
38                 InputEvent => "got_log_line",
39                 Filter => $filter_stack,
40               );
41             },
42             got_log_line => sub {
43               print "Log: $_[ARG0]\n";
44             }
45           }
46         );
47
48         POE::Kernel->run();
49         exit;
50

DESCRIPTION

52       POE::Filter::Map transforms data inside the filter stack.  It may be
53       used to transform input, output, or both depending on how it is
54       constructed.  This filter is named and modeled after Perl's built-in
55       map() function.
56
57       POE::Filter::Map is designed to be combined with other filters through
58       POE::Filter::Stackable.  In the "SYNOPSIS" example, a filter stack is
59       created to parse logs as lines and redact all entries that don't
60       pertain to a sudo process.
61

PUBLIC FILTER METHODS

63       In addition to the usual POE::Filter methods, POE::Filter::Map also
64       supports the following.
65
66   new
67       new() constructs a new POE::Filter::Map object.  It must either be
68       called with a single Code parameter, or both a Put and a Get parameter.
69       The values for Code, Put and Get are code references that, when
70       invoked, return transformed versions of their sole parameters.  A Code
71       function will be used for both input and output, while Get and Put
72       functions allow input and output to be filtered in different ways.
73
74         # Decrypt rot13.
75         sub decrypt_rot13 {
76           my $encrypted = shift;
77           $encrypted =~ tr[a-zA-Z][n-za-mN-ZA-M];
78           return $encrypted;
79         }
80
81         # Encrypt rot13.
82         sub encrypt_rot13 {
83           my $plaintext = shift;
84           $plaintext =~ tr[a-zA-Z][n-za-mN-ZA-M];
85           return $plaintext;
86         }
87
88         # Decrypt rot13 on input, and encrypt it on output.
89         my $rot13_transcrypter = POE::Filter::Map->new(
90           Get => \&decrypt_rot13,
91           Put => \&encrypt_rot13,
92         );
93
94       Rot13 is symmetric, so the above example can be simplified to use a
95       single Code function.
96
97         my $rot13_transcrypter = POE::Filter::Map->new(
98           Code => sub {
99             local $_ = shift;
100             tr[a-zA-Z][n-za-mN-ZA-M];
101             return $_;
102           }
103         );
104
105   modify
106       modify() changes a POE::Filter::Map object's behavior at run-time.  It
107       accepts the same parameters as new(), and it replaces the existing
108       transforms with new ones.
109
110         # Switch to "reverse" encryption for testing.
111         $rot13_transcrypter->modify(
112           Code => sub { return scalar reverse shift }
113         );
114

SEE ALSO

116       POE::Filter for more information about filters in general.
117
118       POE::Filter::Stackable for more details on stacking filters.
119

BUGS

121       None known.
122

AUTHORS & COPYRIGHTS

124       The Map filter was contributed by Dieter Pearcey.  Documentation is
125       provided by Rocco Caputo.
126
127       Please see the POE manpage for more information about authors and
128       contributors.
129
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131
132perl v5.34.0                      2021-07-22               POE::Filter::Map(3)
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