Patricia(3pm) User Contributed Perl Documentation Patricia(3pm)
NAME
Net::Patricia - Patricia Trie perl module for fast IP address lookups
SYNOPSIS
use Net::Patricia;
my $pt = new Net::Patricia;
$pt->add_string('127.0.0.0/8', \$user_data);
$pt->match_string('127.0.0.1');
$pt->match_exact_string('127.0.0.0');
$pt->match_integer(2130706433); # 127.0.0.1
$pt->match_exact_integer(2130706432, 8); # 127.0.0.0
$pt->remove_string('127.0.0.0/8');
$pt->climb(sub { print "climbing at node $_[0]\n" });
undef $pt; # automatically destroys the Patricia Trie
# IPv6 support:
$pt = new Net::Patricia AF_INET6;
$pt->add_string('2001:db8::/32');
$pt->add_string('2001:db8:0:dead::/64');
$pt->add_string('2001:db8:0:beef::/64');
$pt->climb(sub { print "climbing at node $_[0]\n" });
print $pt->match_string('2001:db8:0:dead::1'), "\n";
# IPv4-mapped IPv6 addresses:
$pt->add_string('::ffff:0:0/96');
for my $cidr (qw( 192.0.2.0/24 192.0.2.0/25 192.0.2.128/25 )) {
my($ip, $len) = split(m|/|, $cidr);
$pt->add_string("::ffff:$ip/" .
(96+(defined($len)? $len : 32)), $cidr);
}
$pt->climb(sub { print "climbing at node $_[0]\n" });
print $pt->match_string("::ffff:" . "192.0.2.129"), "\n";
DESCRIPTION
This module uses a Patricia Trie data structure to quickly perform IP
address prefix matching for applications such as IP subnet, network or
routing table lookups. The data structure is based on a radix tree
using a radix of two, so sometimes you see patricia implementations
called "radix" as well. The term "Trie" is derived from the word
"retrieval" but is pronounced like "try". Patricia stands for
"Practical Algorithm to Retrieve Information Coded as Alphanumeric",
and was first suggested for routing table lookups by Van Jacobsen.
Patricia Trie performance characteristics are well-known as it has been
employed for routing table lookups within the BSD kernel since the 4.3
Reno release.
The BSD radix code is thoroughly described in "TCP/IP Illustrated,
Volume 2" by Wright and Stevens and in the paper ``A Tree-Based Packet
Routing Table for Berkeley Unix'' by Keith Sklower.
METHODS
new - create a new Net::Patricia object
$pt = new Net::Patricia;
This is the class' constructor - it returns a "Net::Patricia"
object upon success or undef on failure. The constructor takes an
optional argument (of AF_INET or AF_INET6, defaulting to the
former), and creates a tree with address and mask values of that
type as keys.
The "Net::Patricia" object will be destroyed automatically when
there are no longer any references to it.
add_string
$pt->add_string(key_string[,user_data]);
The first argument, key_string, is a network or subnet
specification in canonical form, e.g. "10.0.0.0/8", where the
number after the slash represents the number of bits in the
netmask. If no mask width is specified, the longest possible mask
is assumed, i.e. 32 bits for AF_INET addresses.
The second argument, user_data, is optional. If supplied, it
should be a SCALAR value (which may be a perl reference) specifying
the user data that will be stored in the Patricia Trie node.
Subsequently, this value will be returned by the match methods
described below to indicate a successful search. Remember that
perl references and objects are represented as SCALAR values and
therefore the user data can be complicated data objects.
If no second argument is passed, the key_string will be stored as
the user data and therfore will likewise be returned by the match
functions.
On success, this method returns the user_data passed as the second
argument or key_string if no user data was specified. It returns
undef on failure.
match_string
$pt->match_string(key_string);
This method searches the Patricia Trie to find a matching node,
according to normal subnetting rules for the address and mask
specified.
The key_string argument is a network or subnet specification in
canonical form, e.g. "10.0.0.0/8", where the number after the slash
represents the number of bits in the netmask. If no mask width
value is specified, the longest mask is assumed, i.e. 32 bits for
AF_INET addresses.
If a matching node is found in the Patricia Trie, this method
returns the user data for the node. This method returns undef on
failure.
match_exact_string
$pt->match_exact_string(key_string);
This method searches the Patricia Trie to find a matching node.
Its semantics are exactly the same as those described for
"match_string" except that the key must match a node exactly. I.e.
it is not sufficient that the address and mask specified merely
falls within the subnet specified by a particular node.
match_integer
$pt->match_integer(integer[,mask_bits]);
This method searches the Patricia Trie to find a matching node,
according to normal subnetting rules for the address and mask
specified. Its semantics are similar to those described for
"match_string" except that the key is specified using an integer
(i.e. SCALAR), such as that returned by perl's "unpack" function
for values converted using the "N" (network-ordered long). Note
that this argument is not a packed network-ordered long.
Just to be completely clear, the integer argument should be a value
of the sort produced by this code:
use Socket;
$integer = unpack("N", inet_aton("10.0.0.0"));
match_exact_integer
$pt->match_exact_integer(integer[,mask_bits]);
This method searches the Patricia Trie to find a matching node.
Its semantics are exactly the same as "match_integer" except that
the key must match a node exactly. I.e. it is not sufficient that
the address and mask specified merely falls within the subnet
specified by a particular node.
remove_string
$pt->remove_string(key_string);
This method removes the node which exactly matches the the address
and mask specified from the Patricia Trie.
If the matching node is found in the Patricia Trie, it is removed,
and this method returns the user data for the node. This method
returns undef on failure.
climb
$pt->climb([CODEREF]);
This method climbs the Patricia Trie, visiting each node as it does
so. It performs a non-recursive, "preorder" traversal.
The CODEREF argument is optional. It is a perl code reference used
to specify a user-defined subroutine to be called when visiting
each node. The node's user data will be passed as the sole
argument to that subroutine.
This method returns the number of nodes successfully visited while
climbing the Trie. That is, without a CODEREF argument, it simply
counts the number of nodes in the Patricia Trie.
Note that currently the return value from your CODEREF subroutine
is ignored. In the future the climb method may return the number
of times your subroutine returned non-zero, as it is called once
per node. So, if you are currently relying on the climb return
value to accurately report a count of the number of nodes in the
Patricia Trie, it would be prudent to have your subroutine return a
non-zero value.
This method is called climb() rather than walk() because climbing
trees (and therfore tries) is a more popular pass-time than walking
them.
climb_inorder
$pt->climb_inorder([CODEREF]);
This method climbs the Patricia Trie, visiting each node in order
as it does so. That is, it performs an "inorder" traversal.
The CODEREF argument is optional. It is a perl code reference used
to specify a user-defined subroutine to be called when visiting
each node. The node's user data will be passed as the sole
argument to that subroutine.
This method returns the number of nodes successfully visited while
climbing the Trie. That is, without a CODEREF argument, it simply
counts the number of nodes in the Patricia Trie.
Note that currently the return value from your CODEREF subroutine
is ignored. In the future the climb method may return the number
of times your subroutine returned non-zero, as it is called once
per node. So, if you are currently relying on the climb return
value to accurately report a count of the number of nodes in the
Patricia Trie, it would be prudent to have your subroutine return a
non-zero value.
This method is called climb() rather than walk() because climbing
trees (and therfore tries) is a more popular pass-time than walking
them.
Serialization
Net::Patricia trees, unlike many classes with XS-level data, can be
frozen and thawed using Storable.
BUGS
When passing a CODEREF argument to the climb method, the return value
from your CODEREF subroutine is currently ignored. In the future the
climb method may return the number of times your subroutine returned
non-zero, as it is called once per node. So, if you are currently
relying on the climb return value to accurately report a count of the
number of nodes in the Patricia Trie, it would be prudent to have your
subroutine return a non-zero value.
AUTHOR
Dave Plonka <plonka@doit.wisc.edu> Philip Prindeville
<philipp@redfish-solutions.com> Anton Berezin <tobez@tobez.org>
Copyright (C) 2000-2005 Dave Plonka. Copyright (C) 2009 Dave Plonka
& Philip Prindeville. This program is free software; you can
redistribute it and/or modify it under the terms of the GNU General
Public License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This product includes software developed by the University of Michigan,
Merit Network, Inc., and their contributors. See the copyright file in
the patricialib sub-directory of the distribution for details.
patricialib, the C library used by this perl extension, is an extracted
version of MRT's patricia code from radix.[ch], which was worked on by
Masaki Hirabaru and Craig Labovitz. For more info on MRT see:
http://www.mrtd.net/
The MRT patricia code owes some heritage to GateD's radix code, which
in turn owes something to the BSD kernel.
SEE ALSO
perl(1), Socket, Net::Netmask, Text::Trie, Tree::Trie.
Tree::Radix and Net::RoutingTable are modules by Daniel Hagerty
<hag@linnaean.org> written entirely in perl, unlike this module. At
the time of this writing, they are works-in-progress but may be
available at:
http://www.linnaean.org/~hag/
perl v5.34.0 2022-02-07 Patricia(3pm)
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