=head1 NAME

Net::SIP::Util - utility functions used by all of L<Net::SIP>

=head1 SYNOPSIS

  use Net::SIP::Util qw( create_rtp_sockets );
  my ($port,@socks) = create_rtp_sockets( '192.168.0.10' ) or die;

=head1 DESCRIPTION

This package implements various utility function used within various
L<Net::SIP> packages and partly usable for the user of L<Net::SIP> too.

Each of this functions is exportable, but none is exported per default.
All functions can be exported at once with the import flag C<:all>.

=head1 SUBROUTINES

=over 4

=item invoke_callback ( CALLBACK, @ARGS )

Invokes callback CALLBACK with additional args @ARGS.
CALLBACK can be:

=over 8

=item A code reference

In this case it will be called as C<< $CALLBACK->(@ARGS) >>
and return the return value of this call.

=item A reference to a scalar

In this case the scalar will be set to C<< $ARGS[0] >> and
the rest of @ARGS will be ignored. If no @ARGS are given the
scalar will be set to TRUE.
It will return with the value of the scalar.

=item An object which has a method B<run>

In this case it will call C<< $CALLBACK->run(@ARGS) >>
and return with the return value of this call.

=item A reference to an array

The first element of the array will be interpreted as code reference,
while the rest as args, e.g. it will do:

  my ($coderef,@cb_args) = @$CALLBACK;
  return $coderef->( @cb_args, @ARGS );

=item A regular expression

In this case it will try to match all @ARGS against the regex.
If anything matches it will return TRUE, else FALSE.

=back

=item create_socket_to ( ADDR, [ PROTO ] )

Creates socket with protocol PROTO (default 'udp') on a local interface,
from where ADDR is reachable.
This is done by first creating a UDP socket with target
ADDR and using getsockname(2) to find out the local address of this
socket. The newly created socket than will be bound to this address.

It will try to bind the socket to port 5060 (default SIP port).
If this fails it will try port 5062..5100 and if it cannot bind
to any of these ports it will just use any port which gets assigned
by the OS.

For multihomed hosts where several addresses are bound to the same
interface it will just use one of these addresses. If you need more
control about the address the socket is bound to (and which will
be used as the local IP in outgoing packets) you need to create the
socket yourself.

In scalar context it just returns the newly created socket.
In array context it will return the socket and the C<< "ip:port" >>
the created socket is bound to.
If the creation of the socket fails it will return C<()> and set C<$!>.

Example:

  my ($sock,$ip_port) = create_socket_to ( '192.168.0.1' )
	or die $!;


=item create_rtp_sockets ( LADDR, [ RANGE, MINPORT, MAXPORT, TRIES ] )

This tries to allocate sockets for RTP. RTP consists usually of a data
socket on an even port number and a control socket (RTCP) and the following
port. It will try to create these sockets. MINPORT is the minimal
port number to use (default 2000), MAXPORT the highest port (default
MINPORT+10000), TRIES is the number of attempts it makes to create such
socket pairs and defaults to 1000.

RANGE is the number of consecutive ports it needs to allocate and
defaults to 2 (e.g. data and control socket).

Allocation will be done by choosing a random even number between MINPORT
and MAXPORT and then trying to allocate all the sockets on this and
the following port numbers.

If the allocation fails after TRIES attempts were made it will return C<()>,
otherwise it will return an array with at first the starting port number
followed by all the allocated sockets.

Example:

  my ($port,$rtp_sock,$rtcp_sock) = create_rtp_sockets( '192.168.0.10' )
	or die "allocation failed";


=item sip_hdrval2parts ( KEY, VALUE )

Interprets VALUE as a value for the SIP header field KEY and splits
it into the parts (prefix, parameter). Because for most keys the
delimiter is C<;>, but for some keys C<,> the field name KEY need to
be known.

KEY needs to be normalized already (lower case, no abbrevation).

Returns array with initial data (up to first delimiter) and
the parameters as hash.

Example for key 'to':

  '"Silver; John" <silver@example.com>; tag=...; protocol=TCP'
  -> ( '"Silver; John" <silver@example.com>', { tag => ..., protocol => 'TCP' } )

Example for key 'www-authenticate':

  'Digest method="md5", qop="auth"'
  -> ( 'Digest', { method => 'md5', qop => 'auth' } )

=item sip_parts2hdrval ( KEY, PREFIX, \%PARAMETER )

Inverse function to B<sip_hdrval2parts>, e.g constructs header value for KEY from
PREFIX and %PARAMETER and returns value.

=item sip_uri2parts ( URI )

Returns parts from URI. If called in scalar context it returns only the domain
part. In array context it returns an array with the following values:

=over 4

=item domain - The domain part (including ports if any)

=item user - The user part of the SIP address

=item proto - The protocol, e.g. "sip" or "sips".

=item data - The part before any parameter, includes SIP address

=item param - A hash reference to any parameter, like in B<sip_hdrval2parts>.

=back

=item sip_uri_eq ( URI1, URI2 )

Returns true if both URIs point to the same SIP address.
This compares user part case sensitive, domain part case insensitive (does
no DNS resolution) protocol and ports in domain (assumes default ports
for protocol if no port is given).

=back