
=head1 NAME

Net::SIP::Debug - debugging of Net::SIP

=head1 SYNOPSIS

  use Net::SIP::Debug '1';
  use Net::SIP::Debug qw( Net::SIP*=0 Registrar=1 );
  Net::SIP::Debug->level(1);

  perl -MNet::SIP::Debug=1 app.pl

=head1 DESCRIPTION

Provides debugging support for L<Net::SIP>.
Debugging can be enabled/disabled globally or per package
and optional per subpackage.

It provides support for different debugging levels, e.g.
the higher the level, the more debugging is done.
The following levels are used:

=over 4

=item

1 - Debug messages for users.

=item

2 - Includes short SIP packet dumps of incoming and outgoing data.

=item

5 - Includes detailed SIP packet dumps for incoming and outgoing data.

=item

10 - Includes information about call flow, e.g. why packets get dropped etc.

=item

50 - Detailed debugging for programmers using L<Net::SIP>.

=item

100 - Detailed debugging for core developers of L<Net::SIP>.

=back

=head1 CLASS METHODS

=over 4

=item import ( @ARGS )

Extracts everything from arguments given to C<use> which might
be usable by B<level> and forwards rest to L<Exporter>.

If the argument is a reference to a subroutine it will be used
for showing the debug message instead of printing it to STDERR.
In this case the usual prefixes incl the time will not be added
(useful for forwarding debug to syslog).

=item level ( @ARGS )

Enables/disables debugging depending on @ARGS. @ARGS might
contain the following specifications:

=over 8

=item NUMBER

NUMBER will be interpreted as the debugging level.
It's used in B<debug> etc to print only debug message which a
level lower or equal to NUMBER.

=item PACKAGE

Enables debugging for package PACKAGE. PACKAGE might be a fully
qualified package (e.g. C<Net::SIP::Registrar>) or the C<Net>
or C<Net::SIP> might be omitted (C<Registrar>). If a C<*> is added
the debugging will also be enabled for subpackages, e.g.
C<Endpoint*> will enable debugging for L<Net::SIP::Endpoint> and
L<Net::SIP::Endpoint::Context> too.

=item PACKAGE=NUMBER

Similar to the previous item, but this sets debugging level to
NUMBER for the specified packages and thus can also be used to
selectively disable debugging for some packages.

=back

If @ARGS is empty it will return the debugging level for the package
which called this method (the first package in the caller stack
which is not Net::SIP::Debug itself).

=item set_prefix ( PREFIX )

Sets prefix used for debug messages to PREFIX. Default prefix
is 'DEBUG:' but for instance for forking applications it might
be useful to change this to "DEBUG($$):" or similar.

=back


=head1 SUBROUTINES

=over 4

=item DEBUG|debug ( [ LEVEL ],( MESSAGE | FMT,@ARG ))

If debugging is enabled it will print debugging info to STDERR.
If multiple arguments are given to the function they will be
fed into B<sprintf> to create a single message.

If the first argument looks like a number (see B<looks_like_number>
in L<Scalar::Util>) it will be interpreted as the debug level
for this message, e.g. if it is higher than the user specified
debug level the message will not be printed.

The MESSAGE (or the result from C<< sprintf(FMT,@ARG) >>) will be
prefixed by the caller package, the caller function and the line
from which DEBUG was called. In front of the prefix the current time
(as float time_t) and the string "DEBUG:" will be added.

If the message consists of multiple lines each line will be prefixed
by the prefix and all but the first line will also have a TAB added
between prefix and message data.

The function is by default exported as B<DEBUG> and can by exported
as B<debug> too.

=item DEBUG_DUMP ( [ LEVEL ], @DATA )

Will call B<debug> with the output from L<Data::Dumper>s B<Dumper>
if debugging is enabled. If @DATA has more than one item it will
be fed as reference into B<Dumper>, otherwise only the single item
will be fed to B<Dumper>.
For the meaning of LEVEL see B<debug>.

This function is exported by default.

=item stacktrace ( MESSAGE | FMT,@ARG )

Uses the arguments in B<debug>, but instead of writing a debug
message to STDERR it will be used in Carp::longmess.
Returns string with stacktrace.

=item LEAK_TRACK ( REF )

This is used internally for tracking leaks. It will rebless REF into
a new class which behaves like the old one. Calls of LEAK_TRACK
and DESTROY on this class will be tracked and shown. If L<Devel::Peek>
can be loaded it will B<Dump> information about the REF on each
call to LEAK_TRACK.

Exported by default.

=back

=head1 exported Variables

=over 4

=item $DEBUG

This variable is set to false if all kind of debugging is disabled.
This variable is exported by default. It should not be changed.
It is intended to be used as a quick check to save expensive calls of debugging
functions if no debugging will be used anyway, i.e.:

    $DEBUG && DEBUG(...)

=back

