perlmroapi
(1)
Name
perlmroapi - Perl method resolution plugin interface
Synopsis
Please see following description for synopsis
Description
Perl Programmers Reference Guide PERLMROAPI(1)
NAME
perlmroapi - Perl method resolution plugin interface
DESCRIPTION
As of Perl 5.10.1 there is a new interface for plugging and
using method resolution orders other than the default
(linear depth first search). The C3 method resolution order
added in 5.10.0 has been re-implemented as a plugin, without
changing its Perl-space interface.
Each plugin should register itself with "Perl_mro_register"
by providing the following structure
struct mro_alg {
AV *(*resolve)(pTHX_ HV *stash, U32 level);
const char *name;
U16 length;
U16 kflags;
U32 hash;
};
resolve
Pointer to the linearisation function, described below.
name
Name of the MRO, either in ISO-8859-1 or UTF-8.
length
Length of the name.
kflags
If the name is given in UTF-8, set this to "HVhek_UTF8".
The value is passed direct as the parameter kflags to
"hv_common()".
hash
A precomputed hash value for the MRO's name, or 0.
Callbacks
The "resolve" function is called to generate a linearised
ISA for the given stash, using this MRO. It is called with a
pointer to the stash, and a level of 0. The core always sets
level to 0 when it calls your function - the parameter is
provided to allow your implementation to track depth if it
needs to recurse.
The function should return a reference to an array
containing the parent classes in order. The caller is
responsible for incrementing the reference count if it wants
to keep the structure. Hence if you have created a temporary
value that you keep no pointer to, "sv_2mortal()" to ensure
that it is disposed of correctly. If you have cached your
perl v5.12.5 Last change: 2012-11-03 1
Perl Programmers Reference Guide PERLMROAPI(1)
return value, then return a pointer to it without changing
the reference count.
Caching
Computing MROs can be expensive. The implementation provides
a cache, in which you can store a single "SV *", or anything
that can be cast to "SV *", such as "AV *". To read your
private value, use the macro "MRO_GET_PRIVATE_DATA()",
passing it the "mro_meta" structure from the stash, and a
pointer to your "mro_alg" structure:
meta = HvMROMETA(stash);
private_sv = MRO_GET_PRIVATE_DATA(meta, &my_mro_alg);
To set your private value, call
"Perl_mro_set_private_data()":
Perl_mro_set_private_data(aTHX_ meta, &c3_alg, private_sv);
The private data cache will take ownership of a reference to
private_sv, much the same way that "hv_store()" takes
ownership of a reference to the value that you pass it.
Examples
For examples of MRO implementations, see
"S_mro_get_linear_isa_c3()" and the "BOOT:" section of
mro/mro.xs, and "S_mro_get_linear_isa_dfs()" in mro.c
AUTHORS
The implementation of the C3 MRO and switchable MROs within
the perl core was written by Brandon L Black. Nicholas Clark
created the pluggable interface, refactored Brandon's
implementation to work with it, and wrote this document.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
perl v5.12.5 Last change: 2012-11-03 2
Perl Programmers Reference Guide PERLMROAPI(1)
Further information about this software can be found on the
open source community website at http://www.perl.org/.
perl v5.12.5 Last change: 2012-11-03 3