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.\" ========================================================================
.\"
.IX Title "PERLMROAPI 1"
.TH PERLMROAPI 1 "2012-11-03" "perl v5.12.5" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
perlmroapi \- Perl method resolution plugin interface
.SH "DESCRIPTION"
.IX Header "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.
.PP
Each plugin should register itself with \f(CW\*(C`Perl_mro_register\*(C'\fR by providing
the following structure
.PP
.Vb 7
\&    struct mro_alg {
\&        AV *(*resolve)(pTHX_ HV *stash, U32 level);
\&        const char *name;
\&        U16 length;
\&        U16 kflags;
\&        U32 hash;
\&    };
.Ve
.IP "resolve" 4
.IX Item "resolve"
Pointer to the linearisation function, described below.
.IP "name" 4
.IX Item "name"
Name of the \s-1MRO\s0, either in \s-1ISO\-8859\-1\s0 or \s-1UTF\-8\s0.
.IP "length" 4
.IX Item "length"
Length of the name.
.IP "kflags" 4
.IX Item "kflags"
If the name is given in \s-1UTF\-8\s0, set this to \f(CW\*(C`HVhek_UTF8\*(C'\fR. The value is passed
direct as the parameter \fIkflags\fR to \f(CW\*(C`hv_common()\*(C'\fR.
.IP "hash" 4
.IX Item "hash"
A precomputed hash value for the \s-1MRO\s0's name, or 0.
.SH "Callbacks"
.IX Header "Callbacks"
The \f(CW\*(C`resolve\*(C'\fR function is called to generate a linearised \s-1ISA\s0 for the
given stash, using this \s-1MRO\s0. It is called with a pointer to the stash, and
a \fIlevel\fR of 0. The core always sets \fIlevel\fR to 0 when it calls your
function \- the parameter is provided to allow your implementation to track
depth if it needs to recurse.
.PP
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, \f(CW\*(C`sv_2mortal()\*(C'\fR to ensure that
it is disposed of correctly. If you have cached your return value, then
return a pointer to it without changing the reference count.
.SH "Caching"
.IX Header "Caching"
Computing MROs can be expensive. The implementation provides a cache, in
which you can store a single \f(CW\*(C`SV *\*(C'\fR, or anything that can be cast to
\&\f(CW\*(C`SV *\*(C'\fR, such as \f(CW\*(C`AV *\*(C'\fR. To read your private value, use the macro
\&\f(CW\*(C`MRO_GET_PRIVATE_DATA()\*(C'\fR, passing it the \f(CW\*(C`mro_meta\*(C'\fR structure from the
stash, and a pointer to your \f(CW\*(C`mro_alg\*(C'\fR structure:
.PP
.Vb 2
\&    meta = HvMROMETA(stash);
\&    private_sv = MRO_GET_PRIVATE_DATA(meta, &my_mro_alg);
.Ve
.PP
To set your private value, call \f(CW\*(C`Perl_mro_set_private_data()\*(C'\fR:
.PP
.Vb 1
\&    Perl_mro_set_private_data(aTHX_ meta, &c3_alg, private_sv);
.Ve
.PP
The private data cache will take ownership of a reference to private_sv,
much the same way that \f(CW\*(C`hv_store()\*(C'\fR takes ownership of a reference to the
value that you pass it.
.SH "Examples"
.IX Header "Examples"
For examples of \s-1MRO\s0 implementations, see \f(CW\*(C`S_mro_get_linear_isa_c3()\*(C'\fR
and the \f(CW\*(C`BOOT:\*(C'\fR section of \fImro/mro.xs\fR, and \f(CW\*(C`S_mro_get_linear_isa_dfs()\*(C'\fR
in \fImro.c\fR
.SH "AUTHORS"
.IX Header "AUTHORS"
The implementation of the C3 \s-1MRO\s0 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.


.\" Oracle has added the ARC stability level to this manual page
.SH ATTRIBUTES
See
.BR attributes (5)
for descriptions of the following attributes:
.sp
.TS
box;
cbp-1 | cbp-1
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE 
=
Availability	runtime/perl-512
=
Stability	Uncommitted
.TE 
.PP

.SH NOTES

.\" Oracle has added source availability information to this manual page
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

Further information about this software can be found on the open source community website at http://www.perl.org/.