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=head1 NAME
perlmroapi - Perl method resolution plugin interface
=head1 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 by providing
the following structure
struct mro_alg {
AV *(*resolve)(pTHX_ HV *stash, U32 level);
const char *name;
U16 length;
U16 kflags;
U32 hash;
};
and calling C:
Perl_mro_register(aTHX_ &my_mro_alg);
=over 4
=item resolve
Pointer to the linearisation function, described below.
=item name
Name of the MRO, either in ISO-8859-1 or UTF-8.
=item length
Length of the name.
=item kflags
If the name is given in UTF-8, set this to C. The value is passed
direct as the parameter I to C.
=item hash
A precomputed hash value for the MRO's name, or 0.
=back
=head1 Callbacks
The C 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 I of 0. The core always sets I 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 string SVs
giving the names of parent classes in order. The names of the classes should
be the result of calling C on the stash. In those cases where
C returns null, C should be used instead.
The caller is responsible for incrementing the reference count of the array
returned if it wants to keep the structure. Hence, if you have created a
temporary value that you keep no pointer to, C 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.
=head1 Caching
Computing MROs can be expensive. The implementation provides a cache, in
which you can store a single C, or anything that can be cast to
C, such as C. To read your private value, use the macro
C, passing it the C structure from the
stash, and a pointer to your C structure:
meta = HvMROMETA(stash);
private_sv = MRO_GET_PRIVATE_DATA(meta, &my_mro_alg);
=for apidoc Amh|struct mro_meta *|HvMROMETA|HV *hv
=for apidoc Amh|SV*|MRO_GET_PRIVATE_DATA|struct mro_meta *const smeta|const struct mro_alg *const which
To set your private value, call C:
Perl_mro_set_private_data(aTHX_ meta, &c3_alg, private_sv);
=for apidoc mro_set_private_data
The private data cache will take ownership of a reference to private_sv,
much the same way that C takes ownership of a reference to the
value that you pass it.
=head1 Examples
For examples of MRO implementations, see C
and the C section of F, and
C in F
=head1 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.
=cut