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.\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.20) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .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 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 .PP and calling \f(CW\*(C`Perl_mro_register\*(C'\fR: .PP .Vb 1 \& Perl_mro_register(aTHX_ &my_mro_alg); .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 names of the classes should be the result of calling \&\f(CW\*(C`HvENAME()\*(C'\fR on the stash. In those cases where \f(CW\*(C`HvENAME()\*(C'\fR returns null, \&\f(CW\*(C`HvNAME()\*(C'\fR should be used instead. .PP 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, \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.