table of contents
XS::Object::Magic(3pm) | User Contributed Perl Documentation | XS::Object::Magic(3pm) |
NAME¶
XS::Object::Magic - Opaque, extensible XS pointer backed objects using "sv_magic"SYNOPSIS¶
package MyObject; use XS::Object::Magic; sub new { my $class = shift; # create any object representation you like my $self = bless {}, $class; $self->build_struct; return $self; } # or using Moose package MyObject; use Moose; sub BUILD { shift->build_struct; } # then in XS MODULE = MyObject PACKAGE = MyObject void build_struct (SV *self) PREINIT: my_struct_t *thingy; CODE: thingy = create_whatever(); /* note that we dereference self first. This * can be done using an XS typemap of course */ xs_object_magic_attach_struct(aTHX_ SvRV(self), thingy); void foo (SV *self) PREINIT: my_struct_t *thingy; INIT: thingy = xs_object_magic_get_struct_rv(aTHX_ self); CODE: my_struct_foo(thingy); /* delegate to C api */ /* using typemap */ void foo (my_struct_t *thingy) CODE: my_struct_foo(thingy); /* or better yet */ PREFIX = my_struct_ void my_struct_foo (thingy) my_struct_t *thingy; /* don't forget a destructor */ void DESTROY (my_struct_t *thingy) CODE: Safefree(thingy); /* note that xs_object_magic_get_struct() will * still return a pointe which is now invalid */
DESCRPTION¶
This way of associating structs with Perl space objects is designed to supercede Perl's builtin "T_PTROBJ" with something that is designed to be:- Extensible
- The association of the pointer using
"sv_magicext" can be done on any data
type, so you can associate C structs with any representation type.
This means that you can add pointers to any object (hand coded, Moose or otherwise), while still having instance data in regular hashes.
- Opaque
- The C pointer is neither visible nor modifiable from Perl space.
This prevents accidental corruption which could lead to segfaults using "T_PTROBJ" (e.g. "$$ptr_obj = 0").
C API¶
- void *xs_object_magic_get_struct_rv(aTHX_ SV *sv)
- When called on the object reference it will check that the
"sv" is a reference, dereference it and
return the associated pointer using
"xs_object_magic_get_struct".
Basically the same as "xs_object_magic_get_struct(aTHX_ SvRV(sv)" but croaks if no magic was found.
Note that storing a "NULL" pointer will not cause an error.
- void *xs_object_magic_get_struct(aTHX_ SV *sv)
- Fetches the pointer associated with
"sv".
Returns "NULL" if no pointer is found. There is no way to distinguish this from having a "NULL" pointer.
- MAGIC *xs_object_magic_get_mg (aTHX_ SV *sv)
- Fetches the appropriate "MAGIC" entry
for the struct pointer storage from
"sv".
This lets you manipulate "mg-"mg_ptr> if you need to.
- void xs_object_magic_attach_struct(aTHX_ SV *sv, void *ptr)
- Associates "ptr" with "sv" by adding a magic entry to "sv".
- SV *xs_object_magic_create(aTHX_ void *ptr, HV *stash)
- Convenience function that creates a hash object blessed to
"stash" and associates it with
"ptr".
Can be used to easily create a constructor:
SV * new(char *class) CODE: RETVAL = xs_object_magic_create( (void *)test_new(), gv_stashpv(class, 0) ); OUTPUT: RETVAL
- int xs_object_magic_has_struct(aTHX_ SV *sv)
- Returns 1 if the SV has XS::Object::Magic magic, 0 otherwise.
- int xs_object_magic_has_struct_rv(aTHX_ SV *self)
- Returns 1 if the SV references an SV that has XS::Object::Magic magic, 0
otherwise.
This lets you write a quick predicate method, like:
void my_struct_has_struct (self) SV *self; PPCODE: EXTEND(SP, 1); if(xs_object_magic_has_struct_rv(aTHX_ self)) PUSHs(&PL_sv_yes); else PUSHs(&PL_sv_no);
Then you can check for the existence of your struct from the Perl side:
if( $object->has_struct ) { ... }
- int xs_object_magic_detach_struct(aTHX_ SV *sv)
- Removes the XS::Object::Magic magic from the given SV. Returns 1 if something is removed, 0 otherwise.
- int xs_object_magic_detach_struct_rv(aTHX_ SV *self)
- Likes "xs_object_magic_detach_struct",
but takes a reference to the magic-containing SV instead of the SV itself.
The reference to the SV is typically $self.
Returns 0 if the SV is not a reference, otherwise returns whatever "xs_object_magic_detach_struct" returns.
TYPEMAP¶
The included typemap provides a "T_PTROBJ_MG" entry which only supports the "INPUT" conversion.This typemap entry lets you declare methods that are invoked directly on the associated pointer. In your own typemap add an entry:
TYPEMAP my_pointer_t * T_PTROBJ_MG
and then you can use "my_pointer_t" as the argument type of the invocant:
I32 method (self) my_pointer_t *self; CODE: ...
Note that there is no "OUTPUT" conversion. In order to return your object you need to use ST(0) or some other means of getting the invocant.
VERSION CONTROL¶
<http://github.com/nothingmuch/xs-object-magic>AUTHOR¶
Florian Ragwitz, Yuval KogmanCOPYRIGHT & LICENSE¶
Copyright (c) 2009 Florian Ragwitz, Yuval Kogman. All rights reserved This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
2018-11-01 | perl v5.28.0 |