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Ross McFarland > Glib-1.043 > GBoxed.xs


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Specifies the vtable of functions to be used for bringing boxed types in and out of perl. The structure is defined like this:

 typedef struct _GPerlBoxedWrapperClass GPerlBoxedWrapperClass;
 struct _GPerlBoxedWrapperClass {
          GPerlBoxedWrapFunc    wrap;
          GPerlBoxedUnwrapFunc  unwrap;
          GPerlBoxedDestroyFunc destroy;

The members are function pointers, each of which serves a specific purpose:


turn a boxed pointer into an SV. gtype is the type of the boxed pointer, and package is the package to which that gtype is registered (the lookup has already been done for you at this point). if own is true, the wrapper is responsible for freeing the object; if it is false, some other code owns the object and you must NOT free it.

 typedef SV*      (*GPerlBoxedWrapFunc)    (GType        gtype,
                                            const char * package,
                                            gpointer     boxed,
                                            gboolean     own);

turn an SV into a boxed pointer. like GPerlBoxedWrapFunc, gtype and package are the registered type pair, already looked up for you (in the process of finding the proper wrapper class). sv is the sv to unwrap.

 typedef gpointer (*GPerlBoxedUnwrapFunc)  (GType        gtype,
                                            const char * package,
                                            SV         * sv);

this will be called by Glib::Boxed::DESTROY, when the wrapper is destroyed. it is a hook that allows you to destroy an object owned by the wrapper; note, however, that you will have had to keep track yourself of whether the object was to be freed.

 typedef void     (*GPerlBoxedDestroyFunc) (SV         * sv);
void gperl_register_boxed (GType gtype, const char * package, GPerlBoxedWrapperClass * wrapper_class)

Register a mapping between the GBoxed derivative gtype and package. The specified, wrapper_class will be used to wrap and unwrap objects of this type; you may pass NULL to use the default wrapper (the same one returned by gperl_default_boxed_wrapper_class()).

In normal usage, the standard opaque wrapper supplied by the library is sufficient and correct. In some cases, however, you want a boxed type to map directly to a native perl type; for example, some struct may be more appropriately represented as a hash in perl. Since the most necessary place for this conversion to happen is in gperl_value_from_sv() and gperl_sv_from_value(), the only reliable and robust way to implement this is a hook into gperl_get_boxed_check() and gperl_new_boxed(); that is exactly the purpose of wrapper_class. See GPerlBoxedWrapperClass.

GType gperl_boxed_type_from_package (const char * package)

Look up the GType associated with package package. Returns 0 if type is not registered.

const char * gperl_boxed_package_from_type (GType type)

Look up the package associated with GBoxed derivative type. Returns NULL if type is not registered.

GPerlBoxedWrapperClass * gperl_default_boxed_wrapper_class (void)

get a pointer to the default wrapper class; handy if you want to use the normal wrapper, with minor modifications. note that you can just pass NULL to gperl_register_boxed(), so you really only need this in fringe cases.

SV * gperl_new_boxed (gpointer boxed, GType gtype, gboolean own)

Export a GBoxed derivative to perl, according to whatever GPerlBoxedWrapperClass is registered for gtype. In the default implementation, this means wrapping an opaque perl object around the pointer to a small wrapper structure which stores some metadata, such as whether the boxed structure should be destroyed when the wrapper is destroyed (controlled by own; if the wrapper owns the object, the wrapper is in charge of destroying it's data).

SV * gperl_new_boxed_copy (gpointer boxed, GType gtype)

Create a new copy of boxed and return an owner wrapper for it. boxed may not be NULL. See gperl_new_boxed.

gpointer gperl_get_boxed_check (SV * sv, GType gtype)

Extract the boxed pointer from a wrapper; croaks if the wrapper sv is not blessed into a derivative of the expected gtype. Does not allow undef.


Glib::Boxed is a generic wrapper mechanism for arbitrary C structures. For the most part you don't care about this as a Perl developer, but it is important to know that all Glib::Boxed descendents can be copied with the copy method.

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