make-foreign-pointer

Arguments: &key foreign-address foreign-type size aligned address type

Creates and returns a foreign-pointer object. These objects are designed to hold integer addresses and in most cases, an integer works as well as a foreign-pointer object. An advantage of foreign-pointer objects is simply that they are different from an integer, allowing for better checking. And because it is an instance of a CLOS class, it can be extended in the normal CLOS way.

foreign-address is the C address that is being pointed to; foreign-type is a user-specifiable type that becomes the value of the foreign-type slot of the foreign-pointer instance being created. size causes allocation of foreign space of that size. Typically, only one of the size and foreign-address keyword arguments is specified. size is ignored if foreign-address is specified.

The aligned argument

If aligned is true and the address or foreign-address keyword was given, then the address is interpreted as an aligned address and is shifted to become a machine integer before storing. (Aligned pointers are described in Aligned Pointers in ftype.htm.)

It is an error if both size and foreign-address are unspecified.

The address and type arguments

address and type are obsolete and should not be used. They are variants of foreign-address and foreign-type. If adress is specified, the value should be as for foreign-type. You should not specify both address and foreign-address.

See foreign-pointer-address, foreign-pointer-type, and foreign-pointer-p.

See ftype.htm for information on foreign types in Allegro CL and foreign-functions.htm for general information on foreign functions in Allegro CL.

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Created 2010.1.21.