• NAME
• SYNOPSIS
• DESCRIPTION
• COPY vs SHARE

NAME

ffi - extern sub types and helpers

SYNOPSIS

    extern sub NAME () :CORETYPE;

    use ffi;
    extern sub NAME () :FFITYPE;

DESCRIPTION

Natively cperl defines the following "coretypes" in perltypes, which are valid ffi types:

    int, Int, num, Num, str, Str, uint, UInt.

TODO: Uni, uni for utf8-encoded strings, and wchar.

Via use ffi there are more types than coretypes supported:

    void, ptr, float, double, long, ulong, char, byte (U8), int8,
    int16, int64, uint8, uint16, uint32, uint64, longlong, num32,
    num64, longdouble, bool, size_t, Pointer,
    OpaquePointer (deprecated).

Matching the perl6 NativeCall types.

COPY vs SHARE

The ffi arguments and return types default to :void. If not void, the declared types are matched to the given argument value and converted if possible.

The primitive types create a new copy of the value.

The aggregate types, such as str or Str (Uni, wchar not yet) try to share the value first, and only if not possible create a copy. As argument an aggregate type is always shared, as return type possibly shared.

E.g.

    extern sub strchr(str $s, int $i) :str;
    print strchr("abcd", ord("c"))

The result ptr of strchr points inside the argument string, to "c" with an offset of 2 from the "a". So we can use the SvOOK interpretation of a string pointing to the delta, and the string is not copied back. But if the result of the ffi call points outside the given string, we need to copy it.

The handling of native arrays and structs (i.e native classes) via ffi is not implemented yet.