FFI - Perl Foreign Function Interface based on libffi


    version 1.15


     # for a more portable interface see FFI::Library
     $clib_file = ($^O eq "MSWin32") ? "MSVCRT40.DLL" : "-lc";
     $clib = DynaLoader::dl_findfile($clib_file);
     $strlen = DynaLoader::dl_find_symbol($clib, "strlen");
     $n = FFI::call($strlen, "cIp", $my_string);


    NOTE: Newer and better maintained FFI modules such as FFI::Platypus
    provide more functionality and so it is strongly recommend that you use
    one of them for new projects and even consider migrating to one of them
    for existing projects.

    This module provides a low-level foreign function interface to Perl. It
    allows the calling of any function for which the user can supply an
    address and calling signature. Furthermore, it provides a method of
    encapsulating Perl subroutines as callback functions whose addresses
    can be passed to C code.



     my $ret = FFI::call($address, $signature, @arguments);

    Call the function at the given $address with the given $signature> (see
    below) and the given @arguments.


     my $address = FFI::callback($signature, \&subref);

    Creates a c callback that will call a Perl subref.


    Function interfaces are defined by signatures. A function's signature
    is a string which specifies the function's return type, argument types
    and calling convention. The first character of the string is the
    function's calling convention. This is one of

        s   The standard calling convention for dynamically linked functions
        c   The calling convention used by C functions

    Note that on many platforms, these two calling conventions may be
    identical. On the Windows platform, the s code corresponds to the
    stdcall calling convention, which is used for most dynamic link
    libraries. The c code corresponds to the cdecl calling convention,
    which is used for C functions, such as those in the C runtime library.

    The remaining characters of the string are the return type of the
    function, followed by the argument types, in left-to-right order. Valid
    values are based on the codes used for the pack function, namely

        c   A signed char value.
        C   An unsigned char value.
        s   A signed short value.
        S   An unsigned short value.
        i   A signed integer value.
        I   An unsigned integer value.
        l   A signed long value.
        L   An unsigned long value.
        f   A single-precision float.
        d   A double-precision float.
        p   A pointer to a Perl scalar.
        o   A opaque pointer, ie, an address.
        v   No value (only valid as a return type).

    Note that all of the above codes refer to "native" format values.

    The p code as an argument type simply passes the address of the Perl
    value's memory to the foreign function. It is the caller's
    responsibility to be sure that the called function does not overwrite
    memory outside that allocated by Perl.

    The p code as a return type treats the returned value as a
    null-terminated string, and passes it back to Perl as such. There is
    currently no support for functions which return pointers to structures,
    or to other blocks of memory which do not contain strings, nor for
    functions which return memory which the caller must free.

    To pass pointers to strings, use the p code. Perl ensures that strings
    are null-terminated for you. To pass pointers to structures, use pack.
    To pass an arbitrary block of memory, use something like the following:

        $buf = ' ' x 100;
        # Use $buf via a 'p' parameter as a 100-byte memory block

    At the present time, there is no direct support for passing pointers to
    'native' types (like int). To work around this, use $buf = pack('i',
    12); to put an integer into a block of memory, then use the p pointer
    type, and obtain any returned value using $n = unpack('i', $buf); In
    the future, better support may be added (but remember that this is
    intended as a low-level interface!)


    Please open any support tickets with this project's GitHub repository



      Higher level interface to libraries using this module.


      Portable functions for finding libraries.


      Platypus is another FFI interface based on libffi. It has a more
      extensive feature set, and libffi has a less restrictive license.


    Original author: Paul Moore <>

    Current maintainer: Graham Ollis <>


    Anatoly Vorobey <>

    Gaal Yahas <>

    Mitchell Charity <>

    Reini Urban <<>


    This software is copyright (c) 2016-2018 by Graham Ollis.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.