package FFI; use strict; use warnings; use Alien::FFCall; our $VERSION = '1.04_01'; require XSLoader; XSLoader::load('FFI'); 1; __END__ =head1 NAME FFI - Perl Foreign Function Interface using libffcall =head1 SYNOPSIS use FFI; $addr =
$signature = $ret = FFI::call($addr, $signature, ...); $cb = FFI::callback($signature, sub {...}); $ret = FFI::call($addr, $signature, $cb->addr, ...); =head1 DESCRIPTION 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. =head1 FUNCTION SIGNATURES Function interfaces are defined by I. 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 C code corresponds to the C calling convention, which is used for most dynamic link libraries. The C code corresponds to the C 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 L 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. v No value (only valid as a return type). Note that all of the above codes refer to "native" format values. The C

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 C

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 C

code. Perl ensures that strings are null-terminated for you. To pass pointers to structures, use L. To pass an arbitrary block of memory, use something like the following: $buf = ' ' x 100; # Use $buf via a 'p' parameter as a 100-byte memory block At the present time, there is no direct support for passing pointers to 'native' types (like int). To work around this, use C<$buf = pack('i', 12);> to put an integer into a block of memory, then use the C

pointer type, and obtain any returned value using C<$n = unpack('i', $buf);> In the future, better support may be added (but remember that this is intended as a low-level interface!) =head1 EXAMPLES It is somewhat difficult to provide examples of using this module in isolation, as it is necessary to (somehow) obtain the address of a function to call. In general, this task is delegated to higher-level wrapper modules. However, the standard C module returns symbol references via the C function. While these references are not documented as being addresses, in practice, they seem to be. Code to obtain the address of various C library functions can be built around this $clib_file = ($^O eq "MSWin32") ? "MSVCRT40.DLL" : "-lc"; $clib = DynaLoader::dl_findfile($clib_file); $strlen = DynaLoader::dl_find_symbol($clib, "strlen"); $n = FFI::call($strlen, "cIp", $my_string); DynaLoader::dl_free_file($clib); Clearly, code like this needs to be encapsulated in a module of some form... NOTE: In fact, the DynaLoader interface has problems in ActiveState Perl, and probably in other binary distributions of Perl. (The issue is related to the way in which the DynaLoader module is built, and may be addressed in future versions of Perl). In the interim, the higher-level wrapper module FFI::Library does not use DynaLoader on Win32 - it uses the (deprecated, but still available) Win32::LoadLibrary and related calls. =head1 TODO =over 4 =item * Improve support for returning pointers to things other than null-terminated strings. =item * Possibly, improve support for passing pointers to "native" types. =back =head1 LICENSE The underlying library for this module is licensed under the GNU General Public License. At the moment, some of that code is still distributed with this module, so under the terms of that license, my understanding is that this module has to be distrubuted under that same license. However, the code from the original library is now distributed under L, so it is likely that the remaining code that is licensed under the GPL will be removed and future releases of this module will have a more relaxed license. =head1 STATUS This is a maintenance release. The future of this module is not entirely certain at the moment, but you can see the latest development at L and/or L. =head1 AUTHOR Paul Moore, C<< >> is the original author of L. Mitchell Charity C<< >> and Reini Urban C<< >> contributed fixes. David Mertens C<< >> created L and updated this module to use it. David Mertens C<< >>, Anatoly Vorobey C<< >> and Gaal Yahas C<< >> are the current maintainers. =head1 SEE ALSO L Bruno Haible's CLisp Common Lisp implementation, from which the underlying foreign function interface code was taken. =cut