VERSION

version 0.43

SYNOPSIS

use FFI::Platypus;

my $ffi = FFI::Platypus->new;
$ffi->lib(undef); # search libc

# call dynamically
$ffi->function( puts => ['string'] => 'int' )->call("hello world");

# attach as a xsub and call (much faster)
$ffi->attach( puts => ['string'] => 'int' );
puts("hello world");

DESCRIPTION

Platypus is a library for creating interfaces to machine code libraries written in languages like C, C++, Fortran, Rust, Pascal. Essentially anything that gets compiled into machine code. This implementation uses "libffi" to accomplish this task. "libffi" is battle tested by a number of other scripting and virtual machine languages, such as Python and Ruby to serve a similar role. There are a number of reasons why you might want to write an extension with Platypus instead of XS:

FFI / Platypus does not require messing with the guts of Perl

XS is less of an API and more of the guts of perl splayed out to do whatever you want. That may at times be very powerful, but it can also be a frustrating exercise in hair pulling.

FFI / Platypus is portable

Lots of languages have FFI interfaces, and it is subjectively easier to port an extension written in FFI in Perl or another language to FFI in another language or Perl. One goal of the Platypus Project is to reduce common interface specifications to a common format like JSON that could be shared between different languages.

FFI / Platypus could be a bridge to Perl 6

One of those ``other'' languages could be Perl 6 and Perl 6 already has an FFI interface I am told.

FFI / Platypus can be reimplemented

In a bright future with multiple implementations of Perl 5, each interpreter will have its own implementation of Platypus, allowing extensions to be written once and used on multiple platforms, in much the same way that Ruby-FFI extensions can be use in Ruby, JRuby and Rubinius.

FFI / Platypus is pure perl (sorta)

One Platypus script or module works on any platform where the libraries it uses are available. That means you can deploy your Platypus script in a shared filesystem where they may be run on different platforms. It also means that Platypus modules do not need to be installed in the platform specific Perl library path.

FFI / Platypus is not C or C++ centric

XS is implemented primarily as a bunch of C macros, which requires at least some understanding of C, the C pre-processor, and some C++ caveats (since on some platforms Perl is compiled and linked with a C++ compiler). Platypus on the other hand could be used to call other compiled languages, like Fortran, Rust, Pascal, C++, or even assembly, allowing you to focus on your strengths.

FFI / Platypus does not require a parser

Inline isolates the extension developer from XS to some extent, but it also requires a parser. The various Inline language bindings are a great technical achievement, but I think writing a parser for every language that you want to interface with is a bit of an anti-pattern.

This document consists of an API reference, a set of examples, some support and development (for contributors) information. If you are new to Platypus or FFI, you may want to skip down to the EXAMPLES to get a taste of what you can do with Platypus.

Platypus has extensive documentation of types at FFI::Platypus::Type and its custom types API at FFI::Platypus::API.

CONSTRUCTORS

new

 my $ffi = FFI::Platypus->new(%options);

Create a new instance of FFI::Platypus.

Any types defined with this instance will be valid for this instance only, so you do not need to worry about stepping on the toes of other CPAN FFI / Platypus Authors.

Any functions found will be out of the list of libraries specified with the lib attribute.

options

lib

Either a pathname (string) or a list of pathnames (array ref of strings) to pre-populate the lib attribute.

ignore_not_found

[version 0.15]

Set the ignore_not_found attribute.

lang

[version 0.18]

Set the lang attribute.

ATTRIBUTES

lib

 $ffi->lib($path1, $path2, ...);
 my @paths = $ffi->lib;

The list of libraries to search for symbols in.

The most portable and reliable way to find dynamic libraries is by using FFI::CheckLib, like this:

 use FFI::CheckLib 0.06;
 $ffi->lib(find_lib_or_die lib => 'archive'); 
   # finds libarchive.so on Linux
   #       libarchive.bundle on OS X
   #       libarchive.dll (or archive.dll) on Windows
   #       cygarchive-13.dll on Cygwin
   #       ...
   # and will die if it isn't found

FFI::CheckLib has a number of options, such as checking for specific symbols, etc. You should consult the documentation for that module.

As a special case, if you add "undef" as a ``library'' to be searched, Platypus will also search the current process for symbols. This is mostly useful for finding functions in the standard C library, without having to know the name of the standard c library for your platform (as it turns out it is different just about everywhere!).

You may also use the ``find_lib'' method as a shortcut:

 $ffi->find_lib( lib => 'archive' );

ignore_not_found

[version 0.15]

 $ffi->ignore_not_found(1);
 my $ignore_not_found = $ffi->ignore_not_found;

Normally the attach and function methods will throw an exception if it cannot find the name of the function you provide it. This will change the behavior such that function will return "undef" when the function is not found and attach will ignore functions that are not found. This is useful when you are writing bindings to a library and have many optional functions and you do not wish to wrap every call to function or attach in an "eval".

lang

[version 0.18]

 $ffi->lang($language);

Specifies the foreign language that you will be interfacing with. The default is C. The foreign language specified with this attribute changes the default native types (for example, if you specify Rust, you will get "i32" as an alias for "sint32" instead of "int" as you do with C).

If the foreign language plugin supports it, this will also enable Platypus to find symbols using the demangled names (for example, if you specify CPP for C++ you can use method names like "Foo::get_bar()" with ``attach'' or ``function''.

METHODS

type

 $ffi->type($typename);
 $ffi->type($typename => $alias);

Define a type. The first argument is the native or C name of the type. The second argument (optional) is an alias name that you can use to refer to this new type. See FFI::Platypus::Type for legal type definitions.

Examples:

 $ffi->type('sint32'); # oly checks to see that sint32 is a valid type
 $ffi->type('sint32' => 'myint'); # creates an alias myint for sint32
 $ffi->type('bogus'); # dies with appropriate diagnostic

custom_type

 $ffi->custom_type($alias => {
   native_type         => $native_type,
   native_to_perl      => $coderef,
   perl_to_native      => $coderef,
   perl_to_native_post => $coderef,
 });

Define a custom type. See FFI::Platypus::Type#Custom-Types for details.

load_custom_type

 $ffi->load_custom_type($name => $alias, @type_args);

Load the custom type defined in the module $name, and make an alias $alias. If the custom type requires any arguments, they may be passed in as @type_args. See FFI::Platypus::Type#Custom-Types for details.

If $name contains "::" then it will be assumed to be a fully qualified package name. If not, then "FFI::Platypus::Type::" will be prepended to it.

types

 my @types = $ffi->types;
 my @types = FFI::Platypus->types;

Returns the list of types that FFI knows about. This will include the native "libffi" types (example: "sint32", "opaque" and "double") and the normal C types (example: "unsigned int", "uint32_t"), any types that you have defined using the type method, and custom types.

The list of types that Platypus knows about varies somewhat from platform to platform, FFI::Platypus::Type includes a list of the core types that you can always count on having access to.

It can also be called as a class method, in which case, no user defined or custom types will be included in the list.

type_meta

 my $meta = $ffi->type_meta($type_name);
 my $meta = FFI::Platypus->type_meta($type_name);

Returns a hash reference with the meta information for the given type.

It can also be called as a class method, in which case, you won't be able to get meta data on user defined types.

The format of the meta data is implementation dependent and subject to change. It may be useful for display or debugging.

Examples:

 my $meta = $ffi->type_meta('int');        # standard int type
 my $meta = $ffi->type_meta('int[64]');    # array of 64 ints
 $ffi->type('int[128]' => 'myintarray');
 my $meta = $ffi->type_meta('myintarray'); # array of 128 ints

function

 my $function = $ffi->function($name => \@argument_types => $return_type);
 my $function = $ffi->function($address => \@argument_types => $return_type);

Returns an object that is similar to a code reference in that it can be called like one.

Caveat: many situations require a real code reference, so at the price of a performance penalty you can get one like this:

 my $function = $ffi->function(...);
 my $coderef = sub { $function->(@_) };

It may be better, and faster to create a real Perl function using the attach method.

In addition to looking up a function by name you can provide the address of the symbol yourself:

 my $address = $ffi->find_symbol('my_functon');
 my $function = $ffi->function($address => ...);

Under the covers, function uses find_symbol when you provide it with a name, but it is useful to keep this in mind as there are alternative ways of obtaining a functions address. Example: a C function could return the address of another C function that you might want to call, or modules such as FFI::TinyCC produce machine code at runtime that you can call from Platypus.

Examples:

 my $function = $ffi->function('my_function_name', ['int', 'string'] => 'string');
 my $return_string = $function->(1, "hi there");

attach

 $ffi->attach($name => \@argument_types => $return_type);
 $ffi->attach([$c_name => $perl_name] => \@argument_types => $return_type);
 $ffi->attach([$address => $perl_name] => \@argument_types => $return_type);
 $ffi->attach($name => \@argument_types => $return_type, sub { ... });
 $ffi->attach([$c_name => $perl_name] => \@argument_types => $return_type, sub { ... });
 $ffi->attach([$address => $perl_name] => \@argument_types => $return_type, sub { ... });

Find and attach a C function as a real live Perl xsub. The advantage of attaching a function over using the function method is that it is much much much faster since no object resolution needs to be done. The disadvantage is that it locks the function and the FFI::Platypus instance into memory permanently, since there is no way to deallocate an xsub.

If just one $name is given, then the function will be attached in Perl with the same name as it has in C. The second form allows you to give the Perl function a different name. You can also provide an address (the third form), just like with the function method.

Examples:

 $ffi->attach('my_functon_name', ['int', 'string'] => 'string');
 $ffi->attach(['my_c_functon_name' => 'my_perl_function_name'], ['int', 'string'] => 'string');
 my $string1 = my_function_name($int);
 my $string2 = my_perl_function_name($int);

[version 0.20]

If the last argument is a code reference, then it will be used as a wrapper around the attached xsub. The first argument to the wrapper will be the inner xsub. This can be used if you need to verify/modify input/output data.

Examples:

 $ffi->attach('my_function', ['int', 'string'] => 'string', sub {
   my($my_function_xsub, $integer, $string) = @_;
   $integer++;
   $string .= " and another thing";
   my $return_string = $my_function_xsub->($integer, $string);
   $return_string =~ s/Belgium//; # HHGG remove profanity
   $return_string;
 });

closure

 my $closure = $ffi->closure($coderef);

Prepares a code reference so that it can be used as a FFI closure (a Perl subroutine that can be called from C code). For details on closures, see FFI::Platypus::Type#Closures.

cast

 my $converted_value = $ffi->cast($original_type, $converted_type, $original_value);

The "cast" function converts an existing $original_value of type $original_type into one of type $converted_type. Not all types are supported, so care must be taken. For example, to get the address of a string, you can do this:

 my $address = $ffi->cast('string' => 'opaque', $string_value);

Something that won't work is trying to cast an array to anything:

 my $address = $ffi->cast('int[10]' => 'opaque', \@list);  # WRONG

attach_cast

 $ffi->attach_cast("cast_name", $original_type, $converted_type);
 my $converted_value = cast_name($original_value);

This function attaches a cast as a permanent xsub. This will make it faster and may be useful if you are calling a particular cast a lot.

sizeof

 my $size = $ffi->sizeof($type);

Returns the total size of the given type in bytes. For example to get the size of an integer:

 my $intsize = $ffi->sizeof('int');   # usually 4
 my $longsize = $ffi->sizeof('long'); # usually 4 or 8 depending on platform

You can also get the size of arrays

 my $intarraysize = $ffi->sizeof('int[64]');  # usually 4*64
 my $intarraysize = $ffi->sizeof('long[64]'); # usually 4*64 or 8*64
                                              # depending on platform

Keep in mind that ``pointer'' types will always be the pointer / word size for the platform that you are using. This includes strings, opaque and pointers to other types.

This function is not very fast, so you might want to save this value as a constant, particularly if you need the size in a loop with many iterations.

alignof

[version 0.21]

 my $align = $ffi->alignof($type);

Returns the alignment of the given type in bytes.

find_lib

[version 0.20]

 $ffi->find_lib( lib => $libname );

This is just a shortcut for calling FFI::CheckLib#find_lib and updating the ``lib'' attribute appropriately. Care should be taken though, as this method simply passes its arguments to FFI::CheckLib#find_lib, so if your module or script is depending on a specific feature in FFI::CheckLib then make sure that you update your prerequisites appropriately.

find_symbol

 my $address = $ffi->find_symbol($name);

Return the address of the given symbol (usually function).

package

[version 0.15]

 $ffi->package($package, $file); # usually __PACKAGE__ and __FILE__ can be used
 $ffi->package;                  # autodetect

If you have used Module::Build::FFI to bundle C code with your distribution, you can use this method to tell the FFI::Platypus instance to look for symbols that came with the dynamic library that was built when your distribution was installed.

abis

 my $href = $ffi->abis;
 my $href = FFI::Platypus->abis;

Get the legal ABIs supported by your platform and underlying implementation. What is supported can vary a lot by CPU and by platform, or even between 32 and 64 bit on the same CPU and platform. They keys are the ``ABI'' names, also known as ``calling conventions''. The values are integers used internally by the implementation to represent those ABIs.

abi

 $ffi->abi($name);

Set the ABI or calling convention for use in subsequent calls to ``function'' or ``attach''. May be either a string name or integer value from the ``abis'' method above.

EXAMPLES

Here are some examples. These examples are provided in full with the Platypus distribution in the ``examples'' directory. There are also some more examples in FFI::Platypus::Type that are related to types.

Integer conversions

 use FFI::Platypus;
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(undef);
 
 $ffi->attach(puts => ['string'] => 'int');
 $ffi->attach(atoi => ['string'] => 'int');
 
 puts(atoi('56'));

Discussion: "puts" and "atoi" should be part of the standard C library on all platforms. "puts" prints a string to standard output, and "atoi" converts a string to integer. Specifying "undef" as a library tells Platypus to search the current process for symbols, which includes the standard c library.

libnotify

 use FFI::CheckLib;
 use FFI::Platypus;
 
 # NOTE: I ported this from the like named eg/notify.pl that came with FFI::Raw
 # and it seems to work most of the time, but also seems to SIGSEGV sometimes.
 # I saw the same behavior in the FFI::Raw version, and am not really familiar
 # with the libnotify API to say what is the cause.  Patches welcome to fix it.
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(find_lib_or_exit lib => 'notify');
 
 $ffi->attach(notify_init   => ['string'] => 'void');
 $ffi->attach(notify_uninit => []       => 'void');
 $ffi->attach([notify_notification_new    => 'notify_new']    => ['string', 'string', 'string']           => 'opaque');
 $ffi->attach([notify_notification_update => 'notify_update'] => ['opaque', 'string', 'string', 'string'] => 'void');
 $ffi->attach([notify_notification_show   => 'notify_show']   => ['opaque', 'opaque']                     => 'void');
 
 notify_init('FFI::Platypus');
 my $n = notify_new('','','');
 notify_update($n, 'FFI::Platypus', 'It works!!!', 'media-playback-start');
 notify_show($n, undef);
 notify_uninit();

Discussion: libnotify is a desktop GUI notification library for the GNOME Desktop environment. This script sends a notification event that should show up as a balloon, for me it did so in the upper right hand corner of my screen.

The most portable way to find the correct name and location of a dynamic library is via the FFI::CheckLib#find_lib family of functions. If you are putting together a CPAN distribution, you should also consider using FFI::CheckLib#check_lib_or_exit function in your "Build.PL" or "Makefile.PL" file (If you are using Dist::Zilla, check out the Dist::Zilla::Plugin::FFI::CheckLib plugin). This will provide a user friendly diagnostic letting the user know that the required library is missing, and reduce the number of bogus CPAN testers results that you will get.

Also in this example, we rename some of the functions when they are placed into Perl space to save typing:

 attach [notify_notification_new => 'notify_new']
   => [string,string,string]
   => opaque;

When you specify a list reference as the ``name'' of the function the first element is the symbol name as understood by the dynamic library. The second element is the name as it will be placed in Perl space.

Later, when we call "notify_new":

 my $n = notify_new('','','');

We are really calling the C function "notify_notification_new".

Allocating and freeing memory

 use FFI::Platypus;
 use FFI::Platypus::Memory qw( malloc free memcpy );
 
 my $ffi = FFI::Platypus->new;
 my $buffer = malloc 12;
 
 memcpy $buffer, $ffi->cast('string' => 'opaque', "hello there"), length "hello there\0";
 
 print $ffi->cast('opaque' => 'string', $buffer), "\n";
 
 free $buffer;

Discussion: "malloc" and "free" are standard memory allocation functions available from the standard c library and. Interfaces to these and other memory related functions are provided by the FFI::Platypus::Memory module.

structured data records

 package My::UnixTime;
 
 use FFI::Platypus::Record;
 
 record_layout(qw(
     int    tm_sec
     int    tm_min
     int    tm_hour
     int    tm_mday
     int    tm_mon
     int    tm_year
     int    tm_wday
     int    tm_yday
     int    tm_isdst
     long   tm_gmtoff
     string tm_zone
 ));
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(undef);
 # define a record class My::UnixTime and alias it to "tm"
 $ffi->type("record(My::UnixTime)" => 'tm');
 
 # attach the C localtime function as a constructor
 $ffi->attach( localtime => ['time_t*'] => 'tm', sub {
   my($inner, $class, $time) = @_;
   $time = time unless defined $time;
   $inner->(\$time);
 });
 
 package main;
 
 # now we can actually use our My::UnixTime class
 my $time = My::UnixTime->localtime;
 printf "time is %d:%d:%d %s\n",
   $time->tm_hour,
   $time->tm_min,
   $time->tm_sec,
   $time->tm_zone;

Discussion: C and other machine code languages frequently provide interfaces that include structured data records (known as ``structs'' in C). They sometimes provide an API in which you are expected to manipulate these records before and/or after passing them along to C functions. There are a few ways of dealing with such interfaces, but the easiest way is demonstrated here defines a record class using a specific layout. For more details see FFI::Platypus::Record. (FFI::Platypus::Type includes some other ways of manipulating structured data records).

libuuid

 use FFI::CheckLib;
 use FFI::Platypus;
 use FFI::Platypus::Memory qw( malloc free );
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(find_lib_or_exit lib => 'uuid');
 $ffi->type('string(37)' => 'uuid_string');
 $ffi->type('record(16)' => 'uuid_t');
 
 $ffi->attach(uuid_generate => ['uuid_t'] => 'void');
 $ffi->attach(uuid_unparse  => ['uuid_t','uuid_string'] => 'void');
 
 my $uuid = "\0" x 16;  # uuid_t
 uuid_generate($uuid);
 
 my $string = "\0" x 37; # 36 bytes to store a UUID string 
                         # + NUL termination
 uuid_unparse($uuid, $string);
 
 print "$string\n";

Discussion: libuuid is a library used to generate unique identifiers (UUID) for objects that may be accessible beyond the local system. The library is or was part of the Linux e2fsprogs package.

Knowing the size of objects is sometimes important. In this example, we use the sizeof function to get the size of 16 characters (in this case it is simply 16 bytes). We also know that the strings ``deparsed'' by "uuid_unparse" are exactly 37 bytes.

puts and getpid

 use FFI::Platypus;
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(undef);
 
 $ffi->attach(puts => ['string'] => 'int');
 $ffi->attach(getpid => [] => 'int');
 
 puts(getpid());

Discussion: "puts" is part of standard C library on all platforms. "getpid" is available on Unix type platforms.

Math library

 use FFI::Platypus;
 use FFI::CheckLib;
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(undef);
 $ffi->attach(puts => ['string'] => 'int');
 $ffi->attach(fdim => ['double','double'] => 'double');
 
 puts(fdim(7.0, 2.0));
 
 $ffi->attach(cos => ['double'] => 'double');
 
 puts(cos(2.0));
 
 $ffi->attach(fmax => ['double', 'double'] => 'double');
 
 puts(fmax(2.0,3.0));

Discussion: On UNIX the standard c library math functions are frequently provided in a separate library "libm", so you could search for those symbols in ``libm.so'', but that won't work on non-UNIX platforms like Microsoft Windows. Fortunately Perl uses the math library so these symbols are already in the current process so you can use "undef" as the library to find them.

Strings

 use FFI::Platypus;
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(undef);
 $ffi->attach(puts => ['string'] => 'int');
 $ffi->attach(strlen => ['string'] => 'int');
 
 puts(strlen('somestring'));
 
 $ffi->attach(strstr => ['string','string'] => 'string');
 
 puts(strstr('somestring', 'string'));
 
 #attach puts => [string] => int;
 
 puts(puts("lol"));
 
 $ffi->attach(strerror => ['int'] => 'string');
 
 puts(strerror(2));

Discussion: Strings are not a native type to "libffi" but the are handled seamlessly by Platypus.

Attach function from pointer

 use FFI::TinyCC;
 use FFI::Platypus;
 
 my $ffi = FFI::Platypus->new;
 my $tcc = FFI::TinyCC->new;
 
 $tcc->compile_string(q{
   int
   add(int a, int b)
   {
     return a+b;
   }
 });
 
 my $address = $tcc->get_symbol('add');
 
 $ffi->attach( [ $address => 'add' ] => ['int','int'] => 'int' );
 
 print add(1,2), "\n";

Discussion: Sometimes you will have a pointer to a function from a source other than Platypus that you want to call. You can use that address instead of a function name for either of the function or attach methods. In this example we use FFI::TinyCC to compile a short piece of C code and to give us the address of one of its functions, which we then use to create a perl xsub to call it.

FFI::TinyCC embeds the Tiny C Compiler (tcc) to provide a just-in-time (JIT) compilation service for FFI.

libzmq

 use constant ZMQ_IO_THREADS  => 1;
 use constant ZMQ_MAX_SOCKETS => 2;
 use constant ZMQ_REQ => 3;
 use constant ZMQ_REP => 4;
 use FFI::CheckLib qw( find_lib_or_exit );
 use FFI::Platypus;
 use FFI::Platypus::Memory qw( malloc );
 use FFI::Platypus::Buffer qw( scalar_to_buffer buffer_to_scalar );
 
 my $endpoint = "ipc://zmq-ffi-$$";
 my $ffi = FFI::Platypus->new;
 
 $ffi->lib(undef); # for puts
 $ffi->attach(puts => ['string'] => 'int');
 
 $ffi->lib(find_lib_or_exit lib => 'zmq');
 $ffi->attach(zmq_version => ['int*', 'int*', 'int*'] => 'void');
 
 my($major,$minor,$patch);
 zmq_version(\$major, \$minor, \$patch);
 puts("libzmq version $major.$minor.$patch");
 die "this script only works with libzmq 3 or better" unless $major >= 3;
 
 $ffi->type('opaque'       => 'zmq_context');
 $ffi->type('opaque'       => 'zmq_socket');
 $ffi->type('opaque'       => 'zmq_msg_t');
 $ffi->attach(zmq_ctx_new  => [] => 'zmq_context');
 $ffi->attach(zmq_ctx_set  => ['zmq_context', 'int', 'int'] => 'int');
 $ffi->attach(zmq_socket   => ['zmq_context', 'int'] => 'zmq_socket');
 $ffi->attach(zmq_connect  => ['opaque', 'string'] => 'int');
 $ffi->attach(zmq_bind     => ['zmq_socket', 'string'] => 'int');
 $ffi->attach(zmq_send     => ['zmq_socket', 'opaque', 'size_t', 'int'] => 'int');
 $ffi->attach(zmq_msg_init => ['zmq_msg_t'] => 'int');
 $ffi->attach(zmq_msg_recv => ['zmq_msg_t', 'zmq_socket', 'int'] => 'int');
 $ffi->attach(zmq_msg_data => ['zmq_msg_t'] => 'opaque');
 $ffi->attach(zmq_errno    => [] => 'int');
 $ffi->attach(zmq_strerror => ['int'] => 'string');
 
 my $context = zmq_ctx_new();
 zmq_ctx_set($context, ZMQ_IO_THREADS, 1);
 
 my $socket1 = zmq_socket($context, ZMQ_REQ);
 zmq_connect($socket1, $endpoint);
 
 my $socket2 = zmq_socket($context, ZMQ_REP);
 zmq_bind($socket2, $endpoint);
 
 do { # send
   our $sent_message = "hello there";
   my($pointer, $size) = scalar_to_buffer $sent_message;
   my $r = zmq_send($socket1, $pointer, $size, 0);
   die zmq_strerror(zmq_errno()) if $r == -1;
 };
 
 do { # recv
   my $msg_ptr  = malloc 100;
   zmq_msg_init($msg_ptr);
   my $size     = zmq_msg_recv($msg_ptr, $socket2, 0);
   die zmq_strerror(zmq_errno()) if $size == -1;
   my $data_ptr = zmq_msg_data($msg_ptr);
   my $recv_message = buffer_to_scalar $data_ptr, $size;
   print "recv_message = $recv_message\n";
 };

Discussion: OMQ is a high-performance asynchronous messaging library. There are a few things to note here.

Firstly, sometimes there may be multiple versions of a library in the wild and you may need to verify that the library on a system meets your needs (alternatively you could support multiple versions and configure your bindings dynamically). Here we use "zmq_version" to ask libzmq which version it is.

"zmq_version" returns the version number via three integer pointer arguments, so we use the pointer to integer type: "int *". In order to pass pointer types, we pass a reference. In this case it is a reference to an undefined value, because zmq_version will write into the pointers the output values, but you can also pass in references to integers, floating point values and opaque pointer types. When the function returns the $major variable (and the others) has been updated and we can use it to verify that it supports the API that we require.

Notice that we define three aliases for the "opaque" type: "zmq_context", "zmq_socket" and "zmq_msg_t". While this isn't strictly necessary, since Platypus and C treat all three of these types the same, it is useful form of documentation that helps describe the functionality of the interface.

Finally we attach the necessary functions, send and receive a message. If you are interested, there is a fully fleshed out OMQ Perl interface implemented using FFI called ZMQ::FFI.

libarchive

 use FFI::Platypus      ();
 use FFI::Platypus::API ();
 use FFI::CheckLib      ();
 
 # This example uses FreeBSD's libarchive to list the contents of any
 # archive format that it suppors.  We've also filled out a part of
 # the ArchiveWrite class that could be used for writing archive formats
 # supported by libarchive
 
 my $ffi = My::Platypus->new;
 $ffi->lib(FFI::CheckLib::find_lib_or_exit lib => 'archive');
 
 $ffi->custom_type(archive => {
   native_type    => 'opaque',
   perl_to_native => sub { ${$_[0]} },
   native_to_perl => sub {
     # this works because archive_read_new ignores any arguments
     # and we pass in the class name which we can get here.
     my $class = FFI::Platypus::API::arguments_get_string(0);
     bless \$_[0], $class;
   },
 });
 
 $ffi->custom_type(archive_entry => {
   native_type => 'opaque',
   perl_to_native => sub { ${$_[0]} },
   native_to_perl => sub {
     # works likewise for archive_entry objects
     my $class = FFI::Platypus::API::arguments_get_string(0);
     bless \$_[0], $class,
   },
 });
 
 package My::Platypus;
 
 use base qw( FFI::Platypus );
 
 sub find_symbol
 {
   my($self, $name) = @_;
   my $prefix = lcfirst caller(2);
   $prefix =~ s{([A-Z])}{"_" . lc $1}eg;
   $self->SUPER::find_symbol(join '_', $prefix, $name);
 }
 
 package Archive;
 
 # base class is "abstract" having no constructor or destructor
 
 $ffi->attach( error_string => ['archive'] => 'string' );
 
 package ArchiveRead;
 
 our @ISA = qw( Archive );
 
 $ffi->attach( new                   => ['string']                    => 'archive' );
 $ffi->attach( [ free => 'DESTROY' ] => ['archive']                   => 'void' );
 $ffi->attach( support_filter_all    => ['archive']                   => 'int' );
 $ffi->attach( support_format_all    => ['archive']                   => 'int' );
 $ffi->attach( open_filename         => ['archive','string','size_t'] => 'int' );
 $ffi->attach( next_header2          => ['archive', 'archive_entry' ] => 'int' );
 $ffi->attach( data_skip             => ['archive']                   => 'int' );
 # ... define additional read methods
 
 package ArchiveWrite;
 
 our @ISA = qw( Archive );
 
 $ffi->attach( new                   => ['string'] => 'archive' );
 $ffi->attach( [ free => 'DESTROY' ] => ['archive'] => 'void' );
 # ... define additional write methods
 
 package ArchiveEntry;
 
 $ffi->attach( new => ['string']     => 'archive_entry' );
 $ffi->attach( [ free => 'DESTROY' ] => ['archive_entry'] => 'void' );
 $ffi->attach( pathname              => ['archive_entry'] => 'string' );
 # ... define additional entry methods
 
 package main;
 
 use constant ARCHIVE_OK => 0;
 
 # this is a Perl version of the C code here:
 # https://github.com/libarchive/libarchive/wiki/Examples#List_contents_of_Archive_stored_in_File
 
 my $archive_filename = shift @ARGV;
 unless(defined $archive_filename)
 {
   print "usage: $0 archive.tar\n";
   exit;
 }
 
 my $archive = ArchiveRead->new;
 $archive->support_filter_all;
 $archive->support_format_all;
 
 my $r = $archive->open_filename($archive_filename, 1024);
 die "error opening $archive_filename: ", $archive->error_string
   unless $r == ARCHIVE_OK;
 
 my $entry = ArchiveEntry->new;
 
 while($archive->next_header2($entry) == ARCHIVE_OK)
 {
   print $entry->pathname, "\n";
   $archive->data_skip;
 }

Discussion: libarchive is the implementation of "tar" for FreeBSD provided as a library and available on a number of platforms.

One interesting thing about libarchive is that it provides a kind of object oriented interface via opaque pointers. This example creates an abstract class "Archive", and concrete classes "ArchiveWrite", "ArchiveRead" and "ArchiveEntry". The concrete classes can even be inherited from and extended just like any Perl classes because of the way the custom types are implemented. For more details on custom types see FFI::Platypus::Type and FFI::Platypus::API.

Another advanced feature of this example is that we extend the FFI::Platypus class to define our own find_symbol method that prefixes the symbol names depending on the class in which they are defined. This means we can do this when we define a method for Archive:

 $ffi->attach( support_filter_all => ['archive'] => 'int' );

Rather than this:

 $ffi->attach(
   [ archive_read_support_filter_all => 'support_read_filter_all' ] => 
   ['archive'] => 'int' );
 );

If you didn't want to create an entire new class just for this little trick you could also use something like Object::Method to extend "find_symbol".

bzip2

 use FFI::Platypus 0.20 (); # 0.20 required for using wrappers
 use FFI::CheckLib qw( find_lib_or_die );
 use FFI::Platypus::Buffer qw( scalar_to_buffer buffer_to_scalar );
 use FFI::Platypus::Memory qw( malloc free );
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib(find_lib_or_die lib => 'bz2');
 
 $ffi->attach(
   [ BZ2_bzBuffToBuffCompress => 'compress' ] => [
     'opaque',                           # dest
     'unsigned int *',                   # dest length
     'opaque',                           # source
     'unsigned int',                     # source length
     'int',                              # blockSize100k
     'int',                              # verbosity
     'int',                              # workFactor
   ] => 'int',
   sub {
     my $sub = shift;
     my($source,$source_length) = scalar_to_buffer $_[0];
     my $dest_length = int(length($source)*1.01) + 1 + 600;
     my $dest = malloc $dest_length;
     my $r = $sub->($dest, \$dest_length, $source, $source_length, 9, 0, 30);
     die "bzip2 error $r" unless $r == 0;
     my $compressed = buffer_to_scalar($dest, $dest_length);
     free $dest;
     $compressed;
   },
 );
 
 $ffi->attach(
   [ BZ2_bzBuffToBuffDecompress => 'decompress' ] => [
     'opaque',                           # dest
     'unsigned int *',                   # dest length
     'opaque',                           # source
     'unsigned int',                     # source length
     'int',                              # small
     'int',                              # verbosity
   ] => 'int',
   sub {
     my $sub = shift;
     my($source, $source_length) = scalar_to_buffer $_[0];
     my $dest_length = $_[1];
     my $dest = malloc $dest_length;
     my $r = $sub->($dest, \$dest_length, $source, $source_length, 0, 0);
     die "bzip2 error $r" unless $r == 0;
     my $decompressed = buffer_to_scalar($dest, $dest_length);
     free $dest;
     $decompressed;
   },
 );
 
 my $original = "hello compression world\n";
 my $compressed = compress($original);
 print decompress($compressed, length $original);

Discussion: bzip2 is a compression library. For simple one shot attempts at compression/decompression when you expect the original and the result to fit within memory it provides two convenience functions "BZ2_bzBuffToBuffCompress" and "BZ2_bzBuffToBuffDecompress".

The first four arguments of both of these C functions are identical, and represent two buffers. One buffer is the source, the second is the destination. For the destination, the length is passed in as a pointer to an integer. On input this integer is the size of the destination buffer, and thus the maximum size of the compressed or decompressed data. When the function returns the actual size of compressed or compressed data is stored in this integer.

This is normal stuff for C, but in Perl our buffers are scalars and they already know how large they are. In this sort of situation, wrapping the C function in some Perl code can make your interface a little more Perl like. In order to do this, just provide a code reference as the last argument to the ``attach'' method. The first argument to this wrapper will be a code reference to the C function. The Perl arguments will come in after that. This allows you to modify / convert the arguments to conform to the C API. What ever value you return from the wrapper function will be returned back to the original caller.

Java

Java:

 // On Linux build .so with
 // % gcj -fPIC -shared -o libexample.so Example.java
 
 public class Example
 {
   public static void print_hello()
   {
     System.out.println("hello world");
   }
 
   public static int add(int a, int b)
   {
     return a + b;
   }
 }

C++:

 #include <gcj/cni.h>
 #include <java/lang/System.h>
 #include <java/io/PrintStream.h>
 #include <java/lang/Throwable.h>
 
 extern "C" void
 gcj_start()
 {
   using namespace java::lang;
 
   JvCreateJavaVM(NULL);
   JvInitClass(&System::class$);
 }
 
 extern "C" void
 gcj_end()
 {
   JvDetachCurrentThread();
 }

Perl:

 use FFI::Platypus;
 
 my $ffi = FFI::Platypus->new;
 $ffi->lib('./libexample.so');
 
 # Java methods are mangled by gcj using the same format as g++
 
 $ffi->attach(
   [ _ZN7Example11print_helloEJvv => 'print_hello' ] => [] => 'void'
 );
 
 $ffi->attach(
   [ _ZN7Example3addEJiii => 'add' ] => ['int', 'int'] => 'int'
 );
 
 # Initialize the Java runtime
 
 $ffi->function( gcj_start => [] => 'void' )->call;
 
 print_hello();
 print add(1,2), "\n";
 
 # Wind the java runtime down
 
 $ffi->function( gcj_end => [] => 'void' )->call;

Makefile:

 GCJ=gcj
 CXX=g++
 CFLAGS=-fPIC
 LDFLAGS=-shared
 RM=rm -f
 
 libexample.so: between.o Example.o
        $(GCJ) $(LDFLAGS) -o libexample.so between.o Example.o
 
 between.o: between.cpp
        $(CXX) $(CFLAGS) -c -o between.o between.cpp
 
 Example.o: Example.java
        $(GCJ) $(CFLAGS) -c -o Example.o Example.java
 
 clean:
        $(RM) *.o *.so

Output:

 % make
 g++ -fPIC -c -o between.o between.cpp
 gcj -fPIC -c -o Example.o Example.java
 gcj -shared -o libexample.so between.o Example.o
 % perl example.pl 
 hello world
 3

Discussion: You can't call Java .class files directly from FFI / Platypus, but you can compile Java source and .class files into a shared library using the GNU Java Compiler "gcj". Because we are calling Java functions from a program (Perl!) that was not started from a Java "main()" we have to initialize the Java runtime ourselves (details <https://gcc.gnu.org/onlinedocs/gcj/Invocation.html>). This can most easily be accomplished from C++.

The GNU Java Compiler uses the same format to mangle method names as GNU C++. The C++ plugin for handles this more transparently by extracting the symbols from the shared library and using either FFI::Platypus::Lang::CPP::Demangle::XS or "c++filt" to determined the unmangled names.

Although the Java source is compiled ahead of time with optimizations, it will not necessarily perform better than a real JVM just because it is compiled. In fact the gcj developers warn than gcj will optimize Java source better than Java .class files. The GNU Java Compiler also lags behind modern Java.

Even so this enables you to call Java from Perl and potentially other Java based languages such as Scala, Groovy or JRuby.

CAVEATS

Platypus and Native Interfaces like libffi rely on the availability of dynamic libraries. Things not supported include:

Systems that lack dynamic library support

Like MS-DOS

Systems that are not supported by libffi

Like OpenVMS

Languages that do not support using dynamic libraries from other languages

Like Google's Go. Although I believe that XS won't help in this regard.

Languages that do not compile to machine code

Like .NET based languages and Java that can't be understood by gcj.

The documentation has a bias toward using FFI / Platypus with C. This is my fault, as my background in mainly in C/C++ programmer (when I am not writing Perl). In many places I use ``C'' as a short form for ``any language that can generate machine code and is callable from C''. I welcome pull requests to the Platypus core to address this issue. In an attempt to ease usage of Platypus by non C programmers, I have written a number of foreign language plugins for various popular languages (see the SEE ALSO below). These plugins come with examples specific to those languages, and documentation on common issues related to using those languages with FFI. In most cases these are available for easy adoption for those with the know-how or the willingness to learn. If your language doesn't have a plugin YET, that is just because you haven't written it yet.

SUPPORT

IRC: #native on irc.perl.org

(click for instant chat room login) <http://chat.mibbit.com/#[email protected]>

If something does not work the way you think it should, or if you have a feature request, please open an issue on this project's GitHub Issue tracker:

<https://github.com/plicease/FFI-Platypus/issues>

CONTRIBUTING

If you have implemented a new feature or fixed a bug then you may make a pull request on this project's GitHub repository:

<https://github.com/plicease/FFI-Platypus/pulls>

This project is developed using Dist::Zilla. The project's git repository also comes with "Build.PL" and "cpanfile" files necessary for building, testing (and even installing if necessary) without Dist::Zilla. Please keep in mind though that these files are generated so if changes need to be made to those files they should be done through the project's "dist.ini" file. If you do use Dist::Zilla and already have the necessary plugins installed, then I encourage you to run "dzil test" before making any pull requests. This is not a requirement, however, I am happy to integrate especially smaller patches that need tweaking to fit the project standards. I may push back and ask you to write a test case or alter the formatting of a patch depending on the amount of time I have and the amount of code that your patch touches.

This project's GitHub issue tracker listed above is not Write-Only. If you want to contribute then feel free to browse through the existing issues and see if there is something you feel you might be good at and take a whack at the problem. I frequently open issues myself that I hope will be accomplished by someone in the future but do not have time to immediately implement myself.

Another good area to help out in is documentation. I try to make sure that there is good document coverage, that is there should be documentation describing all the public features and warnings about common pitfalls, but an outsider's or alternate view point on such things would be welcome; if you see something confusing or lacks sufficient detail I encourage documentation only pull requests to improve things.

The Platypus distribution comes with a test library named "libtest" that is normally automatically built by "./Build test". If you prefer to use "prove" or run tests directly, you can use the "./Build libtest" command to build it. Example:

 % perl Build.PL
 % ./Build
 % ./Build libtest
 % prove -bv t
 # or an individual test
 % perl -Mblib t/ffi_platypus_memory.t

The build process also respects these environment variables:

FFI_PLATYPUS_DEBUG

Build the XS code portion of Platypus with -g3 instead of what ever optimizing flags that your Perl normally uses. This is useful if you need to debug the C or XS code that comes with Platypus, but do not have a debugging Perl.

 % env FFI_PLATYPUS_DEBUG=1 perl Build.PL
 
 
 DEBUG:
   - $Config{lddlflags} = -shared -O2 -L/usr/local/lib -fstack-protector
   + $Config{lddlflags} = -shared -g3 -L/usr/local/lib -fstack-protector
   - $Config{optimize} = -O2
   + $Config{optimize} = -g3
 
 
 Created MYMETA.yml and MYMETA.json
 Creating new 'Build' script for 'FFI-Platypus' version '0.10'

FFI_PLATYPUS_DEBUG_FAKE32

When building Platypus on 32 bit Perls, it will use the Math::Int64 C API and make Math::Int64 a prerequisite. Setting this environment variable will force Platypus to build with both of those options on a 64 bit Perl as well.

 % env FFI_PLATYPUS_DEBUG_FAKE32=1 perl Build.PL
 
 
 DEBUG_FAKE32:
   + making Math::Int64 a prerequisite (not normally done on 64 bit Perls)
   + using Math::Int64's C API to manipulate 64 bit values (not normally done on 64 bit Perls)
 
 Created MYMETA.yml and MYMETA.json
 Creating new 'Build' script for 'FFI-Platypus' version '0.10'

FFI_PLATYPUS_NO_ALLOCA

Platypus uses the non-standard and somewhat controversial C function "alloca" by default on platforms that support it. I believe that Platypus uses it responsibly to allocate small amounts of memory for argument type parameters, and does not use it to allocate large structures like arrays or buffers. If you prefer not to use "alloca" despite these precautions, then you can turn its use off by setting this environment variable when you run "Build.PL":

 % env FFI_PLATYPUS_NO_ALLOCA=1 perl Build.PL
 
 
 NO_ALLOCA:
   + alloca() will not be used, even if your platform supports it.
 
 
  Created MYMETA.yml and MYMETA.json
  Creating new 'Build' script for 'FFI-Platypus' version '0.10'

Coding Guidelines

• Do not hesitate to make code contribution. Making useful contributions is more important than following byzantine bureaucratic coding regulations. We can always tweak things later.
• Please make an effort to follow existing coding style when making pull requests.
• Platypus supports all production Perl releases since 5.8.1. For that reason, please do not introduce any code that requires a newer version of Perl.

Performance Testing

As Mark Twain was fond of saying there are four types of lies: lies, damn lies, statistics and benchmarks. That being said, it can sometimes be helpful to compare the runtime performance of Platypus if you are making significant changes to the Platypus Core. For that I use `FFI-Performance`, which can be found in my GitHub repository here:

<https://github.com/plicease/FFI-Performance>

System integrators

If you are including Platypus in a larger system (for example a Linux distribution), and you already have libffi as part of your system, you may be interested in Alt::Alien::FFI::System. This is an alternative to Alien::FFI that does not require Alien::Base. In fact it has zero non-Core dependencies, and doesn't even need to be installed. Simply include Alt::Alien::FFI::System's "lib" directory in your "PERL5LIB" path when you build Platypus. For example:

 % export PERL5LIB=/path/to/Alt-Alien-FFI-System/lib
 % cpanm FFI::Platypus

ACKNOWLEDGMENTS

In addition to the contributors mentioned below, I would like to acknowledge Brock Wilcox (AWWAIID) and Meredith Howard (MHOWARD) whose work on FFI::Sweet <https://github.com/merrilymeredith/p5-FFI-Sweet> not only helped me get started with FFI but significantly influenced the design of Platypus.

In addition I'd like to thank Alessandro Ghedini (ALEXBIO) who was always responsive to bug reports and pull requests for FFI::Raw, which was important in the development of the ideas on which Platypus is based.

AUTHOR

Author: Graham Ollis <[email protected]>

Contributors:

Bakkiaraj Murugesan (bakkiaraj)

Dylan Cali (calid)

pipcet

Zaki Mughal (zmughal)

Fitz Elliott (felliott)

Vickenty Fesunov (vyf)

Gregor Herrmann (gregoa)

COPYRIGHT AND LICENSE

This software is copyright (c) 2015 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.