++ed by:
CAMSPI AVKHOZOV ZMUGHAL TSIBLEY KARJALA

27 PAUSE users
22 non-PAUSE users.

Graham Ollis 🔥🐉
and 13 contributors

NAME

FFI::Platypus::Bundle - Bundle foreign code with your Perl module

VERSION

version 0.96

SYNOPSIS

ffi/foo.c:

 #include <ffi_platypus_bundle.h>
 #include <string.h>
 
 typedef struct {
   char *name;
   int value;
 } foo_t;
 
 foo_t*
 foo__new(const char *class_name, const char *name, int value)
 {
   (void)class_name;
   foo_t *self = malloc( sizeof( foo_t ) );
   self->name = strdup(name);
   self->value = value;
   return self;
 }
 
 const char *
 foo__name(foo_t *self)
 {
   return self->name;
 }
 
 int
 foo__value(foo_t *self)
 {
   return self->value;
 }
 
 void
 foo__DESTROY(foo_t *self)
 {
   free(self->name);
   free(self);
 }

lib/Foo.pm:

 package Foo;
 
 use strict;
 use warnings;
 use FFI::Platypus;
 
 {
   my $ffi = FFI::Platypus->new( api => 1 );
 
   $ffi->type('object(Foo)' => 'foo_t');
   $ffi->mangler(sub {
     my $name = shift;
     $name =~ s/^/foo__/;
     $name;
   });
 
   $ffi->bundle;
 
   $ffi->attach( new =>     [ 'string', 'string', 'int' ] => 'foo_t'  );
   $ffi->attach( name =>    [ 'foo_t' ]                   => 'string' );
   $ffi->attach( value =>   [ 'foo_t' ]                   => 'int'    );
   $ffi->attach( DESTROY => [ 'foo_t' ]                   => 'void'   );
 }
 
 1;

t/foo.t

 use Test::More;
 use Foo;
 
 my $foo = Foo->new("platypus", 10);
 isa_ok $foo, 'Foo';
 is $foo->name, "platypus";
 is $foo->value, 10;
 
 done_testing;

Makefile.PL:

 use ExtUtils::MakeMaker;
 use FFI::Build::MM;
 my $fbmm = FFI::Build::MM->new;
 WriteMakefile(
   $fbmm->mm_args(
     NAME     => 'Foo',
     DISTNAME => 'Foo',
     VERSION  => '1.00',
     # ...
   )
 );
 
 sub MY::postamble
 {
   $fbmm->mm_postamble;
 }

or dist.ini:

 name    = Foo
 version = 0.01
 ...
 
 [FFI::Build]
 version = 1.04

DESCRIPTION

This document serves as a tutorial for using the new bundling interface provided by FFI::Platypus as of api version 1. It requires FFI::Platypus of at least 1.00.

Sometimes when writing FFI bindings you need to include a little C code (or your favorite compiled language) to finish things off. Alternatively, you might just want to write some C code (or your favorite compiled language) to include with your Perl module to make a tight loop faster. The bundling interface has you covered.

Basic example

To illustrate we will go through the files in the synopsis and explain how and why they work. To start with we have some C code which emulates object oriented code using foo__ as a prefix. We use a C struct that we call foo_t to store our object data. On the C level the struct acts as a class, when combined with its functions that act as methods. The constructor just allocates the memory it needs for the foo_t instance, fills in the appropriate fields and returns the pointer:

 foo_t*
 foo__new(const char *class_name, const char *name, int value)
 {
   (void) class_name;
   foo_t *self = malloc( sizeof( foo_t ) );
   self->name = strdup(name);
   self->value = value;
   return self;
 }

We include a class name as the first argument, because Perl will include that when calling the constructor, but we do not use it here. An exercise for the reader would be to add hierarchical inheritance.

There are also some methods which return member values. This class has only read only members, but you could have read/write or other methods depending on your needs.

 const char *
 foo__name(foo_t *self)
 {
   return self->name;
 }

We also include a destructor so that the memory owned by the object can be freed when it is no longer needed.

 void
 foo__DESTROY(foo_t *self)
 {
   free(self->name);
   free(self);
 }

This might start to look a little like a Perl module, and when we look at the Perl code that binds to this code, you will see why. First lets prepare the FFI::Platypus instance and specify the correct api version:

 my $ffi = FFI::Platypus->new( api => 1 );

The bundle interface is only supported with api version 1, so if you try to use version 0 it will not work. Next we define an object type for foo_t which will associate it with the Perl class Foo.

 $ffi->type('object(Foo)' => 'foo_t');

As object type is a blessed reference to an opaque (default) or integer type which can be used as a Perl object. Platypus does the translating of Perl object to and from the foo_t pointers that the C code understands. For more details on Platypus types see FFI::Platypus::Type.

Next we set the mangler on the Platypus instance so that we can refer to function names without the foo__ prefix. You could just not use the prefix in your C code and skip this step, or you could refer to the function names in their full in your Perl code, however, this saves extra typing and allows you to bundle more than one class with your Perl code without having to worry about name conflicts.

 $ffi->mangler(sub {
   my $name = shift;
   $name =~ s/^/foo__/;
   $name;
 });

Finally we let Platypus know that we will be bundling code.

 $ffi->bundle;

By default, this searches for the appropriate place for your dynamic libraries using the current package. In some cases you may need to override this, for example if your dist is named Foo-Bar but your specific class is named Foo::Bar::Baz, you'd want something like this:

 package Foo::Bar::Baz;
 use FFI::Platypus;
 my $ffi = FFI::Platypus->new( api => 1 );
 $ffi->bundle('Foo::Bar');
 ...

Now, finally we can attach the methods for our class:

 $ffi->attach( new =>     [ 'string', 'int' ] => 'foo_t'  );
 $ffi->attach( name =>    [ 'foo_t' ]         => 'string' );
 $ffi->attach( value =>   [ 'foo_t' ]         => 'int'    );
 $ffi->attach( DESTROY => [ 'foo_t' ]         => 'void'   );

Note that we do not have to include the foo__ prefix because of the way we set up the mangler. If we hadn't done that then we could instead attach with the full names:

 $ffi->attach( [ 'foo__new'  => 'new' ]  => [ 'string', 'int' ] => 'foo_t'  );
 $ffi->attach( [ 'foo__name' => 'name' ] => [ 'foo_t' ]         => 'string' );
 ...

You're done! You can now use this class. Lets write a test to make sure it works,

 use strict;
 use warnings;
 use Test::More;
 use Foo;
 
 my $foo = Foo->new("platypus", 10);
 isa_ok $foo, 'Foo';
 is $foo->name, "platypus";
 is $foo->value, 10;
 
 done_testing;

and use prove to check that it works:

 % prove -lvm
 t/foo.t ..
 ok 1 - An object of class 'Foo' isa 'Foo'
 ok 2
 ok 3
 1..3
 ok
 All tests successful.
 Files=1, Tests=3,  0 wallclock secs ( 0.02 usr  0.00 sys +  0.14 cusr  0.03 csys =  0.19 CPU)
 Result: PASS

Platypus automatically compiles and links the dynamic library for you:

 % ls ffi/_build
 foo.c.o  libFoo.so

The C code will be rebuilt next time if the source code is newer than the object or dynamic libraries files. If the source files are not changed, then it won't be rebuilt to save time. If you are using the code without MakeMaker, or another build system you are responsible for cleaning up these files. This is intended as a convenience to allow you to test your code without having to invoke MakeMaker, or dzil or whatever build system you are using.

When you distribute your module though, you will want the dynamic library built just once at build-time and installed correctly so that it can be found at run-time. You don't need to make any changes to your C or Perl code, but you do need to tell MakeMaker to build and install the appropriate files using FFI::Build::MM:

 use ExtUtils::MakeMaker;
 use FFI::Build::MM;
 my $fbmm = FFI::Build::MM->new;
 WriteMakefile(
   $fbmm->mm_args(
     NAME     => 'Foo',
     DISTNAME => 'Foo',
     VERSION  => '1.00',
     # ...
   )
 );
 
 sub MY::postamble
 {
   $fbmm->mm_postamble;
 }

And we can invoke all the normal MakeMaker style stuff and our C code will be compiled, linked and installed at the appropriate steps.

 % perl Makefile.PL
 Generating a Unix-style Makefile
 Writing Makefile for Foo
 Writing MYMETA.yml and MYMETA.json
 % make
 cp lib/Foo.pm blib/lib/Foo.pm
 "/Users/ollisg/perl5/perlbrew/perls/perl-5.30.0/bin/perl" -MFFI::Build::MM=cmd -e fbx_build
 CC ffi/foo.c
 LD blib/lib/auto/share/dist/Foo/lib/libFoo.dylib
 % make test
 "/Users/ollisg/perl5/perlbrew/perls/perl-5.30.0/bin/perl" -MFFI::Build::MM=cmd -e fbx_build
 "/Users/ollisg/perl5/perlbrew/perls/perl-5.30.0/bin/perl" -MFFI::Build::MM=cmd -e fbx_test
 PERL_DL_NONLAZY=1 "/Users/ollisg/perl5/perlbrew/perls/perl-5.30.0/bin/perl" "-MExtUtils::Command::MM" "-MTest::Harness" "-e" "undef *Test::Harness::Switches; test_harness(0, 'blib/lib', 'blib/arch')" t/*.t
 t/foo.t .. ok
 All tests successful.
 Files=1, Tests=3,  0 wallclock secs ( 0.01 usr  0.00 sys +  0.06 cusr  0.01 csys =  0.08 CPU)
 Result: PASS

If the Makefile.PL file above looks overly complicated, you can use the Dist::Zilla::Plugin::FFI::Build plugin to simplify your life if you are using Dist::Zilla:

 [FFI::Build]
 version = 1.04

Specifying version 1.04 will ensure that any .o or .so files are pruned from your build tree and not distributed by mistake.

Initialization example

The bundle interface also gives you entry points which will be called automatically when your code is loaded and unloaded if they are found.

ffi_pl_bundle_init
 void ffi_pl_bundle_init(const char *package, int argc, void *argv[]);

Called when the dynamic library is loaded. package is the Perl package that called bundle from Perl space. argc and argv represents an array of opaque pointers that can be passed as an array to bundle as the last argument. (the count argc is a little redundant because argv is also NULL terminated).

ffi_pl_bundle_constant
 void ffi_pl_bundle_constant(const char *package, ffi_platypus_constant_t *c);

Called immediately after ffi_pl_bundle_init, and is intended to allow you to set Perl constants from C space. For details on how this works and what methods you can call on the ffi_platypus_constant_t instance, see FFI::Platypus::Constant.

ffi_pl_bundle_fini
 void ffi_pl_bundle_fini(const char *package);

Called when the dynamic library is unloaded. package is the Perl package that called bundle from Perl space when the library was loaded. CAVEAT: if you attach any functions then this will never be called, because attaching functions locks the Platypus instance into memory along with the libraries which it is using.

Here is an example that passes the version and a callback back into Perl space that emulates the Perl 5.10 say feature.

ffi/init.c:

 #include <ffi_platypus_bundle.h>
 
 char buffer[512];
 const char *version;
 void (*say)(const char *);
 
 void
 ffi_pl_bundle_init(const char *package, int argc, void *argv[])
 {
   version = argv[0];
   say     = argv[1];
 
   say("in init!");
 
   snprintf(buffer, 512, "package = %s, version = %s", package, version);
   say(buffer);
 
   snprintf(buffer, 512, "args = %d", argc);
   say(buffer);
 }
 
 void
 ffi_pl_bundle_fini(const char *package)
 {
   say("in fini!");
 }

lib/Init.pm:

 package Init;
 
 use strict;
 use warnings;
 use FFI::Platypus;
 
 our $VERSION = '1.00';
 
 {
   my $ffi = FFI::Platypus->new( api => 1 );
 
   my $say = $ffi->closure(sub {
     my $string = shift;
     print "$string\n";
   });
 
   $ffi->bundle([
     $ffi->cast( 'string' => 'opaque', $VERSION ),
     $ffi->cast( '(string)->void' => 'opaque', $say ),
   ]);
 
   undef $ffi;
   undef $say;
 }
 
 1;

The deinitialization order for the $say callback and the $ffi instance is essential here, so we do it manually with undef:

 undef $ffi;
 undef $say;

First we deallocate $ffi which calls ffi_pl_bundle_fini, which calls $say, so we want to make sure the latter is still allocated. Once ffi_pl_bundle_fini is done, we can safely deallocate $say.

If ffi_pl_bundle_fini didn't call back into Perl space like this then we don't have to be as careful about deallocating things in Perl space.

AUTHOR

Author: Graham Ollis <plicease@cpan.org>

Contributors:

Bakkiaraj Murugesan (bakkiaraj)

Dylan Cali (calid)

pipcet

Zaki Mughal (zmughal)

Fitz Elliott (felliott)

Vickenty Fesunov (vyf)

Gregor Herrmann (gregoa)

Shlomi Fish (shlomif)

Damyan Ivanov

Ilya Pavlov (Ilya33)

Petr Pisar (ppisar)

Mohammad S Anwar (MANWAR)

Håkon Hægland (hakonhagland, HAKONH)

COPYRIGHT AND LICENSE

This software is copyright (c) 2015,2016,2017,2018,2019 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.