Ubuntu Manpage: Inline-API - How to bind a programming language to Perl using Inline.pm

NAME

       Inline-API - How to bind a programming language to Perl using Inline.pm

SYNOPSIS

           #!/usr/bin/perl

           use Inline Foo;
           say_it('foo');  # Use Foo to print "Hello, Foo"

           __Foo__
           foo-sub say_it {
               foo-my $foo = foo-shift;
               foo-print "Hello, $foo\n";
           }

DESCRIPTION

So you think Inline C is pretty cool, but what you really need is for Perl to work with
the brand new programming language "Foo". Well you're in luck. "Inline.pm" has support
for adding your own Inline Language Support Module (ILSM), like "Inline::Foo".

Inline has always been intended to work with lots of different programming languages. Many
of the details can be shared between implementations, so that "Inline::Java" has a similar
interface to "Inline::ASM". All of the common code is in "Inline.pm".

Language specific modules like "Inline::Python" are subclasses of "Inline.pm". They can
inherit as much of the common behaviour as they want, and provide specific behaviour of
their own. This usually comes in the form of Configuration Options and language specific
compilation.

The Inline C support is probably the best boilerplate to copy from. Since version 0.30 all
C support was isolated into the module "Inline::C" and the parsing grammar is further
broken out into "Inline::C::grammar". All of these components come with the Inline
distribution.

This POD gives you all the details you need for implementing an ILSM. For further
assistance, contact inline@perl.org See ["SEE ALSO"] below.

We'll examine the joke language Inline::Foo which is distributed with Inline. It actually
is a full functioning ILSM. I use it in Inline's test harness to test base Inline
functionality. It is very short, and can help you get your head wrapped around the Inline
API.

A SKELETON

       For the remainder of this tutorial, let's assume we're writing an ILSM for the ficticious
       language "Foo". We'll call it "Inline::Foo". Here is the entire (working) implementation.

           package Inline::Foo;
           use strict;
           $Inline::Foo::VERSION = '0.01';
           @Inline::Foo::ISA = qw(Inline);
           require Inline;
           use Carp;

           #===========================================================
           # Register Foo as an Inline Language Support Module (ILSM)
           #===========================================================
           sub register {
               return {
                   language => 'Foo',
                   aliases => ['foo'],
                   type => 'interpreted',
                   suffix => 'foo',
                  };
           }

           #===========================================================
           # Error messages
           #===========================================================
           sub usage_config {
               my ($key) = @_;
               "'$key' is not a valid config option for Inline::Foo\n";
           }

           sub usage_config_bar {
               "Invalid value for Inline::Foo config option BAR";
           }

           #===========================================================
           # Validate the Foo Config Options
           #===========================================================
           sub validate {
               my $o = shift;
               $o->{ILSM}{PATTERN} ||= 'foo-';
               $o->{ILSM}{BAR} ||= 0;
               while (@_) {
               my ($key, $value) = splice @_, 0, 2;
               if ($key eq 'PATTERN') {
                   $o->{ILSM}{PATTERN} = $value;
                   next;
               }
               if ($key eq 'BAR') {
                   croak usage_config_bar
                     unless $value =~ /^[01]$/;
                   $o->{ILSM}{BAR} = $value;
                   next;
               }
               croak usage_config($key);
               }
           }

           #===========================================================
           # Parse and compile Foo code
           #===========================================================
           sub build {
               my $o = shift;
               my $code = $o->{API}{code};
               my $pattern = $o->{ILSM}{PATTERN};
               $code =~ s/$pattern//g;
               $code =~ s/bar-//g if $o->{ILSM}{BAR};
               sleep 1;             # imitate compile delay
               {
                   package Foo::Tester;
                   eval $code;
               }
               croak "Foo build failed:\n$@" if $@;
               my $path = "$o->{API}{install_lib}/auto/$o->{API}{modpname}";
               my $obj = $o->{API}{location};
               $o->mkpath($path) unless -d $path;
               open FOO_OBJ, "> $obj"
                 or croak "Can't open $obj for output\n$!";
               print FOO_OBJ $code;
               close \*FOO_OBJ;
           }

           #===========================================================
           # Only needed for interpreted languages
           #===========================================================
           sub load {
               my $o = shift;
               my $obj = $o->{API}{location};
               open FOO_OBJ, "< $obj"
                 or croak "Can't open $obj for output\n$!";
               my $code = join '', <FOO_OBJ>;
               close \*FOO_OBJ;
               eval "package $o->{API}{pkg};\n$code";
               croak "Unable to load Foo module $obj:\n$@" if $@;
           }

           #===========================================================
           # Return a small report about the Foo code.
           #===========================================================
           sub info {
               my $o = shift;
               my $text = <<'END';
           This is a small report about the Foo code. Perhaps it contains
           information about the functions the parser found which will be
           bound to Perl. It will get included in the text produced by the
           Inline 'INFO' command.
           END
               return $text;
           }

           1;

       Except for "load()", the subroutines in this code are mandatory for an ILSM.  What they do
       is described below. A few things to note:

       •   "Inline::Foo" must be a subclass of Inline. This is accomplished with:

               @Inline::Foo::ISA = qw(Inline);

       •   The line '"require Inline;"' is not necessary. But it is there to remind you not to
           say '"use Inline;"'. This will not work.

       •   Remember, it is not valid for a user to say:

               use Inline::Foo;

           "Inline.pm" will detect such usage for you in its "import" method, which is
           automatically inherited since "Inline::Foo" is a subclass.

       •   In the build function, you normally need to parse your source code. Inline::C uses
           Parse::RecDescent to do this. Inline::Foo simply uses eval. (After we strip out all
           occurrences of 'foo-').

           An alternative parsing method that works well for many ILSMs (like Java and Python) is
           to use the language's compiler itself to parse for you. This works as long as the
           compiler can be made to give back parse information.

THE INLINE API

This section is a more formal specification of what functionality you'll need to provide
to implement an ILSM.

When Inline determines that some "Foo" code needs to be compiled it will automatically
load your ILSM module. It will then call various subroutines which you need to supply.
We'll call these subroutines "callbacks".

You will need to provide the following 5 callback subroutines.

The register() Callback
This subroutine receives no arguments. It returns a reference to a hash of ILSM meta-data.
Inline calls this routine only when it is trying to detect new ILSM-s that have been
installed on a given system. Here is an example of the has ref you would return for Foo:

{
language => 'Foo',
aliases => ['foo'],
type => 'interpreted',
suffix => 'foo',
};

The meta-data items have the following meanings:

language
This is the proper name of the language. It is usually implemented as "Inline::X" for
a given language 'X'.

aliases
This is a reference to an array of language name aliases. The proper name of a
language can only contain word characters. A-Za-z0-9_ An alias can contain any
characters except whitespace and quotes. This is useful for names like 'C++' and 'C#'.

type
Must be set to 'compiled' or 'interpreted'. Indicates the category of the language.

suffix
This is the file extension for the cached object that will be created. For 'compiled'
languages, it will probably be 'so' or 'dll'. The appropriate value is in "Config.pm".

For interpreted languages, this value can be whatever you want. Python uses "pydat".
Foo uses "foo".

The validate() Callback
This routine gets passed all configuration options that were not already handled by the
base Inline module. The options are passed as key/value pairs. It is up to you to
validate each option and store its value in the Inline object (which is also passed in).
If a particular option is invalid, you should croak with an appropriate error message.

Note that all the keywords this routine receives will be converted to upper- case by
"Inline", whatever case the program gave.

The build() Callback
This subroutine is responsible for doing the parsing and compilation of the Foo source
code. The Inline object is passed as the only argument. All pertinent information will be
stored in this object. "build()" is required to create a cache object of a specific name,
or to croak with an appropriate error message.

This is the meat of your ILSM. Since it will most likely be quite complicated, it is
probably best that you study an existing ILSM like "Inline::C".

The load() Callback
This method only needs to be provided for interpreted languages. It's responsibility is to
start the interpreter.

For compiled languages, the load routine from "Inline.pm" is called which uses
"DynaLoader" to load the shared object or DLL.

The info() Callback
This method is called when the user makes use of the "INFO" shortcut. You should return a
string containing a small report about the Inlined code.

THE INLINE OBJECT

"Inline.pm" creates a hash based Perl object for each section of Inlined source code it
receives. This object contains lots of information about the code, the environment, and
the configuration options used.

This object is a hash that is broken into several subhashes. The only two subhashes that
an ILSM should use at all are $o->{API} and $o->{ILSM}. The first one contains all of the
information that Inline has gather for you in order for you to create/load a cached object
of your design. The second one is a repository where your ILSM can freely store data that
it might need later on.

This section will describe all of the Inline object "API" attributes.

The code Attribute
This the actual source code passed in by the user. It is stored as one long string.

The language Attribute
The proper name of the language being used.

The language_id Attribute
The language name specified by the user. Could be 'C++' instead of 'CPP'.

The module Attribute
This is the shared object's file name.

The modfname Attribute
This is the shared object's file name.

The modpname Attribute
This is the shared object's installation path extension.

The version Attribute
The version of "Inline.pm" being used.

The pkg Attribute
The Perl package from which this invocation pf Inline was called.

The install_lib Attribute
This is the directory to write the shared object into.

The build_dir Attribute
This is the directory under which you should write all of your build related files.

The script Attribute
This is the name of the script that invoked Inline.

The location Attribute
This is the full path name of the executable object in question.

The suffix Attribute
This is the shared library extension name. (Usually 'so' or 'dll').

derive_minus_I Method
ILSMs may need to run Perl subprocesses with a similar environment to the current one -
particularly @INC. This method can be called to return a list of absolute paths to pass to
a Perl interpreter to recreate that environment. You will need to prepend "-I" to each
one. This method omits from that list any paths that occur in $ENV{PERL5LIB} or the Perl
default libraries since those will be available already.

THE INLINE NAMESPACE

       "Inline.pm" has been set up so that anyone can write their own language support modules.
       It further allows anyone to write a different implementation of an existing Inline
       language, like C for instance. You can distribute that module on the CPAN.

       If you have plans to implement and distribute an Inline module, I would ask that you
       please work with the Inline community. We can be reached at the Inline mailing list:
       inline@perl.org (Send mail to inline-subscribe@perl.org to subscribe). Here you should
       find the advice and assistance needed to make your module a success.

       The Inline community will decide if your implementation of COBOL will be distributed as
       the official "Inline::COBOL" or should use an alternate namespace. In matters of dispute,
       I (Ingy döt Net) retain final authority.  (and I hope not to need use of it :-) Actually
       modules@perl.org retains the final authority.

       But even if you want to work alone, you are free and welcome to write and distribute
       Inline language support modules on CPAN. You'll just need to distribute them under a
       different package name.

AUTHOR

       Ingy döt Net <ingy@cpan.org>

COPYRIGHT

       Copyright 2000-2019. Ingy döt Net.

       Copyright 2008, 2010, 2011. Sisyphus.

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

       See <http://www.perl.com/perl/misc/Artistic.html>