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Inline-API(3)		       User Contributed Perl Documentation		    Inline-API(3)

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:

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

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

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

       3.  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.

       4.  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
	   occurances 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.

   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').

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 (Brian Ingerson) 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.

SEE ALSO
       For generic information about Inline, see Inline.

       For information about using Inline with C see Inline::C.

       For information on supported languages and platforms see Inline-Support.

       Inline's mailing list is inline@perl.org

       To subscribe, send email to inline-subscribe@perl.org

AUTHOR
       Brian Ingerson <INGY@cpan.org>

COPYRIGHT
       Copyright (c) 2000-2002. Brian Ingerson.

       Copyright (c) 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

perl v5.16.3				    2012-11-20				    Inline-API(3)
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