=pod

=for comment
DO NOT EDIT. This Pod was generated by Swim v0.1.48.
See http://github.com/ingydotnet/swim-pm#readme

=encoding utf8

=head1 NAME

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

=head1 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";
    }

=head1 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.
C<Inline.pm> has support for adding your own Inline Language Support Module
(B<ILSM>), like C<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
C<Inline::Java> has a similar interface to C<Inline::ASM>. All of the common
code is in C<Inline.pm>.

Language specific modules like C<Inline::Python> are subclasses of
C<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 C<Inline::C> and the
parsing grammar is further broken out into C<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.

=head1 A SKELETON

For the remainder of this tutorial, let's assume we're writing an ILSM for the
ficticious language C<Foo>. We'll call it C<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 C<load()>, the subroutines in this code are mandatory for an ILSM.
What they do is described below. A few things to note:

=over

=item * C<Inline::Foo> must be a subclass of Inline. This is accomplished with:

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

=item * The line 'C<require Inline;>' is not necessary. But it is there to remind you not to say 'C<use Inline;>'. This will not work.

=item * Remember, it is not valid for a user to say:

    use Inline::Foo;

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

=item * 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.

=back

=head1 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 C<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.

=head2 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:

=over

=item language

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

=item aliases

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

=item type

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

=item 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 C<Config.pm>.

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

=back

=head2 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 C<Inline>, whatever case the program gave.

=head2 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. C<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 C<Inline::C>.

=head2 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 C<Inline.pm> is called which
uses C<DynaLoader> to load the shared object or DLL.

=head2 The info() Callback

This method is called when the user makes use of the C<INFO> shortcut. You
should return a string containing a small report about the Inlined code.

=head1 THE INLINE OBJECT

C<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.

=over

=item The code Attribute

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

=item The language Attribute

The proper name of the language being used.

=item The language_id Attribute

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

=item The module Attribute

This is the shared object's file name.

=item The modfname Attribute

This is the shared object's file name.

=item The modpname Attribute

This is the shared object's installation path extension.

=item The version Attribute

The version of C<Inline.pm> being used.

=item The pkg Attribute

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

=item The install_lib Attribute

This is the directory to write the shared object into.

=item The build_dir Attribute

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

=item The script Attribute

This is the name of the script that invoked Inline.

=item The location Attribute

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

=item The suffix Attribute

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

=back

=head2 derive_minus_I Method

ILSMs may need to run Perl subprocesses with a similar environment to the
current one - particularly C<@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 C<-I> to each one. This method omits from that list
any paths that occur in C<$ENV{PERL5LIB}> or the Perl default libraries since
those will be available already.

=head1 THE INLINE NAMESPACE

C<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 C<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
B<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.

=head1 SEE ALSO

For generic information about Inline, see L<Inline>.

For information about using Inline with C see L<Inline::C>.

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

Inline's mailing list is inline@perl.org

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

=head1 AUTHOR

Ingy döt Net <ingy@cpan.org>

=head1 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 L<http://www.perl.com/perl/misc/Artistic.html>

=cut
