Inline-API - How to bind a programming language to Perl using Inline.pm
#!/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";
}
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.
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);
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 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.
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.
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:
Inline::X for a given language 'X'.
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.
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.
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.
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.
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.
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.
This the actual source code passed in by the user. It is stored as one long string.
The proper name of the language being used.
The language name specified by the user. Could be 'C++' instead of 'CPP'.
This is the shared object's file name.
This is the shared object's file name.
This is the shared object's installation path extension.
The version of Inline.pm being used.
The Perl package from which this invocation pf Inline was called.
This is the directory to write the shared object into.
This is the directory under which you should write all of your build related files.
This is the name of the script that invoked Inline.
This is the full path name of the executable object in question.
This is the shared library extension name. (Usually 'so' or 'dll').
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.
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
Brian Ingerson <INGY@cpan.org>
Copyright (c) 2000, 2001, 2002. Brian Ingerson. All rights reserved.
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