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, 2010-2012. 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