=head1 XSBuilder - Autogenerating XS-glue Code
O'Reilly OpenSource Convention 2002
Gerald Richter
ecos gmbh
http://www.ecos.de
=head1 XSBuilder - What is it?
=head2 It's purpose is to automaticly generate a Perl interface to C Code
=head2 Solves the problem, that the Perl interface is not always uptodate with the C interface
=head2 Saves a lot of Copy&Paste work
=head2 Systematical changes have to be done only once
For example changes in the memory management of strings.
=head2 Is part of mod_perl 2.0 build system
Most code is developed by Doug MacEachern. Additionaly I have
=over
=item abstracted the code from mod_perl so it's useable for any C code
=item added new features like callbacks and the ability to parse comments
=item Replaced C::Scan with a Parse::RecDescent to be platform and compiler independend
=back
Goal is to replace the current mod_perl XS generation code with XSBuilder
=head2 Inline versus XSBuilder
=over
=item Inline: embed C-Code into Perl
=item XSBuilder: Create interface for existing C-libraries/applicationen
=back
=head1 XSBuilder - What does it do?
=head2 Create Perl functions/methods for every C function
The function can be assigned to different packages, also automaticly
by inspecting the first parameter
=head2 Create a Perl class for every C structure
Every element of structure becomes a Perl method to get/set it's value.
The object can be either a scalar reference (used by mod_perl) or
a reference to a hash (use by Embperl), which allows to store extra
data by the Perl code into this hash.
=head2 Create glue code to handle callbacks
There several sorts of callback, not all are implemented right now
=head2 Create Perl constant subs
Coming soon...
=head1 XSBuilder - How does it work?
=head2 Parse the C header files
Extract
=over
=item Functions, their arguments and return types
=item Structures and it's members
=item Constants
=item Callbacks
=back
and create four tables which contains the results
=head2 Create the XS code
Input is
=over
=item The source tables
=item Mapfiles which contains the mapping from C to Perl
=item Addtional C and Perl code that can be used to customize the interface
=back
Output is
=over
=item The XS files (one form every generated class)
=item Makefile.PL for every class
=item pm files
=back
=head1 Parse the source
=head2 Create your own ParseSource class and override methods...
package Apache::DAV::ParseSource;
use strict;
use vars qw{@ISA $VERSION} ;
use ExtUtils::XSBuilder::ParseSource ;
@ISA = ('ExtUtils::XSBuilder::ParseSource') ;
$VERSION = '0.01';
my $dav_dir = 'C:\perl\msrc\cvs\mod_dav' ;
my $ap_dir = 'c:\programme\apache group\apache' ;
# ============================================================================
sub find_includes {
my $self = shift;
return $self->{includes} if $self->{includes};
my @includes = ("$ap_dir/include/ap_alloc.h", "$dav_dir/mod_dav.h") ;
return $self->{includes} = $self -> sort_includes (\@includes) ;
}
# ============================================================================
sub package { 'Apache::DAV' }
# ============================================================================
sub preprocess {
my $self = shift ;
$_[0] =~ s/(?:API_EXPORT)(?:_NONSTD)?\s*\(\s*(.*?)\s*\)/$1/g ;
}
1;
=head2 ...run it
use FindBin ;
use lib ($FindBin::Bin) ;
require ParseSource ;
Apache::DAV::ParseSource -> run ;
=head2 ...and you get
C:\perl\msrc\davint>perl xsbuilder\source_scan.pl
Will use mod_dav in C:\perl\msrc\cvs\mod_dav
Will use Apache in c:\programme\apache group\apache
Initialize parser
scan c:\programme\apache group\apache/include/ap_alloc.h ...
constant: APACHE_ALLOC_H
func: ap_init_alloc
func: ap_cleanup_alloc
func: ap_make_sub_pool
func: ap_destroy_pool
constant: ap_pool_join
func: ap_pool_join
func: ap_find_pool
func: ap_pool_is_ancestor
func: ap_clear_pool
func: ap_cleanup_for_exec
func: ap_palloc
func: ap_pcalloc
func: ap_pstrdup
func: ap_pstrndup
func: ap_pstrcat
func: ap_pvsprintf
valuefield: ap_pool * : pool
valuefield: int : elt_size
valuefield: int : nelts
valuefield: int : nalloc
valuefield: char * : elts
struct: (type=array_header)
...
=head2 The result is stored in four tables
=over
=item xsbuilder/tables/Apache/DAV/FuntionTable.pm
Contains all function, it arguments and comments
=item xsbuilder/tables/Apache/DAV/ConstantTable.pm
Contains all constants
=item xsbuilder/tables/Apache/DAV/StructureTable.pm
Contains all structures, it's members and their comments
=item xsbuilder/tables/Apache/DAV/CallbackTable.pm
Contains all callback function definitions
=back
=head1 Create the map files
=head2 Mapfiles are used to tell XSBuilder how C datatypes, structures
and function aruments should be mapped into Perl ones.
=head2 Create your own WrapXS class and override methods
package Apache::DAV::WrapXS ;
use strict;
use vars qw{@ISA $VERSION} ;
use ExtUtils::XSBuilder::WrapXS ;
@ISA = ('ExtUtils::XSBuilder::WrapXS') ;
$VERSION = '0.01';
# ============================================================================
sub new_parsesource { [ Apache::DAV::ParseSource->new ] }
# ============================================================================
sub my_xs_prefix { 'davxs_' }
# ============================================================================
sub h_filename_prefix { 'moddav_xs_' }
# ============================================================================
sub xs_includes {
my $self = shift ;
my $i = $self -> SUPER::xs_includes ;
my @i = grep (!/ap_alloc/, @$i) ;
return \@i ;
}
=head2 XSBuilder can create/update initial maps for you
use FindBin ;
use lib ($FindBin::Bin) ;
require ParseSource ;
require WrapXS ;
Apache::DAV::WrapXS->checkmaps (' ');
=head2 run it
C:\perl\msrc\davint>perl xsbuilder\xs_check.pl
Will use mod_dav in C:\perl\msrc\cvs\mod_dav
Will use Apache in c:\programme\apache group\apache
Parse xsbuilder\maps/_types.map...
WARNING: No *_function.map file found in xsbuilder\maps
WARNING: No *_callback.map file found in xsbuilder\maps
WARNING: No *_structure.map file found in xsbuilder\maps
Write xsbuilder\maps/new_function.map...
Write xsbuilder\maps/new_callback.map...
Write xsbuilder\maps/new_structure.map...
Write xsbuilder\maps/new_type.map...
=head2 Now we have four map files
=over 4
=item new_types.map
Contains the mapping from C type to Perl classes
=item new_functions.map
Contains the mapping form C functions to Perl functions. Can be used to
reorder arguments, tell XSBuilder which arguments are actualy return values
and in which Perl package the function will be created.
=item new_structures.map
Contains the mapping from C structures to Perl classes and defines for which
members a access methods should be created. You can also specify if you want a
C<new> method for the class.
=item new_callbacks.map
Contains the mapping form C callback functions to Perl callback functions. Can be used to
reorder arguments, tell XSBuilder which arguments are actualy return values
and in which Perl package the function will be created.
=back
It's a good idea to rename the prefix from C<new_> to something unique, here we use C<dav>
Everytime you rerun checkmaps, XSBuilder will create new_* files with the items
that are not already part of the other maps.
=head2 Next step is to customize the maps...
=head1 type map
=head2 autogenerated dav_type.map
DIR |
FILE |
HANDLE |
array_header |
dav_buffer |
dav_dyn_context |
dav_dyn_hooks |
dav_dyn_module |
dav_dyn_provider |
dav_error |
dav_get_props_result |
dav_hooks_liveprop |
dav_hooks_locks |
dav_hooks_repository |
dav_if_header |
dav_if_state_type |
...
=head2 Add Perl classes
struct array_header | Apache::Array
struct dav_buffer |
struct dav_datum | Apache::DAV::Datum
struct dav_dyn_context | Apache::DAV::DynContext
struct dav_dyn_hooks | Apache::DAV::DynHooks
struct dav_dyn_module | Apache::DAV::DynModule
struct dav_dyn_provider | Apache::DAV::DynProvider
struct dav_error | Apache::DAV::Error
struct dav_get_props_result | Apache::DAV::PropsResult
struct dav_hooks_db | Apache::DAV::HooksDb
struct dav_hooks_liveprop | Apache::DAV::HooksLiveprop
struct dav_hooks_locks | Apache::DAV::HooksLocks
struct dav_hooks_repository | Apache::DAV::HooksRepository
struct dav_hooks_vsn |
struct dav_if_header | Apache::DAV::IfHeader
struct dav_if_state_list | Apache::DAV::StateList
...
struct pool | Apache::Pool
struct request_rec | Apache::
struct server_rec | Apache::Server
...
Defines the mapping from C datatypes to Perl datatypes and classes
and tells XSBuilder which datatype are (like) structures
=head1 function map
Function map defines the mapping from C functions arguments to Perl arguments
=over
=item Tell XSBuilder where to place functions and which prefix to strip
MODULE=Apache::DAV PACKAGE=guess PREFIX=dav_
=item Simple entries in the function map will be mapped 1:1 from C to Perl
dav_add_response
dav_buffer_append
dav_buffer_init
dav_buffer_place
dav_buffer_place_mem
dav_check_bufsize
dav_close_propdb
dav_collect_liveprop_uris
dav_dyn_module_add
dav_empty_elem
...
=item The following map file entry tells XSBuilder that the value of C<res_p> should be returned
dav_get_resource | | r, <res_p
The C function
int dav_get_resource(request_rec *r, dav_resource **res_p) ;
How to call it from Perl
# get a sub request of the actual document
$subr = $r -> lookup_uri($uri);
# get a mod_dav resource object
my ($err, $resource) = $subr->get_resource;
=item You can let XSBuilder insert your custom code, for the interface
If you call C<get_props> from Perl C<glue_dav_get_props> will be called, which can adjust
the arguments and return types as necessary. The actual code for C<glue_dav_get_props>
will be taken from separate include file.
dav_get_props | glue_
dav_get_allprops | glue_
xsinclude\Apache\DAV\PropResult\Apache__DAV__PropResults.h
dav_get_props_result * dav_glue_get_props(dav_propdb * db, dav_xml_doc *doc)
{
dav_get_props_result * result = (dav_get_props_result *)ap_palloc (db -> p, sizeof (dav_get_props_result)) ;
*result = dav_get_props(db, doc) ;
return result ;
}
=item Arguments can be replaced
MODULE=Apache::Array PACKAGE=Apache::Array PREFIX=ap_
ap_make_array | ap_make_array(r->pool, nelts, elt_size) | request_rec *:r, nelts, elt_size
ap_make_array requires a pool a it's first parameter, we pass the request_rec from Perl and
XSBuilder will take the pool from the request_rec.
=back
=head1 structure map
MALLOC=strdup:$dest = ($type)strdup($src)
FREE=strdup:free($src)
<dav_xml_elem>
name
ns
lang
first_cdata
following_cdata
parent
next
first_child
attr
last_child
ns_scope
propid
provider
ns_map
new
</dav_xml_elem>
MALLOC=strdup:$dest = ($type)ap_pstrdup(obj -> pool, $src)
<array_header>
pool
elt_size
nelts
nalloc
elts
private
</array_header>
=head2 Create a accessor functions for every element and, if requested, a new method
$setprop = Apache::DAV::XMLElem -> new ({name => 'prop'}) ;
$elem = Apache::DAV::XMLElem -> new ({name => $name, ns => $namespaces}) ;
$setprop -> first_child($elem) ;
$first = $setprop -> first_child ;
=head2 some datatypes, like strings, requires dynamic allocated memory
From _types.map,which conatins a set of standard types
int | IV
int * | UNDEFINED
unsigned int | UV
signed int | IV
long | IV
long int | IV
unsigned long | UV
unsigned | UV
char * | PV | | | strdup
const char * | PV | | | strdup
const char ** | UNDEFINED
char const * | PV | | | strdup
unsigned char * | PV | | | strdup
const unsigned char * | PV | | | strdup
...
=head1 callback maps
Callback maps have the same options a function maps
# dav_hooks_db -> open
dav_error *(*)(pool * p,const dav_resource * resource,int ro,dav_db * * pdb) | p, resource, ro=0, <pdb
# dav_hooks_lock -> has_locks
dav_error *(*)(dav_lockdb * lockdb,const dav_resource * resource,int * locks_present)
=head1 Generate the XS files
use FindBin ;
use lib ($FindBin::Bin) ;
require ParseSource ;
require WrapXS ;
Apache::DAV::WrapXS->run;
=head2 ...and run...
C:\perl\msrc\davint>perl xsbuilder\xs_generate.pl
Will use mod_dav in C:\perl\msrc\cvs\mod_dav
Will use Apache in c:\programme\apache group\apache
Parse xsbuilder\maps/_types.map...
Parse xsbuilder\maps/dav_type.map...
mkdir xs
writing...xs//typemap
Parse xsbuilder\maps/dav_functions.map...
WARNING: Cannot map type int(*)(void * ,const char * ,const char * ) for function ap_table_do
WARNING: Cannot map type dav_buffer * for function dav_buffer_append
WARNING: Cannot map type dav_buffer * for function dav_buffer_init
WARNING: Cannot map type dav_buffer * for function dav_buffer_place
WARNING: Cannot map type dav_buffer * for function dav_buffer_place_mem
WARNING: Cannot map type dav_buffer * for function dav_check_bufsize
WARNING: Cannot map return type int * for function dav_collect_liveprop_uris
WARNING: Cannot map type dav_resource * * for function dav_ensure_resource_writable
WARNING: Cannot map type dav_buffer * for function dav_lock_get_activelock
WARNING: Cannot map type dav_buffer * for function dav_set_bufsize
WARNING: Cannot map type int * for function dav_xml2text
struct array_header...
Parse xsbuilder\maps/dav_structure.map...
elt_size...
nelts...
nalloc...
elts...
struct dav_buffer...
struct dav_datum...
dptr...
dsize...
struct dav_dyn_context...
=head1 Makefile.PL
=head2 We need create a top level Makefile.PL
use ExtUtils::MakeMaker ();
my $apdir = '/path/to/apache';
my $davdir = '/path/to/moddav';
%MMARGS = (
'INC' => "-I\"$davdir\" -I\"$apdir/include\" -I\"$apdir/os/unix\" -I\"$dir/xs\" -I\"$dir/xsinclude\"",
) ;
open FH, ">xs/mmargs.pl" or die "Cannot open xs/mmargs.pl ($!)" ;
print FH Data::Dumper -> Dump ([\%MMARGS], ['MMARGS']) ;
close FH ;
ExtUtils::MakeMaker::WriteMakefile(
'NAME' => 'Apache::DAV',
'VERSION' => '0.13',
%MMARGS,
);
=head2 Makefile.PL's for all class are generated automaticly
C:\perl\msrc\davint>perl Makefile.PL
Will use Apache in c:\programme\apache group\apache
Will use mod_dav in C:\perl\msrc\cvs\mod_dav
Checking if your kit is complete...
Looks good
Writing Makefile for Apache::Array
Writing Makefile for Apache::DAV::Datum
Writing Makefile for Apache::DAV::DynContext
Writing Makefile for Apache::DAV::DynHooks
Writing Makefile for Apache::DAV::DynModule
Writing Makefile for Apache::DAV::DynProvider
Writing Makefile for Apache::DAV::Error
Writing Makefile for Apache::DAV::HooksDb
Writing Makefile for Apache::DAV::HooksLiveprop
Writing Makefile for Apache::DAV::HooksLocks
Writing Makefile for Apache::DAV::HooksRepository
Writing Makefile for Apache::DAV::IfHeader
Writing Makefile for Apache::DAV::Lock
Writing Makefile for Apache::DAV::LockDB
Writing Makefile for Apache::DAV::LockTokenList
Writing Makefile for Apache::DAV::LockupResult
Writing Makefile for Apache::DAV::PropCtx
Writing Makefile for Apache::DAV::PropsResult
Writing Makefile for Apache::DAV::Resource
Writing Makefile for Apache::DAV::Response
Writing Makefile for Apache::DAV::StateList
Writing Makefile for Apache::DAV::Text
Writing Makefile for Apache::DAV::TextHeader
Writing Makefile for Apache::DAV::WalkerCtx
Writing Makefile for Apache::DAV::XMLAttr
Writing Makefile for Apache::DAV::XMLDoc
Writing Makefile for Apache::DAV::XMLElem
Writing Makefile for Apache::DAV
Writing Makefile for Apache::TableEntry
Writing Makefile for Apache
Writing Makefile for WrapXS
Writing Makefile for Apache::DAV
=head2 and now compile...
=head1 How does it go on...
=head2 Generating documentation
XSBuilder already extracts source comments for functions and structures.
It also parses doxygen comments, which are used in Apache 2.0.
Lyle Brooks has started on automaticly createing POD files from this information.
=head2 Improving callbacks
Callbacks are the main area that needs improvement.
=head2 Bring it back to mod_perl 2.0
=head2 First version will be released just after the conference to CPAN
=head2 Any feedback and help appreciated
=head2 Questions?