Win32::API::Struct - C struct support package for Win32::API
use Win32::API; Win32::API::Struct->typedef( 'POINT', qw( LONG x; LONG y; )); my $Point = Win32::API::Struct->new( 'POINT' ); $Point->{x} = 1024; $Point->{y} = 768;
#### alternatively tie %Point, 'Win32::API::Struct', 'POINT'; $Point{x} = 1024; $Point{y} = 768;
This module enables you to define C structs for use with Win32::API.
See the Win32::API manpage for more info about its usage.
This module is automatically imported by Win32::API, so you don't
need to 'use' it explicitly. The main methods are typedef
and
new
, which are documented below.
typedef NAME, TYPE, MEMBER, TYPE, MEMBER, ...
This method defines a structure named NAME
. The definition consists
of types and member names, just like in C. In fact, most of the
times you can cut the C definition for a structure and paste it
verbatim to your script, enclosing it in a qw()
block. The
function takes care of removing the semicolon after the member
name.
The synopsis example could be written like this:
Win32::API::Struct->typedef('POINT', 'LONG', 'x', 'LONG', 'y');
But it could also be written like this (note the indirect object syntax), which is pretty cool:
typedef Win32::API::Struct POINT => qw{ LONG x; LONG y; };
Also note that typedef
automatically defines an 'LPNAME' type,
which holds a pointer to your structure. In the example above,
'LPPOINT' is also defined and can be used in a call to a
Win32::API (in fact, this is what you're really going to use when
doing API calls).
new NAME
This creates a structure (a Win32::API::Struct object) of the
type NAME
(it must have been defined with typedef
). In Perl,
when you create a structure, all the members are undefined. But
when you use that structure in C (eg. a Win32::API call), you
can safely assume that they will be treated as zero (or NULL).
sizeof
This returns the size, in bytes, of the structure. Acts just like the C function of the same name. It is particularly useful for structures that need a member to be initialized to the structure's own size.
align [SIZE]
Sets or returns the structure alignment (eg. how the structure is
stored in memory). This is a very advanced option, and you normally
don't need to mess with it.
All structures in the Win32 Platform SDK should work without it.
But if you define your own structure, you may need to give it an
explicit alignment. In most cases, passing a SIZE
of 'auto'
should keep the world happy.
tie
INTERFACEInstead of creating an object with the new
method, you can
tie a hash, which will hold the desired structure, using the
tie
builtin function:
tie %structure, Win32::API::Struct => 'NAME';
The differences between the tied and non-tied approaches are:
# tied # non-tied $Point{x} vs. $Point->{x}
print $Point{z}; # this will warn: 'z' is not a member of Win32::API::Struct POINT
# tied # non-tied GetCursorPos( \%Point ) vs. GetCursorPos( $Point )
Aldo Calpini ( dada@perl.it ).
Cosimo Streppone ( cosimo@cpan.org ).