Add addressof function to FFI::C::Util

Changes

@@ -1,6 +1,7 @@
 Revision history for {{$dist->name}}},
 
 {{$NEXT}}
+  - Add addressof function to FFI::C::Util (gh#49)
 
 0.10      2020-09-23 03:16:36 -0600
   - Add tmpfile constructor for FFI::C::File (gh#41)

author.yml

@@ -8,6 +8,7 @@ pod_spelling_system:
   stopwords:
     - ffi
     - nullable
+    - addressof
 
 pod_coverage:
   skip: 0

lib/FFI/C/PosixFile.pm

@@ -11,7 +11,7 @@ use base qw( FFI::C::File );
 =head1 SYNOPSIS
 
  use FFI::C::PosixFile;
-
+ 
  my $stdout = FFI::C::PosixFile->fdopen(1, "w");
  say $stdout->fileno;  # prints 1
 

lib/FFI/C/Util.pm

@@ -9,7 +9,7 @@ use Carp ();
 use Class::Inspector;
 use base qw( Exporter );
 
-our @EXPORT_OK = qw( perl_to_c c_to_perl take owned set_array_count );
+our @EXPORT_OK = qw( perl_to_c c_to_perl take owned set_array_count addressof );
 
 # ABSTRACT: Utility functions for dealing with structured C data
 # VERSION
@@ -174,6 +174,29 @@ sub take ($)
   $ptr;
 }
 
+=head2 addressof
+
+[version 0.11]
+
+ my $ptr = addressof $instance;
+
+This function returns the address (as an C<opaque> type) of the
+instance object.  This is similar to C<take> above in that it gets
+you the address of the object, but doesn't take ownership of it,
+so care needs to be taken when using C<$ptr> that the object
+is still allocated.
+
+=cut
+
+sub addressof ($)
+{
+  my $inst = shift;
+  Carp::croak("Not an object") unless is_blessed_ref $inst;
+  my $ptr = $inst->{ptr};
+  Carp::croak("Object pointer went away") unless $ptr;
+  $ptr;
+}
+
 =head2 set_array_count
 
  set_array_count $inst, $count;

t/ffi_c_util.t

@@ -1,5 +1,5 @@
 use Test2::V0 0.000081 -no_srand => 1;
-use FFI::C::Util qw( owned take perl_to_c c_to_perl set_array_count );
+use FFI::C::Util qw( owned take perl_to_c c_to_perl set_array_count addressof );
 use FFI::Platypus::Memory qw( free );
 use FFI::C::StructDef;
 use FFI::C::UnionDef;
@@ -29,8 +29,23 @@ subtest 'owned / take' => sub {
 
   is owned($inst), T(), 'instance is owned';
 
-  my $ptr = take $inst;
-  is $ptr, match qr/^[0-9]+$/, 'gave us a pointer';
+  my $ptr1 = addressof $inst;
+  is $ptr1, match qr/^[0-9]+$/, 'addressof is a pointer';
+
+  is
+    $inst,
+    object {
+      call [ isa => 'FFI::C::Struct' ] => T();
+      field ptr => match qr/^[0-9]+$/;
+      etc;
+    },
+    'object after addressof',
+  ;
+
+  my $ptr2 = take $inst;
+  is $ptr2, match qr/^[0-9]+$/, 'gave us a pointer';
+
+  is $ptr2, $ptr1, 'pointer from take and addressof are the same';
 
   is
     $inst,