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[Libguestfs] [PATCH v3] perl: Add explicit close() method (RHBZ#602592).



This contains some minor improvements on the previous iteration.  The
only significant change is that we no longer construct the whole hash
from the XS code, since that's quite complex and error-prone.  Instead
the C _create function returns a plain IV and we construct the hashref
on the Perl side.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://et.redhat.com/~rjones/libguestfs/
See what it can do: http://et.redhat.com/~rjones/libguestfs/recipes.html
>From eb566f7dc7974b42ac65729a2e5e5bcee329a0a9 Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones redhat com>
Date: Thu, 10 Jun 2010 15:25:43 +0100
Subject: [PATCH] perl: Add explicit close() method (RHBZ#602592).

This add an optional explicit $g->close method which may be
used to force the handle to be closed immediately.  Note the
provisos about this method in the manual page entry.  Callers
should *not* normally use this method.

The implementation of the handle also changes.  Before, the
handle was a blessed reference to an integer (the integer
being the pointer to the C guestfs_h handle).  Now we change
this to a hashref containing currently the following field:

  _g => pointer to C guestfs_h handle (as an integer)

If this field is not present, it means that the handle has been
explicitly closed.  This avoids double-freeing the handle.

The user may add their own fields to this hash in order to store
per-handle data.  However any fields whose names begin with
an underscore are reserved for use by the Perl bindings.

This commit also adds a regression test.

This commit also changes the existing warning when you call
a method without a Sys::Guestfs handle as the first parameter,
into an error.  This is because such cases are always errors.
---
 perl/t/800-explicit-close.t |   51 +++++++++++++++++++++++++++++++++++++++++++
 perl/typemap                |   17 +++++++++-----
 src/generator.ml            |   41 ++++++++++++++++++++++++++++++++-
 3 files changed, 101 insertions(+), 8 deletions(-)
 create mode 100644 perl/t/800-explicit-close.t

diff --git a/perl/t/800-explicit-close.t b/perl/t/800-explicit-close.t
new file mode 100644
index 0000000..8185168
--- /dev/null
+++ b/perl/t/800-explicit-close.t
@@ -0,0 +1,51 @@
+# libguestfs Perl bindings -*- perl -*-
+# Copyright (C) 2010 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+# Test implicit vs explicit closes of the handle (RHBZ#602592).
+
+use strict;
+use warnings;
+use Test::More tests => 10;
+
+use Sys::Guestfs;
+
+my $g;
+
+$g = Sys::Guestfs->new ();
+ok($g);
+$g->close ();                   # explicit close
+ok($g);
+undef $g;                       # implicit close - should be no error/warning
+ok(1);
+
+# Expect an error if we call a method on a closed handle.
+$g = Sys::Guestfs->new ();
+ok($g);
+$g->close ();
+ok($g);
+eval { $g->set_memsize (512); };
+ok($g);
+ok($@ && $@ =~ /closed handle/);
+undef $g;
+ok(1);
+
+# Try calling a method without a blessed reference.  This should
+# give a different error.
+eval { Sys::Guestfs::set_memsize (undef, 512); };
+ok ($@ && $@ =~ /not.*blessed/);
+eval { Sys::Guestfs::set_memsize (42, 512); };
+ok ($@ && $@ =~ /not.*blessed/);
diff --git a/perl/typemap b/perl/typemap
index 752ca0d..d978e60 100644
--- a/perl/typemap
+++ b/perl/typemap
@@ -6,13 +6,18 @@ int64_t	  	T_IV
 
 INPUT
 O_OBJECT_guestfs_h
-    if (sv_isobject ($arg) && SvTYPE (SvRV ($arg)) == SVt_PVMG)
-        $var = ($type) SvIV ((SV *) SvRV ($arg));
-    else {
-        warn (\"${Package}::$func_name(): $var is not a blessed SV reference\");
-        XSRETURN_UNDEF;
+    if (sv_isobject ($arg) && sv_derived_from ($arg, \"Sys::Guestfs\") &&
+        SvTYPE ($arg) == SVt_RV &&
+        SvTYPE (SvRV ($arg)) == SVt_PVHV) {
+        HV *hv = (HV *) SvRV ($arg);
+        SV **svp = hv_fetch (hv, \"_g\", 2, 0);
+        if (svp == NULL)
+            croak (\"${Package}::$func_name(): called on a closed handle\");
+        $var = ($type) SvIV (*svp);
+    } else {
+        croak (\"${Package}::$func_name(): $var is not a blessed HV reference\");
     }
 
 OUTPUT
 O_OBJECT_guestfs_h
-    sv_setref_pv ($arg, "Sys::Guestfs", (void *) $var);
+    sv_setiv ($arg, PTR2IV ($var));
diff --git a/src/generator.ml b/src/generator.ml
index cf28978..571870d 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -8821,10 +8821,30 @@ _create ()
       RETVAL
 
 void
-DESTROY (g)
+DESTROY (sv)
+      SV *sv;
+ PPCODE:
+      /* For the 'g' argument above we do the conversion explicitly and
+       * don't rely on the typemap, because if the handle has been
+       * explicitly closed we don't want the typemap conversion to
+       * display an error.
+       */
+      HV *hv = (HV *) SvRV (sv);
+      SV **svp = hv_fetch (hv, \"_g\", 2, 0);
+      if (svp != NULL) {
+        guestfs_h *g = (guestfs_h *) SvIV (*svp);
+        assert (g != NULL);
+        guestfs_close (g);
+      }
+
+void
+close (g)
       guestfs_h *g;
  PPCODE:
       guestfs_close (g);
+      /* Avoid double-free in DESTROY method. */
+      HV *hv = (HV *) SvRV (ST(0));
+      (void) hv_delete (hv, \"_g\", 2, G_DISCARD);
 
 ";
 
@@ -9179,11 +9199,28 @@ sub new {
   my $proto = shift;
   my $class = ref ($proto) || $proto;
 
-  my $self = Sys::Guestfs::_create ();
+  my $g = Sys::Guestfs::_create ();
+  my $self = { _g => $g };
   bless $self, $class;
   return $self;
 }
 
+=item $h->close ();
+
+Explicitly close the guestfs handle.
+
+B<Note:> You should not usually call this function.  The handle will
+be closed implicitly when its reference count goes to zero (eg.
+when it goes out of scope or the program ends).  This call is
+only required in some exceptional cases, such as where the program
+may contain cached references to the handle 'somewhere' and you
+really have to have the close happen right away.  After calling
+C<close> the program must not call any method (including C<close>)
+on the handle (but the implicit call to C<DESTROY> that happens
+when the final reference is cleaned up is OK).
+
+=cut
+
 " max_proc_nr;
 
   (* Actions.  We only need to print documentation for these as
-- 
1.6.6.1


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