perl plugin: Added Collectd::call_by_name().

This XSUB passes on a function call to a subroutine identified by its name
passed through $Collectd::cb_name. Collectd::call_by_name does not touch the
stack (unless in case of an error), thus any arguments and return values are
kept in place.

This function is meant to be used inside Collectd.pm only.

Signed-off-by: Sebastian Harl <sh@tokkee.org>
Signed-off-by: Florian Forster <octo@huhu.verplant.org>

diff --git a/src/perl.c b/src/perl.c
index fbbe591..4ae3cd1 100644 (file)
--- a/src/perl.c
+++ b/src/perl.c
@@ -51,6 +51,10 @@
 # error "Perl does not support ithreads!"
 #endif /* !defined(USE_ITHREADS) */
 
+/* clear the Perl sub's stack frame
+ * (this should only be used inside an XSUB) */
+#define CLEAR_STACK_FRAME PL_stack_sp = PL_stack_base + *PL_markstack_ptr
+
 #define PLUGIN_INIT     0
 #define PLUGIN_READ     1
 #define PLUGIN_WRITE    2
@@ -73,6 +77,7 @@ static XS (Collectd_plugin_register_ds);
 static XS (Collectd_plugin_unregister_ds);
 static XS (Collectd_plugin_dispatch_values);
 static XS (Collectd_plugin_log);
+static XS (Collectd_call_by_name);
 
 /*
  * private data types
@@ -121,6 +126,7 @@ static struct {
        { "Collectd::plugin_unregister_data_set", Collectd_plugin_unregister_ds },
        { "Collectd::plugin_dispatch_values",     Collectd_plugin_dispatch_values },
        { "Collectd::plugin_log",                 Collectd_plugin_log },
+       { "Collectd::call_by_name",               Collectd_call_by_name },
        { "", NULL }
 };
 
@@ -735,6 +741,35 @@ static XS (Collectd_plugin_log)
 } /* static XS (Collectd_plugin_log) */
 
 /*
+ * Collectd::call_by_name (...).
+ *
+ * Call a Perl sub identified by its name passed through $Collectd::cb_name.
+ */
+static XS (Collectd_call_by_name)
+{
+       SV   *tmp  = NULL;
+       char *name = NULL;
+
+       if (NULL == (tmp = get_sv ("Collectd::cb_name", 0))) {
+               log_debug ("Collectd::call_by_name: cb_name is not set.");
+               CLEAR_STACK_FRAME;
+               return;
+       }
+
+       name = SvPV_nolen (tmp);
+
+       if (NULL == get_cv (name, 0)) {
+               log_err ("Collectd::call_by_name: Unknown callback \"%s\".", name);
+               CLEAR_STACK_FRAME;
+               return;
+       }
+
+       /* simply pass on the subroutine call without touching the stack,
+        * thus leaving any arguments and return values in place */
+       call_pv (name, 0);
+} /* static XS (Collectd_call_by_name) */
+
+/*
  * collectd's perl interpreter based thread implementation.
  *
  * This has been inspired by Perl's ithreads introduced in version 5.6.0.