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Subject: [OMPI devel] RFC: opal_list iteration macros
From: Nathan Hjelm (hjelmn_at_[hidden])
Date: 2013-01-29 12:08:52


What: Add two new macros to opal_list.h:

#define opal_list_foreach(item, list, type) \
  for (item = (type *) (list)->opal_list_sentinel.opal_list_next ; \
       item != (type *) &(list)->opal_list_sentinel ; \
       item = (type *) ((opal_list_item_t *) (item))->opal_list_next)

#define opal_list_foreach_safe(item, next, list, type) \
  for (item = (type *) (list)->opal_list_sentinel.opal_list_next, \
         next = (type *) ((opal_list_item_t *) (item))->opal_list_next ;\
       item != (type *) &(list)->opal_list_sentinel ; \
       item = next, next = (type *) ((opal_list_item_t *) (item))->opal_list_next)

The first macro provides a simple iterator over an unchanging list and the second macro is safe for opal_list_item_remove(item).

Why: These macros provide a clean way to do the following:

for (item = opal_list_get_first (list) ;
     item != opal_list_get_end (list) ;
     item = opal_list_get_next (item)) {
   some_class_t *foo = (some_class_t *) foo;
   ...
}

becomes:

some_class_t *foo;

opal_list_foreach(foo, list, some_class_t) {
   ...
}

When: This is a very simple addition but I wanted to give a heads up on the devel list because these macros are different from what we usually provide (though they should look familiar to those familiar with the Linux kernel). I intend to commit these macros to the truck (and CMR for 1.7.1) tomorrow (Wed 01/29/13) around 12:00 PM MST.

Thoughs? Comments?

-Nathan Hjelm
HPC-3, LANL