c-list: add reverse iterators

Add reverse versions of each for_each macro, allowing for reverse
iteration of lists.

src/c-list.h

@@ -362,72 +362,136 @@ static inline CList *c_list_last(CList *list) {
  *               it assumes the entire list will be unlinked. You must not
  *               break out of the loop, or the list will be in an inconsistent
  *               state.
+ *
+ *   - "reverse": The list is iterated in reverse order.
+ *
+ * Note: macros starting with "__" are not meant to be used directly.
  */
 
 /* direct/raw iterators */
 
-#define c_list_for_each(_iter, _list)                                           \
-        for (_iter = (_list)->next;                                             \
+#define __c_list_for_each(_iter, _list, _dir)                                   \
+        for (_iter = (_list)->_dir;                                             \
              (_iter) != (_list);                                                \
-             _iter = (_iter)->next)
+             _iter = (_iter)->_dir)
 
-#define c_list_for_each_safe(_iter, _safe, _list)                               \
-        for (_iter = (_list)->next, _safe = (_iter)->next;                      \
+#define __c_list_for_each_safe(_iter, _safe, _list, _dir)                       \
+        for (_iter = (_list)->_dir, _safe = (_iter)->_dir;                      \
              (_iter) != (_list);                                                \
-             _iter = (_safe), _safe = (_safe)->next)
+             _iter = (_safe), _safe = (_safe)->_dir)
 
-#define c_list_for_each_continue(_iter, _list)                                  \
-        for (_iter = (_iter) ? (_iter)->next : (_list)->next;                   \
+#define __c_list_for_each_continue(_iter, _list, _dir)                          \
+        for (_iter = (_iter) ? (_iter)->_dir : (_list)->_dir;                   \
              (_iter) != (_list);                                                \
-             _iter = (_iter)->next)
+             _iter = (_iter)->_dir)
 
-#define c_list_for_each_safe_continue(_iter, _safe, _list)                      \
-        for (_iter = (_iter) ? (_iter)->next : (_list)->next,                   \
-             _safe = (_iter)->next;                                             \
+#define __c_list_for_each_safe_continue(_iter, _safe, _list, _dir)              \
+        for (_iter = (_iter) ? (_iter)->_dir : (_list)->_dir,                   \
+             _safe = (_iter)->_dir;                                             \
              (_iter) != (_list);                                                \
-             _iter = (_safe), _safe = (_safe)->next)
+             _iter = (_safe), _safe = (_safe)->_dir)
 
-#define c_list_for_each_safe_unlink(_iter, _safe, _list)                        \
-        for (_iter = (_list)->next, _safe = (_iter)->next;                      \
+#define __c_list_for_each_safe_unlink(_iter, _safe, _list, _dir)                \
+        for (_iter = (_list)->_dir, _safe = (_iter)->_dir;                      \
              c_list_init(_iter) != (_list);                                     \
-             _iter = (_safe), _safe = (_safe)->next)
+             _iter = (_safe), _safe = (_safe)->_dir)
+
+#define c_list_for_each(_iter, _list)                                           \
+        __c_list_for_each(_iter, _list, next)
+
+#define c_list_for_each_reverse(_iter, _list)                                   \
+        __c_list_for_each(_iter, _list, prev)
+
+#define c_list_for_each_safe(_iter, _safe, _list)                               \
+        __c_list_for_each_safe(_iter, _safe, _list, next)
+
+#define c_list_for_each_safe_reverse(_iter, _safe, _list)                       \
+        __c_list_for_each_safe(_iter, _safe, _list, prev)
+
+#define c_list_for_each_continue(_iter, _list)                                  \
+        __c_list_for_each_continue(_iter, _list, next)
+
+#define c_list_for_each_continue_reverse(_iter, _list)                          \
+        __c_list_for_each_continue(_iter, _list, prev)
+
+#define c_list_for_each_safe_continue(_iter, _safe, _list)                      \
+        __c_list_for_each_safe_continue(_iter, _safe, _list, next)
+
+#define c_list_for_each_safe_continue_reverse(_iter, _safe, _list)              \
+        __c_list_for_each_safe_continue(_iter, _safe, _list, prev)
+
+#define c_list_for_each_safe_unlink(_iter, _safe, _list)                        \
+        __c_list_for_each_safe_unlink(_iter, _safe, _list, next)
+
+#define c_list_for_each_safe_unlink_reverse(_iter, _safe, _list)                \
+        __c_list_for_each_safe_unlink(_iter, _safe, _list, prev)
 
 /* c_list_entry() based iterators */
 
-#define c_list_for_each_entry(_iter, _list, _m)                                 \
-        for (_iter = c_list_entry((_list)->next, __typeof__(*_iter), _m);       \
+#define __c_list_for_each_entry(_iter, _list, _m, _dir)                         \
+        for (_iter = c_list_entry((_list)->_dir, __typeof__(*_iter), _m);       \
              &(_iter)->_m != (_list);                                           \
-             _iter = c_list_entry((_iter)->_m.next, __typeof__(*_iter), _m))
+             _iter = c_list_entry((_iter)->_m._dir, __typeof__(*_iter), _m))
 
-#define c_list_for_each_entry_safe(_iter, _safe, _list, _m)                     \
-        for (_iter = c_list_entry((_list)->next, __typeof__(*_iter), _m),       \
-             _safe = c_list_entry((_iter)->_m.next, __typeof__(*_iter), _m);    \
+#define __c_list_for_each_entry_safe(_iter, _safe, _list, _m, _dir)             \
+        for (_iter = c_list_entry((_list)->_dir, __typeof__(*_iter), _m),       \
+             _safe = c_list_entry((_iter)->_m._dir, __typeof__(*_iter), _m);    \
              &(_iter)->_m != (_list);                                           \
              _iter = (_safe),                                                   \
-             _safe = c_list_entry((_safe)->_m.next, __typeof__(*_iter), _m))
+             _safe = c_list_entry((_safe)->_m._dir, __typeof__(*_iter), _m))
 
-#define c_list_for_each_entry_continue(_iter, _list, _m)                        \
-        for (_iter = c_list_entry((_iter) ? (_iter)->_m.next : (_list)->next,   \
+#define __c_list_for_each_entry_continue(_iter, _list, _m, _dir)                \
+        for (_iter = c_list_entry((_iter) ? (_iter)->_m._dir : (_list)->_dir,   \
                                   __typeof__(*_iter),                           \
                                   _m);                                          \
              &(_iter)->_m != (_list);                                           \
-             _iter = c_list_entry((_iter)->_m.next, __typeof__(*_iter), _m))
+             _iter = c_list_entry((_iter)->_m._dir, __typeof__(*_iter), _m))
 
-#define c_list_for_each_entry_safe_continue(_iter, _safe, _list, _m)            \
-        for (_iter = c_list_entry((_iter) ? (_iter)->_m.next : (_list)->next,   \
+#define __c_list_for_each_entry_safe_continue(_iter, _safe, _list, _m, _dir)    \
+        for (_iter = c_list_entry((_iter) ? (_iter)->_m._dir : (_list)->_dir,   \
                                   __typeof__(*_iter),                           \
                                   _m),                                          \
-             _safe = c_list_entry((_iter)->_m.next, __typeof__(*_iter), _m);    \
+             _safe = c_list_entry((_iter)->_m._dir, __typeof__(*_iter), _m);    \
              &(_iter)->_m != (_list);                                           \
              _iter = (_safe),                                                   \
-             _safe = c_list_entry((_safe)->_m.next, __typeof__(*_iter), _m))
+             _safe = c_list_entry((_safe)->_m._dir, __typeof__(*_iter), _m))
 
-#define c_list_for_each_entry_safe_unlink(_iter, _safe, _list, _m)              \
-        for (_iter = c_list_entry((_list)->next, __typeof__(*_iter), _m),       \
-             _safe = c_list_entry((_iter)->_m.next, __typeof__(*_iter), _m);    \
+#define __c_list_for_each_entry_safe_unlink(_iter, _safe, _list, _m, _dir)      \
+        for (_iter = c_list_entry((_list)->_dir, __typeof__(*_iter), _m),       \
+             _safe = c_list_entry((_iter)->_m._dir, __typeof__(*_iter), _m);    \
              c_list_init(&(_iter)->_m) != (_list);                              \
              _iter = (_safe),                                                   \
-             _safe = c_list_entry((_safe)->_m.next, __typeof__(*_iter), _m))
+             _safe = c_list_entry((_safe)->_m._dir, __typeof__(*_iter), _m))
+
+#define c_list_for_each_entry(_iter, _list, _m)                                 \
+        __c_list_for_each_entry(_iter, _list, _m, next)
+
+#define c_list_for_each_entry_reverse(_iter, _list, _m)                         \
+        __c_list_for_each_entry(_iter, _list, _m, prev)
+
+#define c_list_for_each_entry_safe(_iter, _safe, _list, _m)                     \
+        __c_list_for_each_entry_safe(_iter, _safe, _list, _m, next)
+
+#define c_list_for_each_entry_safe_reverse(_iter, _safe, _list, _m)             \
+        __c_list_for_each_entry_safe(_iter, _safe, _list, _m, prev)
+
+#define c_list_for_each_entry_continue(_iter, _list, _m)                        \
+        __c_list_for_each_entry_continue(_iter, _list, _m, next)
+
+#define c_list_for_each_entry_continue_reverse(_iter, _list, _m)                \
+        __c_list_for_each_entry_continue(_iter, _list, _m, prev)
+
+#define c_list_for_each_entry_safe_continue(_iter, _safe, _list, _m)            \
+        __c_list_for_each_entry_safe_continue(_iter, _safe, _list, _m, next)
+
+#define c_list_for_each_entry_safe_continue_reverse(_iter, _safe, _list, _m)    \
+        __c_list_for_each_entry_safe_continue(_iter, _safe, _list, _m, prev)
+
+#define c_list_for_each_entry_safe_unlink(_iter, _safe, _list, _m)              \
+        __c_list_for_each_entry_safe_unlink(_iter, _safe, _list, _m, next)
+
+#define c_list_for_each_entry_safe_unlink_reverse(_iter, _safe, _list, _m)      \
+        __c_list_for_each_entry_safe_unlink(_iter, _safe, _list, _m, prev)
 
 /**
  * c_list_flush() - flush all entries from a list

src/test-api.c

@@ -86,20 +86,37 @@ static void test_api(void) {
         c_list_for_each(list_iter, &list)
                 assert(list_iter != &list);
 
+        c_list_for_each_reverse(list_iter, &list)
+                assert(list_iter != &list);
+
         c_list_for_each_safe(list_iter, list_safe, &list)
                 assert(list_iter != &list);
 
+        c_list_for_each_safe_reverse(list_iter, list_safe, &list)
+                assert(list_iter != &list);
+
         list_iter = NULL;
         c_list_for_each_continue(list_iter, &list)
                 assert(list_iter != &list);
 
+        list_iter = NULL;
+        c_list_for_each_continue_reverse(list_iter, &list)
+                assert(list_iter != &list);
+
         list_iter = NULL;
         c_list_for_each_safe_continue(list_iter, list_safe, &list)
                 assert(list_iter != &list);
 
+        list_iter = NULL;
+        c_list_for_each_safe_continue_reverse(list_iter, list_safe, &list)
+                assert(list_iter != &list);
+
         c_list_for_each_safe_unlink(list_iter, list_safe, &list)
                 assert(list_iter != &list);
 
+        c_list_for_each_safe_unlink_reverse(list_iter, list_safe, &list)
+                assert(list_iter != &list);
+
         /* list accessors */
 
         assert(!c_list_first(&list));
@@ -118,19 +135,36 @@ static void test_api_gnu(void) {
         c_list_for_each_entry(node_iter, &list, link)
                 assert(&node_iter->link != &list);
 
+        c_list_for_each_entry_reverse(node_iter, &list, link)
+                assert(&node_iter->link != &list);
+
         c_list_for_each_entry_safe(node_iter, node_safe, &list, link)
                 assert(&node_iter->link != &list);
 
+        c_list_for_each_entry_safe_reverse(node_iter, node_safe, &list, link)
+                assert(&node_iter->link != &list);
+
         node_iter = NULL;
         c_list_for_each_entry_continue(node_iter, &list, link)
                 assert(&node_iter->link != &list);
 
+        node_iter = NULL;
+        c_list_for_each_entry_continue_reverse(node_iter, &list, link)
+                assert(&node_iter->link != &list);
+
         node_iter = NULL;
         c_list_for_each_entry_safe_continue(node_iter, node_safe, &list, link)
                 assert(&node_iter->link != &list);
 
+        node_iter = NULL;
+        c_list_for_each_entry_safe_continue_reverse(node_iter, node_safe, &list, link)
+                assert(&node_iter->link != &list);
+
         c_list_for_each_entry_safe_unlink(node_iter, node_safe, &list, link)
                 assert(&node_iter->link != &list);
+
+        c_list_for_each_entry_safe_unlink_reverse(node_iter, node_safe, &list, link)
+                assert(&node_iter->link != &list);
 }
 #else
 static void test_api_gnu(void) {

src/test-basic.c

@@ -123,6 +123,106 @@ static void test_iterators(void) {
         assert(c_list_is_empty(&list));
 }
 
+static void test_iterators_reverse(void) {
+        CList *iter, *safe, a, b, list = C_LIST_INIT(list);
+        unsigned int i;
+
+        assert(!c_list_first(&list));
+        assert(!c_list_last(&list));
+
+        /* link @a and verify iterators see just it */
+
+        c_list_link_tail(&list, &a);
+        assert(c_list_is_linked(&a));
+        assert(c_list_first(&list) == &a);
+        assert(c_list_last(&list) == &a);
+
+        i = 0;
+        c_list_for_each_reverse(iter, &list) {
+                assert(iter == &a);
+                ++i;
+        }
+        assert(i == 1);
+
+        i = 0;
+        iter = NULL;
+        c_list_for_each_continue_reverse(iter, &list) {
+                assert(iter == &a);
+                ++i;
+        }
+        assert(i == 1);
+
+        i = 0;
+        iter = &a;
+        c_list_for_each_continue_reverse(iter, &list)
+                ++i;
+        assert(i == 0);
+
+        /* link @b as well and verify iterators again */
+
+        c_list_link_tail(&list, &b);
+        assert(c_list_is_linked(&a));
+        assert(c_list_is_linked(&b));
+
+        i = 0;
+        c_list_for_each_reverse(iter, &list) {
+                assert((i == 0 && iter == &b) ||
+                       (i == 1 && iter == &a));
+                ++i;
+        }
+        assert(i == 2);
+
+        i = 0;
+        iter = NULL;
+        c_list_for_each_continue_reverse(iter, &list) {
+                assert((i == 0 && iter == &b) ||
+                       (i == 1 && iter == &a));
+                ++i;
+        }
+        assert(i == 2);
+
+        i = 0;
+        iter = &b;
+        c_list_for_each_continue_reverse(iter, &list) {
+                assert(iter == &a);
+                ++i;
+        }
+        assert(i == 1);
+
+        i = 0;
+        iter = &a;
+        c_list_for_each_continue_reverse(iter, &list)
+                ++i;
+        assert(i == 0);
+
+        /* verify safe-iterator while removing elements */
+
+        i = 0;
+        c_list_for_each_safe_reverse(iter, safe, &list) {
+                assert(iter == &a || iter == &b);
+                c_list_unlink_stale(iter);
+                ++i;
+        }
+        assert(i == 2);
+
+        assert(c_list_is_empty(&list));
+
+        /* link both and verify *_unlink() iterators */
+
+        c_list_link_tail(&list, &a);
+        c_list_link_tail(&list, &b);
+
+        i = 0;
+        c_list_for_each_safe_unlink_reverse(iter, safe, &list) {
+                assert(iter == &a || iter == &b);
+                assert(!c_list_is_linked(iter));
+                ++i;
+        }
+        assert(i == 2);
+
+        assert(c_list_is_empty(&list));
+}
+
 static void test_swap(void) {
         CList list1 = (CList)C_LIST_INIT(list1);
         CList list2 = (CList)C_LIST_INIT(list2);
@@ -309,6 +409,7 @@ static void test_gnu(void) {
 
 int main(void) {
         test_iterators();
+        test_iterators_reverse();
         test_swap();
         test_splice();
         test_split();