vppinfra: add pool_foreach_pointer()

Works on pools of pointers...

Type: improvement
Change-Id: I194dec389ca4c5ec2ce3361b54a9968c9caecefc
Signed-off-by: Damjan Marion <damarion@cisco.com>

.clang-format

@@ -13,6 +13,7 @@ ForEachMacros:
   - 'clib_bitmap_foreach'
   - 'pool_foreach'
   - 'pool_foreach_index'
+  - 'pool_foreach_pointer'
   - 'vec_foreach'
   - 'vec_foreach_backwards'
   - 'vec_foreach_index'

src/vppinfra/pool.h

@@ -568,6 +568,13 @@ do {									\
 						(s));                               \
        (i) < (e); (i) = pool_get_next_index ((v), (i)))
 
+/* works only for pool of pointers, e is declared inside macro */
+#define pool_foreach_pointer(e, p)                                            \
+  if (p)                                                                      \
+    for (typeof ((p)[0]) *_t = (p) + pool_get_first_index (p), (e) = *_t;     \
+	 _t < vec_end (p);                                                    \
+	 _t = (p) + pool_get_next_index (p, _t - (p)), (e) = *_t)
+
 /**
  * @brief Remove all elements from a pool in a safe way
  *