Add wmem_map_get_keys.

Mimic functionality of g_hash_table_get_keys

Change-Id: I7702854ed771a5b3bf7ea5295a67c42f0f477cdf
Reviewed-on: https://code.wireshark.org/review/20039
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>

debian/libwireshark0.symbols

@@ -1788,6 +1788,7 @@ libwireshark.so.0 libwireshark0 #MINVER#
  wmem_list_remove_frame@Base 1.12.0~rc1
  wmem_list_tail@Base 1.12.0~rc1
  wmem_map_foreach@Base 2.1.0
+ wmem_map_get_keys@Base 2.3.0
  wmem_map_insert@Base 1.12.0~rc1
  wmem_map_lookup@Base 1.12.0~rc1
  wmem_map_new@Base 1.12.0~rc1

epan/wmem/wmem_map.c

@@ -25,6 +25,7 @@
 #include <glib.h>
 
 #include "wmem_core.h"
+#include "wmem_list.h"
 #include "wmem_map.h"
 #include "wmem_map_int.h"
 #include "wmem_user_cb.h"
@@ -322,6 +323,29 @@ wmem_map_steal(wmem_map_t *map, const void *key)
     return FALSE;
 }
 
+wmem_list_t*
+wmem_map_get_keys(wmem_allocator_t *list_allocator, wmem_map_t *map)
+{
+    size_t capacity, i;
+    wmem_map_item_t *cur;
+    wmem_list_t* list = wmem_list_new(list_allocator);
+
+    if (map->table != NULL) {
+        capacity = CAPACITY(map);
+
+        /* copy all the elements into the list over from table */
+        for (i=0; i<capacity; i++) {
+            cur = map->table[i];
+            while (cur) {
+                wmem_list_prepend(list, (void*)cur->key);
+                cur = cur->next;
+            }
+        }
+    }
+
+    return list;
+}
+
 void
 wmem_map_foreach(wmem_map_t *map, GHFunc foreach_func, gpointer user_data)
 {

epan/wmem/wmem_map.h

@@ -131,6 +131,16 @@ WS_DLL_PUBLIC
 gboolean
 wmem_map_steal(wmem_map_t *map, const void *key);
 
+/** Retrieves a list of keys inside the map
+ *
+ * @param list_allocator The allocator scope for the returned list.
+ * @param map The map to extract keys from
+ * @return list of keys in the map
+ */
+WS_DLL_PUBLIC
+wmem_list_t*
+wmem_map_get_keys(wmem_allocator_t *list_allocator, wmem_map_t *map);
+
 /** Run a function against all key/value pairs in the map. The order
  * of the calls is unpredictable, since it is based on the internal
  * storage of data.