Add wmem_map_new_autoreset

This can be used similarly to wmem_tree_new_autoreset for hash tables that need
reset after capture file change.

Change-Id: I3a2f0b0a0cad3eca46266523c594d3d7aac17489
Reviewed-on: https://code.wireshark.org/review/19794
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Evan Huus <eapache@gmail.com>

3 files changed, 122 insertions, 4 deletions

diff --git a/epan/wmem/wmem_map.c b/epan/wmem/wmem_map.c
index 4355ce5c50..c91d062ba9 100644
--- a/epan/wmem/wmem_map.c
+++ b/epan/wmem/wmem_map.c
@@ -20,12 +20,14 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
+#include "config.h"
 
 #include <glib.h>
 
 #include "wmem_core.h"
 #include "wmem_map.h"
 #include "wmem_map_int.h"
+#include "wmem_user_cb.h"
 
 static guint32 x; /* Used for universal integer hashing (see the HASH macro) */
 
@@ -64,6 +66,10 @@ struct _wmem_map_t {
     GHashFunc  hash_func;
     GEqualFunc eql_func;
 
+    guint      master_cb_id;
+    guint      slave_cb_id;
+
+    wmem_allocator_t *master;
     wmem_allocator_t *allocator;
 };
 
@@ -81,6 +87,14 @@ struct _wmem_map_t {
 #define HASH(MAP, KEY) \
     ((guint32)(((MAP)->hash_func(KEY) * x) >> (32 - (MAP)->capacity)))
 
+static void
+wmem_map_init_table(wmem_map_t *map)
+{
+    map->count     = 0;
+    map->capacity  = WMEM_MAP_DEFAULT_CAPACITY;
+    map->table     = wmem_alloc0_array(map->allocator, wmem_map_item_t*, CAPACITY(map));
+}
+
 wmem_map_t *
 wmem_map_new(wmem_allocator_t *allocator,
         GHashFunc hash_func, GEqualFunc eql_func)
@@ -89,12 +103,59 @@ wmem_map_new(wmem_allocator_t *allocator,
 
     map = wmem_new(allocator, wmem_map_t);
 
-    map->count     = 0;
-    map->capacity  = WMEM_MAP_DEFAULT_CAPACITY;
-    map->table     = wmem_alloc0_array(allocator, wmem_map_item_t*, CAPACITY(map));
     map->hash_func = hash_func;
     map->eql_func  = eql_func;
+    map->master    = allocator;
     map->allocator = allocator;
+    wmem_map_init_table(map);
+
+    return map;
+}
+
+static gboolean
+wmem_map_reset_cb(wmem_allocator_t *allocator _U_, wmem_cb_event_t event,
+        void *user_data)
+{
+    wmem_map_t *map = (wmem_map_t*)user_data;
+
+    map->count = 0;
+    map->table = NULL;
+
+    if (event == WMEM_CB_DESTROY_EVENT) {
+        wmem_unregister_callback(map->master, map->master_cb_id);
+        wmem_free(map->master, map);
+    }
+
+    return TRUE;
+}
+
+static gboolean
+wmem_map_destroy_cb(wmem_allocator_t *allocator _U_, wmem_cb_event_t event _U_,
+        void *user_data)
+{
+    wmem_map_t *map = (wmem_map_t*)user_data;
+
+    wmem_unregister_callback(map->allocator, map->slave_cb_id);
+
+    return FALSE;
+}
+
+wmem_map_t *
+wmem_map_new_autoreset(wmem_allocator_t *master, wmem_allocator_t *slave,
+        GHashFunc hash_func, GEqualFunc eql_func)
+{
+    wmem_map_t *map;
+
+    map = wmem_new(master, wmem_map_t);
+
+    map->hash_func = hash_func;
+    map->eql_func  = eql_func;
+    map->master    = master;
+    map->allocator = slave;
+    wmem_map_init_table(map);
+
+    map->master_cb_id = wmem_register_callback(master, wmem_map_destroy_cb, map);
+    map->slave_cb_id  = wmem_register_callback(slave, wmem_map_reset_cb, map);
 
     return map;
 }
@@ -137,6 +198,11 @@ wmem_map_insert(wmem_map_t *map, const void *key, void *value)
     wmem_map_item_t **item;
     void *old_val;
 
+    /* Make sure we have a table */
+    if (map->table == NULL) {
+        wmem_map_init_table(map);
+    }
+
     /* get a pointer to the slot */
     item = &(map->table[HASH(map, key)]);
 
@@ -174,6 +240,11 @@ wmem_map_lookup(wmem_map_t *map, const void *key)
 {
     wmem_map_item_t *item;
 
+    /* Make sure we have a table */
+    if (map->table == NULL) {
+        return NULL;
+    }
+
     /* find correct slot */
     item = map->table[HASH(map, key)];
 
@@ -194,6 +265,11 @@ wmem_map_remove(wmem_map_t *map, const void *key)
     wmem_map_item_t **item, *tmp;
     void *value;
 
+    /* Make sure we have a table */
+    if (map->table == NULL) {
+        return NULL;
+    }
+
     /* get a pointer to the slot */
     item = &(map->table[HASH(map, key)]);
 
@@ -221,6 +297,11 @@ wmem_map_foreach(wmem_map_t *map, GHFunc foreach_func, gpointer user_data)
     wmem_map_item_t *cur;
     unsigned i;
 
+    /* Make sure we have a table */
+    if (map->table == NULL) {
+        return;
+    }
+
     for (i = 0; i < CAPACITY(map); i++) {
         cur = map->table[i];
         while (cur) {
diff --git a/epan/wmem/wmem_map.h b/epan/wmem/wmem_map.h
index 3e10c9a6dc..1ea4cf3350 100644
--- a/epan/wmem/wmem_map.h
+++ b/epan/wmem/wmem_map.h
@@ -70,6 +70,24 @@ wmem_map_new(wmem_allocator_t *allocator,
         GHashFunc hash_func, GEqualFunc eql_func)
 G_GNUC_MALLOC;
 
+/** Creates a map with two allocator scopes. The base structure lives in the
+ * master scope, however the data lives in the slave scope. Every time free_all
+ * occurs in the slave scope the map is transparently emptied without affecting
+ * the location of the master structure.
+ *
+ * WARNING: None of the map (even the part in the master scope) can be used
+ * after the slave scope has been *destroyed*.
+ *
+ * The primary use for this function is to create maps that reset for each new
+ * capture file that is loaded. This can be done by specifying wmem_epan_scope()
+ * as the master and wmem_file_scope() as the slave.
+ */
+WS_DLL_PUBLIC
+wmem_map_t *
+wmem_map_new_autoreset(wmem_allocator_t *master, wmem_allocator_t *slave,
+        GHashFunc hash_func, GEqualFunc eql_func)
+G_GNUC_MALLOC;
+
 /** Inserts a value into the map.
  *
  * @param map The map to insert into.
diff --git a/epan/wmem/wmem_test.c b/epan/wmem/wmem_test.c
index ecbae8973b..96338946c5 100644
--- a/epan/wmem/wmem_test.c
+++ b/epan/wmem/wmem_test.c
@@ -816,13 +816,14 @@ check_val_map(gpointer key _U_, gpointer val, gpointer user_data)
 static void
 wmem_test_map(void)
 {
-    wmem_allocator_t *allocator;
+    wmem_allocator_t   *allocator, *extra_allocator;
     wmem_map_t       *map;
     gchar            *str_key;
     unsigned int      i;
     void             *ret;
 
     allocator = wmem_allocator_new(WMEM_ALLOCATOR_STRICT);
+    extra_allocator = wmem_allocator_new(WMEM_ALLOCATOR_STRICT);
 
     /* insertion, lookup and removal of simple integer keys */
     map = wmem_map_new(allocator, g_direct_hash, g_direct_equal);
@@ -848,6 +849,23 @@ wmem_test_map(void)
     }
     wmem_free_all(allocator);
 
+    /* test auto-reset functionality */
+    map = wmem_map_new_autoreset(allocator, extra_allocator, g_direct_hash, g_direct_equal);
+    g_assert(map);
+    for (i=0; i<CONTAINER_ITERS; i++) {
+        ret = wmem_map_insert(map, GINT_TO_POINTER(i), GINT_TO_POINTER(777777));
+        g_assert(ret == NULL);
+        ret = wmem_map_insert(map, GINT_TO_POINTER(i), GINT_TO_POINTER(i));
+        g_assert(ret == GINT_TO_POINTER(777777));
+        ret = wmem_map_insert(map, GINT_TO_POINTER(i), GINT_TO_POINTER(i));
+        g_assert(ret == GINT_TO_POINTER(i));
+    }
+    wmem_free_all(extra_allocator);
+    for (i=0; i<CONTAINER_ITERS; i++) {
+        g_assert(wmem_map_lookup(map, GINT_TO_POINTER(i)) == NULL);
+    }
+    wmem_free_all(allocator);
+
     map = wmem_map_new(allocator, wmem_str_hash, g_str_equal);
     g_assert(map);
 
@@ -876,6 +894,7 @@ wmem_test_map(void)
     }
     g_assert(wmem_map_size(map) == CONTAINER_ITERS);
 
+    wmem_destroy_allocator(extra_allocator);
     wmem_destroy_allocator(allocator);
 }