3 files changed, 60 insertions, 0 deletions
diff --git a/src/common/container.c b/src/common/container.c
index ec59dccf62..1448ab403c 100644
--- a/src/common/container.c
+++ b/src/common/container.c
@@ -132,6 +132,24 @@ smartlist_remove(smartlist_t *sl, const void *element)
     }
 }
 
+/** As <b>smartlist_remove</b>, but do not change the order of
+ * any elements not removed */
+void
+smartlist_remove_keeporder(smartlist_t *sl, const void *element)
+{
+  int i, j, num_used_orig = sl->num_used;
+  if (element == NULL)
+    return;
+
+  for (i=j=0; j < num_used_orig; ++j) {
+    if (sl->list[j] == element) {
+      --sl->num_used;
+    } else {
+      sl->list[i++] = sl->list[j];
+    }
+  }
+}
+
 /** If <b>sl</b> is nonempty, remove and return the final element.  Otherwise,
  * return NULL. */
 void *
diff --git a/src/common/container.h b/src/common/container.h
index 71495b660a..00c3ca81ad 100644
--- a/src/common/container.h
+++ b/src/common/container.h
@@ -33,6 +33,7 @@ void smartlist_clear(smartlist_t *sl);
 void smartlist_add(smartlist_t *sl, void *element);
 void smartlist_add_all(smartlist_t *sl, const smartlist_t *s2);
 void smartlist_remove(smartlist_t *sl, const void *element);
+void smartlist_remove_keeporder(smartlist_t *sl, const void *element);
 void *smartlist_pop_last(smartlist_t *sl);
 void smartlist_reverse(smartlist_t *sl);
 void smartlist_string_remove(smartlist_t *sl, const char *element);
diff --git a/src/test/test_containers.c b/src/test/test_containers.c
index d7291a2ce2..41f3f873de 100644
--- a/src/test/test_containers.c
+++ b/src/test/test_containers.c
@@ -882,6 +882,46 @@ test_container_strmap(void *arg)
   tor_free(v105);
 }
 
+static void
+test_container_smartlist_remove(void *arg)
+{
+  (void) arg;
+  int array[5];
+  smartlist_t *sl = smartlist_new();
+  int i,j;
+
+  for (j=0; j < 2; ++j)
+    for (i=0; i < 5; ++i)
+      smartlist_add(sl, &array[i]);
+
+  smartlist_remove(sl, &array[0]);
+  smartlist_remove(sl, &array[3]);
+  smartlist_remove(sl, &array[4]);
+  tt_assert(! smartlist_contains(sl, &array[0]));
+  tt_assert(smartlist_contains(sl, &array[1]));
+  tt_assert(smartlist_contains(sl, &array[2]));
+  tt_assert(! smartlist_contains(sl, &array[3]));
+  tt_assert(! smartlist_contains(sl, &array[4]));
+  tt_int_op(smartlist_len(sl), OP_EQ, 4);
+
+  smartlist_clear(sl);
+  for (j=0; j < 2; ++j)
+    for (i=0; i < 5; ++i)
+      smartlist_add(sl, &array[i]);
+
+  smartlist_remove_keeporder(sl, &array[0]);
+  smartlist_remove_keeporder(sl, &array[3]);
+  smartlist_remove_keeporder(sl, &array[4]);
+  tt_int_op(smartlist_len(sl), OP_EQ, 4);
+  tt_ptr_op(smartlist_get(sl, 0), OP_EQ, &array[1]);
+  tt_ptr_op(smartlist_get(sl, 1), OP_EQ, &array[2]);
+  tt_ptr_op(smartlist_get(sl, 2), OP_EQ, &array[1]);
+  tt_ptr_op(smartlist_get(sl, 3), OP_EQ, &array[2]);
+
+ done:
+  smartlist_free(sl);
+}
+
 /** Run unit tests for getting the median of a list. */
 static void
 test_container_order_functions(void *arg)
@@ -1239,6 +1279,7 @@ struct testcase_t container_tests[] = {
   CONTAINER_LEGACY(smartlist_digests),
   CONTAINER_LEGACY(smartlist_join),
   CONTAINER_LEGACY(smartlist_pos),
+  CONTAINER(smartlist_remove, 0),
   CONTAINER(smartlist_ints_eq, 0),
   CONTAINER_LEGACY(bitarray),
   CONTAINER_LEGACY(digestset),