Make entry_guards_update_primary() shorter

src/feature/client/entrynodes.c

@@ -1883,28 +1883,24 @@ entry_guards_update_primary(guard_selection_t *gs)
     smartlist_add(new_primary_guards, guard);
   } SMARTLIST_FOREACH_END(guard);
 
-  /* Can we keep any older primary guards? First remove all the ones
-   * that we already kept. */
   SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
+    /* Can we keep any older primary guards? First remove all the ones
+     * that we already kept. */
     if (smartlist_contains(new_primary_guards, guard)) {
       SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
-    }
-  } SMARTLIST_FOREACH_END(guard);
-
-  /* Now add any that are still good. */
-  SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
-    if (smartlist_len(new_primary_guards) >= N_PRIMARY_GUARDS)
-      break;
-    if (! guard->is_filtered_guard)
       continue;
-    guard->is_primary = 1;
-    smartlist_add(new_primary_guards, guard);
-    SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
-  } SMARTLIST_FOREACH_END(guard);
+    }
 
-  /* Mark the remaining previous primary guards as non-primary */
-  SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
-    guard->is_primary = 0;
+    /* Now add any that are still good. */
+    if (smartlist_len(new_primary_guards) < N_PRIMARY_GUARDS &&
+        guard->is_filtered_guard) {
+      guard->is_primary = 1;
+      smartlist_add(new_primary_guards, guard);
+      SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
+    } else {
+      /* Mark the remaining previous primary guards as non-primary */
+      guard->is_primary = 0;
+    }
   } SMARTLIST_FOREACH_END(guard);
 
   /* Finally, fill out the list with sampled guards. */
@@ -1928,18 +1924,8 @@ entry_guards_update_primary(guard_selection_t *gs)
   });
 #endif /* 1 */
 
-  int any_change = 0;
-  if (smartlist_len(gs->primary_entry_guards) !=
-      smartlist_len(new_primary_guards)) {
-    any_change = 1;
-  } else {
-    SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, g) {
-      if (g != smartlist_get(new_primary_guards, g_sl_idx)) {
-        any_change = 1;
-      }
-    } SMARTLIST_FOREACH_END(g);
-  }
-
+  const int any_change = !smartlist_ptrs_eq(gs->primary_entry_guards,
+                                            new_primary_guards);
   if (any_change) {
     log_info(LD_GUARD, "Primary entry guards have changed. "
              "New primary guard list is: ");

src/lib/container/smartlist.c

@@ -189,6 +189,33 @@ smartlist_ints_eq(const smartlist_t *sl1, const smartlist_t *sl2)
   return 1;
 }
 
+/**
+ * Return true if there is shallow equality between smartlists -
+ * i.e. all indices correspond to exactly same object (pointer
+ * values are matching). Otherwise, return false.
+ */
+int
+smartlist_ptrs_eq(const smartlist_t *s1, const smartlist_t *s2)
+{
+  if (s1 == s2)
+    return 1;
+
+  // Note: pointers cannot both be NULL at this point, because
+  // above check.
+  if (s1 == NULL || s2 == NULL)
+    return 0;
+
+  if (smartlist_len(s1) != smartlist_len(s2))
+    return 0;
+
+  for (int i = 0; i < smartlist_len(s1); i++) {
+    if (smartlist_get(s1, i) != smartlist_get(s2, i))
+      return 0;
+  }
+
+  return 1;
+}
+
 /** Return true iff <b>sl</b> has some element E such that
  * tor_memeq(E,<b>element</b>,DIGEST_LEN)
  */

src/lib/container/smartlist.h

@@ -37,6 +37,9 @@ int smartlist_overlap(const smartlist_t *sl1, const smartlist_t *sl2);
 void smartlist_intersect(smartlist_t *sl1, const smartlist_t *sl2);
 void smartlist_subtract(smartlist_t *sl1, const smartlist_t *sl2);
 
+int smartlist_ptrs_eq(const smartlist_t *s1,
+                      const smartlist_t *s2);
+
 void smartlist_sort(smartlist_t *sl,
                     int (*compare)(const void **a, const void **b));
 void *smartlist_get_most_frequent_(const smartlist_t *sl,