Lower branches in red-black tree (#58)

The changes in this commit are aiming to remove if statements
to achieve better performance by producing less branches.

Indirect pointers are used to store the pointer pointing to the
left or right child node. So we would not need to check whether it
is a right or left node.

Co-authored-by: Steven Lung <steven_lung@trendmicro.com>

src/map.c

@@ -81,9 +81,7 @@ static inline void rb_set_parent_color(map_node_t *node,
  */
 static inline bool rb_is_red(map_node_t *node)
 {
-    if (node && (rb_color(node) == RB_RED))
-        return true;
-    return false;
+    return node && (rb_color(node) == RB_RED);
 }
 
 /* Create a node to be attached in the map internal tree structure */
@@ -524,34 +522,20 @@ bool map_insert(map_t obj, void *key, void *value)
     }
 
     /* Traverse the tree until we hit the end or find a side that is NULL */
-    map_node_t *cur = obj->head;
+    map_node_t **indirect = &obj->head;
 
-    while (1) {
-        int res = obj->comparator(new_node->key, cur->key);
-        if (res == 0) { /* If the key matches something else, don't insert */
+    while (*indirect) {
+        int res = obj->comparator(new_node->key, (*indirect)->key);
+        if (res == 0) { /* If the key matches something, don't insert */
             map_delete_node(obj, new_node);
             return false;
         }
-
-        if (res < 0) {
-            if (!cur->left) {
-                cur->left = new_node;
-                rb_set_parent(new_node, cur);
-                map_fix_colors(obj, new_node);
-                break;
-            }
-            cur = cur->left;
-        } else {
-            if (!cur->right) {
-                cur->right = new_node;
-                rb_set_parent(new_node, cur);
-                map_fix_colors(obj, new_node);
-                break;
-            }
-            cur = cur->right;
-        }
+        indirect = res < 0 ? &(*indirect)->left : &(*indirect)->right;
     }
 
+    *indirect = new_node;
+    rb_set_parent(new_node, *indirect);
+    map_fix_colors(obj, new_node);
     map_calibrate(obj);
     return true;
 }
@@ -635,7 +619,7 @@ bool map_empty(map_t obj)
     return (obj->size == 0);
 }
 
-/* Return true if at the the rend of the map */
+/* Return true if at the the end of the map */
 bool map_at_end(map_t obj UNUSED, map_iter_t *it)
 {
     return (it->node == NULL);