WebSVN – HelenOS-historic – Diff – /kernel/trunk/generic/src/adt/btree.c

 #include <panic.h>
 #include <typedefs.h>
 #include <print.h>
 static void _btree_insert(btree_t *t, __native key, void *value, btree_node_t *rsubtree, btree_node_t *node);
+static void _btree_remove(btree_t *t, __native key, btree_node_t *node);
 static void node_initialize(btree_node_t *node);
-static void node_insert_key_left(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
+static void node_insert_key_and_lsubtree(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
-static void node_insert_key_right(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
+static void node_insert_key_and_rsubtree(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
 static btree_node_t *node_split(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree, __native *median);
+static btree_node_t *node_combine(btree_node_t *node);
-static void node_remove_key_left(btree_node_t *node, __native key);
+static void node_remove_key_and_lsubtree(btree_node_t *node, __native key);
-static void node_remove_key_right(btree_node_t *node, __native key);
+static void node_remove_key_and_rsubtree(btree_node_t *node, __native key);
 static index_t find_key_by_subtree(btree_node_t *node, btree_node_t *subtree, bool right);
+static void rotate_from_right(btree_node_t *lnode, btree_node_t *rnode, index_t idx);
+static void rotate_from_left(btree_node_t *lnode, btree_node_t *rnode, index_t idx);
-static bool try_insert_by_left_rotation(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
+static bool try_insert_by_rotation_to_left(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
-static bool try_insert_by_right_rotation(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
+static bool try_insert_by_rotation_to_right(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree);
+static bool try_rotation_from_left(btree_node_t *rnode);
+static bool try_rotation_from_right(btree_node_t *lnode);
 #define ROOT_NODE(n)        (!(n)->parent)
 #define INDEX_NODE(n)       ((n)->subtree[0] != NULL)
 #define LEAF_NODE(n)        ((n)->subtree[0] == NULL)
+{
     if (node->keys < BTREE_MAX_KEYS) {
         /*
          * Node conatins enough space, the key can be stored immediately.
          */
-        node_insert_key_right(node, key, value, rsubtree);
+        node_insert_key_and_rsubtree(node, key, value, rsubtree);
-    } else if (try_insert_by_left_rotation(node, key, value, rsubtree)) {
+    } else if (try_insert_by_rotation_to_left(node, key, value, rsubtree)) {
         /*
          * The key-value-rsubtree triplet has been inserted because
          * some keys could have been moved to the left sibling.
          */
-    } else if (try_insert_by_right_rotation(node, key, value, rsubtree)) {
+    } else if (try_insert_by_rotation_to_right(node, key, value, rsubtree)) {
         /*
          * The key-value-rsubtree triplet has been inserted because
          * some keys could have been moved to the right sibling.
          */
     } else {
  */
 void btree_remove(btree_t *t, __native key, btree_node_t *leaf_node)
+{
     btree_node_t *lnode;
+    panic("%s needs testing and is disabled in revision %s\n", __FUNCTION__, REVISION);
     lnode = leaf_node;
     if (!lnode) {
         if (!btree_search(t, key, &lnode)) {
             panic("B-tree %P does not contain key %d\n", t, key);
+        }
+    }
+    _btree_remove(t, key, lnode);
+}
+/** Recursively remove B-tree node.
+ *
+ * @param B-tree.
+ * @param key Key to be removed from the B-tree along with its associated value.
+ * @param node Node where the key being removed resides.
+ */
+void _btree_remove(btree_t *t, __native key, btree_node_t *node)
+{
+    if (ROOT_NODE(node)) {
+        if (node->keys == 1 && node->subtree[0]) {
+            /*
+             * Free the current root and set new root.
+             */
+            t->root = node->subtree[0];
+            t->root->parent = NULL;
+            free(node);
-    /* TODO */
+        } else {
+            /*
+             * Remove the key from the root node.
+             * Note that the right subtree is removed because when
+             * combining two nodes, the left-side sibling is preserved
+             * and the right-side sibling is freed.
+             */
+            node_remove_key_and_rsubtree(node, key);
+        }
+        return;
+    }
+    if (node->keys <= FILL_FACTOR) {
+        /*
+         * If the node is below the fill factor,
+         * try to borrow keys from left or right sibling.
+         */
+        if (!try_rotation_from_left(node))
+            try_rotation_from_right(node);
+    }
+    if (node->keys > FILL_FACTOR) {
+        int i;
+        /*
+         * The key can be immediatelly removed.
+         *
+         * Note that the right subtree is removed because when
+         * combining two nodes, the left-side sibling is preserved
+         * and the right-side sibling is freed.
+         */
+        node_remove_key_and_rsubtree(node, key);
+        for (i = 0; i < node->parent->keys; i++) {
+            if (node->parent->key[i] == key)
+                node->parent->key[i] = node->key[0];
+        }
+    } else {
+        index_t idx;
+        btree_node_t *rnode, *parent;
+        /*
+         * The node is below the fill factor as well as its left and right sibling.
+         * Resort to combining the node with one of its siblings.
+         * The node which is on the left is preserved and the node on the right is
+         * freed.
+         */
+        parent = node->parent;
+        node_remove_key_and_rsubtree(node, key);
+        rnode = node_combine(node);
+        if (LEAF_NODE(rnode))
+            list_remove(&rnode->leaf_link);
+        idx = find_key_by_subtree(parent, rnode, true);
+        ASSERT((int) idx != -1);
+        free(rnode);
+        _btree_remove(t, parent->key[idx], parent);
+    }
+}
 /** Search key in a B-tree.
+ *
  * @param t B-tree.
      * The key was not found in the *leaf_node and is smaller than any of its keys.
      */
     return NULL;
+}
-/** Get pointer to value with the smallest key within the node.
- *
- * Can be only used on leaf-level nodes.
- *
- * @param node B-tree node.
- *
- * @return Pointer to value assiciated with the smallest key.
- */
-void *btree_node_min(btree_node_t *node)
-{
-    ASSERT(LEAF_NODE(node));
-    ASSERT(node->keys);
-    return node->value[0];
-}
-/** Get pointer to value with the biggest key within the node.
- *
- * Can be only used on leaf-level nodes.
- *
- * @param node B-tree node.
- *
- * @return Pointer to value assiciated with the biggest key.
- */
-void *btree_node_max(btree_node_t *node)
-{
-    ASSERT(LEAF_NODE(node));
-    ASSERT(node->keys);
-    return node->value[node->keys - 1];
-}
 /** Initialize B-tree node.
+ *
  * @param node B-tree node.
  */
 void node_initialize(btree_node_t *node)
  * @param node B-tree node into wich the new key is to be inserted.
  * @param key The key to be inserted.
  * @param value Pointer to value to be inserted.
  * @param lsubtree Pointer to the left subtree.
  */
-void node_insert_key_left(btree_node_t *node, __native key, void *value, btree_node_t *lsubtree)
+void node_insert_key_and_lsubtree(btree_node_t *node, __native key, void *value, btree_node_t *lsubtree)
+{
     int i;
     for (i = 0; i < node->keys; i++) {
         if (key < node->key[i]) {
     node->subtree[i] = lsubtree;
     node->keys++;
+}
 /** Insert key-value-rsubtree triplet into B-tree node.
+ *
  * It is actually possible to have more keys than BTREE_MAX_KEYS.
  * This feature is used during splitting the node when the
  * number of keys is BTREE_MAX_KEYS + 1. Insert by left rotation
  * @param node B-tree node into wich the new key is to be inserted.
  * @param key The key to be inserted.
  * @param value Pointer to value to be inserted.
  * @param rsubtree Pointer to the right subtree.
  */
-void node_insert_key_right(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree)
+void node_insert_key_and_rsubtree(btree_node_t *node, __native key, void *value, btree_node_t *rsubtree)
+{
     int i;
     for (i = 0; i < node->keys; i++) {
         if (key < node->key[i]) {
     ASSERT(node->keys == BTREE_MAX_KEYS);
     /*
      * Use the extra space to store the extra node.
      */
-    node_insert_key_right(node, key, value, rsubtree);
+    node_insert_key_and_rsubtree(node, key, value, rsubtree);
     /*
      * Compute median of keys.
      */
     *median = MEDIAN_HIGH(node);
     node->keys /= 2;    /* Shrink the old node. */
     return rnode;
+}
+/** Combine node with any of its siblings.
+ *
+ * The siblings are required to be below the fill factor.
+ *
+ * @param node Node to combine with one of its siblings.
+ *
+ * @return Pointer to the rightmost of the two nodes.
+ */
+btree_node_t *node_combine(btree_node_t *node)
+{
+    index_t idx;
+    btree_node_t *rnode;
+    int i;
+    ASSERT(!ROOT_NODE(node));
+    idx = find_key_by_subtree(node->parent, node, false);
+    if (idx == node->parent->keys) {
+        /*
+         * Rightmost subtree of its parent, combine with the left sibling.
+         */
+        idx--;
+        rnode = node;
+        node = node->parent->subtree[idx];
+    } else {
+        rnode = node->parent->subtree[idx + 1];
+    }
+    /* Index nodes need to insert parent node key in between left and right node. */
+    if (INDEX_NODE(node))
+        node->key[node->keys++] = node->parent->key[idx];
+    /* Copy the key-value-subtree triplets from the right node. */
+    for (i = 0; i < rnode->keys; i++) {
+        node->key[node->keys + i] = rnode->key[i];
+        node->value[node->keys + i] = rnode->value[i];
+        if (INDEX_NODE(node)) {
+            node->subtree[node->keys + i] = rnode->subtree[i];
+            rnode->subtree[i]->parent = node;
+        }
+    }
+    if (INDEX_NODE(node)) {
+        node->subtree[node->keys + i] = rnode->subtree[i];
+        rnode->subtree[i]->parent = node;
+    }
+    node->keys += rnode->keys;
+    return rnode;
+}
 /** Remove key and its left subtree pointer from B-tree node.
+ *
  * Remove the key and eliminate gaps in node->key array.
  * Note that the value pointer and the left subtree pointer
  * is removed from the node as well.
+ *
  * @param node B-tree node.
  * @param key Key to be removed.
  */
-void node_remove_key_left(btree_node_t *node, __native key)
+void node_remove_key_and_lsubtree(btree_node_t *node, __native key)
+{
     int i, j;
     for (i = 0; i < node->keys; i++) {
         if (key == node->key[i]) {
  * is removed from the node as well.
+ *
  * @param node B-tree node.
  * @param key Key to be removed.
  */
-void node_remove_key_right(btree_node_t *node, __native key)
+void node_remove_key_and_rsubtree(btree_node_t *node, __native key)
+{
     int i, j;
     for (i = 0; i < node->keys; i++) {
         if (key == node->key[i]) {
             return i - (int) (right != false);
+    }
     panic("node %P does not contain subtree %P\n", node, subtree);
+}
+/** Rotate one key-value-rsubtree triplet from the left sibling to the right sibling.
+ *
+ * The biggest key and its value and right subtree is rotated from the left node
+ * to the right. If the node is an index node, than the parent node key belonging to
+ * the left node takes part in the rotation.
+ *
+ * @param lnode Left sibling.
+ * @param rnode Right sibling.
+ * @param idx Index of the parent node key that is taking part in the rotation.
+ */
+void rotate_from_left(btree_node_t *lnode, btree_node_t *rnode, index_t idx)
+{
+    __native key;
+    key = lnode->key[lnode->keys - 1];
+    if (LEAF_NODE(lnode)) {
+        void *value;
+        value = lnode->value[lnode->keys - 1];
+        node_remove_key_and_rsubtree(lnode, key);
+        node_insert_key_and_lsubtree(rnode, key, value, NULL);
+        lnode->parent->key[idx] = key;
+    } else {
+        btree_node_t *rsubtree;
+        rsubtree = lnode->subtree[lnode->keys];
+        node_remove_key_and_rsubtree(lnode, key);
+        node_insert_key_and_lsubtree(rnode, lnode->parent->key[idx], NULL, rsubtree);
+        lnode->parent->key[idx] = key;
+        /* Fix parent link of the reconnected right subtree. */
+        rsubtree->parent = rnode;
+    }
+}
+/** Rotate one key-value-lsubtree triplet from the right sibling to the left sibling.
+ *
+ * The smallest key and its value and left subtree is rotated from the right node
+ * to the left. If the node is an index node, than the parent node key belonging to
+ * the right node takes part in the rotation.
+ *
+ * @param lnode Left sibling.
+ * @param rnode Right sibling.
+ * @param idx Index of the parent node key that is taking part in the rotation.
+ */
+void rotate_from_right(btree_node_t *lnode, btree_node_t *rnode, index_t idx)
+{
+    __native key;
+    key = rnode->key[0];
+    if (LEAF_NODE(rnode)) {
+        void *value;
+        value = rnode->value[0];
+        node_remove_key_and_lsubtree(rnode, key);
+        node_insert_key_and_rsubtree(lnode, key, value, NULL);
+        rnode->parent->key[idx] = rnode->key[0];
+    } else {
+        btree_node_t *lsubtree;
+        lsubtree = rnode->subtree[0];
+        node_remove_key_and_lsubtree(rnode, key);
+        node_insert_key_and_rsubtree(lnode, rnode->parent->key[idx], NULL, lsubtree);
+        rnode->parent->key[idx] = key;
+        /* Fix parent link of the reconnected left subtree. */
+        lsubtree->parent = lnode;
+    }
+}
 /** Insert key-value-rsubtree triplet and rotate the node to the left, if this operation can be done.
+ *
  * Left sibling of the node (if it exists) is checked for free space.
  * If there is free space, the key is inserted and the smallest key of
  * the node is moved there. The index node which is the parent of both
  * @param insvalue Value to be inserted.
  * @param rsubtree Right subtree of inskey.
+ *
  * @return True if the rotation was performed, false otherwise.
  */
-bool try_insert_by_left_rotation(btree_node_t *node, __native inskey, void *insvalue, btree_node_t *rsubtree)
+bool try_insert_by_rotation_to_left(btree_node_t *node, __native inskey, void *insvalue, btree_node_t *rsubtree)
+{
     index_t idx;
     btree_node_t *lnode;
     /*
          */
         return false;
+    }
     lnode = node->parent->subtree[idx];
     if (lnode->keys < BTREE_MAX_KEYS) {
-        __native key;
         /*
          * The rotaion can be done. The left sibling has free space.
          */
-        node_insert_key_right(node, inskey, insvalue, rsubtree);
+        node_insert_key_and_rsubtree(node, inskey, insvalue, rsubtree);
-        key = node->key[0];
-        if (LEAF_NODE(node)) {
-            void *value;
-            value = node->value[0];
-            node_remove_key_left(node, key);
-            node_insert_key_right(lnode, key, value, NULL);
+        rotate_from_right(lnode, node, idx);
-            node->parent->key[idx] = node->key[0];
-        } else {
-            btree_node_t *lsubtree;
-            lsubtree = node->subtree[0];
-            node_remove_key_left(node, key);
-            node_insert_key_right(lnode, node->parent->key[idx], NULL, lsubtree);
-            node->parent->key[idx] = key;
-            /* Fix parent link of the reconnected left subtree. */
-            lsubtree->parent = lnode;
-        }
         return true;
+    }
     return false;
+}
  * @param insvalue Value to be inserted.
  * @param rsubtree Right subtree of inskey.
+ *
  * @return True if the rotation was performed, false otherwise.
  */
-bool try_insert_by_right_rotation(btree_node_t *node, __native inskey, void *insvalue, btree_node_t *rsubtree)
+bool try_insert_by_rotation_to_right(btree_node_t *node, __native inskey, void *insvalue, btree_node_t *rsubtree)
+{
     index_t idx;
     btree_node_t *rnode;
     /*
          */
         return false;
+    }
     rnode = node->parent->subtree[idx + 1];
     if (rnode->keys < BTREE_MAX_KEYS) {
-        __native key;
         /*
          * The rotaion can be done. The right sibling has free space.
          */
+        node_insert_key_and_rsubtree(node, inskey, insvalue, rsubtree);
+        rotate_from_left(node, rnode, idx);
+        return true;
+    }
-        node_insert_key_right(node, inskey, insvalue, rsubtree);
-        key = node->key[node->keys - 1];
-        if (LEAF_NODE(node)) {
-            void *value;
+    return false;
+}
-            value = node->value[node->keys - 1];
-            node_remove_key_right(node, key);
-            node_insert_key_left(rnode, key, value, NULL);
-            node->parent->key[idx] = key;
-        } else {
-            btree_node_t *rsubt;
+/** Rotate in a key from the left sibling or from the index node, if this operation can be done.
+ *
-            rsubt = node->subtree[node->keys];
+ * @param rnode Node into which to add key from its left sibling or from the index node.
+ *
-            node_remove_key_right(node, key);
+ * @return True if the rotation was performed, false otherwise.
+ */
-            node_insert_key_left(rnode, node->parent->key[idx], NULL, rsubt);
+bool try_rotation_from_left(btree_node_t *rnode)
+{
+    index_t idx;
-            node->parent->key[idx] = key;
+    btree_node_t *lnode;
+    /*
+     * If this is root node, the rotation can not be done.
+     */
+    if (ROOT_NODE(rnode))
+        return false;
+    idx = find_key_by_subtree(rnode->parent, rnode, true);
+    if ((int) idx == -1) {
+        /*
-            /* Fix parent link of the reconnected right subtree. */
+         * If this node is the leftmost subtree of its parent,
+         * the rotation can not be done.
+         */
-            rsubt->parent = rnode;
+        return false;
+    }
-        }
+    lnode = rnode->parent->subtree[idx];
+    if (lnode->keys > FILL_FACTOR) {
+        rotate_from_left(lnode, rnode, idx);
         return true;
+    }
+    return false;
+}
+/** Rotate in a key from the right sibling or from the index node, if this operation can be done.
+ *
+ * @param rnode Node into which to add key from its right sibling or from the index node.
+ *
+ * @return True if the rotation was performed, false otherwise.
+ */
+bool try_rotation_from_right(btree_node_t *lnode)
+{
+    index_t idx;
+    btree_node_t *rnode;
+    /*
+     * If this is root node, the rotation can not be done.
+     */
+    if (ROOT_NODE(lnode))
+        return false;
+    idx = find_key_by_subtree(lnode->parent, lnode, false);
+    if (idx == lnode->parent->keys) {
+        /*
+         * If this node is the rightmost subtree of its parent,
+         * the rotation can not be done.
+         */
+        return false;
+    }
+    rnode = lnode->parent->subtree[idx + 1];
+    if (rnode->keys > FILL_FACTOR) {
+        rotate_from_right(lnode, rnode, idx);
+        return true;
+    }
     return false;
+}
 /** Print B-tree.

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/adt/btree.c – Rev 1140 → 1142