1 files changed, 478 insertions, 0 deletions
diff --git a/kern/rbtree.c b/kern/rbtree.c
new file mode 100644
index 0000000..1c04c5c
--- /dev/null
+++ b/kern/rbtree.c
@@ -0,0 +1,478 @@
+/*
+ * Copyright (c) 2010 Richard Braun.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <kern/assert.h>
+#include <kern/rbtree.h>
+#include <kern/rbtree_i.h>
+#include <sys/types.h>
+
+#define unlikely(expr) __builtin_expect(!!(expr), 0)
+
+/*
+ * Return the index of a node in the children array of its parent.
+ *
+ * The parent parameter must not be null, and must be the parent of the
+ * given node.
+ */
+static inline int rbtree_index(const struct rbtree_node *node,
+                               const struct rbtree_node *parent)
+{
+    assert(parent != NULL);
+    assert((node == NULL) || (rbtree_parent(node) == parent));
+
+    if (parent->children[RBTREE_LEFT] == node)
+        return RBTREE_LEFT;
+
+    assert(parent->children[RBTREE_RIGHT] == node);
+
+    return RBTREE_RIGHT;
+}
+
+/*
+ * Return the color of a node.
+ */
+static inline int rbtree_color(const struct rbtree_node *node)
+{
+    return node->parent & RBTREE_COLOR_MASK;
+}
+
+/*
+ * Return true if the node is red.
+ */
+static inline int rbtree_is_red(const struct rbtree_node *node)
+{
+    return rbtree_color(node) == RBTREE_COLOR_RED;
+}
+
+/*
+ * Return true if the node is black.
+ */
+static inline int rbtree_is_black(const struct rbtree_node *node)
+{
+    return rbtree_color(node) == RBTREE_COLOR_BLACK;
+}
+
+/*
+ * Set the parent of a node, retaining its current color.
+ */
+static inline void rbtree_set_parent(struct rbtree_node *node,
+                                     struct rbtree_node *parent)
+{
+    assert(rbtree_check_alignment(node));
+    assert(rbtree_check_alignment(parent));
+
+    node->parent = (unsigned long)parent | (node->parent & RBTREE_COLOR_MASK);
+}
+
+/*
+ * Set the color of a node, retaining its current parent.
+ */
+static inline void rbtree_set_color(struct rbtree_node *node, int color)
+{
+    assert((color & ~RBTREE_COLOR_MASK) == 0);
+    node->parent = (node->parent & RBTREE_PARENT_MASK) | color;
+}
+
+/*
+ * Set the color of a node to red, retaining its current parent.
+ */
+static inline void rbtree_set_red(struct rbtree_node *node)
+{
+    rbtree_set_color(node, RBTREE_COLOR_RED);
+}
+
+/*
+ * Set the color of a node to black, retaining its current parent.
+ */
+static inline void rbtree_set_black(struct rbtree_node *node)
+{
+    rbtree_set_color(node, RBTREE_COLOR_BLACK);
+}
+
+/*
+ * Perform a tree rotation, rooted at the given node.
+ *
+ * The direction parameter defines the rotation direction and is either
+ * RBTREE_LEFT or RBTREE_RIGHT.
+ */
+static void rbtree_rotate(struct rbtree *tree, struct rbtree_node *node,
+                          int direction)
+{
+    struct rbtree_node *parent, *rnode;
+    int left, right;
+
+    left = direction;
+    right = 1 - left;
+    parent = rbtree_parent(node);
+    rnode = node->children[right];
+
+    node->children[right] = rnode->children[left];
+
+    if (rnode->children[left] != NULL)
+        rbtree_set_parent(rnode->children[left], node);
+
+    rnode->children[left] = node;
+    rbtree_set_parent(rnode, parent);
+
+    if (unlikely(parent == NULL))
+        tree->root = rnode;
+    else
+        parent->children[rbtree_index(node, parent)] = rnode;
+
+    rbtree_set_parent(node, rnode);
+}
+
+void rbtree_insert_rebalance(struct rbtree *tree, struct rbtree_node *parent,
+                             int index, struct rbtree_node *node)
+{
+    struct rbtree_node *grand_parent, *uncle, *tmp;
+    int left, right;
+
+    assert(rbtree_check_alignment(parent));
+    assert(rbtree_check_alignment(node));
+
+    node->parent = (unsigned long)parent | RBTREE_COLOR_RED;
+    node->children[RBTREE_LEFT] = NULL;
+    node->children[RBTREE_RIGHT] = NULL;
+
+    if (unlikely(parent == NULL))
+        tree->root = node;
+    else
+        parent->children[index] = node;
+
+    for (;;) {
+        if (parent == NULL) {
+            rbtree_set_black(node);
+            break;
+        }
+
+        if (rbtree_is_black(parent))
+            break;
+
+        grand_parent = rbtree_parent(parent);
+        assert(grand_parent != NULL);
+
+        left = rbtree_index(parent, grand_parent);
+        right = 1 - left;
+
+        uncle = grand_parent->children[right];
+
+        /*
+         * Case 1: uncle is red. Flip colors and repeat at grand parent.
+         */
+        if ((uncle != NULL) && rbtree_is_red(uncle)) {
+            rbtree_set_black(uncle);
+            rbtree_set_black(parent);
+            rbtree_set_red(grand_parent);
+            node = grand_parent;
+            parent = rbtree_parent(node);
+            continue;
+        }
+
+        /*
+         * Case 2: node is the right child of its parent. Rotate left at parent
+         * to reduce to case 3.
+         */
+        if (parent->children[right] == node) {
+            rbtree_rotate(tree, parent, left);
+            tmp = node;
+            node = parent;
+            parent = tmp;
+        }
+
+        /*
+         * Case 3: node is the left child of its parent. Handle colors, rotate
+         * right at grand parent, and leave.
+         */
+        rbtree_set_black(parent);
+        rbtree_set_red(grand_parent);
+        rbtree_rotate(tree, grand_parent, right);
+        break;
+    }
+
+    assert(rbtree_is_black(tree->root));
+}
+
+void rbtree_remove(struct rbtree *tree, struct rbtree_node *node)
+{
+    struct rbtree_node *child, *parent, *brother;
+    int color, left, right;
+
+    if (node->children[RBTREE_LEFT] == NULL)
+        child = node->children[RBTREE_RIGHT];
+    else if (node->children[RBTREE_RIGHT] == NULL)
+        child = node->children[RBTREE_LEFT];
+    else {
+        struct rbtree_node *successor;
+
+        /*
+         * Two-children case: replace the node with its successor.
+         */
+
+        successor = node->children[RBTREE_RIGHT];
+
+        while (successor->children[RBTREE_LEFT] != NULL)
+            successor = successor->children[RBTREE_LEFT];
+
+        color = rbtree_color(successor);
+        child = successor->children[RBTREE_RIGHT];
+        parent = rbtree_parent(node);
+
+        if (unlikely(parent == NULL))
+            tree->root = successor;
+        else
+            parent->children[rbtree_index(node, parent)] = successor;
+
+        parent = rbtree_parent(successor);
+
+        /*
+         * Set parent directly to keep the original color.
+         */
+        successor->parent = node->parent;
+        successor->children[RBTREE_LEFT] = node->children[RBTREE_LEFT];
+        rbtree_set_parent(successor->children[RBTREE_LEFT], successor);
+
+        if (node == parent)
+            parent = successor;
+        else {
+            successor->children[RBTREE_RIGHT] = node->children[RBTREE_RIGHT];
+            rbtree_set_parent(successor->children[RBTREE_RIGHT], successor);
+            parent->children[RBTREE_LEFT] = child;
+
+            if (child != NULL)
+                rbtree_set_parent(child, parent);
+        }
+
+        goto update_color;
+    }
+
+    /*
+     * Node has at most one child.
+     */
+
+    color = rbtree_color(node);
+    parent = rbtree_parent(node);
+
+    if (child != NULL)
+        rbtree_set_parent(child, parent);
+
+    if (unlikely(parent == NULL))
+        tree->root = child;
+    else
+        parent->children[rbtree_index(node, parent)] = child;
+
+    /*
+     * The node has been removed, update the colors. The child pointer can
+     * be null, in which case it is considered a black leaf.
+     */
+update_color:
+    if (color == RBTREE_COLOR_RED)
+        return;
+
+    for (;;) {
+        if ((child != NULL) && rbtree_is_red(child)) {
+            rbtree_set_black(child);
+            break;
+        }
+
+        if (parent == NULL)
+            break;
+
+        left = rbtree_index(child, parent);
+        right = 1 - left;
+
+        brother = parent->children[right];
+
+        /*
+         * Case 1: brother is red. Recolor and rotate left at parent so that
+         * brother becomes black.
+         */
+        if (rbtree_is_red(brother)) {
+            rbtree_set_black(brother);
+            rbtree_set_red(parent);
+            rbtree_rotate(tree, parent, left);
+            brother = parent->children[right];
+        }
+
+        /*
+         * Case 2: brother has no red child. Recolor and repeat at parent.
+         */
+        if (((brother->children[RBTREE_LEFT] == NULL)
+             || rbtree_is_black(brother->children[RBTREE_LEFT]))
+            && ((brother->children[RBTREE_RIGHT] == NULL)
+                || rbtree_is_black(brother->children[RBTREE_RIGHT]))) {
+            rbtree_set_red(brother);
+            child = parent;
+            parent = rbtree_parent(child);
+            continue;
+        }
+
+        /*
+         * Case 3: brother's right child is black. Recolor and rotate right
+         * at brother to reduce to case 4.
+         */
+        if ((brother->children[right] == NULL)
+            || rbtree_is_black(brother->children[right])) {
+            rbtree_set_black(brother->children[left]);
+            rbtree_set_red(brother);
+            rbtree_rotate(tree, brother, right);
+            brother = parent->children[right];
+        }
+
+        /*
+         * Case 4: brother's left child is black. Exchange parent and brother
+         * colors (we already know brother is black), set brother's right child
+         * black, rotate left at parent and leave.
+         */
+        rbtree_set_color(brother, rbtree_color(parent));
+        rbtree_set_black(parent);
+        rbtree_set_black(brother->children[right]);
+        rbtree_rotate(tree, parent, left);
+        break;
+    }
+
+    assert((tree->root == NULL) || rbtree_is_black(tree->root));
+}
+
+struct rbtree_node * rbtree_nearest(struct rbtree_node *parent, int index,
+                                    int direction)
+{
+    assert(rbtree_check_index(direction));
+
+    if (parent == NULL)
+        return NULL;
+
+    assert(rbtree_check_index(index));
+
+    if (index != direction)
+        return parent;
+
+    return rbtree_walk(parent, direction);
+}
+
+struct rbtree_node * rbtree_firstlast(const struct rbtree *tree, int direction)
+{
+    struct rbtree_node *prev, *cur;
+
+    assert(rbtree_check_index(direction));
+
+    prev = NULL;
+
+    for (cur = tree->root; cur != NULL; cur = cur->children[direction])
+        prev = cur;
+
+    return prev;
+}
+
+struct rbtree_node * rbtree_walk(struct rbtree_node *node, int direction)
+{
+    int left, right;
+
+    assert(rbtree_check_index(direction));
+
+    left = direction;
+    right = 1 - left;
+
+    if (node == NULL)
+        return NULL;
+
+    if (node->children[left] != NULL) {
+        node = node->children[left];
+
+        while (node->children[right] != NULL)
+            node = node->children[right];
+    } else {
+        struct rbtree_node *parent;
+        int index;
+
+        for (;;) {
+            parent = rbtree_parent(node);
+
+            if (parent == NULL)
+                return NULL;
+
+            index = rbtree_index(node, parent);
+            node = parent;
+
+            if (index == right)
+                break;
+        }
+    }
+
+    return node;
+}
+
+/*
+ * Return the left-most deepest child node of the given node.
+ */
+static struct rbtree_node * rbtree_find_deepest(struct rbtree_node *node)
+{
+    struct rbtree_node *parent;
+
+    assert(node != NULL);
+
+    for (;;) {
+        parent = node;
+        node = node->children[RBTREE_LEFT];
+
+        if (node == NULL) {
+            node = parent->children[RBTREE_RIGHT];
+
+            if (node == NULL)
+                return parent;
+        }
+    }
+}
+
+struct rbtree_node * rbtree_postwalk_deepest(const struct rbtree *tree)
+{
+    struct rbtree_node *node;
+
+    node = tree->root;
+
+    if (node == NULL)
+        return NULL;
+
+    return rbtree_find_deepest(node);
+}
+
+struct rbtree_node * rbtree_postwalk_unlink(struct rbtree_node *node)
+{
+    struct rbtree_node *parent;
+    int index;
+
+    if (node == NULL)
+        return NULL;
+
+    assert(node->children[RBTREE_LEFT] == NULL);
+    assert(node->children[RBTREE_RIGHT] == NULL);
+
+    parent = rbtree_parent(node);
+
+    if (parent == NULL)
+        return NULL;
+
+    index = rbtree_index(node, parent);
+    parent->children[index] = NULL;
+    node = parent->children[RBTREE_RIGHT];
+
+    if (node == NULL)
+        return parent;
+
+    return rbtree_find_deepest(node);
+}