+++ /dev/null
-// Copyright (C) 2003 Adam Megacz <adam@xwt.org> all rights reserved.
-//
-// You may modify, copy, and redistribute this code under the terms of
-// the GNU Library Public License version 2.1, with the exception of
-// the portion of clause 6a after the semicolon (aka the "obnoxious
-// relink clause")
-
-package org.xwt.util;
-
-// FEATURE: private void intersection() { }
-// FEATURE: private void union() { }
-// FEATURE: private void subset() { }
-// FEATURE: grow if we run out of slots
-
-/** a weight-balanced tree with fake leaves */
-public class BalancedTree {
-
-
- // Instance Variables ///////////////////////////////////////////////////////////////////
-
- private int root = 0; ///< the slot of the root element
-
- private int cached_index = -1;
- private int cached_slot = -1;
-
- // Public API //////////////////////////////////////////////////////////////////////////
-
- /** the number of elements in the tree */
- public final int treeSize() { return root == 0 ? 0 : size[root]; }
-
- /** clamps index to [0..treeSize()] and inserts object o *before* the specified index */
- public final synchronized void insertNode(int index, Object o) {
- if(o == null) throw new Error("can't insert nulls in the balanced tree");
- cached_slot = cached_index = -1;
- if (index < 0) index = 0;
- if (index > treeSize()) index = treeSize();
- int arg = allocateSlot(o);
- if (root != 0) {
- insert(index, arg, root, 0, false, false);
- } else {
- root = arg;
- left[arg] = right[arg] = parent[arg] = 0;
- size[arg] = 1;
- }
- }
-
- /** clamps index to [0..treeSize()-1] and replaces the object at that index with object o */
- public final synchronized void replaceNode(int index, Object o) {
- if(o == null) throw new Error("can't insert nulls in the balanced tree");
- cached_slot = cached_index = -1;
- if(root == 0) throw new Error("called replaceNode() on an empty tree");
- if (index < 0) index = 0;
- if (index >= treeSize()) index = treeSize() - 1;
- int arg = allocateSlot(o);
- insert(index, arg, root, 0, true, false);
- }
-
- /** returns the index of o; runs in O((log n)^2) time unless cache hit */
- public final synchronized int indexNode(Object o) {
- if(o == null) return -1;
- if (cached_slot != -1 && objects[cached_slot] == o) return cached_index;
-
- int slot = getSlot(o);
- if(slot == -1) return -1;
-
- int index = 0;
- while(true) {
- // everything to the left is before us so add that to the index
- index += sizeof(left[slot]);
- // we are before anything on the right
- while(left[parent[slot]] == slot) slot = parent[slot];
- // we end of the first node who isn't on the left, go to the node that has as its child
- slot = parent[slot];
- // if we just processed the root we're done
- if(slot == 0) break;
- // count the node we're currently on towards the index
- index++;
- }
- return index;
- }
-
- /** returns the object at index; runs in O(log n) time unless cache hit */
- public final synchronized Object getNode(int index) {
- if (index == cached_index) return objects[cached_slot];
-
- if (cached_index != -1) {
- int distance = Math.abs(index - cached_index);
- // if the in-order distance between the cached node and the
- // target node is less than log(n), it's probably faster to
- // search directly.
- if ((distance < 16) && ((2 << distance) < treeSize())) {
- while(cached_index > index) { cached_slot = prev(cached_slot); cached_index--; }
- while(cached_index < index) { cached_slot = next(cached_slot); cached_index++; }
- return objects[cached_slot];
- }
- }
- /*
- cached_index = index;
- cached_slot = get(index, root);
- return objects[cached_slot];
- */
- return objects[get(index, root)];
- }
-
- /** deletes the object at index, returning the deleted object */
- public final synchronized Object deleteNode(int index) {
- cached_slot = cached_index = -1;
- // FIXME: left[], right[], size[], and parent[] aren't getting cleared properly somewhere in here where a node had two children
- int del = delete(index, root, 0);
- left[del] = right[del] = size[del] = parent[del] = 0;
- Object ret = objects[del];
- objects[del] = null;
- return ret;
- }
-
- public final synchronized void clear() {
- if(root == 0) return;
- int i = leftmost(root);
- do {
- int next = next(i);
- objects[i] = null;
- left[i] = right[i] = size[i] = parent[i] = 0;
- i = next;
- } while(i != 0);
- root = 0;
- }
-
- protected void finalize() { clear(); }
-
-
- // Node Data /////////////////////////////////////////////////////////////////////////
-
- private final static int NUM_SLOTS = 64 * 1024;
- // FEATURE: GROW - private final static int MAX_SLOT_DISTANCE = 32;
-
- /**
- * Every object inserted into *any* tree gets a "slot" in this
- * array. The slot is determined by hashcode modulo the length of
- * the array, with quadradic probing to resolve collisions. NOTE
- * that the "slot" of a node is NOT the same as its index.
- * Furthermore, if an object is inserted into multiple trees, that
- * object will have multiple slots.
- */
- private static Object[] objects = new Object[NUM_SLOTS];
-
- /// These two arrays hold the left and right children of each
- /// slot; in other words, left[x] is the *slot* of the left child
- /// of the node in slot x.
- ///
- /// If x has no left child, then left[x] is -1 multiplied by the
- /// slot of the node that precedes x; if x is the first node, then
- /// left[x] is 0. The right[] array works the same way.
- ///
- private static int[] left = new int[NUM_SLOTS];
- private static int[] right = new int[NUM_SLOTS];
-
- /// The parent of this node (0 if it is the root node)
- private static int[] parent = new int[NUM_SLOTS];
-
- ///< the number of descendants of this node *including the node itself*
- private static int[] size = new int[NUM_SLOTS];
-
-
- // Slot Management //////////////////////////////////////////////////////////////////////
-
- /** if alloc == false returns the slot holding object o. if alloc is true returns a new slot for obejct o */
- private int getSlot(Object o, boolean alloc) {
- // we XOR with our own hashcode so that we don't get tons of
- // collisions when a single Object is inserted into multiple
- // trees
- int dest = Math.abs(o.hashCode() ^ this.hashCode()) % objects.length;
- Object search = alloc ? null : o;
- int odest = dest;
- boolean plus = true;
- int tries = 1;
- while (objects[dest] != search || !(alloc || root(dest) == root)) {
- if (dest == 0) dest++;
- dest = Math.abs((odest + (plus ? 1 : -1) * tries * tries) % objects.length);
- if (plus) tries++;
- plus = !plus;
- // FEATURE: GROW - if(tries > MAX_SLOT_DISTANCE) return -1;
- }
- return dest;
- }
-
- /** returns the slots holding object o */
- private int getSlot(Object o) { return getSlot(o,false); }
-
- /** allocates a new slot holding object o*/
- private int allocateSlot(Object o) {
- int slot = getSlot(o, true);
- // FEATURE: GROW - if(slot == -1) throw new Error("out of slots");
- objects[slot] = o;
- return slot;
- }
-
-
-
- // Helpers /////////////////////////////////////////////////////////////////////////
-
- private final int leftmost(int slot) { return left[slot] <= 0 ? slot : leftmost(left[slot]); }
- private final int rightmost(int slot) { return right[slot] <= 0 ? slot : rightmost(right[slot]); }
- private final int next(int slot) { return right[slot] <= 0 ? -1 * right[slot] : leftmost(right[slot]); }
- private final int prev(int slot) { return left[slot] <= 0 ? -1 * left[slot] : rightmost(left[slot]); }
- private final int sizeof(int slot) { return slot <= 0 ? 0 : size[slot]; }
- private final int root(int slot) { return parent[slot] == 0 ? slot : root(parent[slot]); }
-
-
- // Rotation and Balancing /////////////////////////////////////////////////////////////
-
- // p p
- // | |
- // b d
- // / \ / \
- // a d < == > b e
- // / \ / \
- // c e a c
- // FIXME might be doing too much work here
- private void rotate(boolean toTheLeft, int b, int p) {
- int[] left = toTheLeft ? BalancedTree.left : BalancedTree.right;
- int[] right = toTheLeft ? BalancedTree.right : BalancedTree.left;
- int d = right[b];
- int c = left[d];
- if (d <= 0) throw new Error("rotation error");
- left[d] = b;
- if(size[b] <= 3) // b is now a leaf
- right[b] = -d;
- else
- right[b] = c;
- parent[b] = d;
- parent[d] = p;
- if(c > 0) parent[c] = b;
- if (p == 0) root = d;
- else if (left[p] == b) left[p] = d;
- else if (right[p] == b) right[p] = d;
- else throw new Error("rotate called with invalid parent");
- size[b] = 1 + sizeof(left[b]) + sizeof(right[b]);
- size[d] = 1 + sizeof(left[d]) + sizeof(right[d]);
- }
-
- private void balance(int slot, int p) {
- if (slot <= 0) return;
- size[slot] = 1 + sizeof(left[slot]) + sizeof(right[slot]);
- if (sizeof(left[slot]) - 1 > 2 * sizeof(right[slot])) rotate(false, slot, p);
- else if (sizeof(left[slot]) * 2 < sizeof(right[slot]) - 1) rotate(true, slot, p);
- }
-
-
-
- // Insert /////////////////////////////////////////////////////////////////////////
-
- private void insert(int index, int arg, int slot, int p, boolean replace, boolean wentLeft) {
- int diff = slot <= 0 ? 0 : index - sizeof(left[slot]);
- if (slot > 0 && diff != 0) {
- if (diff < 0) insert(index, arg, left[slot], slot, replace, true);
- else insert(index - sizeof(left[slot]) - 1, arg, right[slot], slot, replace, false);
- balance(slot, p);
- return;
- }
-
- if (size[arg] != 0) throw new Error("double insertion");
-
- // we are replacing an existing node
- if (replace) {
- if (diff != 0) throw new Error("this should never happen"); // since we already clamped the index
- if (p == 0) root = arg;
- else if (left[p] == slot) left[p] = arg;
- else if (right[p] == slot) right[p] = arg;
- left[arg] = left[slot];
- right[arg] = right[slot];
- size[arg] = size[slot];
- parent[arg] = parent[slot];
- if(left[slot] > 0) parent[left[slot]] = arg;
- if(right[slot] > 0) parent[right[slot]] = arg;
- objects[slot] = null;
- left[slot] = right[slot] = size[slot] = parent[slot] = 0;
-
- // we become the child of a former leaf
- } else if (slot <= 0) {
- int[] left = wentLeft ? BalancedTree.left : BalancedTree.right;
- int[] right = wentLeft ? BalancedTree.right : BalancedTree.left;
- left[arg] = slot;
- left[p] = arg;
- right[arg] = -1 * p;
- parent[arg] = p;
- balance(arg, p);
-
- // we take the place of a preexisting node
- } else {
- left[arg] = left[slot]; // steal slot's left subtree
- left[slot] = -1 * arg;
- right[arg] = slot; // make slot our right subtree
- parent[arg] = parent[slot];
- parent[slot] = arg;
- if (slot == root) {
- root = arg;
- balance(slot, arg);
- balance(arg, 0);
- } else {
- if (left[p] == slot) left[p] = arg;
- else if (right[p] == slot) right[p] = arg;
- else throw new Error("should never happen");
- balance(slot, arg);
- balance(arg, p);
- }
- }
- }
-
-
- // Retrieval //////////////////////////////////////////////////////////////////////
-
- private int get(int index, int slot) {
- int diff = index - sizeof(left[slot]);
- if (diff > 0) return get(diff - 1, right[slot]);
- else if (diff < 0) return get(index, left[slot]);
- else return slot;
- }
-
-
- // Deletion //////////////////////////////////////////////////////////////////////
-
- private int delete(int index, int slot, int p) {
- int diff = index - sizeof(left[slot]);
- if (diff < 0) {
- int ret = delete(index, left[slot], slot);
- balance(slot, p);
- return ret;
-
- } else if (diff > 0) {
- int ret = delete(diff - 1, right[slot], slot);
- balance(slot, p);
- return ret;
-
- // we found the node to delete
- } else {
-
- // fast path: it has no children
- if (left[slot] <= 0 && right[slot] <= 0) {
- if (p == 0) root = 0;
- else {
- int[] side = left[p] == slot ? left : right;
- side[p] = side[slot]; // fix parent's pointer
- }
-
- // fast path: it has no left child, so we replace it with its right child
- } else if (left[slot] <= 0) {
- if (p == 0) root = right[slot];
- else (left[p] == slot ? left : right)[p] = right[slot]; // fix parent's pointer
- parent[right[slot]] = p;
- left[leftmost(right[slot])] = left[slot]; // fix our successor-leaf's fake right ptr
- balance(right[slot], p);
-
- // fast path; it has no right child, so we replace it with its left child
- } else if (right[slot] <= 0) {
- if (p == 0) root = left[slot];
- else (left[p] == slot ? left : right)[p] = left[slot]; // fix parent's pointer
- parent[left[slot]] = p;
- right[rightmost(left[slot])] = right[slot]; // fix our successor-leaf's fake right ptr
- balance(left[slot], p);
-
- // node to be deleted has two children, so we replace it with its left child's rightmost descendant
- } else {
- int left_childs_rightmost = delete(sizeof(left[slot]) - 1, left[slot], slot);
- left[left_childs_rightmost] = left[slot];
- right[left_childs_rightmost] = right[slot];
- if(left[slot] > 0) parent[left[slot]] = left_childs_rightmost;
- if(right[slot] > 0) parent[right[slot]] = left_childs_rightmost;
- parent[left_childs_rightmost] = parent[slot];
- if (p == 0) root = left_childs_rightmost;
- else (left[p] == slot ? left : right)[p] = left_childs_rightmost; // fix parent's pointer
- balance(left_childs_rightmost, p);
- }
-
- return slot;
- }
- }
-
- // Debugging ///////////////////////////////////////////////////////////////////////////
-
- public void printTree() {
- if(root == 0) System.err.println("Tree is empty");
- else printTree(root,0,false);
- }
- private void printTree(int node,int indent,boolean l) {
- for(int i=0;i<indent;i++) System.err.print(" ");
- if(node < 0) System.err.println((l?"Prev: " : "Next: ") + -node);
- else if(node == 0) System.err.println(l ? "Start" : "End");
- else {
- System.err.print("" + node + ": " + objects[node]);
- System.err.println(" Parent: " + parent[node]);
- printTree(left[node],indent+1,true);
- printTree(right[node],indent+1,false);
- }
- }
-}
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