--- /dev/null
+// Copyright (C) 2003 Adam Megacz <adam@ibex.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.ibex.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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