http://hsqldb.org: HSQLDB - Lightweight 100% Java SQL Database Engine
(The HSQL Development Group)
- Blaine Simpson
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package org.hsqldb.lib;
import java.util.Comparator;
An HsqlHeap implementation backed by an array of objects and an ObjectComparator. This implementation is non-blocking, dynamically resizing and thread-safe. Author: Campbell Burnet (campbell-burnet@users dot sourceforge.net) Version: 1.9.0 Since: 1.7.2
/**
* An HsqlHeap implementation backed by an array of objects and an
* {@link ObjectComparator ObjectComparator}. This implementation
* is non-blocking, dynamically resizing and thread-safe.
*
* @author Campbell Burnet (campbell-burnet@users dot sourceforge.net)
* @version 1.9.0
* @since 1.7.2
*/
public class HsqlArrayHeap implements HsqlHeap {
// --------------------------------- members -----------------------------------
protected Comparator oc;
protected int count;
protected Object[] heap;
// ------------------------------ constructors ---------------------------------
Creates a new HsqlArrayHeap with the given initial capacity, using
the specified ObjectComparator to maintain the heap invariant.
Throws: - IllegalArgumentException – if capacity less or equal to zero
or comparator is null
/**
* Creates a new HsqlArrayHeap with the given initial capacity, using
* the specified ObjectComparator to maintain the heap invariant.
*
* @exception IllegalArgumentException if capacity less or equal to zero
* or comparator is null
*/
public HsqlArrayHeap(int capacity,
Comparator comparator)
throws IllegalArgumentException {
if (capacity <= 0) {
throw new IllegalArgumentException("" + capacity);
}
if (comparator == null) {
throw new IllegalArgumentException("null comparator");
}
heap = new Object[capacity];
oc = comparator;
}
// /** Copy constructor (optional) */
// public HsqlArrayHeap(HsqlArrayHeap other) {
// count = other.count;
// oc = other.oc;
// heap = new Object[count];
// System.arraycopy(other.heap,0, heap, 0, count);
// }
// -------------------------- interface Implementation -------------------------
public synchronized void clear() {
for (int i = 0; i < count; ++i) {
heap[i] = null;
}
count = 0;
}
public synchronized void add(Object o)
throws IllegalArgumentException, RuntimeException {
int ci; // current index
int pi; // parent index
if (o == null) {
throw new IllegalArgumentException("null element");
}
if (isFull()) {
throw new RuntimeException("full");
}
if (count >= heap.length) {
increaseCapacity();
}
ci = count;
count++;
do {
if (ci <= 0) {
break;
}
pi = (ci - 1) >>> 1;
try {
if (oc.compare(o, heap[pi]) >= 0) {
break;
}
} catch (Exception e) {
throw new IllegalArgumentException(e.toString());
}
heap[ci] = heap[pi];
ci = pi;
} while (true);
heap[ci] = o;
}
public synchronized boolean isEmpty() {
return count == 0;
}
public synchronized boolean isFull() {
// almost impossible for this to happen
return count == Integer.MAX_VALUE;
}
public synchronized Object peek() {
return heap[0];
}
public synchronized Object remove() {
int ci; // current index
int li; // left index
int ri; // right index
int chi; // child index
Object co;
Object ro;
if (count == 0) {
return null;
}
ci = 0;
ro = heap[ci];
count--;
if (count == 0) {
heap[0] = null;
return ro;
}
co = heap[count];
heap[count] = null;
do {
li = (ci << 1) + 1;
if (li >= count) {
break;
}
ri = (ci << 1) + 2;
chi = (ri >= count || oc.compare(heap[li], heap[ri]) < 0) ? li
: ri;
if (oc.compare(co, heap[chi]) <= 0) {
break;
}
heap[ci] = heap[chi];
ci = chi;
} while (true);
heap[ci] = co;
return ro;
}
public synchronized int size() {
return count;
}
// ------------- standard object and collection methods (optional) -------------
// public synchronized Object clone() throws CloneNotSupportedException {
// return new HsqlArrayHeap(this);
// }
//
// public synchronized java.util.Enumeration elements() {
//
// Object[] elements;
//
// elements = new Object[count];
//
// System.arraycopy(heap, 0, elements, 0, count);
//
// return new HsqlEnumeration(elements);
// }
//
// public synchronized boolean equals(Object o) {
//
// HsqlArrayHeap other;
// HsqlArrayHeap thiscopy;
// HsqlArrayHeap othercopy;
//
// if (this == o) {
// return true;
// }
//
// if (!(o instanceof HsqlArrayHeap)) {
// return false;
// }
//
// other = (HsqlArrayHeap) o;
//
// if (count != other.size()) {
// return false;
// }
//
// // this is a bit "iffy"... non-equal comparators _might_ still
// // be _equivalent_ under current element content...
//
// if (!oc.equals(other.oc)) {
// return false;
// }
//
// thiscopy = new HsqlArrayHeap(this);
// othercopy = new HsqlArrayHeap(other);
//
// while(!thiscopy.isEmpty()) {
// if (!thiscopy.remove().equals(othercopy.remove())) {
// return false;
// }
// }
//
// return true;
// }
//
// public synchronized Object[] toArray(Object a[]) {
//
// if (a == null) {
// a = new Object[count];
// } else if ( a.length < count) {
// a = (Object[]) java.lang.reflect.Array.newInstance(
// a.getClass().getComponentType(), count);
// }
//
// System.arraycopy(heap, 0, a, 0, count);
//
// for (int i = count; i < a.length; i++) {
// a[i] = null;
// }
//
// return a;
// }
//
public synchronized String toString() {
StringBuilder sb = new StringBuilder();
sb.append(super.toString());
sb.append(" : size=");
sb.append(count);
sb.append(' ');
sb.append('[');
for (int i = 0; i < count; i++) {
sb.append(heap[i]);
if (i + 1 < count) {
sb.append(',');
sb.append(' ');
}
}
sb.append(']');
return sb.toString();
}
//
// public void trim() {
//
// Object[] oldheap;
//
// oldheap = heap;
//
// heap = new Object[count == 0 ? 16 : count];
//
// System.arraycopy(oldheap, 0, heap, 0, count);
// }
// -------------------- internal implementation methods ------------------------
private void increaseCapacity() {
Object[] oldheap;
// no handling of boundary conditions.
// In the highly unlikely event of a rollover,
// in theory, an exception will be thrown (negative array index in
// array allocation?)
oldheap = heap;
// as per java collections, v.s. JDK 1.1 java util.
heap = new Object[3 * heap.length / 2 + 1];
System.arraycopy(oldheap, 0, heap, 0, count);
}
}