//
// Copyright (C) 2006 United States Government as represented by the
// Administrator of the National Aeronautics and Space Administration
// (NASA). All Rights Reserved.
//
// This software is distributed under the NASA Open Source Agreement
// (NOSA), version 1.3. The NOSA has been approved by the Open Source
// Initiative. See the file NOSA-1.3-JPF at the top of the distribution
// directory tree for the complete NOSA document.
//
// THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
// KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
// LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
// SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
// A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
// THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
// DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
//
package gov.nasa.jpf.util;
import java.util.Iterator;
/**
* simplistic Object array that differentiates from ArrayList by
* using chunks instead of exponential growth, thus efficiently dealing
* with huge, potentially sparse arrays
*
* the motivation for this class is memory optimization, i.e. space efficient
* storage of potentially huge arrays without good a-priori size guesses
*
* this class is awfully lifted from DynamicIntArray (same motivation, but
* primitive types - not much factorizable functionality w/o excessive
* casting/boxing)
*
* the API of this class is between a primitive array and a AbstractList. Since
* it handles Objects, we could turn this into a Collection (and probably should)
*
* NOTE: like standard Collection implementations/arrays, this class is not
* synchronized
*/
public final class DynamicObjectArray<E> implements Iterable<E> {
final static int DEFAULT_CHUNKBITS = 8;
final static int INIT_CHUNKS = 16;
/** growth strategy */
Growth growth;
/** our allocation sizes */
int chunkBits;
int nPerChunk; // just a cache for (1<<chunkBits)
/** mask for index within chunk */
int chunkMask;
/** the real data. limitations in generics prevent use of E[][] */
Object[][] data;
/** the maximum index set so far */
int maxIndex = -1;
class DynIterator implements Iterator<E> {
int i;
public boolean hasNext() {
return (i<size());
}
public E next() {
return get(i++);
}
public void remove() {
throw new UnsupportedOperationException();
}
}
public DynamicObjectArray () {
this(Growth.defaultGrowth, DEFAULT_CHUNKBITS, INIT_CHUNKS);
}
/**
* Creates a DynamicObjectArray in which each chunk has 2**chunkBits elements
* and initChunks chunks are initially allocated.
*/
public DynamicObjectArray (int chunkBits, int initChunks) {
this(Growth.defaultGrowth, chunkBits, initChunks);
}
public DynamicObjectArray (Growth strategy, int chunkBits, int initChunks) {
if (chunkBits > 20) throw new IllegalArgumentException();
this.chunkBits = chunkBits;
nPerChunk = 1<<chunkBits;
this.chunkMask = nPerChunk - 1;
data = new Object[initChunks][];
growth = strategy;
}
public Iterator<E> iterator() {
return new DynIterator();
}
@SuppressWarnings("unchecked")
public E get (int index) {
int i = index >> chunkBits;
if (i < data.length && data[i] != null) {
int j = index & chunkMask;
return (E) data[i][j];
} else {
return null;
}
}
// this is only the max size, not the max index that was accessed/set
public int size() {
return data.length * nPerChunk;
}
public int getMaxIndex() {
return maxIndex;
}
public void set (int index, E value) {
if (index > maxIndex) {
maxIndex = index;
}
int i = index >> chunkBits;
int j = index & chunkMask;
if (i >= data.length) {
int nChunks = growth.grow(data.length, i+1);
Object[][] newChunks = new Object[nChunks][];
System.arraycopy(data, 0, newChunks, 0, data.length);
data = newChunks;
}
if (data[i] == null) {
data[i] = new Object[1 << chunkBits];
}
data[i][j] = value;
}
public String toString() {
int length = data.length * (1 << chunkBits);
while (length > 1 && get(length-1) == null) length--;
StringBuilder sb = new StringBuilder(length);
sb.append('{');
int l = length-1;
for (int i=0; i<l; i++) {
sb.append(get(i));
sb.append(',');
}
sb.append(get(l));
sb.append('}');
return sb.toString();
}
// removed toArray method, which is confusing for 1.5
}