/*******************************************************************************
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* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html.
*
* This file is a derivative of code released by the University of
* California under the terms listed below.
*
* Refinement Analysis Tools is Copyright (c) 2007 The Regents of the
* University of California (Regents). Provided that this notice and
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* IN NO EVENT SHALL REGENTS BE LIABLE TO ANY PARTY FOR DIRECT,
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package com.ibm.wala.util.collections;
import java.util.Arrays;
import java.util.EmptyStackException;
import java.util.Iterator;
/**
* An immutable stack of objects. The {@link #push(Object)} and {@link #pop()}
* operations create new stacks.
*
* @param <T>
*/
public class ImmutableStack<T> implements Iterable<T> {
private static final ImmutableStack<Object> EMPTY = new ImmutableStack<Object>(
new Object[0]);
private static final int MAX_SIZE = Integer.MAX_VALUE;
public static int getMaxSize() {
return MAX_SIZE;
}
@SuppressWarnings("unchecked")
public static final <T> ImmutableStack<T> emptyStack() {
return (ImmutableStack<T>) EMPTY;
}
final private T[] entries;
private final int cachedHashCode;
protected ImmutableStack(T[] entries) {
this.entries = entries;
this.cachedHashCode = Arrays.hashCode(entries);
}
@SuppressWarnings("rawtypes")
@Override
public boolean equals(Object o) {
if (this == o)
return true;
if (o != null && o instanceof ImmutableStack) {
ImmutableStack other = (ImmutableStack) o;
return Arrays.equals(entries, other.entries);
}
return false;
}
@Override
public int hashCode() {
return cachedHashCode;
// return Util.hashArray(this.entries);
}
@SuppressWarnings("unused")
public ImmutableStack<T> push(T entry) {
if (entry == null) {
throw new IllegalArgumentException("null entry");
}
if (MAX_SIZE == 0) {
return emptyStack();
}
int size = entries.length + 1;
T[] tmpEntries = null;
if (size <= MAX_SIZE) {
tmpEntries = makeInternalArray(size);
System.arraycopy(entries, 0, tmpEntries, 0, entries.length);
tmpEntries[size - 1] = entry;
} else {
tmpEntries = makeInternalArray(MAX_SIZE);
System.arraycopy(entries, 1, tmpEntries, 0, entries.length - 1);
tmpEntries[MAX_SIZE - 1] = entry;
}
return makeStack(tmpEntries);
}
@SuppressWarnings("unchecked")
protected T[] makeInternalArray(int size) {
return (T[]) new Object[size];
}
protected ImmutableStack<T> makeStack(T[] tmpEntries) {
return new ImmutableStack<T>(tmpEntries);
}
/**
* @return the element on the top of the stack
* @throws EmptyStackException
* if stack is empty
*/
public T peek() {
if (entries.length == 0) {
throw new EmptyStackException();
}
return entries[entries.length - 1];
}
/**
* @throws EmptyStackException
* if stack is empty
*/
public ImmutableStack<T> pop() {
if (entries.length == 0) {
throw new EmptyStackException();
}
int size = entries.length - 1;
T[] tmpEntries = makeInternalArray(size);
System.arraycopy(entries, 0, tmpEntries, 0, size);
return makeStack(tmpEntries);
}
public boolean isEmpty() {
return entries.length == 0;
}
public int size() {
return entries.length;
}
public T get(int i) {
try {
return entries[i];
} catch (ArrayIndexOutOfBoundsException e) {
throw new IllegalArgumentException("invalid i: " + i);
}
}
@Override
public String toString() {
String objArrayToString = Arrays.toString(entries);
assert entries.length <= MAX_SIZE : objArrayToString;
return objArrayToString;
}
public boolean contains(T entry) {
if (entry == null) {
return false;
}
for (int i = 0; i < entries.length; i++) {
if (entries[i] != null && entries[i].equals(entry))
return true;
}
return false;
}
/**
* @return <code>true</code> iff other.size() = k, k <= this.size(), and the
* top k elements of this equal other
* @throws IllegalArgumentException
* if other == null
*/
public boolean topMatches(ImmutableStack<T> other)
throws IllegalArgumentException {
if (other == null) {
throw new IllegalArgumentException("other == null");
}
if (other.size() > size()) {
return false;
}
for (int i = other.size() - 1, j = this.size() - 1; i >= 0; i--, j--) {
if (!other.get(i).equals(get(j)))
return false;
}
return true;
}
@SuppressWarnings("unchecked")
public ImmutableStack<T> reverse() {
T[] tmpEntries = (T[]) new Object[entries.length];
for (int i = entries.length - 1, j = 0; i >= 0; i--, j++) {
tmpEntries[j] = entries[i];
}
return new ImmutableStack<T>(tmpEntries);
}
@SuppressWarnings("unchecked")
public ImmutableStack<T> popAll(ImmutableStack<T> other) {
if (!topMatches(other)) {
throw new IllegalArgumentException("top does not match");
}
int size = entries.length - other.entries.length;
T[] tmpEntries = (T[]) new Object[size];
System.arraycopy(entries, 0, tmpEntries, 0, size);
return new ImmutableStack<T>(tmpEntries);
}
@SuppressWarnings("unchecked")
public ImmutableStack<T> pushAll(ImmutableStack<T> other) {
if (other == null) {
throw new IllegalArgumentException("null other");
}
int size = entries.length + other.entries.length;
T[] tmpEntries = null;
if (size <= MAX_SIZE) {
tmpEntries = (T[]) new Object[size];
System.arraycopy(entries, 0, tmpEntries, 0, entries.length);
System.arraycopy(other.entries, 0, tmpEntries, entries.length,
other.entries.length);
} else {
tmpEntries = (T[]) new Object[MAX_SIZE];
// other has size at most MAX_SIZE
// must keep all in other
// top MAX_SIZE - other.size from this
int numFromThis = MAX_SIZE - other.entries.length;
System.arraycopy(entries, entries.length - numFromThis, tmpEntries,
0, numFromThis);
System.arraycopy(other.entries, 0, tmpEntries, numFromThis,
other.entries.length);
}
return new ImmutableStack<T>(tmpEntries);
}
@Override
public Iterator<T> iterator() {
if (entries.length == 0) {
return EmptyIterator.instance();
}
return new ArrayIterator<T>(entries);
}
/**
* return a new stack with the top replaced with t
*
* @throws EmptyStackException
*/
public ImmutableStack<T> replaceTop(T t) {
if (isEmpty()) {
throw new EmptyStackException();
}
int size = entries.length;
T[] tmpEntries = makeInternalArray(size);
System.arraycopy(entries, 0, tmpEntries, 0, entries.length - 1);
tmpEntries[size - 1] = t;
return makeStack(tmpEntries);
}
}