277 lines
7.9 KiB
Java
277 lines
7.9 KiB
Java
/*******************************************************************************
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* This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html.
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*
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* This file is a derivative of code released by the University of
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* California under the terms listed below.
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*
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* Refinement Analysis Tools is Copyright (c) 2007 The Regents of the
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* University of California (Regents). Provided that this notice and
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* the following two paragraphs are included in any distribution of
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* Refinement Analysis Tools or its derivative work, Regents agrees
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* not to assert any of Regents' copyright rights in Refinement
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* Analysis Tools against recipient for recipient's reproduction,
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* preparation of derivative works, public display, public
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* performance, distribution or sublicensing of Refinement Analysis
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* Tools and derivative works, in source code and object code form.
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* This agreement not to assert does not confer, by implication,
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* estoppel, or otherwise any license or rights in any intellectual
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* property of Regents, including, but not limited to, any patents
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* of Regents or Regents' employees.
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*
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* IN NO EVENT SHALL REGENTS BE LIABLE TO ANY PARTY FOR DIRECT,
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* INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
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* INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE
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* AND ITS DOCUMENTATION, EVEN IF REGENTS HAS BEEN ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* REGENTS SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE AND FURTHER DISCLAIMS ANY STATUTORY
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* WARRANTY OF NON-INFRINGEMENT. THE SOFTWARE AND ACCOMPANYING
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* DOCUMENTATION, IF ANY, PROVIDED HEREUNDER IS PROVIDED "AS
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* IS". REGENTS HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT,
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* UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*/
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package com.ibm.wala.util.collections;
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import java.util.Arrays;
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import java.util.EmptyStackException;
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import java.util.Iterator;
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/**
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* An immutable stack of objects. The {@link #push(Object)} and {@link #pop()}
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* operations create new stacks.
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*
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* @param <T>
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*/
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public class ImmutableStack<T> implements Iterable<T> {
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private static final ImmutableStack<Object> EMPTY = new ImmutableStack<Object>(
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new Object[0]);
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private static final int MAX_SIZE = Integer.MAX_VALUE;
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public static int getMaxSize() {
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return MAX_SIZE;
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}
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@SuppressWarnings("unchecked")
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public static final <T> ImmutableStack<T> emptyStack() {
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return (ImmutableStack<T>) EMPTY;
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}
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final private T[] entries;
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private final int cachedHashCode;
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protected ImmutableStack(T[] entries) {
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this.entries = entries;
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this.cachedHashCode = Arrays.hashCode(entries);
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}
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@SuppressWarnings("rawtypes")
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@Override
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public boolean equals(Object o) {
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if (this == o)
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return true;
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if (o != null && o instanceof ImmutableStack) {
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ImmutableStack other = (ImmutableStack) o;
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return Arrays.equals(entries, other.entries);
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}
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return false;
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}
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@Override
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public int hashCode() {
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return cachedHashCode;
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// return Util.hashArray(this.entries);
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}
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@SuppressWarnings("unused")
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public ImmutableStack<T> push(T entry) {
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if (entry == null) {
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throw new IllegalArgumentException("null entry");
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}
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if (MAX_SIZE == 0) {
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return emptyStack();
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}
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int size = entries.length + 1;
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T[] tmpEntries = null;
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if (size <= MAX_SIZE) {
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tmpEntries = makeInternalArray(size);
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System.arraycopy(entries, 0, tmpEntries, 0, entries.length);
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tmpEntries[size - 1] = entry;
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} else {
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tmpEntries = makeInternalArray(MAX_SIZE);
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System.arraycopy(entries, 1, tmpEntries, 0, entries.length - 1);
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tmpEntries[MAX_SIZE - 1] = entry;
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}
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return makeStack(tmpEntries);
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}
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@SuppressWarnings("unchecked")
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protected T[] makeInternalArray(int size) {
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return (T[]) new Object[size];
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}
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protected ImmutableStack<T> makeStack(T[] tmpEntries) {
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return new ImmutableStack<T>(tmpEntries);
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}
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/**
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* @return the element on the top of the stack
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* @throws EmptyStackException
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* if stack is empty
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*/
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public T peek() {
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if (entries.length == 0) {
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throw new EmptyStackException();
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}
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return entries[entries.length - 1];
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}
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/**
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* @throws EmptyStackException
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* if stack is empty
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*/
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public ImmutableStack<T> pop() {
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if (entries.length == 0) {
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throw new EmptyStackException();
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}
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int size = entries.length - 1;
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T[] tmpEntries = makeInternalArray(size);
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System.arraycopy(entries, 0, tmpEntries, 0, size);
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return makeStack(tmpEntries);
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}
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public boolean isEmpty() {
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return entries.length == 0;
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}
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public int size() {
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return entries.length;
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}
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public T get(int i) {
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try {
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return entries[i];
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} catch (ArrayIndexOutOfBoundsException e) {
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throw new IllegalArgumentException("invalid i: " + i);
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}
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}
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@Override
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public String toString() {
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String objArrayToString = Arrays.toString(entries);
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assert entries.length <= MAX_SIZE : objArrayToString;
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return objArrayToString;
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}
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public boolean contains(T entry) {
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if (entry == null) {
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return false;
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}
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for (int i = 0; i < entries.length; i++) {
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if (entries[i] != null && entries[i].equals(entry))
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return true;
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}
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return false;
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}
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/**
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* @return <code>true</code> iff {@code other.size() = k}, {@code k <= this.size()}, and the
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* top k elements of this equal other
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* @throws IllegalArgumentException
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* if other == null
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*/
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public boolean topMatches(ImmutableStack<T> other)
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throws IllegalArgumentException {
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if (other == null) {
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throw new IllegalArgumentException("other == null");
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}
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if (other.size() > size()) {
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return false;
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}
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for (int i = other.size() - 1, j = this.size() - 1; i >= 0; i--, j--) {
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if (!other.get(i).equals(get(j)))
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return false;
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}
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return true;
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}
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@SuppressWarnings("unchecked")
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public ImmutableStack<T> reverse() {
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T[] tmpEntries = (T[]) new Object[entries.length];
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for (int i = entries.length - 1, j = 0; i >= 0; i--, j++) {
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tmpEntries[j] = entries[i];
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}
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return new ImmutableStack<T>(tmpEntries);
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}
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@SuppressWarnings("unchecked")
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public ImmutableStack<T> popAll(ImmutableStack<T> other) {
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if (!topMatches(other)) {
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throw new IllegalArgumentException("top does not match");
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}
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int size = entries.length - other.entries.length;
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T[] tmpEntries = (T[]) new Object[size];
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System.arraycopy(entries, 0, tmpEntries, 0, size);
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return new ImmutableStack<T>(tmpEntries);
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}
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@SuppressWarnings("unchecked")
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public ImmutableStack<T> pushAll(ImmutableStack<T> other) {
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if (other == null) {
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throw new IllegalArgumentException("null other");
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}
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int size = entries.length + other.entries.length;
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T[] tmpEntries = null;
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if (size <= MAX_SIZE) {
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tmpEntries = (T[]) new Object[size];
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System.arraycopy(entries, 0, tmpEntries, 0, entries.length);
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System.arraycopy(other.entries, 0, tmpEntries, entries.length,
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other.entries.length);
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} else {
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tmpEntries = (T[]) new Object[MAX_SIZE];
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// other has size at most MAX_SIZE
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// must keep all in other
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// top MAX_SIZE - other.size from this
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int numFromThis = MAX_SIZE - other.entries.length;
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System.arraycopy(entries, entries.length - numFromThis, tmpEntries,
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0, numFromThis);
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System.arraycopy(other.entries, 0, tmpEntries, numFromThis,
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other.entries.length);
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}
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return new ImmutableStack<T>(tmpEntries);
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}
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@Override
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public Iterator<T> iterator() {
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if (entries.length == 0) {
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return EmptyIterator.instance();
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}
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return new ArrayIterator<T>(entries);
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}
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/**
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* return a new stack with the top replaced with t
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*
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* @throws EmptyStackException
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*/
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public ImmutableStack<T> replaceTop(T t) {
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if (isEmpty()) {
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throw new EmptyStackException();
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}
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int size = entries.length;
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T[] tmpEntries = makeInternalArray(size);
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System.arraycopy(entries, 0, tmpEntries, 0, entries.length - 1);
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tmpEntries[size - 1] = t;
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return makeStack(tmpEntries);
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}
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}
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