duke@1: /*
duke@1:  * Copyright 1999-2006 Sun Microsystems, Inc.  All Rights Reserved.
duke@1:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@1:  *
duke@1:  * This code is free software; you can redistribute it and/or modify it
duke@1:  * under the terms of the GNU General Public License version 2 only, as
duke@1:  * published by the Free Software Foundation.  Sun designates this
duke@1:  * particular file as subject to the "Classpath" exception as provided
duke@1:  * by Sun in the LICENSE file that accompanied this code.
duke@1:  *
duke@1:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@1:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@1:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@1:  * version 2 for more details (a copy is included in the LICENSE file that
duke@1:  * accompanied this code).
duke@1:  *
duke@1:  * You should have received a copy of the GNU General Public License version
duke@1:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@1:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@1:  *
duke@1:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@1:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@1:  * have any questions.
duke@1:  */
duke@1: 
duke@1: package com.sun.tools.javac.util;
duke@1: 
duke@1: import java.util.Collection;
duke@1: import java.util.Iterator;
duke@1: import java.util.NoSuchElementException;
duke@1: 
duke@1: /** A class for constructing lists by appending elements. Modelled after
duke@1:  *  java.lang.StringBuffer.
duke@1:  *
duke@1:  *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
duke@1:  *  you write code that depends on this, you do so at your own risk.
duke@1:  *  This code and its internal interfaces are subject to change or
duke@1:  *  deletion without notice.</b>
duke@1:  */
duke@1: public class ListBuffer<A> implements Collection<A> {
duke@1: 
duke@1:     public static <T> ListBuffer<T> lb() {
duke@1:         return new ListBuffer<T>();
duke@1:     }
duke@1: 
duke@1:     /** The list of elements of this buffer.
duke@1:      */
duke@1:     public List<A> elems;
duke@1: 
duke@1:     /** A pointer pointing to the last, sentinel element of `elems'.
duke@1:      */
duke@1:     public List<A> last;
duke@1: 
duke@1:     /** The number of element in this buffer.
duke@1:      */
duke@1:     public int count;
duke@1: 
duke@1:     /** Has a list been created from this buffer yet?
duke@1:      */
duke@1:     public boolean shared;
duke@1: 
duke@1:     /** Create a new initially empty list buffer.
duke@1:      */
duke@1:     public ListBuffer() {
duke@1:         clear();
duke@1:     }
duke@1: 
duke@1:     public final void clear() {
duke@1:         this.elems = new List<A>(null,null);
duke@1:         this.last = this.elems;
duke@1:         count = 0;
duke@1:         shared = false;
duke@1:     }
duke@1: 
duke@1:     /** Return the number of elements in this buffer.
duke@1:      */
duke@1:     public int length() {
duke@1:         return count;
duke@1:     }
duke@1:     public int size() {
duke@1:         return count;
duke@1:     }
duke@1: 
duke@1:     /** Is buffer empty?
duke@1:      */
duke@1:     public boolean isEmpty() {
duke@1:         return count == 0;
duke@1:     }
duke@1: 
duke@1:     /** Is buffer not empty?
duke@1:      */
duke@1:     public boolean nonEmpty() {
duke@1:         return count != 0;
duke@1:     }
duke@1: 
duke@1:     /** Copy list and sets last.
duke@1:      */
duke@1:     private void copy() {
duke@1:         List<A> p = elems = new List<A>(elems.head, elems.tail);
duke@1:         while (true) {
duke@1:             List<A> tail = p.tail;
duke@1:             if (tail == null) break;
duke@1:             tail = new List<A>(tail.head, tail.tail);
duke@1:             p.setTail(tail);
duke@1:             p = tail;
duke@1:         }
duke@1:         last = p;
duke@1:         shared = false;
duke@1:     }
duke@1: 
duke@1:     /** Prepend an element to buffer.
duke@1:      */
duke@1:     public ListBuffer<A> prepend(A x) {
duke@1:         elems = elems.prepend(x);
duke@1:         count++;
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** Append an element to buffer.
duke@1:      */
duke@1:     public ListBuffer<A> append(A x) {
duke@1:         if (shared) copy();
duke@1:         last.head = x;
duke@1:         last.setTail(new List<A>(null,null));
duke@1:         last = last.tail;
duke@1:         count++;
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** Append all elements in a list to buffer.
duke@1:      */
duke@1:     public ListBuffer<A> appendList(List<A> xs) {
duke@1:         while (xs.nonEmpty()) {
duke@1:             append(xs.head);
duke@1:             xs = xs.tail;
duke@1:         }
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** Append all elements in a list to buffer.
duke@1:      */
duke@1:     public ListBuffer<A> appendList(ListBuffer<A> xs) {
duke@1:         return appendList(xs.toList());
duke@1:     }
duke@1: 
duke@1:     /** Append all elements in an array to buffer.
duke@1:      */
duke@1:     public ListBuffer<A> appendArray(A[] xs) {
duke@1:         for (int i = 0; i < xs.length; i++) {
duke@1:             append(xs[i]);
duke@1:         }
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** Convert buffer to a list of all its elements.
duke@1:      */
duke@1:     public List<A> toList() {
duke@1:         shared = true;
duke@1:         return elems;
duke@1:     }
duke@1: 
duke@1:     /** Does the list contain the specified element?
duke@1:      */
duke@1:     public boolean contains(Object x) {
duke@1:         return elems.contains(x);
duke@1:     }
duke@1: 
duke@1:     /** Convert buffer to an array
duke@1:      */
duke@1:     public <T> T[] toArray(T[] vec) {
duke@1:         return elems.toArray(vec);
duke@1:     }
duke@1:     public Object[] toArray() {
duke@1:         return toArray(new Object[size()]);
duke@1:     }
duke@1: 
duke@1:     /** The first element in this buffer.
duke@1:      */
duke@1:     public A first() {
duke@1:         return elems.head;
duke@1:     }
duke@1: 
duke@1:     /** Remove the first element in this buffer.
duke@1:      */
duke@1:     public void remove() {
duke@1:         if (elems != last) {
duke@1:             elems = elems.tail;
duke@1:             count--;
duke@1:         }
duke@1:     }
duke@1: 
duke@1:     /** Return first element in this buffer and remove
duke@1:      */
duke@1:     public A next() {
duke@1:         A x = elems.head;
duke@1:         remove();
duke@1:         return x;
duke@1:     }
duke@1: 
duke@1:     /** An enumeration of all elements in this buffer.
duke@1:      */
duke@1:     public Iterator<A> iterator() {
duke@1:         return new Iterator<A>() {
duke@1:             List<A> elems = ListBuffer.this.elems;
duke@1:             public boolean hasNext() {
duke@1:                 return elems != last;
duke@1:             }
duke@1:             public A next() {
duke@1:                 if (elems == last)
duke@1:                     throw new NoSuchElementException();
duke@1:                 A elem = elems.head;
duke@1:                 elems = elems.tail;
duke@1:                 return elem;
duke@1:             }
duke@1:             public void remove() {
duke@1:                 throw new UnsupportedOperationException();
duke@1:             }
duke@1:         };
duke@1:     }
duke@1: 
duke@1:     public boolean add(A a) {
duke@1:         throw new UnsupportedOperationException();
duke@1:     }
duke@1:     public boolean remove(Object o) {
duke@1:         throw new UnsupportedOperationException();
duke@1:     }
duke@1:     public boolean containsAll(Collection<?> c) {
duke@1:         throw new UnsupportedOperationException();
duke@1:     }
duke@1:     public boolean addAll(Collection<? extends A> c) {
duke@1:         throw new UnsupportedOperationException();
duke@1:     }
duke@1:     public boolean removeAll(Collection<?> c) {
duke@1:         throw new UnsupportedOperationException();
duke@1:     }
duke@1:     public boolean retainAll(Collection<?> c) {
duke@1:         throw new UnsupportedOperationException();
duke@1:     }
duke@1: }