/Users/parrt/antlr/code/antlr/main/runtime/Java/src/main/java/org/antlr/runtime/tree/RewriteRuleElementStream.java

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/*
 [The "BSD license"]
 Copyright (c) 2005-2009 Terence Parr
 All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
 2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
 3. The name of the author may not be used to endorse or promote products
     derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.antlr.runtime.tree;

import java.util.ArrayList;
import java.util.List;

public abstract class RewriteRuleElementStream {
        protected int cursor = 0;

        protected Object singleElement;

        protected List elements;

        protected boolean dirty = false;

        protected String elementDescription;
        protected TreeAdaptor adaptor;

        public RewriteRuleElementStream(TreeAdaptor adaptor, String elementDescription) {
                this.elementDescription = elementDescription;
                this.adaptor = adaptor;
        }

        public RewriteRuleElementStream(TreeAdaptor adaptor,
                                                                        String elementDescription,
                                                                        Object oneElement)
        {
                this(adaptor, elementDescription);
                add(oneElement);
        }

        public RewriteRuleElementStream(TreeAdaptor adaptor,
                                                                        String elementDescription,
                                                                        List elements)
        {
                this(adaptor, elementDescription);
                this.singleElement = null;
                this.elements = elements;
        }

        public void reset() {
                cursor = 0;
                dirty = true;
        }

        public void add(Object el) {
                //System.out.println("add '"+elementDescription+"' is "+el);
                if ( el==null ) {
                        return;
                }
                if ( elements!=null ) { // if in list, just add
                        elements.add(el);
                        return;
                }
                if ( singleElement == null ) { // no elements yet, track w/o list
                        singleElement = el;
                        return;
                }
                // adding 2nd element, move to list
                elements = new ArrayList(5);
                elements.add(singleElement);
                singleElement = null;
                elements.add(el);
        }

        public Object nextTree() {
                int n = size();
                if ( dirty || (cursor>=n && n==1) ) {
                        // if out of elements and size is 1, dup
                        Object el = _next();
                        return dup(el);
                }
                // test size above then fetch
                Object el = _next();
                return el;
        }

        protected Object _next() {
                int n = size();
                if ( n ==0 ) {
                        throw new RewriteEmptyStreamException(elementDescription);
                }
                if ( cursor>= n) { // out of elements?
                        if ( n ==1 ) {  // if size is 1, it's ok; return and we'll dup
                                return toTree(singleElement);
                        }
                        // out of elements and size was not 1, so we can't dup
                        throw new RewriteCardinalityException(elementDescription);
                }
                // we have elements
                if ( singleElement!=null ) {
                        cursor++; // move cursor even for single element list
                        return toTree(singleElement);
                }
                // must have more than one in list, pull from elements
                Object o = toTree(elements.get(cursor));
                cursor++;
                return o;
        }

        protected abstract Object dup(Object el);

        protected Object toTree(Object el) {
                return el;
        }

        public boolean hasNext() {
                 return (singleElement != null && cursor < 1) ||
                           (elements!=null && cursor < elements.size());
        }

        public int size() {
                int n = 0;
                if ( singleElement != null ) {
                        n = 1;
                }
                if ( elements!=null ) {
                        return elements.size();
                }
                return n;
        }

        public String getDescription() {
                return elementDescription;
        }
}

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