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

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/*
[The "BSD licence"]
Copyright (c) 2005-2008 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 org.antlr.runtime.Token;
import org.antlr.runtime.TokenStream;

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

public class UnBufferedTreeNodeStream implements TreeNodeStream {
        public static final int INITIAL_LOOKAHEAD_BUFFER_SIZE = 5;

        protected boolean uniqueNavigationNodes = false;

        protected Object root;

        protected TokenStream tokens;

        TreeAdaptor adaptor;

        protected Stack nodeStack = new Stack();

        protected Stack indexStack = new Stack();

        protected Object currentNode;

        protected Object previousNode;

        protected int currentChildIndex;

        protected int absoluteNodeIndex;

        protected Object[] lookahead = new Object[INITIAL_LOOKAHEAD_BUFFER_SIZE];

        protected int head;

        protected int tail;

        protected class TreeWalkState {
                int currentChildIndex;
                int absoluteNodeIndex;
                Object currentNode;
                Object previousNode;
                int nodeStackSize;
                int indexStackSize;
                Object[] lookahead;
        }

        protected List markers;

        protected int markDepth = 0;

        protected int lastMarker;

        // navigation nodes

        protected Object down;
        protected Object up;
        protected Object eof;

        public UnBufferedTreeNodeStream(Object tree) {
                this(new CommonTreeAdaptor(), tree);
        }

        public UnBufferedTreeNodeStream(TreeAdaptor adaptor, Object tree) {
                this.root = tree;
                this.adaptor = adaptor;
                reset();
                down = adaptor.create(Token.DOWN, "DOWN");
                up = adaptor.create(Token.UP, "UP");
                eof = adaptor.create(Token.EOF, "EOF");
        }

        public void reset() {
                currentNode = root;
                previousNode = null;
                currentChildIndex = -1;
                absoluteNodeIndex = -1;
                head = tail = 0;
        }

        // Satisfy TreeNodeStream

        public Object get(int i) {
                throw new UnsupportedOperationException("stream is unbuffered");
        }

        public Object LT(int k) {
                //System.out.println("LT("+k+"); head="+head+", tail="+tail);
                if ( k==-1 ) {
                        return previousNode;
                }
                if ( k<0 ) {
                        throw new IllegalArgumentException("tree node streams cannot look backwards more than 1 node");
                }
                if ( k==0 ) {
                        return Tree.INVALID_NODE;
                }
                fill(k);
                return lookahead[(head+k-1)%lookahead.length];
        }

        public Object getTreeSource() {
                return root;
        }

        public String getSourceName() {
                return getTokenStream().getSourceName();
        }

        public TokenStream getTokenStream() {
                return tokens;
        }

        public void setTokenStream(TokenStream tokens) {
                this.tokens = tokens;
        }

        protected void fill(int k) {
                int n = getLookaheadSize();
                //System.out.println("we have "+n+" nodes; need "+(k-n));
                for (int i=1; i<=k-n; i++) {
                        next(); // get at least k-depth lookahead nodes
                }
        }

        protected void addLookahead(Object node) {
                //System.out.println("addLookahead head="+head+", tail="+tail);
                lookahead[tail] = node;
                tail = (tail+1)%lookahead.length;
                if ( tail==head ) {
                        // buffer overflow: tail caught up with head
                        // allocate a buffer 2x as big
                        Object[] bigger = new Object[2*lookahead.length];
                        // copy head to end of buffer to beginning of bigger buffer
                        int remainderHeadToEnd = lookahead.length-head;
                        System.arraycopy(lookahead, head, bigger, 0, remainderHeadToEnd);
                        // copy 0..tail to after that
                        System.arraycopy(lookahead, 0, bigger, remainderHeadToEnd, tail);
                        lookahead = bigger; // reset to bigger buffer
                        head = 0;
                        tail += remainderHeadToEnd;
                }
        }

        // Satisfy IntStream interface

        public void consume() {
                /*
                System.out.println("consume: currentNode="+currentNode.getType()+
                                                   " childIndex="+currentChildIndex+
                                                   " nodeIndex="+absoluteNodeIndex);
                                                   */
                // make sure there is something in lookahead buf, which might call next()
                fill(1);
                absoluteNodeIndex++;
                previousNode = lookahead[head]; // track previous node before moving on
                head = (head+1) % lookahead.length;
        }

        public int LA(int i) {
                Object t = LT(i);
                if ( t==null ) {
                        return Token.INVALID_TOKEN_TYPE;
                }
                return adaptor.getType(t);
        }

        public int mark() {
                if ( markers==null ) {
                        markers = new ArrayList();
                        markers.add(null); // depth 0 means no backtracking, leave blank
                }
                markDepth++;
                TreeWalkState state = null;
                if ( markDepth>=markers.size() ) {
                        state = new TreeWalkState();
                        markers.add(state);
                }
                else {
                        state = (TreeWalkState)markers.get(markDepth);
                }
                state.absoluteNodeIndex = absoluteNodeIndex;
                state.currentChildIndex = currentChildIndex;
                state.currentNode = currentNode;
                state.previousNode = previousNode;
                state.nodeStackSize = nodeStack.size();
                state.indexStackSize = indexStack.size();
                // take snapshot of lookahead buffer
                int n = getLookaheadSize();
                int i=0;
                state.lookahead = new Object[n];
                for (int k=1; k<=n; k++,i++) {
                        state.lookahead[i] = LT(k);
                }
                lastMarker = markDepth;
                return markDepth;
        }

        public void release(int marker) {
                // unwind any other markers made after marker and release marker
                markDepth = marker;
                // release this marker
                markDepth--;
        }

        public void rewind(int marker) {
                if ( markers==null ) {
                        return;
                }
                TreeWalkState state = (TreeWalkState)markers.get(marker);
                absoluteNodeIndex = state.absoluteNodeIndex;
                currentChildIndex = state.currentChildIndex;
                currentNode = state.currentNode;
                previousNode = state.previousNode;
                // drop node and index stacks back to old size
                nodeStack.setSize(state.nodeStackSize);
                indexStack.setSize(state.indexStackSize);
                head = tail = 0; // wack lookahead buffer and then refill
                for (; tail<state.lookahead.length; tail++) {
                        lookahead[tail] = state.lookahead[tail];
                }
                release(marker);
        }

        public void rewind() {
                rewind(lastMarker);
        }

        public void seek(int index) {
                if ( index<this.index() ) {
                        throw new IllegalArgumentException("can't seek backwards in node stream");
                }
                // seek forward, consume until we hit index
                while ( this.index()<index ) {
                        consume();
                }
        }

        public int index() {
                return absoluteNodeIndex+1;
        }

        public int size() {
                CommonTreeNodeStream s = new CommonTreeNodeStream(root);
                return s.size();
        }

        public Object next() {
                // already walked entire tree; nothing to return
                if ( currentNode==null ) {
                        addLookahead(eof);
                        // this is infinite stream returning EOF at end forever
                        // so don't throw NoSuchElementException
                        return null;
                }

                // initial condition (first time method is called)
                if ( currentChildIndex==-1 ) {
                        return handleRootNode();
                }

                // index is in the child list?
                if ( currentChildIndex<adaptor.getChildCount(currentNode) ) {
                        return visitChild(currentChildIndex);
                }

                // hit end of child list, return to parent node or its parent ...
                walkBackToMostRecentNodeWithUnvisitedChildren();
                if ( currentNode!=null ) {
                        return visitChild(currentChildIndex);
                }

                return null;
        }

        protected Object handleRootNode() {
                Object node;
                node = currentNode;
                // point to first child in prep for subsequent next()
                currentChildIndex = 0;
                if ( adaptor.isNil(node) ) {
                        // don't count this root nil node
                        node = visitChild(currentChildIndex);
                }
                else {
                        addLookahead(node);
                        if ( adaptor.getChildCount(currentNode)==0 ) {
                                // single node case
                                currentNode = null; // say we're done
                        }
                }
                return node;
        }

        protected Object visitChild(int child) {
                Object node = null;
                // save state
                nodeStack.push(currentNode);
                indexStack.push(new Integer(child));
                if ( child==0 && !adaptor.isNil(currentNode) ) {
                        addNavigationNode(Token.DOWN);
                }
                // visit child
                currentNode = adaptor.getChild(currentNode,child);
                currentChildIndex = 0;
                node = currentNode;  // record node to return
                addLookahead(node);
                walkBackToMostRecentNodeWithUnvisitedChildren();
                return node;
        }

        protected void addNavigationNode(final int ttype) {
                Object navNode = null;
                if ( ttype==Token.DOWN ) {
                        if ( hasUniqueNavigationNodes() ) {
                                navNode = adaptor.create(Token.DOWN, "DOWN");
                        }
                        else {
                                navNode = down;
                        }
                }
                else {
                        if ( hasUniqueNavigationNodes() ) {
                                navNode = adaptor.create(Token.UP, "UP");
                        }
                        else {
                                navNode = up;
                        }
                }
                addLookahead(navNode);
        }

        protected void walkBackToMostRecentNodeWithUnvisitedChildren() {
                while ( currentNode!=null &&
                                currentChildIndex>=adaptor.getChildCount(currentNode) )
                {
                        currentNode = nodeStack.pop();
                        if ( currentNode==null ) { // hit the root?
                                return;
                        }
                        currentChildIndex = ((Integer)indexStack.pop()).intValue();
                        currentChildIndex++; // move to next child
                        if ( currentChildIndex>=adaptor.getChildCount(currentNode) ) {
                                if ( !adaptor.isNil(currentNode) ) {
                                        addNavigationNode(Token.UP);
                                }
                                if ( currentNode==root ) { // we done yet?
                                        currentNode = null;
                                }
                        }
                }
        }

        public TreeAdaptor getTreeAdaptor() {
                return adaptor;
        }

        public boolean hasUniqueNavigationNodes() {
                return uniqueNavigationNodes;
        }

        public void setUniqueNavigationNodes(boolean uniqueNavigationNodes) {
                this.uniqueNavigationNodes = uniqueNavigationNodes;
        }

        public void replaceChildren(Object parent, int startChildIndex, int stopChildIndex, Object t) {
                throw new UnsupportedOperationException("can't do stream rewrites yet");
        }

        public String toString() {
                return toString(root, null);
        }

        protected int getLookaheadSize() {
                return tail<head?(lookahead.length-head+tail):(tail-head);
        }

        public String toString(Object start, Object stop) {
                if ( start==null ) {
                        return null;
                }
                // if we have the token stream, use that to dump text in order
                if ( tokens!=null ) {
                        // don't trust stop node as it's often an UP node etc...
                        // walk backwards until you find a non-UP, non-DOWN node
                        // and ask for it's token index.
                        int beginTokenIndex = adaptor.getTokenStartIndex(start);
                        int endTokenIndex = adaptor.getTokenStopIndex(stop);
                        if ( stop!=null && adaptor.getType(stop)==Token.UP ) {
                                endTokenIndex = adaptor.getTokenStopIndex(start);
                        }
                        else {
                                endTokenIndex = size()-1;
                        }
                        return tokens.toString(beginTokenIndex, endTokenIndex);
                }
                StringBuffer buf = new StringBuffer();
                toStringWork(start, stop, buf);
                return buf.toString();
        }

        protected void toStringWork(Object p, Object stop, StringBuffer buf) {
                if ( !adaptor.isNil(p) ) {
                        String text = adaptor.getText(p);
                        if ( text==null ) {
                                text = " "+String.valueOf(adaptor.getType(p));
                        }
                        buf.append(text); // ask the node to go to string
                }
                if ( p==stop ) {
                        return;
                }
                int n = adaptor.getChildCount(p);
                if ( n>0 && !adaptor.isNil(p) ) {
                        buf.append(" ");
                        buf.append(Token.DOWN);
                }
                for (int c=0; c<n; c++) {
                        Object child = adaptor.getChild(p,c);
                        toStringWork(child, stop, buf);
                }
                if ( n>0 && !adaptor.isNil(p) ) {
                        buf.append(" ");
                        buf.append(Token.UP);
                }
        }
}

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