antlr-3.4/runtime/Java/src/main/java/org/antlr/runtime/ANTLRStringStream.java

/*
 [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;

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

/** A pretty quick CharStream that pulls all data from an array
 *  directly.  Every method call counts in the lexer.  Java's
 *  strings aren't very good so I'm avoiding.
 */
public class ANTLRStringStream implements CharStream {
	/** The data being scanned */
	protected char[] data;

	/** How many characters are actually in the buffer */
	protected int n;

	/** 0..n-1 index into string of next char */
	protected int p=0;

	/** line number 1..n within the input */
	protected int line = 1;

	/** The index of the character relative to the beginning of the line 0..n-1 */
	protected int charPositionInLine = 0;

	/** tracks how deep mark() calls are nested */
	protected int markDepth = 0;

	/** A list of CharStreamState objects that tracks the stream state
	 *  values line, charPositionInLine, and p that can change as you
	 *  move through the input stream.  Indexed from 1..markDepth.
     *  A null is kept @ index 0.  Create upon first call to mark().
	 */
	protected List markers;

	/** Track the last mark() call result value for use in rewind(). */
	protected int lastMarker;

	/** What is name or source of this char stream? */
	public String name;

	public ANTLRStringStream() {
	}

	/** Copy data in string to a local char array */
	public ANTLRStringStream(String input) {
		this();
		this.data = input.toCharArray();
		this.n = input.length();
	}

	/** This is the preferred constructor as no data is copied */
	public ANTLRStringStream(char[] data, int numberOfActualCharsInArray) {
		this();
		this.data = data;
		this.n = numberOfActualCharsInArray;
	}

	/** Reset the stream so that it's in the same state it was
	 *  when the object was created *except* the data array is not
	 *  touched.
	 */
	public void reset() {
		p = 0;
		line = 1;
		charPositionInLine = 0;
		markDepth = 0;
	}

    public void consume() {
		//System.out.println("prev p="+p+", c="+(char)data[p]);
        if ( p < n ) {
			charPositionInLine++;
			if ( data[p]=='\n' ) {
				/*
				System.out.println("newline char found on line: "+line+
								   "@ pos="+charPositionInLine);
				*/
				line++;
				charPositionInLine=0;
			}
            p++;
			//System.out.println("p moves to "+p+" (c='"+(char)data[p]+"')");
        }
    }

    public int LA(int i) {
		if ( i==0 ) {
			return 0; // undefined
		}
		if ( i<0 ) {
			i++; // e.g., translate LA(-1) to use offset i=0; then data[p+0-1]
			if ( (p+i-1) < 0 ) {
				return CharStream.EOF; // invalid; no char before first char
			}
		}

		if ( (p+i-1) >= n ) {
            //System.out.println("char LA("+i+")=EOF; p="+p);
            return CharStream.EOF;
        }
        //System.out.println("char LA("+i+")="+(char)data[p+i-1]+"; p="+p);
		//System.out.println("LA("+i+"); p="+p+" n="+n+" data.length="+data.length);
		return data[p+i-1];
    }

	public int LT(int i) {
		return LA(i);
	}

	/** Return the current input symbol index 0..n where n indicates the
     *  last symbol has been read.  The index is the index of char to
	 *  be returned from LA(1).
     */
    public int index() {
        return p;
    }

	public int size() {
		return n;
	}

	public int mark() {
        if ( markers==null ) {
            markers = new ArrayList();
            markers.add(null); // depth 0 means no backtracking, leave blank
        }
        markDepth++;
		CharStreamState state = null;
		if ( markDepth>=markers.size() ) {
			state = new CharStreamState();
			markers.add(state);
		}
		else {
			state = (CharStreamState)markers.get(markDepth);
		}
		state.p = p;
		state.line = line;
		state.charPositionInLine = charPositionInLine;
		lastMarker = markDepth;
		return markDepth;
    }

    public void rewind(int m) {
		CharStreamState state = (CharStreamState)markers.get(m);
		// restore stream state
		seek(state.p);
		line = state.line;
		charPositionInLine = state.charPositionInLine;
		release(m);
	}

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

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

	/** consume() ahead until p==index; can't just set p=index as we must
	 *  update line and charPositionInLine.
	 */
	public void seek(int index) {
		if ( index<=p ) {
			p = index; // just jump; don't update stream state (line, ...)
			return;
		}
		// seek forward, consume until p hits index
		while ( p<index ) {
			consume();
		}
	}

	public String substring(int start, int stop) {
		return new String(data,start,stop-start+1);
	}

	public int getLine() {
		return line;
	}

	public int getCharPositionInLine() {
		return charPositionInLine;
	}

	public void setLine(int line) {
		this.line = line;
	}

	public void setCharPositionInLine(int pos) {
		this.charPositionInLine = pos;
	}

	public String getSourceName() {
		return name;
	}

    public String toString() { return new String(data); }
}