ReaderCharStream.java

/**
 * Copyright (c) 2005-2011 by Appcelerator, Inc. All Rights Reserved.
 * Licensed under the terms of the Eclipse Public License (EPL).
 * Please see the license.txt included with this distribution for details.
 * Any modifications to this file must keep this entire header intact.
 */
package org.python.parser;

import java.io.IOException;

import org.python.pydev.core.ObjectsPool.ObjectsPoolMap;
import org.python.pydev.core.log.Log;


/**
 * An implementation of interface CharStream, where the data is read from a Reader. Completely recreated so that we can read data directly from a String, as the
 * initial implementation was highly inefficient when working only with a string (actually, if it was small, there would be no noticeable
 * delays, but if it became big, then the improvement would be HUGE).
 * 
 * It keeps the same semantics for line and column stuff (and shares the previous approach of keeping a buffer for this info).
 * If we wanted we could optimize it for also taking less memory, but as there is usually not so many concurrent parses, this 
 * is probably not worth it -- and it would probably be a little slower)
 */

public final class ReaderCharStream implements CharStream {

    private char[] buffer;

    private int bufline[];

    private int bufcolumn[];

    private boolean prevCharIsCR = false;

    private boolean prevCharIsLF = false;

    private int column = 0;

    private int line = 1;

    private int bufpos = -1;

    private int updatePos;

    private int tokenBegin;

    private static IOException ioException;

    private static final boolean DEBUG = false;

    public ReaderCharStream(char cs[]) {
        this.buffer = cs;
        this.bufline = new int[cs.length];
        this.bufcolumn = new int[cs.length];
    }

    public int getCurrentPos() {
        return bufpos;
    }

    public void restorePos(int pos) {
        bufpos = pos;
    }

    /**
     * Restores a previous position.
     * Don't forget to restore the level if eof was already found!
     */
    public void restoreLineColPos(final int endLine, final int endColumn) {
        final int initialBufPos = bufpos;
        final int currLine = getEndLine();

        int attempts = 0;
        if (currLine < endLine) {
            //note: we could do it, but it's not what we want!
            Log.log("Cannot backtrack to a later position -- current line: " + getEndLine() + " requested line:"
                    + endLine);
            return;
        } else if (currLine == endLine && getEndColumn() < endColumn) {
            Log.log("Cannot backtrack to a later position -- current col: " + getEndColumn() + " requested col:"
                    + endColumn);
            return;
        }

        while ((getEndLine() != endLine || getEndColumn() != endColumn) && bufpos >= 0) {
            attempts += 1;
            bufpos--;
        }

        if (bufpos < 0 || getEndLine() != endLine) {
            //we couldn't find it. Let's restore the position when we started it.
            bufpos = initialBufPos;
            Log.log("Couldn't backtrack to position: line" + endLine + " -- col:" + endColumn);
        }
    }

    public final char readChar() throws IOException {
        try {
            bufpos++;
            char r = this.buffer[bufpos];

            if (bufpos >= updatePos) {
                updatePos++;

                //start UpdateLineCol
                column++;

                if (prevCharIsLF) {
                    prevCharIsLF = false;
                    line += (column = 1);

                } else if (prevCharIsCR) {

                    prevCharIsCR = false;
                    if (r == '\n') {
                        prevCharIsLF = true;
                    } else {
                        line += (column = 1);
                    }
                }

                if (r == '\r') {
                    prevCharIsCR = true;

                } else if (r == '\n') {
                    prevCharIsLF = true;

                }

                bufline[bufpos] = line;
                bufcolumn[bufpos] = column;
                //end UpdateLineCol
            }

            return r;
        } catch (ArrayIndexOutOfBoundsException e) {
            bufpos--;
            if (ioException == null) {
                ioException = new IOException();
            }
            throw ioException;
        }
    }

    /**
     * @deprecated
     * @see #getEndColumn
     */

    public final int getColumn() {
        return bufcolumn[bufpos];
    }

    /**
     * @deprecated
     * @see #getEndLine
     */

    public final int getLine() {
        return bufline[bufpos];
    }

    public final int getEndColumn() {
        return bufcolumn[bufpos];
    }

    public final int getEndLine() {
        return bufline[bufpos];
    }

    public final int getBeginColumn() {
        return bufcolumn[tokenBegin];
    }

    public final int getBeginLine() {
        return bufline[tokenBegin];
    }

    public final void backup(int amount) {
        if (DEBUG) {
            System.out.println("FastCharStream: backup >>" + amount + "<<");
        }
        bufpos -= amount;
    }

    public final char BeginToken() throws IOException {
        char c = readChar();
        tokenBegin = bufpos;
        if (DEBUG) {
            System.out.println("FastCharStream: BeginToken >>" + (int) c + "<<");
        }
        return c;
    }

    private final ObjectsPoolMap interned = new ObjectsPoolMap();

    public final String GetImage() {
        String string;
        if (bufpos >= tokenBegin) {
            string = new String(buffer, tokenBegin, bufpos - tokenBegin + 1);
        } else {
            string = new String(buffer, tokenBegin, buffer.length - tokenBegin + 1);
        }
        String existing = interned.get(string);
        if (existing == null) {
            existing = string;
            interned.put(string, string);
        }
        return existing;
    }

    public final char[] GetSuffix(int len) {

        char[] ret = new char[len];
        if (len > 0) {
            try {
                int initial = bufpos - len + 1;
                if (initial < 0) {
                    int initial0 = initial;
                    len += initial;
                    initial = 0;
                    System.arraycopy(buffer, initial, ret, -initial0, len);
                } else {
                    System.arraycopy(buffer, initial, ret, 0, len);
                }
            } catch (Exception e) {
                Log.log(e);
            }
        }
        if (DEBUG) {
            System.out.println("FastCharStream: GetSuffix:" + len + " >>" + new String(ret) + "<<");
        }
        return ret;
    }

    public final void Done() {
        buffer = null;
        bufline = null;
        bufcolumn = null;
    }

}