alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

What this is

This file is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Other links

The source code

/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2000 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.netbeans.editor;

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import javax.swing.text.BadLocationException;
import javax.swing.text.Segment;

/**
* Encapsulation of a special static segment used
* by syntax scanners. Unfortunately document cache cannot
* guarantee that its fragment(s) will hold more than one character
* at the time so syntax scanning cannot be done by finder. Instead
* all the syntax analyzes are done over the syntax segment's data.
* Although it's shared across all instances of editors
* the loads into it should be fast as they are done from cache fragments
* by arraycopy() method.
* The syntax segment is separated into the slots because there
* can be more scanning necessary at one time.
* All the scanning must be done 
*
* @author Miloslav Metelka
* @version 1.00
*/
class SyntaxSeg extends Segment {

    private static final char[] EMPTY_CHAR_ARRAY = new char[0];

    private static final int MAX_SLOT_COUNT = 100;

    private static final int REALLOC_INCREMENT = 2048;

    private static ArrayList slotList = new ArrayList();

    static synchronized Slot getFreeSlot() {
        int cnt = slotList.size();
        return (cnt > 0) ? (Slot)slotList.remove(cnt - 1) : new Slot();
    }

    static synchronized void releaseSlot(Slot slot) {
        slotList.add(slot);
    }

    /** From this position on, the data in syntax segment must be marked
    * invalid.
    */
    static synchronized void invalidate(BaseDocument doc, int pos) {
        int cnt = slotList.size();
        for (int i = 0; i < cnt; i++) {
            ((Slot)slotList.get(i)).invalidate(doc, pos);
        }
    }

    static class Slot extends Segment {

        /** Document from which the data in syntax segment come from */
        WeakReference segDocRef = new WeakReference(null);

        /** Begining of valid data in syntax segment */
        int segPos;

        /** Begining of valid data in syntax segment */
        int segLen;

        Slot() {
            this.array = EMPTY_CHAR_ARRAY;
        }

        /** Load the syntax segment if necessary from some location in some
        * document. For best performance there's no pos or len correctness
        * checking. Therefore caller must guarantee the correctness.
        * @return real length that was loaded (syntax segment has limitation
        *   in size)
        */
        int load(BaseDocument doc, int pos, int len)
        throws BadLocationException {
            if (len <= 0) {
                if (len == 0) {
                    count = 0;
                    return 0;
                }
                throw new RuntimeException("len=" + len); // Critical error NOI18N
            }

            BaseDocument segDoc = (BaseDocument)segDocRef.get();
            boolean difDoc = (doc != segDoc);
            if (difDoc) {
                segDoc = doc;
                segDocRef = new WeakReference(segDoc);
            }

            if (difDoc // different documents
                    || pos < segPos // position too low
                    || pos > segPos + segLen // position too high
                    || pos - segPos + len > array.length
               ) { // wouldn't fit

                // possibly realloc the array
                if (len > array.length) {
                    char tmp[] = new char[len + REALLOC_INCREMENT];
                    array = tmp; // original data are not recopied
                }

                segPos = pos;
                segLen = len;

                doc.getChars(pos, array, 0, len); // read chars into array

            } else { // inside array and will fit

                int endSegPos = segPos + segLen;
                int restLen = pos + len - endSegPos;
                if (restLen > 0) { // not fully inside
                    doc.getChars(endSegPos, array, segLen, restLen);
                    segLen += restLen;
                }

            }

            offset = pos - segPos;
            count = len;
            if (offset < 0 || len < 0) {
                throw new BadLocationException("pos=" + pos + ", offset=" + offset // NOI18N
                                + "len=" + len, offset); // Critical error NOI18N
            }
            return len;
        }

        /** Is the area inside the segment? */
        boolean isAreaInside(BaseDocument doc, int pos, int len) {
            return (doc == (BaseDocument)segDocRef.get()
                    && pos >= segPos && pos + len <= segPos + segLen);
        }

        /** Invalidate the slot if it contains the data from the given document.
        * @param doc document in which the change occured
        * @param pos position in the document where the change occured
        */
        void invalidate(BaseDocument doc, int pos) {
            if (doc == (BaseDocument)segDocRef.get()) {
                if (pos < segPos) {
                    segLen = 0;
                } else if (pos < segPos + segLen) {
                    segLen = pos - segPos;
                }
            }
        }

    }

}
... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.