Quadcap Embeddable Database

com/quadcap/util/text/TextMatch.java

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package com.quadcap.util.text;

/* Copyright 1997 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.InputStream;
import java.io.IOException;

import com.quadcap.util.Debug;

/**
 *
 * @author Stan Bailes
 */
public class TextMatch {
    public static int match(byte[] string, int slen,
                            byte[] pattern, int plen) {
        int[] qmap = new int[256];
        for (int i = 0; i < 256; i++) {
            qmap[i] = plen + 1;
        }
        for (int i = 0; i < plen; i++) {
            qmap[pattern[i]] = plen - i;
        }
        for (int i = 0; i <= slen - plen; ) {
            //Debug.println("i = " + i);
            boolean match = true;
            for (int j = 0; j < plen; j++) {
                byte c = string[i + j];
                //Debug.println("             c = " + ((char)c));
                if (string[i + j] != pattern[j]) {
                    match = false;
                    break;
                }
            }
            if (match) return i;

            byte c = string[i + plen];
            //Debug.println("qmap[" + ((char)c) + "] = " + qmap[c]);
            i += qmap[string[i + plen]];
        }
        return -1;
    }

    public static int match(byte[] string, byte[] pattern) {
        return match(string, string.length, pattern, pattern.length);
    }

    public static int match(InputStream is, byte[] pattern)
        throws IOException
    {
        int[] qmap = new int[256];
        for (int i = 0; i < 256; i++) {
            qmap[i] = pattern.length + 1;
        }
        for (int i = 0; i < pattern.length; i++) {
            qmap[pattern[i]] = pattern.length - i;
        }
        int cnt = 0;
        while (true) {
            //Debug.println("cnt = " + cnt);
            is.mark(pattern.length);
            boolean match = true;
            int j, c;
            for (j = 0; j < pattern.length; j++) {
                if ((c = is.read()) < 0) return -1;
                //Debug.println("             c = " + ((char)c));
                if (c != pattern[j]) {
                    match = false;
                    break;
                }
            }
            if (match) return cnt;
            is.skip(pattern.length - j - 1);
            if ((c = is.read()) < 0) return -1;
            is.reset();
            //Debug.println("qmap[" + ((char)c) + "] = " + qmap[c]);
            int skip = qmap[c];
            if (is.skip(skip) < skip) return -1;
            cnt += skip;
        }
    }
}