like.java

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/* Copyright (c) 1995-2000, The Hypersonic SQL Group.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 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.
 *
 * Neither the name of the Hypersonic SQL Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 HYPERSONIC SQL GROUP,
 * OR CONTRIBUTORS 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.
 *
 * This software consists of voluntary contributions made by many individuals 
 * on behalf of the Hypersonic SQL Group.
 *
 *
 * For work added by the HSQL Development Group:
 *
 * Copyright (c) 2001-2005, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 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.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS 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.hsqldb;

import org.hsqldb.lib.StringUtil;

/**
 * Reusable object for processing LIKE queries.
 *
 * Enhanced in successive versions of HSQLDB.
 *
 * @author Thomas Mueller (Hypersonic SQL Group)
 * @version 1.8.0
 * @since Hypersonic SQL
 */

// boucherb@users 20030930 - patch 1.7.2 - optimize into joins if possible
// fredt@users 20031006 - patch 1.7.2 - reuse Like objects for all rows
class Like {

    private char[]   cLike;
    private int[]    wildCardType;
    private int      iLen;
    private boolean  isIgnoreCase;
    private int      iFirstWildCard;
    private boolean  isNull;
    Character        escapeChar;
    boolean          hasCollation;
    boolean          optimised;
    static final int UNDERSCORE_CHAR = 1;
    static final int PERCENT_CHAR    = 2;

    Like(Character escape, boolean collation) {
        escapeChar   = escape;
        hasCollation = collation;
    }

    /**
     * param setter
     *
     * @param s
     * @param ignorecase
     */
    void setParams(Session session, String s, boolean ignorecase) {

        isIgnoreCase = ignorecase;

        normalize(session, s);

        optimised = true;
    }

    /**
     * Resets the search pattern;
     */
    void resetPattern(Session session, String s) {
        normalize(session, s);
    }

    private String getStartsWith() {

        if (iLen == 0) {
            return "";
        }

        StringBuffer s = new StringBuffer();
        int          i = 0;

        for (; (i < iLen) && (wildCardType[i] == 0); i++) {
            s.append(cLike[i]);
        }

        if (i == 0) {
            return null;
        }

        return s.toString();
    }

    /**
     * Method declaration
     *
     *
     * @param o
     *
     * @return
     */
    Boolean compare(Session session, String s) {

        if (s == null) {
            return null;
        }

        if (isIgnoreCase) {
            s = session.database.collation.toUpperCase(s);
        }

        return compareAt(s, 0, 0, s.length()) ? Boolean.TRUE
                                              : Boolean.FALSE;
    }

    /**
     * Method declaration
     *
     *
     * @param s
     * @param i
     * @param j
     * @param jLen
     *
     * @return
     */
    private boolean compareAt(String s, int i, int j, int jLen) {

        for (; i < iLen; i++) {
            switch (wildCardType[i]) {

                case 0 :                  // general character
                    if ((j >= jLen) || (cLike[i] != s.charAt(j++))) {
                        return false;
                    }
                    break;

                case UNDERSCORE_CHAR :    // underscore: do not test this character
                    if (j++ >= jLen) {
                        return false;
                    }
                    break;

                case PERCENT_CHAR :       // percent: none or any character(s)
                    if (++i >= iLen) {
                        return true;
                    }

                    while (j < jLen) {
                        if ((cLike[i] == s.charAt(j))
                                && compareAt(s, i, j, jLen)) {
                            return true;
                        }

                        j++;
                    }

                    return false;
            }
        }

        if (j != jLen) {
            return false;
        }

        return true;
    }

    /**
     * Method declaration
     *
     *
     * @param pattern
     * @param b
     */
    private void normalize(Session session, String pattern) {

        isNull = pattern == null;

        if (!isNull && isIgnoreCase) {
            pattern = session.database.collation.toUpperCase(pattern);
        }

        iLen           = 0;
        iFirstWildCard = -1;

        int l = pattern == null ? 0
                                : pattern.length();

        cLike        = new char[l];
        wildCardType = new int[l];

        boolean bEscaping = false,
                bPercent  = false;

        for (int i = 0; i < l; i++) {
            char c = pattern.charAt(i);

            if (bEscaping == false) {
                if (escapeChar != null && escapeChar.charValue() == c) {
                    bEscaping = true;

                    continue;
                } else if (c == '_') {
                    wildCardType[iLen] = UNDERSCORE_CHAR;

                    if (iFirstWildCard == -1) {
                        iFirstWildCard = iLen;
                    }
                } else if (c == '%') {
                    if (bPercent) {
                        continue;
                    }

                    bPercent           = true;
                    wildCardType[iLen] = PERCENT_CHAR;

                    if (iFirstWildCard == -1) {
                        iFirstWildCard = iLen;
                    }
                } else {
                    bPercent = false;
                }
            } else {
                bPercent  = false;
                bEscaping = false;
            }

            cLike[iLen++] = c;
        }

        for (int i = 0; i < iLen - 1; i++) {
            if ((wildCardType[i] == PERCENT_CHAR)
                    && (wildCardType[i + 1] == UNDERSCORE_CHAR)) {
                wildCardType[i]     = UNDERSCORE_CHAR;
                wildCardType[i + 1] = PERCENT_CHAR;
            }
        }
    }

    boolean hasWildcards() {
        return iFirstWildCard != -1;
    }

    boolean isEquivalentToFalsePredicate() {
        return isNull;
    }

    boolean isEquivalentToEqualsPredicate() {
        return iFirstWildCard == -1;
    }

    boolean isEquivalentToNotNullPredicate() {

        if (isNull ||!hasWildcards()) {
            return false;
        }

        for (int i = 0; i < wildCardType.length; i++) {
            if (wildCardType[i] != PERCENT_CHAR) {
                return false;
            }
        }

        return true;
    }

    boolean isEquivalentToBetweenPredicate() {

        return iFirstWildCard > 0
               && iFirstWildCard == wildCardType.length - 1
               && cLike[iFirstWildCard] == '%';
    }

    boolean isEquivalentToBetweenPredicateAugmentedWithLike() {
        return iFirstWildCard > 0 && cLike[iFirstWildCard] == '%';
    }

    String getRangeLow() {
        return getStartsWith();
    }

    String getRangeHigh() {

        String s = getStartsWith();

        return s == null ? null
                         : s.concat("\uffff");
    }

    public String describe(Session session) {

        StringBuffer sb = new StringBuffer();

        sb.append(super.toString()).append("[\n");
        sb.append("escapeChar=").append(escapeChar).append('\n');
        sb.append("isNull=").append(isNull).append('\n');
        sb.append("optimised=").append(optimised).append('\n');
        sb.append("isIgnoreCase=").append(isIgnoreCase).append('\n');
        sb.append("iLen=").append(iLen).append('\n');
        sb.append("iFirstWildCard=").append(iFirstWildCard).append('\n');
        sb.append("cLike=");
        sb.append(StringUtil.arrayToString(cLike));
        sb.append('\n');
        sb.append("wildCardType=");
        sb.append(StringUtil.arrayToString(wildCardType));
        sb.append(']');

        return sb.toString();
    }
}