Files
alfresco-community-repo/source/java/org/alfresco/repo/domain/CrcHelper.java
Raluca Munteanu 6afb44e712 Merged 5.1.N (5.1.2) to 5.2.N (5.2.1)
125606 rmunteanu: Merged 5.1.1 (5.1.1) to 5.1.N (5.1.2)
      125515 slanglois: MNT-16155 Update source headers - add new Copyrights for Java and JSP source files + automatic check in the build


git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/BRANCHES/DEV/5.2.N/root@125788 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261
2016-04-26 13:45:01 +00:00

123 lines
4.5 KiB
Java

/*
* #%L
* Alfresco Repository
* %%
* Copyright (C) 2005 - 2016 Alfresco Software Limited
* %%
* This file is part of the Alfresco software.
* If the software was purchased under a paid Alfresco license, the terms of
* the paid license agreement will prevail. Otherwise, the software is
* provided under the following open source license terms:
*
* Alfresco is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Alfresco is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
* #L%
*/
package org.alfresco.repo.domain;
import java.io.UnsupportedEncodingException;
import java.util.zip.CRC32;
import org.alfresco.util.Pair;
/**
* Helper class to calculate CRC values for string persistence.
*
* @author Derek Hulley
* @since 3.2
*/
public class CrcHelper
{
public static final String EMPTY_STRING = ".empty";
/**
* Calculate a persistable, unique pair of values that can be persisted in a database unique
* key and guarantee correct case-sensitivity.
* <p>
* While the short-string version of the value is always lowercase, the CRC is
* calculated from the virgin string if case-sensitivity is enforced; in the case-insensitive
* case, the CRC is calculated from a lowercase version of the string.
* <p>
* If the value is an empty string, then {@link #EMPTY_STRING} is used instead. This ensures
* that persisted values don't fall foul of the Oracle empty string comparison "behaviour" i.e
* you should never persist an empty string in Oracle as it equates to a SQL <b>NULL</b>.
*
* @param value the raw value that will be persisted
* @param dataLength the maximum number of characters that can be persisted
* @param useCharsFromStart <tt>true</tt> if the shortened string value must be made from
* the first characters of the string or <tt>false</tt> to use
* characters from the end of the string.
* @param caseSensitive <tt>true</tt> if the resulting pair must be case-sensitive or
* <tt>false</tt> if the pair must be case-insensitive.
* @return Return the persistable pair. The result will never be <tt>null</tt>,
* but the individual pair values will be <tt>null</tt> if the
* value given is <tt>null</tt>
*/
public static Pair<String, Long> getStringCrcPair(
String value,
int dataLength,
boolean useCharsFromStart,
boolean caseSensitive)
{
String valueLowerCase;
if (value == null)
{
return new Pair<String, Long>(null, null);
}
else if (value.length() == 0)
{
value = CrcHelper.EMPTY_STRING;
valueLowerCase = value;
}
else
{
valueLowerCase = value.toLowerCase();
}
Long valueCrc;
try
{
CRC32 crc = new CRC32();
if (caseSensitive)
{
crc.update(value.getBytes("UTF-8"));
}
else
{
crc.update(valueLowerCase.getBytes("UTF-8"));
}
valueCrc = crc.getValue();
}
catch (UnsupportedEncodingException e)
{
throw new RuntimeException("UTF-8 encoding is not supported");
}
// Get the short value (case-sensitive or not)
String valueShort = null;
int valueLen = valueLowerCase.length();
if (valueLen < dataLength)
{
valueShort = valueLowerCase;
}
else if (useCharsFromStart)
{
valueShort = valueLowerCase.substring(0, dataLength - 1);
}
else
{
valueShort = valueLowerCase.substring(valueLen - dataLength);
}
return new Pair<String, Long>(valueShort, valueCrc);
}
}