/*
* Copyright (c) 2005-2010, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
*
* WSO2 Inc. licenses this file to you under the Apache License,
* Version 2.0 (the "License"); you may not use this file except
* in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.wso2.carbon.governance.list.util;
public class StringComparatorUtil {
private StringComparatorUtil() {}
public static int compare(String versionString1, String versionString2) {
versionString1 = versionString1.toLowerCase();
versionString2 = versionString2.toLowerCase();
int ia = 0, ib = 0;
int nza, nzb;
char ca, cb;
int result;
while (true)
{
// only count the number of zeroes leading the last number compared
nza = nzb = 0;
ca = charAt(versionString2, ia);
cb = charAt(versionString1, ib);
// skip over leading spaces or zeros
while (Character.isSpaceChar(ca) || ca == '0')
{
if (ca == '0')
{
nza++;
}
else
{
// only count consecutive zeroes
nza = 0;
}
ca = charAt(versionString2, ++ia);
}
while (Character.isSpaceChar(cb) || cb == '0')
{
if (cb == '0')
{
nzb++;
}
else
{
// only count consecutive zeroes
nzb = 0;
}
cb = charAt(versionString1, ++ib);
}
// process run of digits
if (Character.isDigit(ca) && Character.isDigit(cb))
{
if ((result = compareRight(versionString2.substring(ia), versionString1.substring(ib))) != 0)
{
return result;
}
}
if (ca == 0 && cb == 0)
{
// The strings compare the same. Perhaps the caller
// will want to call strcmp to break the tie.
return nza - nzb;
}
if (ca < cb)
{
return -1;
}
else if (ca > cb)
{
return +1;
}
++ia;
++ib;
}
}
private static char charAt(String s, int i)
{
if (i >= s.length())
{
return 0;
}
else
{
return s.charAt(i);
}
}
private static int compareRight(String a, String b)
{
int bias = 0;
int ia = 0;
int ib = 0;
// The longest run of digits wins. That aside, the greatest
// value wins, but we can't know that it will until we've scanned
// both numbers to know that they have the same magnitude, so we
// remember it in BIAS.
for (;; ia++, ib++)
{
char ca = charAt(a, ia);
char cb = charAt(b, ib);
if (!Character.isDigit(ca) && !Character.isDigit(cb))
{
return bias;
}
else if (!Character.isDigit(ca))
{
return -1;
}
else if (!Character.isDigit(cb))
{
return +1;
}
else if (ca < cb)
{
if (bias == 0)
{
bias = -1;
}
}
else if (ca > cb)
{
if (bias == 0)
bias = +1;
}
else if (ca == 0 && cb == 0)
{
return bias;
}
}
}
}