/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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.exoplatform.services.jcr.impl.core.query.lucene;
/**
* The <code>DoubleField</code> class is a utility to convert double
* values into <code>String</code> values that are lexicographically ordered
* according to the double value.
*/
public class DoubleField {
private static final long SIGN_MASK = 0x8000000000000000L;
private static final int STRING_DOUBLE_LEN
= Long.toString(Long.MAX_VALUE, Character.MAX_RADIX).length() + 1;
private DoubleField() {
}
public static String doubleToString(double value) {
long longValue = Double.doubleToLongBits(value);
StringBuilder sb = new StringBuilder(STRING_DOUBLE_LEN);
if ((longValue & SIGN_MASK) == 0) {
// positive
String s = Long.toString(longValue, Character.MAX_RADIX);
// add sign character
sb.append('1');
while ((sb.length() + s.length()) < STRING_DOUBLE_LEN) {
sb.append('0');
}
sb.append(s);
} else {
// negative
// fold value by reversing sign
longValue = -longValue;
String s = Long.toString(longValue, Character.MAX_RADIX);
// pad with leading zeros
while ((sb.length() + s.length()) < STRING_DOUBLE_LEN) {
sb.append('0');
}
sb.append(s);
}
return sb.toString();
}
public static double stringToDouble(String value) {
if (value.charAt(0) == '1') {
// positive
long longValue = Long.parseLong(value.substring(1), Character.MAX_RADIX);
return Double.longBitsToDouble(longValue);
} else if (value.charAt(0) == '0') {
// negative
long longValue = Long.parseLong(value, Character.MAX_RADIX);
// switch sign
longValue = -longValue;
return Double.longBitsToDouble(longValue);
} else {
throw new IllegalArgumentException("not a valid string representation of a double: " + value);
}
}
}