/**
* Licensed 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.brixcms.workspace;
/**
* Encodes long values into the specified alphabet. Encoding is useful when long values need to be represented in their
* string form and shorter values are preferred; by using alphabets of length greater than ten shorter values can be
* obtained. For example, to encode values into their hexadecimal representations the {@code 0123456789ABCDEF-} can be
* used. Long values can be shortened even further by using longer alphabets. The last character in the alphabet is used
* as the negative sign.
*
* @author igor
*/
public class LongEncoder {
/**
* default alphabet that should be safe to use in most circumstances, while still providing good shortening of long
* values
*/
public static String DEFAULT = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
/**
* Encodes the value into the default alphabet: {@value #DEFAULT}
*
* @param value
* @return encoded value
*/
public static String encode(long value) {
return encode(value, DEFAULT);
}
/**
* Encodes value into the specified alphabet
*
* @param value
* @param alphabet
* @return encoded value
*/
public static String encode(long value, String alphabet) {
final int len = alphabet.length() - 1;
StringBuilder buff = new StringBuilder();
final boolean negative = value < 0;
if (negative) {
value = -value;
}
do {
int mod = (int) (value % len);
buff.insert(0, alphabet.charAt(mod));
value = value / len;
}
while (value > 0);
if (negative) {
buff.insert(0, alphabet.charAt(len));
}
return buff.toString();
}
/**
* Decodes value using the default alphabet: {@value #DEFAULT}
*
* @param value
* @return decoded value
*/
public static long decode(String value) {
return decode(value, DEFAULT);
}
/**
* Decodes value using the specified alphabet
*
* @param value
* @param alphabet
* @return decoded value
*/
public static long decode(String value, String alphabet) {
final int factor = alphabet.length() - 1;
final boolean negative = alphabet.charAt(factor) == value.charAt(0);
long num = 0;
for (int i = (negative) ? 1 : 0, len = value.length(); i < len; i++) {
num = num * factor + alphabet.indexOf(value.charAt(i));
}
if (negative) {
num = -num;
}
return num;
}
private LongEncoder() {
}
}