com.devskiller.friendly_id.Base62 Maven / Gradle / Ivy
package com.devskiller.friendly_id;
import java.math.BigInteger;
import java.util.regex.Pattern;
import static java.util.Objects.requireNonNull;
/**
* Base62 encoder/decoder.
*
* This is free and unencumbered public domain software
*
* Source: https://github.com/opencoinage/opencoinage/blob/master/src/java/org/opencoinage/util/Base62.java
*/
class Base62 {
private static final BigInteger BASE = BigInteger.valueOf(62);
private static final String DIGITS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
/**
* Encodes a number using Base62 encoding.
*
* @param number a positive integer
* @return a Base62 string
*
* @throws IllegalArgumentException if number is a negative integer
*/
static String encode(BigInteger number) {
if (number.compareTo(BigInteger.ZERO) < 0) {
throwIllegalArgumentException("number must not be negative");
}
StringBuilder result = new StringBuilder();
while (number.compareTo(BigInteger.ZERO) > 0) {
BigInteger[] divmod = number.divideAndRemainder(BASE);
number = divmod[0];
int digit = divmod[1].intValue();
result.insert(0, DIGITS.charAt(digit));
}
return (result.length() == 0) ? DIGITS.substring(0, 1) : result.toString();
}
private static BigInteger throwIllegalArgumentException(String format, Object... args) {
throw new IllegalArgumentException(String.format(format, args));
}
/**
* Decodes a string using Base62 encoding.
*
* @param string a Base62 string
* @return a positive integer
*
* @throws IllegalArgumentException if string is empty
*/
static BigInteger decode(final String string) {
return decode(string, 128);
}
static BigInteger decode(final String string, int bitLimit) {
requireNonNull(string, "Decoded string must not be null");
if (string.length() == 0) {
return throwIllegalArgumentException("String '%s' must not be empty", string);
}
if (!Pattern.matches("[" + DIGITS + "]*", string)) {
throwIllegalArgumentException("String '%s' contains illegal characters, only '%s' are allowed", string, DIGITS);
}
BigInteger result = BigInteger.ZERO;
int digits = string.length();
for (int index = 0; index < digits; index++) {
int digit = DIGITS.indexOf(string.charAt(digits - index - 1));
result = result.add(BigInteger.valueOf(digit).multiply(BASE.pow(index)));
if (bitLimit > 0 && result.bitLength() > bitLimit) {
throwIllegalArgumentException("String contains '%s' more than 128bit information (%sbit)", string, result.bitLength());
}
}
return result;
}
}