src/main/java/com/baidu/hugegraph/util/LongEncoding.java

/*
 * Copyright 2017 HugeGraph Authors
 *
 * 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 com.baidu.hugegraph.util;

/**
 * Utility class for encoding longs in strings based on:
 * @see <a href="http://stackoverflow.com/questions/2938482/encode-decode-a-long-to-a-string-using-a-fixed-set-of-letters-in-java">encode decode long to string</a>
 */
public final class LongEncoding {

    private static final String BASE_SYMBOLS =
            "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-~";

    public static long decode(String s) {
        return decode(s, BASE_SYMBOLS);
    }

    public static String encode(long num) {
        return encode(num, BASE_SYMBOLS);
    }

    public static long decode(String s, String symbols) {
        final int B = symbols.length();
        long num = 0;
        for (char ch : s.toCharArray()) {
            num *= B;
            int pos = symbols.indexOf(ch);
            if (pos < 0)
                throw new NumberFormatException(
                          "Symbol set does not match string");
            num += pos;
        }
        return num;
    }

    public static String encode(long num, String symbols) {
        E.checkArgument(num >= 0, "Expected non-negative number: %s", num);
        final int B = symbols.length();
        StringBuilder sb = new StringBuilder();
        while (num != 0) {
            sb.append(symbols.charAt((int) (num % B)));
            num /= B;
        }
        return sb.reverse().toString();
    }
}