| commit | author | age | ||
| a8280b | 1 | |
| U | 2 | package de.uhilger.filecms.web; |
| 3 | ||
| 4 | /* | |
| 5 | * ShortURL (https://github.com/delight-im/ShortURL) | |
| 6 | * Copyright (c) delight.im (https://www.delight.im/) | |
| 7 | * Licensed under the MIT License (https://opensource.org/licenses/MIT) | |
| 8 | */ | |
| 9 | ||
| 10 | /** | |
| 11 | * ShortURL: Bijective conversion between natural numbers (IDs) and short strings | |
| 12 | * | |
| 13 | * ShortURL.encode() takes an ID and turns it into a short string | |
| 14 | * ShortURL.decode() takes a short string and turns it into an ID | |
| 15 | * | |
| 16 | * Features: | |
| 17 | * + large alphabet (51 chars) and thus very short resulting strings | |
| 18 | * + proof against offensive words (removed 'a', 'e', 'i', 'o' and 'u') | |
| 19 | * + unambiguous (removed 'I', 'l', '1', 'O' and '0') | |
| 20 | * | |
| 21 | * Example output: | |
| 22 | * 123456789 <=> pgK8p | |
| 23 | */ | |
| 24 | public class ShortURL { | |
| 25 | ||
| 26 | public static final String ALPHABET = "23456789bcdfghjkmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ-_"; | |
| 27 | public static final int BASE = ALPHABET.length(); | |
| 28 | ||
| 29 | public static String encode(int num) { | |
| 30 | StringBuilder str = new StringBuilder(); | |
| 31 | while (num > 0) { | |
| 32 | str.insert(0, ALPHABET.charAt(num % BASE)); | |
| 33 | num = num / BASE; | |
| 34 | } | |
| 35 | return str.toString(); | |
| 36 | } | |
| 37 | ||
| 38 | public static int decode(String str) { | |
| 39 | int num = 0; | |
| 40 | for (int i = 0; i < str.length(); i++) { | |
| 41 | num = num * BASE + ALPHABET.indexOf(str.charAt(i)); | |
| 42 | } | |
| 43 | return num; | |
| 44 | } | |
| 45 | ||
| 46 | } | |
