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package de.uhilger.filecms.web;
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/*
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* ShortURL (https://github.com/delight-im/ShortURL)
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* Copyright (c) delight.im (https://www.delight.im/)
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* Licensed under the MIT License (https://opensource.org/licenses/MIT)
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*/
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/**
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* ShortURL: Bijective conversion between natural numbers (IDs) and short strings
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*
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* ShortURL.encode() takes an ID and turns it into a short string
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* ShortURL.decode() takes a short string and turns it into an ID
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*
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* Features:
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* + large alphabet (51 chars) and thus very short resulting strings
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* + proof against offensive words (removed 'a', 'e', 'i', 'o' and 'u')
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* + unambiguous (removed 'I', 'l', '1', 'O' and '0')
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*
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* Example output:
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* 123456789 <=> pgK8p
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*/
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public class ShortURL {
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public static final String ALPHABET = "23456789bcdfghjkmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ-_";
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public static final int BASE = ALPHABET.length();
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public static String encode(int num) {
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StringBuilder str = new StringBuilder();
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while (num > 0) {
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str.insert(0, ALPHABET.charAt(num % BASE));
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num = num / BASE;
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}
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return str.toString();
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}
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public static int decode(String str) {
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int num = 0;
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for (int i = 0; i < str.length(); i++) {
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num = num * BASE + ALPHABET.indexOf(str.charAt(i));
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}
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return num;
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}
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}
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