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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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