129 lines
4.5 KiB
Java
129 lines
4.5 KiB
Java
/**
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* Copyright (c) 2017 The JNanoID Authors
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* Copyright (c) 2017 Aventrix LLC
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* Copyright (c) 2017 Andrey Sitnik
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package net.gepafin.tendermanagement.model.util;
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import java.security.SecureRandom;
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import java.util.Random;
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public final class NanoIdUtils {
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/**
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* <code>NanoIdUtils</code> instances should NOT be constructed in standard programming.
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* Instead, the class should be used as <code>NanoIdUtils.randomNanoId();</code>.
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*/
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private NanoIdUtils() {
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//Do Nothing
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}
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/**
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* The default random number generator used by this class.
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* Creates cryptographically strong NanoId Strings.
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*/
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public static final SecureRandom DEFAULT_NUMBER_GENERATOR = new SecureRandom();
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/**
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* The default alphabet used by this class.
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* Creates url-friendly NanoId Strings using 64 unique symbols.
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*/
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public static final char[] DEFAULT_ALPHABET =
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"_-0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
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/**
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* The default size used by this class.
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* Creates NanoId Strings with slightly more unique values than UUID v4.
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*/
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public static final int DEFAULT_SIZE = 21;
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/**
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* Static factory to retrieve a url-friendly, pseudo randomly generated, NanoId String.
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*
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* The generated NanoId String will have 21 symbols.
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*
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* The NanoId String is generated using a cryptographically strong pseudo random number
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* generator.
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*
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* @return A randomly generated NanoId String.
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*/
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public static String randomNanoId() {
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return randomNanoId(DEFAULT_NUMBER_GENERATOR, DEFAULT_ALPHABET, DEFAULT_SIZE);
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}
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/**
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* Static factory to retrieve a NanoId String.
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*
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* The string is generated using the given random number generator.
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*
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* @param random The random number generator.
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* @param alphabet The symbols used in the NanoId String.
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* @param size The number of symbols in the NanoId String.
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* @return A randomly generated NanoId String.
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*/
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public static String randomNanoId(final Random random, final char[] alphabet, final int size) {
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if (random == null) {
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throw new IllegalArgumentException("random cannot be null.");
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}
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if (alphabet == null) {
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throw new IllegalArgumentException("alphabet cannot be null.");
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}
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if (alphabet.length == 0 || alphabet.length >= 256) {
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throw new IllegalArgumentException("alphabet must contain between 1 and 255 symbols.");
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}
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if (size <= 0) {
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throw new IllegalArgumentException("size must be greater than zero.");
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}
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double value = (double) (alphabet.length - 1);
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final int mask = (2 << (int) Math.floor(Math.log(value) / Math.log(2))) - 1;
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final int step = (int) Math.ceil(1.6 * mask * size / alphabet.length);
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final StringBuilder idBuilder = new StringBuilder();
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while (true) {
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final byte[] bytes = new byte[step];
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random.nextBytes(bytes);
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for (int i = 0; i < step; i++) {
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final int alphabetIndex = bytes[i] & mask;
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if (alphabetIndex < alphabet.length) {
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idBuilder.append(alphabet[alphabetIndex]);
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if (idBuilder.length() == size) {
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return idBuilder.toString();
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}
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}
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}
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}
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}
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} |