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/*
 * 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 org.apache.commons.codec.digest;

import java.security.SecureRandom;
import java.util.Random;

/**
 * Base64-like method to convert binary bytes into ASCII chars.
 * 

* TODO: Can Base64 be reused? *

*

* This class is immutable and thread-safe. *

* * @since 1.7 */ class B64 { /** * Table with characters for Base64 transformation. */ static final String B64T_STRING = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"; /** * Table with characters for Base64 transformation. */ static final char[] B64T_ARRAY = B64T_STRING.toCharArray(); /** * Base64 like conversion of bytes to ASCII chars. * * @param b2 * A byte from the result. * @param b1 * A byte from the result. * @param b0 * A byte from the result. * @param outLen * The number of expected output chars. * @param buffer * Where the output chars is appended to. */ static void b64from24bit(final byte b2, final byte b1, final byte b0, final int outLen, final StringBuilder buffer) { // The bit masking is necessary because the JVM byte type is signed! int w = ((b2 << 16) & 0x00ffffff) | ((b1 << 8) & 0x00ffff) | (b0 & 0xff); // It's effectively a "for" loop but kept to resemble the original C code. int n = outLen; while (n-- > 0) { buffer.append(B64T_ARRAY[w & 0x3f]); w >>= 6; } } /** * Generates a string of random chars from the B64T set. *

* The salt is generated with {@link SecureRandom}. *

* * @param num Number of chars to generate. * @return a random salt {@link String}. */ static String getRandomSalt(final int num) { return getRandomSalt(num, new SecureRandom()); } /** * Generates a string of random chars from the B64T set. *

* The salt is generated with the {@link Random} provided. *

* * @param num Number of chars to generate. * @param random an instance of {@link Random}. * @return a random salt {@link String}. */ static String getRandomSalt(final int num, final Random random) { final StringBuilder saltString = new StringBuilder(num); for (int i = 1; i <= num; i++) { saltString.append(B64T_STRING.charAt(random.nextInt(B64T_STRING.length()))); } return saltString.toString(); } }




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