Java tutorial
/* * Copyright (c) 2016-2017, Joyent, Inc. All rights reserved. * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ package com.joyent.manta.benchmark; import org.apache.commons.lang3.RandomUtils; import java.io.IOException; import java.io.InputStream; import java.util.concurrent.atomic.AtomicLong; /** * {@link InputStream} implementation that generates random data. * * @author <a href="https://github.com/dekobon">Elijah Zupancic</a> */ public class RandomInputStream extends InputStream { /** * End of file magic number. */ private static final int EOF = -1; /** * Maximum number of bytes to generate. */ private final long maximumBytes; /** * Current generated byte count. */ private AtomicLong count = new AtomicLong(0L); /** * Creates a new instance. * @param maximumBytes maximum number of random bytes in stream */ public RandomInputStream(final long maximumBytes) { this.maximumBytes = maximumBytes; } @Override public int read() throws IOException { if (count.getAndIncrement() >= maximumBytes) { return EOF; } return RandomUtils.nextInt(0, Integer.MAX_VALUE); } @Override public int read(final byte[] b, final int off, final int len) throws IOException { if (count.get() >= maximumBytes) { return EOF; } final int bytesToRead; if (maximumBytes - count.get() >= len) { bytesToRead = len; } else { bytesToRead = (int) (maximumBytes - count.get()); } count.addAndGet(bytesToRead); final byte[] randomBytes = RandomUtils.nextBytes(bytesToRead); System.arraycopy(randomBytes, 0, b, off, bytesToRead); return bytesToRead; } }