/*

 * Copyright (c) 2009, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/**

 * IOUtils: A collection of IO-related public static methods.

 */

package sun.security.util;

import java.io.EOFException;

import java.io.IOException;

import java.io.InputStream;

public class IOUtils {

    /**

     * Read exactly {@code length} of bytes from {@code in}.

     *

     * <p> Note that this method is safe to be called with unknown large

     * {@code length} argument. The memory used is proportional to the

     * actual bytes available. An exception is thrown if there are not

     * enough bytes in the stream.

     *

     * @param is input stream, must not be null

     * @param length number of bytes to read

     * @return bytes read

     * @throws EOFException if there are not enough bytes in the stream

     * @throws IOException if an I/O error occurs or {@code length} is negative

     * @throws OutOfMemoryError if an array of the required size cannot be

     *         allocated.

     */

    public static byte[] readExactlyNBytes(InputStream is, int length)

            throws IOException {

        if (length < 0) {

            throw new IOException("length cannot be negative: " + length);

        }

        byte[] data = is.readNBytes(length);

        if (data.length < length) {

            throw new EOFException();

        }

        return data;

    }

}