/*

 * Copyright (c) 2009, 2017 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;

import java.util.Arrays;

public class IOUtils {

    /**

     * Read up to {@code length} of bytes from {@code in}

     * until EOF is detected.

     * @param is input stream, must not be null

     * @param length number of bytes to read

     * @param readAll if true, an EOFException will be thrown if not enough

     *        bytes are read.

     * @return bytes read

     * @throws IOException Any IO error or a premature EOF is detected

     */

    public static byte[] readFully(InputStream is, int length, boolean readAll)

            throws IOException {

        if (length < 0) {

            throw new IOException("Invalid length");

        }

        byte[] output = {};

        int pos = 0;

        while (pos < length) {

            int bytesToRead;

            if (pos >= output.length) { // Only expand when there's no room

                bytesToRead = Math.min(length - pos, output.length + 1024);

                if (output.length < pos + bytesToRead) {

                    output = Arrays.copyOf(output, pos + bytesToRead);

                }

            } else {

                bytesToRead = output.length - pos;

            }

            int cc = is.read(output, pos, bytesToRead);

            if (cc < 0) {

                if (readAll) {

                    throw new EOFException("Detect premature EOF");

                } else {

                    if (output.length != pos) {

                        output = Arrays.copyOf(output, pos);

                    }

                    break;

                }

            }

            pos += cc;

        }

        return output;

    }

    /**

     * Read {@code length} of bytes from {@code in}. 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, must not be negative

     * @return bytes read

     * @throws IOException if any IO error or a premature EOF is detected, or

     *      if {@code length} is negative since this length is usually also

     *      read from {@code is}.

     */

    public static byte[] readNBytes(InputStream is, int length) throws IOException {

        if (length < 0) {

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

        }

        return readFully(is, length, true);

    }

}