/*
 * Copyright (c) 2014, 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.
 */

package sun.misc;

import java.io.*;

/**
 * Implementation of SystemRandom for UNIX-like operating systems
 * with /dev/urandom file.
 */
final class SystemRandomImpl extends SystemRandom {

    private static final String RANDOM_FILE = "/dev/urandom";

    private final InputStream randomStream;

    SystemRandomImpl() {
        InputStream rs;
        try {
            rs = new FileInputStream(RANDOM_FILE);
        } catch (IOException e1) {
            // are we out of file descriptors?
            System.gc();
            System.runFinalization();
            // try again
            try {
                rs = new FileInputStream(RANDOM_FILE);
            } catch (IOException e2) {
                throw new UnsupportedOperationException(e2);
            }
        }
        randomStream = rs;
    }

    public void getBytes(byte[] bytes) {
        if (bytes == null) throw new NullPointerException();
        try {
            readFully(randomStream, bytes);
        } catch (IOException e2) {
            throw new UncheckedIOException(e2);
        }
    }

    private static void readFully(InputStream s, byte[] bytes) throws IOException {
        for (int offset = 0, nread; offset < bytes.length; offset += nread) {
            nread = s.read(bytes, offset, bytes.length - offset);
            if (nread < 0) {
                throw new EOFException("Unexpected end of file: " + RANDOM_FILE);
            }
        }
    }
}