/*

 * 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

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

 *

 * 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.

 *

 */

package java.lang;

import java.io.*;

/* java.lang.Process subclass in the UNIX environment.

 *

 * @author Mario Wolczko and Ross Knippel.

 * @author Konstantin Kladko (ported to Linux)

 */

final class UNIXProcess extends Process {

    private static final sun.misc.JavaIOFileDescriptorAccess fdAccess

        = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();

    private int pid;

    private int exitcode;

    private boolean hasExited;

    private OutputStream stdin_stream;

    private InputStream  stdout_stream;

    private InputStream  stderr_stream;

    /* this is for the reaping thread */

    private native int waitForProcessExit(int pid);

    /**

     * Create a process using fork(2) and exec(2).

     *

     * @param std_fds array of file descriptors.  Indexes 0, 1, and

     *        2 correspond to standard input, standard output and

     *        standard error, respectively.  On input, a value of -1

     *        means to create a pipe to connect child and parent

     *        processes.  On output, a value which is not -1 is the

     *        parent pipe fd corresponding to the pipe which has

     *        been created.  An element of this array is -1 on input

     *        if and only if it is <em>not</em> -1 on output.

     * @return the pid of the subprocess

     */

    private native int forkAndExec(byte[] prog,

                                   byte[] argBlock, int argc,

                                   byte[] envBlock, int envc,

                                   byte[] dir,

                                   int[] std_fds,

                                   boolean redirectErrorStream)

        throws IOException;

    /* In the process constructor we wait on this gate until the process    */

    /* has been created. Then we return from the constructor.               */

    /* fork() is called by the same thread which later waits for the process */

    /* to terminate */

    private static class Gate {

        private boolean exited = false;

        private IOException savedException;

        synchronized void exit() { /* Opens the gate */

           exited = true;

           this.notify();

        }

        synchronized void waitForExit() { /* wait until the gate is open */

            boolean interrupted = false;

            while (!exited) {

                try {

                    this.wait();

                } catch (InterruptedException e) {

                    interrupted = true;

                }

            }

            if (interrupted) {

                Thread.currentThread().interrupt();

            }

        }

        void setException (IOException e) {

            savedException = e;

        }

        IOException getException() {

            return savedException;

        }

    }

    UNIXProcess(final byte[] prog,

                final byte[] argBlock, final int argc,

                final byte[] envBlock, final int envc,

                final byte[] dir,

                final int[] std_fds,

                final boolean redirectErrorStream)

    throws IOException {

        final Gate gate = new Gate();

        /*

         * For each subprocess forked a corresponding reaper thread

         * is started.  That thread is the only thread which waits

         * for the subprocess to terminate and it doesn't hold any

         * locks while doing so.  This design allows waitFor() and

         * exitStatus() to be safely executed in parallel (and they

         * need no native code).

         */

        java.security.AccessController.doPrivileged(

        new java.security.PrivilegedAction<Void>() {

        public Void run() {

            Thread t = new Thread("process reaper") {

                    public void run() {

                        try {

                            pid = forkAndExec(prog,

                                              argBlock, argc,

                                              envBlock, envc,

                                              dir,

                                              std_fds,

                                              redirectErrorStream);

                        } catch (IOException e) {

                            gate.setException(e); /*remember to rethrow later*/

                            gate.exit();

                            return;

                        }

                        java.security.AccessController.doPrivileged(

                    new java.security.PrivilegedAction<Void>() {

                    public Void run() {

                        if (std_fds[0] == -1)

                            stdin_stream = new ProcessBuilder.NullOutputStream();

                        else {

                            FileDescriptor stdin_fd = new FileDescriptor();

                            fdAccess.set(stdin_fd, std_fds[0]);

                            stdin_stream = new BufferedOutputStream(

                                new FileOutputStream(stdin_fd));

                        }

                        if (std_fds[1] == -1)

                            stdout_stream = new ProcessBuilder.NullInputStream();

                        else {

                            FileDescriptor stdout_fd = new FileDescriptor();

                            fdAccess.set(stdout_fd, std_fds[1]);

                            stdout_stream = new BufferedInputStream(

                                new FileInputStream(stdout_fd));

                        }

                        if (std_fds[2] == -1)

                            stderr_stream = new ProcessBuilder.NullInputStream();

                        else {

                            FileDescriptor stderr_fd = new FileDescriptor();

                            fdAccess.set(stderr_fd, std_fds[2]);

                            stderr_stream = new FileInputStream(stderr_fd);

                        }

                        return null; }});

                        gate.exit(); /* exit from constructor */

                        int res = waitForProcessExit(pid);

                        synchronized (UNIXProcess.this) {

                            hasExited = true;

                            exitcode = res;

                            UNIXProcess.this.notifyAll();

                        }

                    }

                };

                t.setDaemon(true);

                t.start();

                return null; }});

        gate.waitForExit();

        IOException e = gate.getException();

        if (e != null)

            throw new IOException(e.toString());

    }

    public OutputStream getOutputStream() {

        return stdin_stream;

    }

    public InputStream getInputStream() {

        return stdout_stream;

    }

    public InputStream getErrorStream() {

        return stderr_stream;

    }

    public synchronized int waitFor() throws InterruptedException {

        while (!hasExited) {

            wait();

        }

        return exitcode;

    }

    public synchronized int exitValue() {

        if (!hasExited) {

            throw new IllegalThreadStateException("process hasn't exited");

        }

        return exitcode;

    }

    private static native void destroyProcess(int pid);

    public void destroy() {

        // There is a risk that pid will be recycled, causing us to

        // kill the wrong process!  So we only terminate processes

        // that appear to still be running.  Even with this check,

        // there is an unavoidable race condition here, but the window

        // is very small, and OSes try hard to not recycle pids too

        // soon, so this is quite safe.

        synchronized (this) {

            if (!hasExited)

                destroyProcess(pid);

        }

        try {

            stdin_stream.close();

            stdout_stream.close();

            stderr_stream.close();

        } catch (IOException e) {

            // ignore

        }

    }

    /* This routine initializes JNI field offsets for the class */

    private static native void initIDs();

    static {

        initIDs();

    }

}