/* 

 * Copyright 1995-2006 Sun Microsystems, Inc.  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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

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 FileDescriptor stdin_fd;

    private FileDescriptor stdout_fd;

    private FileDescriptor stderr_fd;

    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);

    private native int forkAndExec(byte[] prog,

				   byte[] argBlock, int argc,

				   byte[] envBlock, int envc,

				   byte[] dir,

				   boolean redirectErrorStream,

				   FileDescriptor stdin_fd,

				   FileDescriptor stdout_fd,

				   FileDescriptor stderr_fd)

	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 boolean redirectErrorStream)

    throws IOException {

	stdin_fd  = new FileDescriptor();

	stdout_fd = new FileDescriptor();

	stderr_fd = new FileDescriptor();

        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() {

	    public Object run() {

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

		    public void run() {

                        try {

                            pid = forkAndExec(prog,

					      argBlock, argc,

					      envBlock, envc,

					      dir,

					      redirectErrorStream,

					      stdin_fd, stdout_fd, stderr_fd);

                        } catch (IOException e) {

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

                            gate.exit();

                            return;

                        }

                        java.security.AccessController.doPrivileged(

                        new java.security.PrivilegedAction() {

                            public Object run() {

                            stdin_stream = new BufferedOutputStream(new

                                                    FileOutputStream(stdin_fd));

                            stdout_stream = new BufferedInputStream(new

                                                    FileInputStream(stdout_fd));

                            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();

    }

}