/*
 * @(#)UNIXProcess.java.linux	1.40 10/03/23
 *
 * Copyright (c) 1995, 2000, Oracle and/or its affiliates. All rights reserved.
 *
 * This software is the proprietary information of Sun Microsystems, Inc.
 * Use is subject to license terms.
 */

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();
    }
}
