src/solaris/classes/java/lang/UNIXProcess.java.linux

/*
 * Copyright (c) 1995, 2008, 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
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 */

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();
    }
}