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 * 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.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Locale;
import java.util.concurrent.Executors;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadFactory;
import java.security.AccessController;
import static java.security.AccessController.doPrivileged;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;

java.lang.Process subclass in the UNIX environment.
Author:
Mario Wolczko and Ross Knippel., Konstantin Kladko (ported to Linux), Martin Buchholz/**
 * java.lang.Process subclass in the UNIX environment.
 *
 * @author Mario Wolczko and Ross Knippel.
 * @author Konstantin Kladko (ported to Linux)
 * @author Martin Buchholz
 */
final class UNIXProcess extends Process {
    private static final sun.misc.JavaIOFileDescriptorAccess fdAccess
        = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();

    private final int pid;
    private int exitcode;
    private boolean hasExited;

    private /* final */ OutputStream stdin;
    private /* final */ InputStream  stdout;
    private /* final */ InputStream  stderr;

    private static enum LaunchMechanism {
        FORK(1),
        VFORK(3);

        private int value;
        LaunchMechanism(int x) {value = x;}
    };

    /* default is VFORK on Linux */
    private static final LaunchMechanism launchMechanism;
    private static byte[] helperpath;

    private static byte[] toCString(String s) {
        if (s == null)
            return null;
        byte[] bytes = s.getBytes();
        byte[] result = new byte[bytes.length + 1];
        System.arraycopy(bytes, 0,
                         result, 0,
                         bytes.length);
        result[result.length-1] = (byte)0;
        return result;
    }

    static {
        launchMechanism = AccessController.doPrivileged(
                new PrivilegedAction<LaunchMechanism>()
        {
            public LaunchMechanism run() {
                String javahome = System.getProperty("java.home");
                String osArch = System.getProperty("os.arch");

                helperpath = toCString(javahome + "/lib/" + osArch + "/jspawnhelper");
                String s = System.getProperty(
                    "jdk.lang.Process.launchMechanism", "vfork");

                try {
                    return LaunchMechanism.valueOf(s.toUpperCase(Locale.ENGLISH));
                } catch (IllegalArgumentException e) {
                    throw new Error(s + " is not a supported " +
                        "process launch mechanism on this platform.");
                }
            }
        });
    }

    /* this is for the reaping thread */
    private native int waitForProcessExit(int pid);

    
Create a process. Depending on the mode flag, this is done by
one of the following mechanisms.
- fork(2) and exec(2)
- clone(2) and exec(2)
- vfork(2) and exec(2)
Params:
fds – an array of three 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 not -1 on
       output.
Returns:
the pid of the subprocess/**
     * Create a process. Depending on the mode flag, this is done by
     * one of the following mechanisms.
     * - fork(2) and exec(2)
     * - clone(2) and exec(2)
     * - vfork(2) and exec(2)
     *
     * @param fds an array of three 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(int mode, byte[] helperpath,
                                   byte[] prog,
                                   byte[] argBlock, int argc,
                                   byte[] envBlock, int envc,
                                   byte[] dir,
                                   int[] fds,
                                   boolean redirectErrorStream)
        throws IOException;

    
The thread factory used to create "process reaper" daemon threads.
/**
     * The thread factory used to create "process reaper" daemon threads.
     */
    private static class ProcessReaperThreadFactory implements ThreadFactory {
        private final static ThreadGroup group = getRootThreadGroup();

        private static ThreadGroup getRootThreadGroup() {
            return doPrivileged(new PrivilegedAction<ThreadGroup> () {
                public ThreadGroup run() {
                    ThreadGroup root = Thread.currentThread().getThreadGroup();
                    while (root.getParent() != null)
                        root = root.getParent();
                    return root;
                }});
        }

        public Thread newThread(Runnable grimReaper) {
            // Our thread stack requirement is quite modest.
            Thread t = new Thread(group, grimReaper, "process reaper", 32768);
            t.setDaemon(true);
            // A small attempt (probably futile) to avoid priority inversion
            t.setPriority(Thread.MAX_PRIORITY);
            return t;
        }
    }

    
The thread pool of "process reaper" daemon threads.
/**
     * The thread pool of "process reaper" daemon threads.
     */
    private static final Executor processReaperExecutor =
        doPrivileged(new PrivilegedAction<Executor>() {
            public Executor run() {
                return Executors.newCachedThreadPool
                    (new ProcessReaperThreadFactory());
            }});

    UNIXProcess(final byte[] prog,
                final byte[] argBlock, final int argc,
                final byte[] envBlock, final int envc,
                final byte[] dir,
                final int[] fds,
                final boolean redirectErrorStream)
            throws IOException {

        pid = forkAndExec(launchMechanism.value,
                          helperpath,
                          prog,
                          argBlock, argc,
                          envBlock, envc,
                          dir,
                          fds,
                          redirectErrorStream);

        try {
            doPrivileged(new PrivilegedExceptionAction<Void>() {
                public Void run() throws IOException {
                    initStreams(fds);
                    return null;
                }});
        } catch (PrivilegedActionException ex) {
            throw (IOException) ex.getException();
        }
    }

    static FileDescriptor newFileDescriptor(int fd) {
        FileDescriptor fileDescriptor = new FileDescriptor();
        fdAccess.set(fileDescriptor, fd);
        return fileDescriptor;
    }

    void initStreams(int[] fds) throws IOException {
        stdin = (fds[0] == -1) ?
            ProcessBuilder.NullOutputStream.INSTANCE :
            new ProcessPipeOutputStream(fds[0]);

        stdout = (fds[1] == -1) ?
            ProcessBuilder.NullInputStream.INSTANCE :
            new ProcessPipeInputStream(fds[1]);

        stderr = (fds[2] == -1) ?
            ProcessBuilder.NullInputStream.INSTANCE :
            new ProcessPipeInputStream(fds[2]);

        processReaperExecutor.execute(new Runnable() {
            public void run() {
                int exitcode = waitForProcessExit(pid);
                UNIXProcess.this.processExited(exitcode);
            }});
    }

    void processExited(int exitcode) {
        synchronized (this) {
            this.exitcode = exitcode;
            hasExited = true;
            notifyAll();
        }

        if (stdout instanceof ProcessPipeInputStream)
            ((ProcessPipeInputStream) stdout).processExited();

        if (stderr instanceof ProcessPipeInputStream)
            ((ProcessPipeInputStream) stderr).processExited();

        if (stdin instanceof ProcessPipeOutputStream)
            ((ProcessPipeOutputStream) stdin).processExited();
    }

    public OutputStream getOutputStream() {
        return stdin;
    }

    public InputStream getInputStream() {
        return stdout;
    }

    public InputStream getErrorStream() {
        return stderr;
    }

    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.close();  } catch (IOException ignored) {}
        try { stdout.close(); } catch (IOException ignored) {}
        try { stderr.close(); } catch (IOException ignored) {}
    }

    private static native void init();

    static {
        init();
    }

    
A buffered input stream for a subprocess pipe file descriptor
that allows the underlying file descriptor to be reclaimed when
the process exits, via the processExited hook.
This is tricky because we do not want the user-level InputStream to be
closed until the user invokes close(), and we need to continue to be
able to read any buffered data lingering in the OS pipe buffer.
/**
     * A buffered input stream for a subprocess pipe file descriptor
     * that allows the underlying file descriptor to be reclaimed when
     * the process exits, via the processExited hook.
     *
     * This is tricky because we do not want the user-level InputStream to be
     * closed until the user invokes close(), and we need to continue to be
     * able to read any buffered data lingering in the OS pipe buffer.
     */
    static class ProcessPipeInputStream extends BufferedInputStream {
        private final Object closeLock = new Object();

        ProcessPipeInputStream(int fd) {
            super(new FileInputStream(newFileDescriptor(fd)));
        }
        private static byte[] drainInputStream(InputStream in)
                throws IOException {
            int n = 0;
            int j;
            byte[] a = null;
            while ((j = in.available()) > 0) {
                a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
                n += in.read(a, n, j);
            }
            return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
        }

        
Called by the process reaper thread when the process exits. /** Called by the process reaper thread when the process exits. */
        synchronized void processExited() {
            synchronized (closeLock) {
                try {
                    InputStream in = this.in;
                    // this stream is closed if and only if: in == null
                    if (in != null) {
                        byte[] stragglers = drainInputStream(in);
                        in.close();
                        this.in = (stragglers == null) ?
                            ProcessBuilder.NullInputStream.INSTANCE :
                            new ByteArrayInputStream(stragglers);
                    }
                } catch (IOException ignored) {}
            }
        }

        @Override
        public void close() throws IOException {
            // BufferedInputStream#close() is not synchronized unlike most other methods.
            // Synchronizing helps avoid race with processExited().
            synchronized (closeLock) {
                super.close();
            }
        }
    }

    
A buffered output stream for a subprocess pipe file descriptor
that allows the underlying file descriptor to be reclaimed when
the process exits, via the processExited hook.
/**
     * A buffered output stream for a subprocess pipe file descriptor
     * that allows the underlying file descriptor to be reclaimed when
     * the process exits, via the processExited hook.
     */
    static class ProcessPipeOutputStream extends BufferedOutputStream {
        ProcessPipeOutputStream(int fd) {
            super(new FileOutputStream(newFileDescriptor(fd)));
        }

        
Called by the process reaper thread when the process exits. /** Called by the process reaper thread when the process exits. */
        synchronized void processExited() {
            OutputStream out = this.out;
            if (out != null) {
                try {
                    out.close();
                } catch (IOException ignored) {
                    // We know of no reason to get an IOException, but if
                    // we do, there's nothing else to do but carry on.
                }
                this.out = ProcessBuilder.NullOutputStream.INSTANCE;
            }
        }
    }
}