/*

 * 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

 * or visit www.oracle.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.

 */

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 OutputStream stdin_stream;

    private InputStream stdout_stream;

    private DeferredCloseInputStream stdout_inner_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;

    UNIXProcess(final byte[] prog,

                final byte[] argBlock, int argc,

                final byte[] envBlock, int envc,

                final byte[] dir,

                final int[] std_fds,

                final boolean redirectErrorStream)

    throws IOException {

        pid = forkAndExec(prog,

                          argBlock, argc,

                          envBlock, envc,

                          dir,

                          std_fds,

                          redirectErrorStream);

        java.security.AccessController.doPrivileged(

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

            if (std_fds[0] == -1)

            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)

            else {

                FileDescriptor stdout_fd = new FileDescriptor();

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

                stdout_inner_stream = new DeferredCloseInputStream(stdout_fd);

                stdout_stream = new BufferedInputStream(stdout_inner_stream);

            }

            if (std_fds[2] == -1)

            else {

                FileDescriptor stderr_fd = new FileDescriptor();

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

                stderr_stream = new DeferredCloseInputStream(stderr_fd);

            }

            return null; }});

        /*

         * 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() {

                        int res = waitForProcessExit(pid);

                        synchronized (UNIXProcess.this) {

                            hasExited = true;

                            exitcode = res;

                            UNIXProcess.this.notifyAll();

                        }

                    }

                };

                t.setDaemon(true);

                t.start();

                return null; }});

    }

    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 synchronized 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.

        if (!hasExited)

            destroyProcess(pid);

        try {

            stdin_stream.close();

            if (stdout_inner_stream != null)

                stdout_inner_stream.closeDeferred(stdout_stream);

            if (stderr_stream instanceof DeferredCloseInputStream)

                ((DeferredCloseInputStream) stderr_stream)

                    .closeDeferred(stderr_stream);

        } catch (IOException e) {

            // ignore

        }

    }

    // A FileInputStream that supports the deferment of the actual close

    // operation until the last pending I/O operation on the stream has

    // finished.  This is required on Solaris because we must close the stdin

    // and stdout streams in the destroy method in order to reclaim the

    // underlying file descriptors.  Doing so, however, causes any thread

    // currently blocked in a read on one of those streams to receive an

    // IOException("Bad file number"), which is incompatible with historical

    // behavior.  By deferring the close we allow any pending reads to see -1

    // (EOF) as they did before.

    //

    private static class DeferredCloseInputStream

        extends FileInputStream

    {

        private DeferredCloseInputStream(FileDescriptor fd) {

            super(fd);

        }

        private Object lock = new Object();     // For the following fields

        private boolean closePending = false;

        private int useCount = 0;

        private InputStream streamToClose;

        private void raise() {

            synchronized (lock) {

                useCount++;

            }

        }

        private void lower() throws IOException {

            synchronized (lock) {

                useCount--;

                if (useCount == 0 && closePending) {

                    streamToClose.close();

                }

            }

        }

        // stc is the actual stream to be closed; it might be this object, or

        // it might be an upstream object for which this object is downstream.

        //

        private void closeDeferred(InputStream stc) throws IOException {

            synchronized (lock) {

                if (useCount == 0) {

                    stc.close();

                } else {

                    closePending = true;

                    streamToClose = stc;

                }

            }

        }

        public void close() throws IOException {

            synchronized (lock) {

                useCount = 0;

                closePending = false;

            }

            super.close();

        }

        public int read() throws IOException {

            raise();

            try {

                return super.read();

            } finally {

                lower();

            }

        }

        public int read(byte[] b) throws IOException {

            raise();

            try {

                return super.read(b);

            } finally {

                lower();

            }

        }

        public int read(byte[] b, int off, int len) throws IOException {

            raise();

            try {

                return super.read(b, off, len);

            } finally {

                lower();

            }

        }

        public long skip(long n) throws IOException {

            raise();

            try {

                return super.skip(n);

            } finally {

                lower();

            }

        }

        public int available() throws IOException {

            raise();

            try {

                return super.available();

            } finally {

                lower();

            }

        }

    }

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

    private static native void initIDs();

    static {

        initIDs();

    }

}