/*

 * Copyright (c) 2005, 2014, 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 sun.tools.attach;

import com.sun.tools.attach.AttachOperationFailedException;

import com.sun.tools.attach.AgentLoadException;

import com.sun.tools.attach.AttachNotSupportedException;

import com.sun.tools.attach.spi.AttachProvider;

import java.io.InputStream;

import java.io.IOException;

import java.io.File;

import java.io.FileNotFoundException;

/*

 * Solaris implementation of HotSpotVirtualMachine.

 */

public class VirtualMachineImpl extends HotSpotVirtualMachine {

    // "/tmp" is used as a global well-known location for the files

    // .java_pid<pid>. and .attach_pid<pid>. It is important that this

    // location is the same for all processes, otherwise the tools

    // will not be able to find all Hotspot processes.

    // Any changes to this needs to be synchronized with HotSpot.

    private static final String tmpdir = "/tmp";

    // door descriptor;

    private int fd = -1;

    /**

     * Attaches to the target VM

     */

    VirtualMachineImpl(AttachProvider provider, String vmid)

        throws AttachNotSupportedException, IOException

    {

        super(provider, vmid);

        // This provider only understands process-ids (pids).

        int pid;

        try {

            pid = Integer.parseInt(vmid);

        } catch (NumberFormatException x) {

            throw new AttachNotSupportedException("invalid process identifier");

        }

        // Opens the door file to the target VM. If the file is not

        // found it might mean that the attach mechanism isn't started in the

        // target VM so we attempt to start it and retry.

        try {

            fd = openDoor(pid);

        } catch (FileNotFoundException fnf1) {

            File f = createAttachFile(pid);

            try {

                sigquit(pid);

                // give the target VM time to start the attach mechanism

                final int delay_step = 100;

                final long timeout = attachTimeout();

                long time_spend = 0;

                long delay = 0;

                do {

                    // Increase timeout on each attempt to reduce polling

                    delay += delay_step;

                    try {

                        Thread.sleep(delay);

                    } catch (InterruptedException x) { }

                    try {

                        fd = openDoor(pid);

                    } catch (FileNotFoundException fnf2) {

                        // pass

                    }

                    time_spend += delay;

                    if (time_spend > timeout/2 && fd == -1) {

                        // Send QUIT again to give target VM the last chance to react

                        sigquit(pid);

                    }

                } while (time_spend <= timeout && fd == -1);

                if (fd  == -1) {

                    throw new AttachNotSupportedException(

                        String.format("Unable to open door %s: " +

                          "target process %d doesn't respond within %dms " +

                          "or HotSpot VM not loaded", f.getPath(), pid, time_spend));

                }

            } finally {

                f.delete();

            }

        }

        assert fd >= 0;

    }

    /**

     * Detach from the target VM

     */

    public void detach() throws IOException {

        synchronized (this) {

            if (fd != -1) {

                close(fd);

                fd = -1;

            }

        }

    }

    /**

     * Execute the given command in the target VM.

     */

    InputStream execute(String cmd, Object ... args) throws AgentLoadException, IOException {

        assert args.length <= 3;                // includes null

        // first check that we are still attached

        int door;

        synchronized (this) {

            if (fd == -1) {

                throw new IOException("Detached from target VM");

            }

            door = fd;

        }

        // enqueue the command via a door call

        int s = enqueue(door, cmd, args);

        assert s >= 0;                          // valid file descriptor

        // The door call returns a file descriptor (one end of a socket pair).

        // Create an input stream around it.

        SocketInputStream sis = new SocketInputStream(s);

        // Read the command completion status

        int completionStatus;

        try {

            completionStatus = readInt(sis);

        } catch (IOException ioe) {

            sis.close();

            throw ioe;

        }

        // If non-0 it means an error but we need to special-case the

        // "load" command to ensure that the right exception is thrown.

        if (completionStatus != 0) {

            // read from the stream and use that as the error message

            String message = readErrorMessage(sis);

            sis.close();

            if (cmd.equals("load")) {

                String msg = "Failed to load agent library";

                if (!message.isEmpty())

                    msg += ": " + message;

                throw new AgentLoadException(msg);

            } else {

                if (message.isEmpty())

                    message = "Command failed in target VM";

                throw new AttachOperationFailedException(message);

            }

        }

        // Return the input stream so that the command output can be read

        return sis;

    }

    // InputStream over a socket

    private class SocketInputStream extends InputStream {

        int s;

        public SocketInputStream(int s) {

            this.s = s;

        }

        public synchronized int read() throws IOException {

            byte b[] = new byte[1];

            int n = this.read(b, 0, 1);

            if (n == 1) {

                return b[0] & 0xff;

            } else {

                return -1;

            }

        }

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

            if ((off < 0) || (off > bs.length) || (len < 0) ||

                ((off + len) > bs.length) || ((off + len) < 0)) {

                throw new IndexOutOfBoundsException();

            } else if (len == 0)

                return 0;

            return VirtualMachineImpl.read(s, bs, off, len);

        }

        public void close() throws IOException {

            VirtualMachineImpl.close(s);

        }

    }

    // The door is attached to .java_pid<pid> in the temporary directory.

    private int openDoor(int pid) throws IOException {

        String path = tmpdir + "/.java_pid" + pid;;

        fd = open(path);

        // Check that the file owner/permission to avoid attaching to

        // bogus process

        try {

            checkPermissions(path);

        } catch (IOException ioe) {

            close(fd);

            throw ioe;

        }

        return fd;

    }

    // On Solaris/Linux a simple handshake is used to start the attach mechanism

    // if not already started. The client creates a .attach_pid<pid> file in the

    // target VM's working directory (or temporary directory), and the SIGQUIT

    // handler checks for the file.

    private File createAttachFile(int pid) throws IOException {

        String fn = ".attach_pid" + pid;

        String path = "/proc/" + pid + "/cwd/" + fn;

        File f = new File(path);

        try {

            f.createNewFile();

        } catch (IOException x) {

            f = new File(tmpdir, fn);

            f.createNewFile();

        }

        return f;

    }

    //-- native methods

    static native int open(String path) throws IOException;

    static native void close(int fd) throws IOException;

    static native int read(int fd, byte buf[], int off, int buflen) throws IOException;

    static native void checkPermissions(String path) throws IOException;

    static native void sigquit(int pid) throws IOException;

    // enqueue a command (and arguments) to the given door

    static native int enqueue(int fd, String cmd, Object ... args)

        throws IOException;

    static {

        System.loadLibrary("attach");

    }

}