/*

 * Copyright (c) 2005, 2018, 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 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 sun.tools.attach.HotSpotVirtualMachine;

import java.io.IOException;

import java.io.InputStream;

import java.util.Random;

public class VirtualMachineImpl extends HotSpotVirtualMachine {

    // the enqueue code stub (copied into each target VM)

    private static byte[] stub;

    private volatile long hProcess;     // handle to the process

    VirtualMachineImpl(AttachProvider provider, String id)

        throws AttachNotSupportedException, IOException

    {

        super(provider, id);

        int pid;

        try {

            pid = Integer.parseInt(id);

        } catch (NumberFormatException x) {

            throw new AttachNotSupportedException("Invalid process identifier");

        }

        hProcess = openProcess(pid);

        // The target VM might be a pre-6.0 VM so we enqueue a "null" command

        // which minimally tests that the enqueue function exists in the target

        // VM.

        try {

            enqueue(hProcess, stub, null, null);

        } catch (IOException x) {

            throw new AttachNotSupportedException(x.getMessage());

        }

    }

    public void detach() throws IOException {

        synchronized (this) {

            if (hProcess != -1) {

                closeProcess(hProcess);

                hProcess = -1;

            }

        }

    }

    InputStream execute(String cmd, Object ... args)

        throws AgentLoadException, IOException

    {

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

        // create a pipe using a random name

        Random rnd = new Random();

        int r = rnd.nextInt();

        String pipeprefix = "\\\\.\\pipe\\javatool";

        String pipename = pipeprefix + r;

        long hPipe;

        try {

            hPipe = createPipe(pipename);

        } catch (IOException ce) {

            // Retry with another random pipe name.

            r = rnd.nextInt();

            pipename = pipeprefix + r;

            hPipe = createPipe(pipename);

        }

        // check if we are detached - in theory it's possible that detach is invoked

        // after this check but before we enqueue the command.

        if (hProcess == -1) {

            closePipe(hPipe);

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

        }

        try {

            // enqueue the command to the process

            enqueue(hProcess, stub, cmd, pipename, args);

            // wait for command to complete - process will connect with the

            // completion status

            connectPipe(hPipe);

            // create an input stream for the pipe

            PipedInputStream in = new PipedInputStream(hPipe);

            // read completion status

            int status = readInt(in);

            if (status != 0) {

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

                String message = readErrorMessage(in);

                in.close();

                // special case the load command so that the right exception is thrown

                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

            return in;

        } catch (IOException ioe) {

            closePipe(hPipe);

            throw ioe;

        }

    }

    // An InputStream based on a pipe to the target VM

    private class PipedInputStream extends InputStream {

        private long hPipe;

        public PipedInputStream(long hPipe) {

            this.hPipe = hPipe;

        }

        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.readPipe(hPipe, bs, off, len);

        }

        public void close() throws IOException {

            if (hPipe != -1) {

                VirtualMachineImpl.closePipe(hPipe);

                hPipe = -1;

           }

        }

    }

    //-- native methods

    static native void init();

    static native byte[] generateStub();

    static native long openProcess(int pid) throws IOException;

    static native void closeProcess(long hProcess) throws IOException;

    static native long createPipe(String name) throws IOException;

    static native void closePipe(long hPipe) throws IOException;

    static native void connectPipe(long hPipe) throws IOException;

    static native int readPipe(long hPipe, byte buf[], int off, int buflen) throws IOException;

    static native void enqueue(long hProcess, byte[] stub,

        String cmd, String pipename, Object ... args) throws IOException;

    static {

        System.loadLibrary("attach");

        init();                                 // native initialization

        stub = generateStub();                  // generate stub to copy into target process

    }

}