/*
 * 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
    }
}