com/android/server/clipboard/EmulatorClipboardMonitor.java

/*
 * Copyright (C) 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server.clipboard;

import android.annotation.Nullable;
import android.content.ClipData;
import android.system.ErrnoException;
import android.system.Os;
import android.system.OsConstants;
import android.system.VmSocketAddress;
import android.util.Slog;

import java.io.FileDescriptor;
import java.io.InterruptedIOException;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.function.Consumer;

// The following class is Android Emulator specific. It is used to read and
// write contents of the host system's clipboard.
class EmulatorClipboardMonitor implements Consumer<ClipData> {
    private static final String TAG = "EmulatorClipboardMonitor";
    private static final String PIPE_NAME = "pipe:clipboard";
    private static final int HOST_PORT = 5000;
    private final Thread mHostMonitorThread;
    private FileDescriptor mPipe = null;

    private static byte[] createOpenHandshake() {
        // String.getBytes doesn't include the null terminator,
        // but the QEMU pipe device requires the pipe service name
        // to be null-terminated.

        final byte[] bits = Arrays.copyOf(PIPE_NAME.getBytes(), PIPE_NAME.length() + 1);
        bits[PIPE_NAME.length()] = 0;
        return bits;
    }

    private boolean isPipeOpened() {
        return mPipe != null;
    }

    private synchronized boolean openPipe() {
        if (mPipe != null) {
            return true;
        }

        try {
            final FileDescriptor fd = Os.socket(OsConstants.AF_VSOCK, OsConstants.SOCK_STREAM, 0);

            try {
                Os.connect(fd, new VmSocketAddress(HOST_PORT, OsConstants.VMADDR_CID_HOST));

                final byte[] handshake = createOpenHandshake();
                Os.write(fd, handshake, 0, handshake.length);
                mPipe = fd;
                return true;
            } catch (ErrnoException | SocketException | InterruptedIOException e) {
                Os.close(fd);
            }
        } catch (ErrnoException e) {
        }

        return false;
    }

    private synchronized void closePipe() {
        try {
            final FileDescriptor fd = mPipe;
            mPipe = null;
            if (fd != null) {
                Os.close(fd);
            }
        } catch (ErrnoException ignore) {
        }
    }

    private byte[] receiveMessage() throws ErrnoException, InterruptedIOException {
        final byte[] lengthBits = new byte[4];
        Os.read(mPipe, lengthBits, 0, lengthBits.length);

        final ByteBuffer bb = ByteBuffer.wrap(lengthBits);
        bb.order(ByteOrder.LITTLE_ENDIAN);
        final int msgLen = bb.getInt();

        final byte[] msg = new byte[msgLen];
        Os.read(mPipe, msg, 0, msg.length);

        return msg;
    }

    private void sendMessage(final byte[] msg) throws ErrnoException, InterruptedIOException {
        final byte[] lengthBits = new byte[4];
        final ByteBuffer bb = ByteBuffer.wrap(lengthBits);
        bb.order(ByteOrder.LITTLE_ENDIAN);
        bb.putInt(msg.length);

        Os.write(mPipe, lengthBits, 0, lengthBits.length);
        Os.write(mPipe, msg, 0, msg.length);
    }

    EmulatorClipboardMonitor(final Consumer<ClipData> setAndroidClipboard) {
        this.mHostMonitorThread = new Thread(() -> {
            while (!Thread.interrupted()) {
                try {
                    // There's no guarantee that QEMU pipes will be ready at the moment
                    // this method is invoked. We simply try to get the pipe open and
                    // retry on failure indefinitely.
                    while (!openPipe()) {
                        Thread.sleep(100);
                    }

                    final byte[] receivedData = receiveMessage();

                    final String str = new String(receivedData);
                    final ClipData clip = new ClipData("host clipboard",
                                                       new String[]{"text/plain"},
                                                       new ClipData.Item(str));

                    setAndroidClipboard.accept(clip);
                } catch (ErrnoException | InterruptedIOException e) {
                    closePipe();
                } catch (InterruptedException | IllegalArgumentException e) {
                }
            }
        });

        this.mHostMonitorThread.start();
    }

    @Override
    public void accept(final @Nullable ClipData clip) {
        if (clip == null) {
            setHostClipboardImpl("");
        } else if (clip.getItemCount() > 0) {
            final CharSequence text = clip.getItemAt(0).getText();
            if (text != null) {
                setHostClipboardImpl(text.toString());
            }
        }
    }

    private void setHostClipboardImpl(final String value) {
        try {
            if (isPipeOpened()) {
                sendMessage(value.getBytes());
            }
        } catch (ErrnoException | InterruptedIOException e) {
            Slog.e(TAG, "Failed to set host clipboard " + e.getMessage());
        } catch (IllegalArgumentException e) {
        }
    }
}