/*
 * Copyright (C) 2012 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 android.bluetooth;

import android.annotation.FlaggedApi;
import android.annotation.RequiresNoPermission;
import android.annotation.RequiresPermission;
import android.annotation.SystemApi;
import android.bluetooth.annotations.RequiresBluetoothConnectPermission;
import android.compat.annotation.UnsupportedAppUsage;
import android.content.AttributionSource;
import android.net.LocalSocket;
import android.os.Build;
import android.os.ParcelFileDescriptor;
import android.os.ParcelUuid;
import android.os.RemoteException;
import android.util.Log;

import com.android.bluetooth.flags.Flags;

import java.io.Closeable;
import java.io.FileDescriptor;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.Locale;
import java.util.UUID;

/**
 * A connected or connecting Bluetooth socket.
 *
 * <p>The interface for Bluetooth Sockets is similar to that of TCP sockets: {@link java.net.Socket}
 * and {@link java.net.ServerSocket}. On the server side, use a {@link BluetoothServerSocket} to
 * create a listening server socket. When a connection is accepted by the {@link
 * BluetoothServerSocket}, it will return a new {@link BluetoothSocket} to manage the connection. On
 * the client side, use a single {@link BluetoothSocket} to both initiate an outgoing connection and
 * to manage the connection.
 *
 * <p>The most common type of Bluetooth socket is RFCOMM, which is the type supported by the Android
 * APIs. RFCOMM is a connection-oriented, streaming transport over Bluetooth. It is also known as
 * the Serial Port Profile (SPP).
 *
 * <p>To create a {@link BluetoothSocket} for connecting to a known device, use {@link
 * BluetoothDevice#createRfcommSocketToServiceRecord
 * BluetoothDevice.createRfcommSocketToServiceRecord()}. Then call {@link #connect()} to attempt a
 * connection to the remote device. This call will block until a connection is established or the
 * connection fails.
 *
 * <p>To create a {@link BluetoothSocket} as a server (or "host"), see the {@link
 * BluetoothServerSocket} documentation.
 *
 * <p>Once the socket is connected, whether initiated as a client or accepted as a server, open the
 * IO streams by calling {@link #getInputStream} and {@link #getOutputStream} in order to retrieve
 * {@link java.io.InputStream} and {@link java.io.OutputStream} objects, respectively, which are
 * automatically connected to the socket.
 *
 * <p>{@link BluetoothSocket} is thread safe. In particular, {@link #close} will always immediately
 * abort ongoing operations and close the socket.
 *
 * <p><div class="special reference">
 *
 * <h3>Developer Guides</h3>
 *
 * <p>For more information about using Bluetooth, read the <a
 * href="{@docRoot}guide/topics/connectivity/bluetooth.html">Bluetooth</a> developer guide. </div>
 *
 * @see BluetoothServerSocket
 * @see java.io.InputStream
 * @see java.io.OutputStream
 */
public final class BluetoothSocket implements Closeable {
    private static final String TAG = "BluetoothSocket";
    private static final boolean DBG = Log.isLoggable(TAG, Log.DEBUG);
    private static final boolean VDBG = Log.isLoggable(TAG, Log.VERBOSE);

    /** @hide */
    public static final int MAX_RFCOMM_CHANNEL = 30;

    /*package*/ static final int MAX_L2CAP_PACKAGE_SIZE = 0xFFFF;

    /** RFCOMM socket */
    public static final int TYPE_RFCOMM = 1;

    /** SCO socket */
    public static final int TYPE_SCO = 2;

    /** L2CAP socket */
    public static final int TYPE_L2CAP = 3;

    /**
     * L2CAP socket on BR/EDR transport
     *
     * @hide
     */
    public static final int TYPE_L2CAP_BREDR = TYPE_L2CAP;

    /**
     * L2CAP socket on LE transport
     *
     * @hide
     */
    public static final int TYPE_L2CAP_LE = 4;

    /*package*/ static final int EBADFD = 77;

    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
    /*package*/ static final int EADDRINUSE = 98;

    /*package*/ static final int SEC_FLAG_ENCRYPT = 1;
    /*package*/ static final int SEC_FLAG_AUTH = 1 << 1;
    /*package*/ static final int BTSOCK_FLAG_NO_SDP = 1 << 2;
    /*package*/ static final int SEC_FLAG_AUTH_MITM = 1 << 3;
    /*package*/ static final int SEC_FLAG_AUTH_16_DIGIT = 1 << 4;

    private final int mType; /* one of TYPE_RFCOMM etc */
    private BluetoothDevice mDevice; /* remote device */
    private String mAddress; /* remote address */
    private final boolean mAuth;
    private final boolean mEncrypt;
    private final BluetoothInputStream mInputStream;
    private final BluetoothOutputStream mOutputStream;
    private final ParcelUuid mUuid;

    /** when true no SPP SDP record will be created */
    private boolean mExcludeSdp = false;

    /** when true Person-in-the-middle protection will be enabled */
    private boolean mAuthMitm = false;

    /** Minimum 16 digit pin for sec mode 2 connections */
    private boolean mMin16DigitPin = false;

    @UnsupportedAppUsage(publicAlternatives = "Use {@link BluetoothSocket} public API instead.")
    private ParcelFileDescriptor mPfd;

    @UnsupportedAppUsage private LocalSocket mSocket;
    private InputStream mSocketIS;
    private OutputStream mSocketOS;
    @UnsupportedAppUsage private int mPort; /* RFCOMM channel or L2CAP psm */
    private String mServiceName;

    private static final int SOCK_SIGNAL_SIZE = 36;

    private ByteBuffer mL2capBuffer = null;
    private int mMaxTxPacketSize = 0; // The l2cap maximum packet size supported by the peer.
    private int mMaxRxPacketSize = 0; // The l2cap maximum packet size that can be received.
    private ParcelUuid mConnectionUuid;

    private long mSocketCreationTimeNanos = 0;
    private long mSocketCreationLatencyNanos = 0;

    private enum SocketState {
        INIT,
        CONNECTED,
        LISTENING,
        CLOSED,
    }

    /** prevents all native calls after destroyNative() */
    private volatile SocketState mSocketState;

    /** protects mSocketState */
    // private final ReentrantReadWriteLock mLock;

    /**
     * Construct a BluetoothSocket.
     *
     * @param type type of socket
     * @param auth require the remote device to be authenticated
     * @param encrypt require the connection to be encrypted
     * @param device remote device that this socket can connect to
     * @param port remote port
     * @param uuid SDP uuid
     * @throws IOException On error, for example Bluetooth not available, or insufficient privileges
     */
    /*package*/ BluetoothSocket(
            int type,
            boolean auth,
            boolean encrypt,
            BluetoothDevice device,
            int port,
            ParcelUuid uuid)
            throws IOException {
        this(type, auth, encrypt, device, port, uuid, false, false);
    }

    /**
     * Construct a BluetoothSocket.
     *
     * @param type type of socket
     * @param auth require the remote device to be authenticated
     * @param encrypt require the connection to be encrypted
     * @param device remote device that this socket can connect to
     * @param port remote port
     * @param uuid SDP uuid
     * @param mitm enforce person-in-the-middle protection.
     * @param min16DigitPin enforce a minimum length of 16 digits for a sec mode 2 connection
     * @throws IOException On error, for example Bluetooth not available, or insufficient privileges
     */
    /*package*/ BluetoothSocket(
            int type,
            boolean auth,
            boolean encrypt,
            BluetoothDevice device,
            int port,
            ParcelUuid uuid,
            boolean mitm,
            boolean min16DigitPin)
            throws IOException {
        if (VDBG) Log.d(TAG, "Creating new BluetoothSocket of type: " + type);
        mSocketCreationTimeNanos = System.nanoTime();
        if (type == BluetoothSocket.TYPE_RFCOMM
                && uuid == null
                && port != BluetoothAdapter.SOCKET_CHANNEL_AUTO_STATIC_NO_SDP) {
            if (port < 1 || port > MAX_RFCOMM_CHANNEL) {
                throw new IOException("Invalid RFCOMM channel: " + port);
            }
        }
        if (uuid != null) {
            mUuid = uuid;
        } else {
            mUuid = new ParcelUuid(new UUID(0, 0));
        }
        mType = type;
        mAuth = auth;
        mAuthMitm = mitm;
        mMin16DigitPin = min16DigitPin;
        mEncrypt = encrypt;
        mDevice = device;
        mPort = port;

        mSocketState = SocketState.INIT;

        if (device == null) {
            // Server socket
            mAddress = BluetoothAdapter.getDefaultAdapter().getAddress();
        } else {
            // Remote socket
            mAddress = device.getAddress();
        }
        mInputStream = new BluetoothInputStream(this);
        mOutputStream = new BluetoothOutputStream(this);
        mSocketCreationLatencyNanos = System.nanoTime() - mSocketCreationTimeNanos;
    }

    /**
     * Creates a BluetoothSocket from a {@link ParcelFileDescriptor}. This is used for when the
     * underlying mPfd is transferred to a separate process (e.g. over a binder), and the socket
     * must be reconstructed.
     *
     * <p>The socket should already be connected in this case, so {@link #connect()} should not be
     * called.
     *
     * @param pfd is the {@link ParcelFileDescriptor} for an already connected BluetoothSocket
     * @param device is the remote {@link BluetoothDevice} that this socket is connected to
     * @param uuid is the service ID that this RFCOMM connection is using
     * @throws IOException if socket creation fails.
     */
    /*package*/ static BluetoothSocket createSocketFromOpenFd(
            ParcelFileDescriptor pfd, BluetoothDevice device, ParcelUuid uuid) throws IOException {
        BluetoothSocket bluetoothSocket =
                new BluetoothSocket(TYPE_RFCOMM, true, true, device, -1, uuid);

        bluetoothSocket.mPfd = pfd;
        bluetoothSocket.mSocket = new LocalSocket(pfd.getFileDescriptor());
        bluetoothSocket.mSocketIS = bluetoothSocket.mSocket.getInputStream();
        bluetoothSocket.mSocketOS = bluetoothSocket.mSocket.getOutputStream();
        bluetoothSocket.mSocketState = SocketState.CONNECTED;

        return bluetoothSocket;
    }

    private BluetoothSocket(BluetoothSocket s) {
        if (VDBG) Log.d(TAG, "Creating new Private BluetoothSocket of type: " + s.mType);
        mUuid = s.mUuid;
        mType = s.mType;
        mAuth = s.mAuth;
        mEncrypt = s.mEncrypt;
        mPort = s.mPort;
        mInputStream = new BluetoothInputStream(this);
        mOutputStream = new BluetoothOutputStream(this);
        mMaxRxPacketSize = s.mMaxRxPacketSize;
        mMaxTxPacketSize = s.mMaxTxPacketSize;
        mConnectionUuid = s.mConnectionUuid;

        mServiceName = s.mServiceName;
        mExcludeSdp = s.mExcludeSdp;
        mAuthMitm = s.mAuthMitm;
        mMin16DigitPin = s.mMin16DigitPin;
        mSocketCreationTimeNanos = s.mSocketCreationTimeNanos;
        mSocketCreationLatencyNanos = s.mSocketCreationLatencyNanos;
    }

    private BluetoothSocket acceptSocket(String remoteAddr) throws IOException {
        BluetoothSocket as = new BluetoothSocket(this);
        as.mSocketState = SocketState.CONNECTED;
        FileDescriptor[] fds = mSocket.getAncillaryFileDescriptors();
        if (DBG) Log.d(TAG, "acceptSocket: socket fd passed by stack fds:" + Arrays.toString(fds));
        if (fds == null || fds.length != 1) {
            Log.e(TAG, "socket fd passed from stack failed, fds: " + Arrays.toString(fds));
            as.close();
            throw new IOException("bt socket accept failed");
        }

        as.mPfd = ParcelFileDescriptor.dup(fds[0]);
        as.mSocket = new LocalSocket(fds[0]);
        as.mSocketIS = as.mSocket.getInputStream();
        as.mSocketOS = as.mSocket.getOutputStream();
        as.mAddress = remoteAddr;
        as.mDevice = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(remoteAddr);
        return as;
    }

    /** @hide */
    @Override
    @SuppressWarnings("Finalize") // TODO(b/314811467)
    protected void finalize() throws Throwable {
        try {
            close();
        } finally {
            super.finalize();
        }
    }

    private int getSecurityFlags() {
        int flags = 0;
        if (mAuth) {
            flags |= SEC_FLAG_AUTH;
        }
        if (mEncrypt) {
            flags |= SEC_FLAG_ENCRYPT;
        }
        if (mExcludeSdp) {
            flags |= BTSOCK_FLAG_NO_SDP;
        }
        if (mAuthMitm) {
            flags |= SEC_FLAG_AUTH_MITM;
        }
        if (mMin16DigitPin) {
            flags |= SEC_FLAG_AUTH_16_DIGIT;
        }
        return flags;
    }

    /**
     * Get the remote device this socket is connecting, or connected, to.
     *
     * @return remote device
     */
    @RequiresNoPermission
    public BluetoothDevice getRemoteDevice() {
        return mDevice;
    }

    /**
     * Get the input stream associated with this socket.
     *
     * <p>The input stream will be returned even if the socket is not yet connected, but operations
     * on that stream will throw IOException until the associated socket is connected.
     *
     * @return InputStream
     */
    @RequiresNoPermission
    public InputStream getInputStream() throws IOException {
        return mInputStream;
    }

    /**
     * Get the output stream associated with this socket.
     *
     * <p>The output stream will be returned even if the socket is not yet connected, but operations
     * on that stream will throw IOException until the associated socket is connected.
     *
     * @return OutputStream
     */
    @RequiresNoPermission
    public OutputStream getOutputStream() throws IOException {
        return mOutputStream;
    }

    /**
     * Get the connection status of this socket, ie, whether there is an active connection with
     * remote device.
     *
     * @return true if connected false if not connected
     */
    @RequiresNoPermission
    public boolean isConnected() {
        return mSocketState == SocketState.CONNECTED;
    }

    /*package*/ void setServiceName(String name) {
        mServiceName = name;
    }

    /*package*/ boolean isAuth() {
        return mAuth;
    }

    /**
     * Attempt to connect to a remote device.
     *
     * <p>This method will block until a connection is made or the connection fails. If this method
     * returns without an exception then this socket is now connected.
     *
     * <p>Creating new connections to remote Bluetooth devices should not be attempted while device
     * discovery is in progress. Device discovery is a heavyweight procedure on the Bluetooth
     * adapter and will significantly slow a device connection. Use {@link
     * BluetoothAdapter#cancelDiscovery()} to cancel an ongoing discovery. Discovery is not managed
     * by the Activity, but is run as a system service, so an application should always call {@link
     * BluetoothAdapter#cancelDiscovery()} even if it did not directly request a discovery, just to
     * be sure.
     *
     * <p>{@link #close} can be used to abort this call from another thread.
     *
     * @throws BluetoothSocketException in case of failure, with the corresponding error code.
     * @throws IOException for other errors (eg: InputStream read failures etc.).
     */
    @RequiresBluetoothConnectPermission
    @RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
    public void connect() throws IOException {
        IBluetooth bluetoothProxy = BluetoothAdapter.getDefaultAdapter().getBluetoothService();
        long socketConnectionTimeNanos = System.nanoTime();
        if (bluetoothProxy == null) {
            throw new BluetoothSocketException(BluetoothSocketException.BLUETOOTH_OFF_FAILURE);
        }
        try {
            if (mDevice == null) {
                throw new BluetoothSocketException(BluetoothSocketException.NULL_DEVICE);
            }
            if (mSocketState == SocketState.CLOSED) {
                throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
            }

            IBluetoothSocketManager socketManager = bluetoothProxy.getSocketManager();
            if (socketManager == null) {
                throw new BluetoothSocketException(BluetoothSocketException.SOCKET_MANAGER_FAILURE);
            }
            mPfd = socketManager.connectSocket(mDevice, mType, mUuid, mPort, getSecurityFlags());
            synchronized (this) {
                Log.i(TAG, "connect(), SocketState: " + mSocketState + ", mPfd: " + mPfd);
                if (mSocketState == SocketState.CLOSED) {
                    throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
                }
                if (mPfd == null) {
                    throw new BluetoothSocketException(
                            BluetoothSocketException.UNIX_FILE_SOCKET_CREATION_FAILURE);
                }
                FileDescriptor fd = mPfd.getFileDescriptor();
                mSocket = new LocalSocket(fd);
                mSocketIS = mSocket.getInputStream();
                mSocketOS = mSocket.getOutputStream();
            }
            int channel = readInt(mSocketIS);
            if (channel == 0) {
                int errCode = (int) mSocketIS.read();
                throw new BluetoothSocketException(errCode);
            }
            if (channel < 0) {
                throw new BluetoothSocketException(
                        BluetoothSocketException.SOCKET_CONNECTION_FAILURE);
            }
            mPort = channel;
            waitSocketSignal(mSocketIS);
            synchronized (this) {
                if (mSocketState == SocketState.CLOSED) {
                    throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
                }
                mSocketState = SocketState.CONNECTED;
                Log.i(TAG, "connect(), socket connected. mPort=" + mPort);
            }
        } catch (BluetoothSocketException e) {
            SocketMetrics.logSocketConnect(
                    e.getErrorCode(),
                    socketConnectionTimeNanos,
                    mType,
                    mDevice,
                    mPort,
                    mAuth,
                    mSocketCreationTimeNanos,
                    mSocketCreationLatencyNanos);
            throw e;
        } catch (RemoteException e) {
            Log.e(TAG, e.toString() + "\n" + Log.getStackTraceString(new Throwable()));
            SocketMetrics.logSocketConnect(
                    BluetoothSocketException.RPC_FAILURE,
                    socketConnectionTimeNanos,
                    mType,
                    mDevice,
                    mPort,
                    mAuth,
                    mSocketCreationTimeNanos,
                    mSocketCreationLatencyNanos);
            throw new BluetoothSocketException(
                    BluetoothSocketException.RPC_FAILURE, "unable to send RPC: " + e.getMessage());
        }
        SocketMetrics.logSocketConnect(
                SocketMetrics.SOCKET_NO_ERROR,
                socketConnectionTimeNanos,
                mType,
                mDevice,
                mPort,
                mAuth,
                mSocketCreationTimeNanos,
                mSocketCreationLatencyNanos);
    }

    /**
     * Currently returns unix errno instead of throwing IOException, so that BluetoothAdapter can
     * check the error code for EADDRINUSE
     */
    @RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
    /*package*/ int bindListen() {
        int ret;
        if (mSocketState == SocketState.CLOSED) return EBADFD;
        IBluetooth bluetoothProxy = BluetoothAdapter.getDefaultAdapter().getBluetoothService();
        if (bluetoothProxy == null) {
            Log.e(TAG, "bindListen fail, reason: bluetooth is off");
            return -1;
        }
        try {
            if (DBG) Log.d(TAG, "bindListen(): mPort=" + mPort + ", mType=" + mType);
            IBluetoothSocketManager socketManager = bluetoothProxy.getSocketManager();
            if (socketManager == null) {
                Log.e(TAG, "bindListen() bt get socket manager failed");
                return -1;
            }
            mPfd =
                    socketManager.createSocketChannel(
                            mType, mServiceName, mUuid, mPort, getSecurityFlags());
        } catch (RemoteException e) {
            Log.e(TAG, e.toString() + "\n" + Log.getStackTraceString(new Throwable()));
            return -1;
        }

        // read out port number
        try {
            synchronized (this) {
                if (DBG) {
                    Log.d(TAG, "bindListen(), SocketState: " + mSocketState + ", mPfd: " + mPfd);
                }
                if (mSocketState != SocketState.INIT) return EBADFD;
                if (mPfd == null) return -1;
                FileDescriptor fd = mPfd.getFileDescriptor();
                if (fd == null) {
                    Log.e(TAG, "bindListen(), null file descriptor");
                    return -1;
                }

                if (DBG) Log.d(TAG, "bindListen(), Create LocalSocket");
                mSocket = new LocalSocket(fd);
                if (DBG) Log.d(TAG, "bindListen(), new LocalSocket.getInputStream()");
                mSocketIS = mSocket.getInputStream();
                mSocketOS = mSocket.getOutputStream();
            }
            if (DBG) Log.d(TAG, "bindListen(), readInt mSocketIS: " + mSocketIS);
            int channel = readInt(mSocketIS);
            synchronized (this) {
                if (mSocketState == SocketState.INIT) {
                    mSocketState = SocketState.LISTENING;
                }
            }
            if (DBG) Log.d(TAG, "bindListen(): channel=" + channel + ", mPort=" + mPort);
            if (mPort <= -1) {
                mPort = channel;
            } // else ASSERT(mPort == channel)
            ret = 0;
        } catch (IOException e) {
            if (mPfd != null) {
                try {
                    mPfd.close();
                } catch (IOException e1) {
                    Log.e(TAG, "bindListen, close mPfd: " + e1);
                }
                mPfd = null;
            }
            Log.e(TAG, "bindListen, fail to get port number, exception: " + e);
            return -1;
        }
        return ret;
    }

    /*package*/ BluetoothSocket accept(int timeout) throws IOException {
        BluetoothSocket acceptedSocket;
        if (mSocketState != SocketState.LISTENING) {
            throw new IOException("bt socket is not in listen state");
        }
        Log.d(TAG, "accept(), timeout (ms):" + timeout);
        if (timeout > 0) {
            mSocket.setSoTimeout(timeout);
        }
        String RemoteAddr = waitSocketSignal(mSocketIS);
        if (timeout > 0) {
            mSocket.setSoTimeout(0);
        }
        synchronized (this) {
            if (mSocketState != SocketState.LISTENING) {
                throw new IOException("bt socket is not in listen state");
            }
            acceptedSocket = acceptSocket(RemoteAddr);
            // quick drop the reference of the file handle
        }
        return acceptedSocket;
    }

    /*package*/ int available() throws IOException {
        if (VDBG) Log.d(TAG, "available: " + mSocketIS);
        return mSocketIS.available();
    }

    /*package*/ int read(byte[] b, int offset, int length) throws IOException {
        int ret = 0;
        if (VDBG) Log.d(TAG, "read in:  " + mSocketIS + " len: " + length);
        if ((mType == TYPE_L2CAP) || (mType == TYPE_L2CAP_LE)) {
            int bytesToRead = length;
            if (VDBG) {
                Log.v(
                        TAG,
                        "l2cap: read(): offset: "
                                + offset
                                + " length:"
                                + length
                                + "mL2capBuffer= "
                                + mL2capBuffer);
            }
            if (mL2capBuffer == null) {
                createL2capRxBuffer();
            }
            if (mL2capBuffer.remaining() == 0) {
                if (VDBG) Log.v(TAG, "l2cap buffer empty, refilling...");
                if (fillL2capRxBuffer() == -1) {
                    return -1;
                }
            }
            if (bytesToRead > mL2capBuffer.remaining()) {
                bytesToRead = mL2capBuffer.remaining();
            }
            if (VDBG) {
                Log.v(TAG, "get(): offset: " + offset + " bytesToRead: " + bytesToRead);
            }
            mL2capBuffer.get(b, offset, bytesToRead);
            ret = bytesToRead;
        } else {
            if (VDBG) Log.v(TAG, "default: read(): offset: " + offset + " length:" + length);
            ret = mSocketIS.read(b, offset, length);
        }
        if (ret < 0) {
            throw new IOException("bt socket closed, read return: " + ret);
        }
        if (VDBG) Log.d(TAG, "read out:  " + mSocketIS + " ret: " + ret);
        return ret;
    }

    /*package*/ int write(byte[] b, int offset, int length) throws IOException {

        // TODO: Since bindings can exist between the SDU size and the
        //      protocol, we might need to throw an exception instead of just
        //      splitting the write into multiple smaller writes.
        //      Rfcomm uses dynamic allocation, and should not have any bindings
        //      to the actual message length.
        if (VDBG) Log.d(TAG, "write: " + mSocketOS + " length: " + length);
        if ((mType == TYPE_L2CAP) || (mType == TYPE_L2CAP_LE)) {
            if (length <= mMaxTxPacketSize) {
                mSocketOS.write(b, offset, length);
            } else {
                if (DBG) {
                    Log.w(
                            TAG,
                            "WARNING: Write buffer larger than L2CAP packet size!\n"
                                    + "Packet will be divided into SDU packets of size "
                                    + mMaxTxPacketSize);
                }
                int tmpOffset = offset;
                int bytesToWrite = length;
                while (bytesToWrite > 0) {
                    int tmpLength =
                            (bytesToWrite > mMaxTxPacketSize) ? mMaxTxPacketSize : bytesToWrite;
                    mSocketOS.write(b, tmpOffset, tmpLength);
                    tmpOffset += tmpLength;
                    bytesToWrite -= tmpLength;
                }
            }
        } else {
            mSocketOS.write(b, offset, length);
        }
        // There is no good way to confirm since the entire process is asynchronous anyway
        if (VDBG) Log.d(TAG, "write out: " + mSocketOS + " length: " + length);
        return length;
    }

    @Override
    public void close() throws IOException {
        Log.d(
                TAG,
                "close() this: "
                        + this
                        + ", channel: "
                        + mPort
                        + ", mSocketIS: "
                        + mSocketIS
                        + ", mSocketOS: "
                        + mSocketOS
                        + ", mSocket: "
                        + mSocket
                        + ", mSocketState: "
                        + mSocketState);
        if (mSocketState == SocketState.CLOSED) {
            return;
        } else {
            synchronized (this) {
                if (mSocketState == SocketState.CLOSED) {
                    return;
                }
                mSocketState = SocketState.CLOSED;
                if (mSocket != null) {
                    if (DBG) Log.d(TAG, "Closing mSocket: " + mSocket);
                    mSocket.shutdownInput();
                    mSocket.shutdownOutput();
                    mSocket.close();
                    mSocket = null;
                }
                if (mPfd != null) {
                    mPfd.close();
                    mPfd = null;
                }
                mConnectionUuid = null;
            }
        }
    }

    /*package */ void removeChannel() {}

    /*package */ int getPort() {
        return mPort;
    }

    /*package */ long getSocketCreationTime() {
        return mSocketCreationTimeNanos;
    }

    /**
     * Get the maximum supported Transmit packet size for the underlying transport. Use this to
     * optimize the writes done to the output socket, to avoid sending half full packets.
     *
     * @return the maximum supported Transmit packet size for the underlying transport.
     */
    @RequiresNoPermission
    public int getMaxTransmitPacketSize() {
        return mMaxTxPacketSize;
    }

    /**
     * Get the maximum supported Receive packet size for the underlying transport. Use this to
     * optimize the reads done on the input stream, as any call to read will return a maximum of
     * this amount of bytes - or for some transports a multiple of this value.
     *
     * @return the maximum supported Receive packet size for the underlying transport.
     */
    @RequiresNoPermission
    public int getMaxReceivePacketSize() {
        return mMaxRxPacketSize;
    }

    /**
     * Get the type of the underlying connection.
     *
     * @return one of {@link #TYPE_RFCOMM}, {@link #TYPE_SCO} or {@link #TYPE_L2CAP}
     */
    @RequiresNoPermission
    public int getConnectionType() {
        if (mType == TYPE_L2CAP_LE) {
            // Treat the LE CoC to be the same type as L2CAP.
            return TYPE_L2CAP;
        }
        return mType;
    }

    /**
     * Change if a SDP entry should be automatically created. Must be called before calling .bind,
     * for the call to have any effect.
     *
     * @param excludeSdp
     *     <li>TRUE - do not auto generate SDP record.
     *     <li>FALSE - default - auto generate SPP SDP record.
     * @hide
     */
    @RequiresNoPermission
    public void setExcludeSdp(boolean excludeSdp) {
        mExcludeSdp = excludeSdp;
    }

    /**
     * Set the LE Transmit Data Length to be the maximum that the BT Controller is capable of. This
     * parameter is used by the BT Controller to set the maximum transmission packet size on this
     * connection. This function is currently used for testing only.
     *
     * @hide
     */
    @RequiresBluetoothConnectPermission
    @RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
    public void requestMaximumTxDataLength() throws IOException {
        if (mDevice == null) {
            throw new IOException("requestMaximumTxDataLength is called on null device");
        }

        try {
            if (mSocketState == SocketState.CLOSED) {
                throw new IOException("socket closed");
            }
            IBluetooth bluetoothProxy = BluetoothAdapter.getDefaultAdapter().getBluetoothService();
            if (bluetoothProxy == null) {
                throw new IOException("Bluetooth is off");
            }

            if (DBG) Log.d(TAG, "requestMaximumTxDataLength");
            IBluetoothSocketManager socketManager = bluetoothProxy.getSocketManager();
            if (socketManager == null) throw new IOException("bt get socket manager failed");
            socketManager.requestMaximumTxDataLength(mDevice);
        } catch (RemoteException e) {
            Log.e(TAG, e.toString() + "\n" + Log.getStackTraceString(new Throwable()));
            throw new IOException("unable to send RPC: " + e.getMessage());
        }
    }

    /**
     * Returns the L2CAP local channel ID associated with an open connection to this socket.
     *
     * @return the L2CAP local channel ID.
     * @throws BluetoothSocketException in case of failure, with the corresponding error code.
     * @hide
     */
    @SystemApi
    @FlaggedApi(Flags.FLAG_BT_SOCKET_API_L2CAP_CID)
    @RequiresPermission(
            allOf = {
                android.Manifest.permission.BLUETOOTH_CONNECT,
                android.Manifest.permission.BLUETOOTH_PRIVILEGED,
            })
    public int getL2capLocalChannelId() throws IOException {
        if (mType != TYPE_L2CAP_LE) {
            throw new BluetoothSocketException(BluetoothSocketException.L2CAP_UNKNOWN);
        }
        if (mSocketState != SocketState.CONNECTED || mConnectionUuid == null) {
            throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
        }
        int cid;
        IBluetooth bluetoothProxy = BluetoothAdapter.getDefaultAdapter().getBluetoothService();
        if (bluetoothProxy == null) {
            throw new BluetoothSocketException(BluetoothSocketException.BLUETOOTH_OFF_FAILURE);
        }
        try {
            IBluetoothSocketManager socketManager = bluetoothProxy.getSocketManager();
            if (socketManager == null) {
                throw new BluetoothSocketException(BluetoothSocketException.SOCKET_MANAGER_FAILURE);
            }
            cid =
                    socketManager.getL2capLocalChannelId(
                            mConnectionUuid, AttributionSource.myAttributionSource());
        } catch (RemoteException e) {
            Log.e(TAG, e.toString() + "\n" + Log.getStackTraceString(new Throwable()));
            throw new IOException("unable to send RPC: " + e.getMessage());
        }
        if (cid == -1) {
            throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
        }
        return cid;
    }

    /**
     * Returns the L2CAP remote channel ID associated with an open connection to this socket.
     *
     * @return the L2CAP remote channel ID.
     * @throws BluetoothSocketException in case of failure, with the corresponding error code.
     * @hide
     */
    @SystemApi
    @FlaggedApi(Flags.FLAG_BT_SOCKET_API_L2CAP_CID)
    @RequiresPermission(
            allOf = {
                android.Manifest.permission.BLUETOOTH_CONNECT,
                android.Manifest.permission.BLUETOOTH_PRIVILEGED,
            })
    public int getL2capRemoteChannelId() throws IOException {
        if (mType != TYPE_L2CAP_LE) {
            throw new BluetoothSocketException(BluetoothSocketException.L2CAP_UNKNOWN);
        }
        if (mSocketState != SocketState.CONNECTED || mConnectionUuid == null) {
            throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
        }
        int cid;
        IBluetooth bluetoothProxy = BluetoothAdapter.getDefaultAdapter().getBluetoothService();
        if (bluetoothProxy == null) {
            throw new BluetoothSocketException(BluetoothSocketException.BLUETOOTH_OFF_FAILURE);
        }
        try {
            IBluetoothSocketManager socketManager = bluetoothProxy.getSocketManager();
            if (socketManager == null) {
                throw new BluetoothSocketException(BluetoothSocketException.SOCKET_MANAGER_FAILURE);
            }
            cid =
                    socketManager.getL2capRemoteChannelId(
                            mConnectionUuid, AttributionSource.myAttributionSource());
        } catch (RemoteException e) {
            Log.e(TAG, e.toString() + "\n" + Log.getStackTraceString(new Throwable()));
            throw new IOException("unable to send RPC: " + e.getMessage());
        }
        if (cid == -1) {
            throw new BluetoothSocketException(BluetoothSocketException.SOCKET_CLOSED);
        }
        return cid;
    }

    /** @hide */
    public ParcelFileDescriptor getParcelFileDescriptor() {
        return mPfd;
    }

    private String convertAddr(final byte[] addr) {
        return String.format(
                Locale.US,
                "%02X:%02X:%02X:%02X:%02X:%02X",
                addr[0],
                addr[1],
                addr[2],
                addr[3],
                addr[4],
                addr[5]);
    }

    private String waitSocketSignal(InputStream is) throws IOException {
        byte[] sig = new byte[SOCK_SIGNAL_SIZE];
        int ret = readAll(is, sig);
        if (VDBG) {
            Log.d(TAG, "waitSocketSignal read " + SOCK_SIGNAL_SIZE + " bytes signal ret: " + ret);
        }
        ByteBuffer bb = ByteBuffer.wrap(sig);
        /* the struct in native is decorated with __attribute__((packed)), hence this is possible */
        bb.order(ByteOrder.nativeOrder());
        int size = bb.getShort();
        if (size != SOCK_SIGNAL_SIZE) {
            throw new IOException("Connection failure, wrong signal size: " + size);
        }
        byte[] addr = new byte[6];
        bb.get(addr);
        int channel = bb.getInt();
        int status = bb.getInt();
        mMaxTxPacketSize = (bb.getShort() & 0xffff); // Convert to unsigned value
        mMaxRxPacketSize = (bb.getShort() & 0xffff); // Convert to unsigned value
        long uuidLsb = bb.getLong();
        long uuidMsb = bb.getLong();
        mConnectionUuid = new ParcelUuid(new UUID(uuidMsb, uuidLsb));
        String RemoteAddr = convertAddr(addr);
        if (VDBG) {
            Log.d(
                    TAG,
                    "waitSocketSignal: sig size: "
                            + size
                            + ", remote addr: "
                            + RemoteAddr
                            + ", channel: "
                            + channel
                            + ", status: "
                            + status
                            + " MaxRxPktSize: "
                            + mMaxRxPacketSize
                            + " MaxTxPktSize: "
                            + mMaxTxPacketSize
                            + " mConnectionUuid: "
                            + mConnectionUuid.toString());
        }
        if (status != 0) {
            throw new IOException("Connection failure, status: " + status);
        }
        return RemoteAddr;
    }

    private void createL2capRxBuffer() {
        if ((mType == TYPE_L2CAP) || (mType == TYPE_L2CAP_LE)) {
            // Allocate the buffer to use for reads.
            if (VDBG) Log.v(TAG, "  Creating mL2capBuffer: mMaxPacketSize: " + mMaxRxPacketSize);
            mL2capBuffer = ByteBuffer.wrap(new byte[mMaxRxPacketSize]);
            if (VDBG) Log.v(TAG, "mL2capBuffer.remaining()" + mL2capBuffer.remaining());
            mL2capBuffer.limit(0); // Ensure we do a real read at the first read-request
            if (VDBG) {
                Log.v(TAG, "mL2capBuffer.remaining() after limit(0):" + mL2capBuffer.remaining());
            }
        }
    }

    private int readAll(InputStream is, byte[] b) throws IOException {
        int left = b.length;
        while (left > 0) {
            int ret = is.read(b, b.length - left, left);
            if (ret <= 0) {
                throw new IOException(
                        "read failed, socket might closed or timeout, read ret: " + ret);
            }
            left -= ret;
            if (left != 0) {
                Log.w(
                        TAG,
                        "readAll() looping, read partial size: "
                                + (b.length - left)
                                + ", expect size: "
                                + b.length);
            }
        }
        return b.length;
    }

    private int readInt(InputStream is) throws IOException {
        byte[] ibytes = new byte[4];
        int ret = readAll(is, ibytes);
        if (VDBG) Log.d(TAG, "inputStream.read ret: " + ret);
        ByteBuffer bb = ByteBuffer.wrap(ibytes);
        bb.order(ByteOrder.nativeOrder());
        return bb.getInt();
    }

    private int fillL2capRxBuffer() throws IOException {
        mL2capBuffer.rewind();
        int ret = mSocketIS.read(mL2capBuffer.array());
        if (ret == -1) {
            // reached end of stream - return -1
            mL2capBuffer.limit(0);
            return -1;
        }
        mL2capBuffer.limit(ret);
        return ret;
    }

    @Override
    public String toString() {
        return BluetoothUtils.toAnonymizedAddress(mAddress);
    }
}