在Android上使用LocalSocket实现上层Java和底层C++的通信

在看android代码的时候发现有使用LocalSocket，比java本身的socket效率要高，好像没有经过协议栈，是android自己实现的类似共享内存一样的东东，在传输大量数据的时候就需要用到，比如视频数据,在RIL电话那部分也用到。刚好项目用到视频传输，我试用了一把，果然不错！public static final String SOCKET_ADDRESS = "socket_cmmb_sim_command";//这个名字要记好，在接受端要用到，可以理解为共享内存的设备文件名。.....            try {                LocalServerSocket server = new LocalServerSocket(SOCKET_ADDRESS);                while (true) {                    //Log.i(TAG, "begin accept");                    LocalSocket receiver = server.accept();                    if (receiver != null) {                        InputStream input = receiver.getInputStream();                        byte[] bytes = new byte[4];                        int size = input.read(bytes, 0, 4);                        if(size!=4) Log.i(TAG, "received command len:" + String.valueOf(size));                        int cmd_len = ((bytes[0] & 0xFF)                                 |((bytes[2] & 0xFF)                         Log.i(TAG, "received cmd_len:"+String.valueOf(cmd_len));                        if(cmd_len>0){                            byte[] ArrayOfByte = new byte[cmd_len];                            size = input.read(ArrayOfByte, 0, cmd_len);                            Log.i(TAG, "received data len:" + String.valueOf(size));                            Parcel parcel = Parcel.obtain();                            parcel.unmarshall(ArrayOfByte, 0, ArrayOfByte.length);                            parcel.setDataPosition(0);                            processRequest(receiver,parcel);                        }                    }                }            } catch (IOException e) {                Log.e(getClass().getName(), e.getMessage());            }        private void sendResult(LocalSocket paramLocalSocket, Parcel paramParcel) throws IOException{            byte[] arrayOfByte1 = new byte[4];            byte[] arrayOfByte2 = paramParcel.marshall();            Log.i(TAG, "enter sendResult!");            arrayOfByte1[0] = 0;            arrayOfByte1[1] = 0;            arrayOfByte1[2] = (byte)(arrayOfByte2.length >> 8 & 0xFF);            arrayOfByte1[3] = (byte)(arrayOfByte2.length & 0xFF);            paramLocalSocket.getOutputStream().write(arrayOfByte1);            paramLocalSocket.getOutputStream().write(arrayOfByte2);        }private void processRequest(LocalSocket paramLocalSocket, Parcel paramParcel){          int cmd = paramParcel.readInt();          //Log.i(TAG,"parcel:"+String.valueOf(cmd));          if(cmd>0&&cmd          //String info = "unknown";          Parcel parcel_info = Parcel.obtain();          TelephonyManager tm = (TelephonyManager) getSystemService(TELEPHONY_SERVICE);          switch (cmd)          {          case CMMB_REQUEST_GET_IMSI:{              Log.i(TAG, "received CMMB_REQUEST_GET_IMSI command!");              /*               * 唯一的用户ID：               * 例如：IMSI(国际移动用户识别码) for a GSM phone.               * 需要权限：READ_PHONE_STATE               */              String info = tm.getSubscriberId();//String              if(info!=null) Log.i(TAG, info);              parcel_info.writeInt(CMMB_REQUEST_GET_IMSI);              parcel_info.writeString(info);            }            break;....          try {             sendResult(paramLocalSocket, parcel_info);          } catch (IOException e) {            // TODO Auto-generated catch block            Log.e(getClass().getName(), e.getMessage());            e.printStackTrace();          }}以上是服务器端，下面是客户端#define  SOCKET_NAME_CMMB_SIM_COMMAND   "socket_cmmb_sim_command"...    fd = socket_local_client(                            SOCKET_NAME_CMMB_SIM_COMMAND,                            ANDROID_SOCKET_NAMESPACE_ABSTRACT,                            SOCK_STREAM );    //check open failed    if (fd     {           LOGE("Failed to open socket: %s\n\r'", SOCKET_NAME_CMMB_SIM_COMMAND);        goto error;        }    //get command data    p_request.writeInt32 (CMMB_REQUEST_GET_IMSI);    data = (char *)p_request.data();    datasize = (int)p_request.dataSize();    //get command length    dataLength[0] = dataLength[1] = 0;    dataLength[2] = (char)((datasize >> 8) & 0xff);    dataLength[3] = (char)(datasize & 0xff);    //write command getimsi length    if(SmsMbbmsSimSocketWrite(fd, dataLength, sizeof(dataLength)) != sizeof(dataLength))    {        LOGE("Failed to write cmmand %d 's length to socket: %s!!!!!\n'", CMMB_REQUEST_GET_IMSI, SOCKET_NAME_CMMB_SIM_COMMAND);        goto error;    }    //write command getimsi    if(SmsMbbmsSimSocketWrite(fd, data, datasize) != datasize)    {        LOGE("Failed to write cmmand %d to socket: %s!!!!\n'", CMMB_REQUEST_GET_IMSI, SOCKET_NAME_CMMB_SIM_COMMAND);        goto error;    }    //write end, start read response    //read head, include length of data, 4 byte    if(SmsMbbmsSimSocketRead(fd, response_data, 4) != 4)    {        LOGE("Failed to read response command %d 's length from socket: %s!!!!!\n'", CMMB_REQUEST_GET_IMSI, SOCKET_NAME_CMMB_SIM_COMMAND);        goto error;    }    //LOGD("response_data of length: %d, %d, %d, %d!!!\n", response_data[0], response_data[1], response_data[2], response_data[3]);    //calculate length    response_length = ((response_data[0] & 0xff)                     | ((response_data[1] & 0xff)                     | ((response_data[2] & 0xff)                     | (response_data[3] & 0xff);    //LOGD("response_length = %d\n", response_length);    //check length    if(response_length == 0)    {        LOGE("response %d 's length from socket: %s is not right!!!!!\n'", CMMB_REQUEST_GET_IMSI, SOCKET_NAME_CMMB_SIM_COMMAND);        goto error;    }...这样就是实现了客户端和服务器之间的通信。