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      1 /*
      2  * Copyright (C) 2015 Intel Corporation
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ACQUISITION_THREAD_HPP
     18 #define ACQUISITION_THREAD_HPP
     19 
     20 #include <pthread.h>
     21 #include "Sensor.hpp"
     22 
     23 class Sensor;
     24 
     25 /**
     26  * AcquisitionThread is used for implementing sensors polling
     27  *
     28  * The class creates a thread to periodically poll data from a
     29  * sensor and write it to a pipe. The main thread can use the
     30  * pipe read endpoint to retrieve sensor events.
     31  *
     32  * One can also wake up the thread via the wakeup method after
     33  * changing the sensor parameters.
     34  *
     35  * It includes support for generating a flush complete event.
     36  */
     37 class AcquisitionThread {
     38   public:
     39     /**
     40      * AcquisitionThread constructor
     41      * @param pollFd poll file descriptor
     42      * @param sensor the sensor to associate with the thread
     43      */
     44     AcquisitionThread(int pollFd, Sensor *sensor);
     45 
     46     /**
     47      * AcquistionThread destructor
     48      */
     49     ~AcquisitionThread();
     50 
     51     /**
     52      * Get sensor associated with the thread
     53      * @return the associated sensor
     54      */
     55     Sensor * getSensor() { return sensor; }
     56 
     57     /**
     58      * Get the file descriptor of the pipe read endpoint
     59      * @return the pipe read file descriptor
     60      */
     61     int getReadPipeFd() { return pipeFds[0]; }
     62 
     63     /**
     64      * Get the file descriptor of the pipe write endpoint
     65      * @return the pipe write file descriptor
     66      */
     67     int getWritePipeFd() { return pipeFds[1]; }
     68 
     69     /**
     70      * Initialize the acquisition thread
     71      * @return true if successful, false otherwise
     72      */
     73     bool init();
     74 
     75     /**
     76      * Generate a flush event and send it via the associated pipe
     77      * @return true if successful, false otherwise
     78      */
     79     bool generateFlushCompleteEvent();
     80 
     81     /**
     82      * Wake up thread if it is sleeping
     83      * @return 0 if successful, < 0 otherwise
     84      */
     85     int wakeup();
     86 
     87   private:
     88     static void * acquisitionRoutine(void *param);
     89 
     90     int pollFd;
     91     int pipeFds[2];
     92     pthread_t pthread;
     93     pthread_condattr_t pthreadCondAttr;
     94     pthread_cond_t pthreadCond;
     95     pthread_mutex_t pthreadMutex;
     96     Sensor *sensor;
     97     bool initialized;
     98 };
     99 
    100 #endif  // ACQUISITION_THREAD_HPP
    101