nci/jni/CondVar.cpp

/*
 * 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.
 */

/*
 *  Encapsulate a condition variable for thread synchronization.
 */

#include "CondVar.h"
#include "NfcJniUtil.h"
#include <errno.h>


/*******************************************************************************
**
** Function:        CondVar
**
** Description:     Initialize member variables.
**
** Returns:         None.
**
*******************************************************************************/
CondVar::CondVar ()
{
    memset (&mCondition, 0, sizeof(mCondition));
    int const res = pthread_cond_init (&mCondition, NULL);
    if (res)
    {
        ALOGE ("CondVar::CondVar: fail init; error=0x%X", res);
    }
}


/*******************************************************************************
**
** Function:        ~CondVar
**
** Description:     Cleanup all resources.
**
** Returns:         None.
**
*******************************************************************************/
CondVar::~CondVar ()
{
    int const res = pthread_cond_destroy (&mCondition);
    if (res)
    {
        ALOGE ("CondVar::~CondVar: fail destroy; error=0x%X", res);
    }
}


/*******************************************************************************
**
** Function:        wait
**
** Description:     Block the caller and wait for a condition.
**
** Returns:         None.
**
*******************************************************************************/
void CondVar::wait (Mutex& mutex)
{
    int const res = pthread_cond_wait (&mCondition, mutex.nativeHandle());
    if (res)
    {
        ALOGE ("CondVar::wait: fail wait; error=0x%X", res);
    }
}


/*******************************************************************************
**
** Function:        wait
**
** Description:     Block the caller and wait for a condition.
**                  millisec: Timeout in milliseconds.
**
** Returns:         True if wait is successful; false if timeout occurs.
**
*******************************************************************************/
bool CondVar::wait (Mutex& mutex, long millisec)
{
    bool retVal = false;
    struct timespec absoluteTime;

    if (clock_gettime (CLOCK_MONOTONIC, &absoluteTime) == -1)
    {
        ALOGE ("CondVar::wait: fail get time; errno=0x%X", errno);
    }
    else
    {
        absoluteTime.tv_sec += millisec / 1000;
        long ns = absoluteTime.tv_nsec + ((millisec % 1000) * 1000000);
        if (ns > 1000000000)
        {
            absoluteTime.tv_sec++;
            absoluteTime.tv_nsec = ns - 1000000000;
        }
        else
            absoluteTime.tv_nsec = ns;
    }

    //pthread_cond_timedwait_monotonic_np() is an Android-specific function
    //declared in /development/ndk/platforms/android-9/include/pthread.h;
    //it uses monotonic clock.
    //the standard pthread_cond_timedwait() uses realtime clock.
    int waitResult = pthread_cond_timedwait_monotonic_np (&mCondition, mutex.nativeHandle(), &absoluteTime);
    if ((waitResult != 0) && (waitResult != ETIMEDOUT))
        ALOGE ("CondVar::wait: fail timed wait; error=0x%X", waitResult);
    retVal = (waitResult == 0); //waited successfully
    return retVal;
}


/*******************************************************************************
**
** Function:        notifyOne
**
** Description:     Unblock the waiting thread.
**
** Returns:         None.
**
*******************************************************************************/
void CondVar::notifyOne ()
{
    int const res = pthread_cond_signal (&mCondition);
    if (res)
    {
        ALOGE ("CondVar::notifyOne: fail signal; error=0x%X", res);
    }
}