Creating -a Periodic Timer

diff -r 48780e181b38 -r 578be2adaf3e Symbian3/PDK/Source/GUID-B4039418-6499-555D-AC24-9B49161299F2.dita --- a/Symbian3/PDK/Source/GUID-B4039418-6499-555D-AC24-9B49161299F2.dita Tue Jul 20 12:00:49 2010 +0100 +++ b/Symbian3/PDK/Source/GUID-B4039418-6499-555D-AC24-9B49161299F2.dita Fri Aug 13 16:47:46 2010 +0100 @@ -1,107 +1,107 @@ - - - - - -Creating -a Periodic Timer -

You can use a periodic timer to provide repeated signals to your process.

The following example illustrates a periodic timer with a delay of a second -and a repeating interval of ten milliseconds. It also configures a thread -function as the timer expiry notification using SIGEV_THREAD.

The following example code performs the following tasks:

Creates a notification -function (thread function) that must be invoked after timer expiry.
Sets the thread priority -to 255 using the thread scheduling parameters (struct sched_param). -This ensures that the thread function has the highest priority when it is -invoked as a result of a timer expiry.
Creates a timer based -on the current system time (CLOCK_REALTIME) and a notification -function (struct sigevent sig) that must be -invoked when the timer expires.
Defines the input values -for timer_settime(). The key input values are the timer -value (in.it_value.tv_sec = 1;) and the interval (in.it_interval.tv_nsec -= 100000000;). The periodic timer will expire after a second and -then invoke the notification function every one-tenth of a second until it -is destroyed.
Starts the periodic -timer using timer_settime().
Uses sleep(2) to -pause the program execution for two seconds before destroying the timer.

-#include <time.h> -#include <stdio.h> -#include <signal.h> -#include <pthread.h> -#include <unistd.h> -#include <errno.h> -static int i = 0; - -//Thread function to be invoked when the periodic timer expires -void sighler (union sigval val) - { - printf("Handler entered with value :%d for %d times\n", val.sival_int, ++i); - } -int main() - { - int Ret; - - pthread_attr_t attr; - pthread_attr_init( &attr ); - - struct sched_param parm; - parm.sched_priority = 255; - pthread_attr_setschedparam(&attr, &parm); - - struct sigevent sig; - sig.sigev_notify = SIGEV_THREAD; - sig.sigev_notify_function = sighler; - sig.sigev_value.sival_int =20; - sig.sigev_notify_attributes = &attr; - - //create a new timer. - timer_t timerid; - Ret = timer_create(CLOCK_REALTIME, &sig, &timerid); - if (Ret == 0) - { - struct itimerspec in, out; - in.it_value.tv_sec = 1; - in.it_value.tv_nsec = 0; - in.it_interval.tv_sec = 0; - in.it_interval.tv_nsec = 100000000; - //issue the periodic timer request here. - Ret = timer_settime(timerid, 0, &in, &out); - if(Ret == 0) - sleep(2); - else - printf("timer_settime() failed with %d\n", errno); - //delete the timer. - timer_delete(timerid); - } - else - printf("timer_create() failed with %d\n", errno); - return Ret; - } -

The output of the above program is:

-Handler entered with value :20 for 1 times -Handler entered with value :20 for 2 times -Handler entered with value :20 for 3 times -Handler entered with value :20 for 4 times -Handler entered with value :20 for 5 times -Handler entered with value :20 for 6 times -Handler entered with value :20 for 7 times -Handler entered with value :20 for 8 times -

Note: Ideally, in the preceding output the handler must have entered 10 times. -This is not the case on the Symbian platform as there is some -latency due to the timer emulation solution and the underlying Symbian platform -clock resolution.

+ + + + + +Creating +a Periodic Timer +

You can use a periodic timer to provide repeated signals to your process.

The following example illustrates a periodic timer with a delay of a second +and a repeating interval of ten milliseconds. It also configures a thread +function as the timer expiry notification using SIGEV_THREAD.

The following example code performs the following tasks:

Creates a notification +function (thread function) that must be invoked after timer expiry.
Sets the thread priority +to 255 using the thread scheduling parameters (struct sched_param). +This ensures that the thread function has the highest priority when it is +invoked as a result of a timer expiry.
Creates a timer based +on the current system time (CLOCK_REALTIME) and a notification +function (struct sigevent sig) that must be +invoked when the timer expires.
Defines the input values +for timer_settime(). The key input values are the timer +value (in.it_value.tv_sec = 1;) and the interval (in.it_interval.tv_nsec += 100000000;). The periodic timer will expire after a second and +then invoke the notification function every one-tenth of a second until it +is destroyed.
Starts the periodic +timer using timer_settime().
Uses sleep(2) to +pause the program execution for two seconds before destroying the timer.

+#include <time.h> +#include <stdio.h> +#include <signal.h> +#include <pthread.h> +#include <unistd.h> +#include <errno.h> +static int i = 0; + +//Thread function to be invoked when the periodic timer expires +void sighler (union sigval val) + { + printf("Handler entered with value :%d for %d times\n", val.sival_int, ++i); + } +int main() + { + int Ret; + + pthread_attr_t attr; + pthread_attr_init( &attr ); + + struct sched_param parm; + parm.sched_priority = 255; + pthread_attr_setschedparam(&attr, &parm); + + struct sigevent sig; + sig.sigev_notify = SIGEV_THREAD; + sig.sigev_notify_function = sighler; + sig.sigev_value.sival_int =20; + sig.sigev_notify_attributes = &attr; + + //create a new timer. + timer_t timerid; + Ret = timer_create(CLOCK_REALTIME, &sig, &timerid); + if (Ret == 0) + { + struct itimerspec in, out; + in.it_value.tv_sec = 1; + in.it_value.tv_nsec = 0; + in.it_interval.tv_sec = 0; + in.it_interval.tv_nsec = 100000000; + //issue the periodic timer request here. + Ret = timer_settime(timerid, 0, &in, &out); + if(Ret == 0) + sleep(2); + else + printf("timer_settime() failed with %d\n", errno); + //delete the timer. + timer_delete(timerid); + } + else + printf("timer_create() failed with %d\n", errno); + return Ret; + } +

The output of the above program is:

+Handler entered with value :20 for 1 times +Handler entered with value :20 for 2 times +Handler entered with value :20 for 3 times +Handler entered with value :20 for 4 times +Handler entered with value :20 for 5 times +Handler entered with value :20 for 6 times +Handler entered with value :20 for 7 times +Handler entered with value :20 for 8 times +

Note: Ideally, in the preceding output the handler must have entered 10 times. +This is not the case on the Symbian platform as there is some +latency due to the timer emulation solution and the underlying Symbian platform +clock resolution.

\ No newline at end of file