原文网址:http://blog.csdn.net/hongszh/article/details/8608781
最强大的定时器接口来自POSIX时钟系列,其创建、初始化以及删除一个定时器的行动被分为三个不同的函数:timer_create()(创建定时器)、timer_settime()(初始化定时器)以及timer_delete(销毁它)。
man timer_create/timer_settime,可以看到man帮助的详细文档:
- TIMER_CREATE(2) Linux Programmer's Manual
- NAME
- timer_create - create a POSIX per-process timer
- SYNOPSIS
- #include <signal.h>
- #include <time.h>
- int timer_create(clockid_t clockid, struct sigevent *sevp,
- timer_t *timerid);
- int timer_settime(timer_t timerid, int flags,
- const struct itimerspec *new_value,
- struct itimerspec * old_value);
- int timer_gettime(timer_t timerid, struct itimerspec *curr_value);
我的实现如下:
1. 定义timer timeout的函数指针类型:
- typedef void (*timerTimeout)(union sigval sig);
2. 为我们的GstPlayer定义两个timer ID:
- timer_t mSeekTimer;
- timer_t mPrepareAsyncTimer;
3. 定义createTimer函数,创建timer,设置timeout函数
timerId: 输入输出参数
func: timer timeout函数
- void createTimer(timer_t *timerId, timerTimeout func)
- {
- struct sigevent sev;
- sev.sigev_notify = SIGEV_THREAD;
- sev.sigev_signo = SIGRTMIN;
- sev.sigev_value.sival_ptr = gPlayer;
- sev.sigev_notify_function = func;
- sev.sigev_notify_attributes = NULL;
- /* create timer */
- if (timer_create (CLOCK_REALTIME, &sev, timerId) == -1)
- {
- ERR ("timer_create, error");
- return;
- }
- if (*timerId == -1)
- ERR ("timer_create error, id is -1");
- return;
- }
4. setTimer函数, 调用linux的timer_settime, 如果还没到time out,重置之前的timer
如果已经time out,那就得重新调用createTimer生成有效的timer ID,然后才能调用setTimer开始定时器计时。
-这里,将interval参数设置为0,指定我的定时器不工作在循环模式。
-timeMSec是输入参数,指定time out的时间,单位为毫秒。
- void setTimer(timer_t *timerId, int timeMSec)
- {
- struct itimerspec its;
- /* Start the timer */
- its.it_value.tv_sec = timeMSec / 1000;
- its.it_value.tv_nsec = (timeMSec % 1000) * 1000000;
- its.it_interval.tv_sec = 0;
- its.it_interval.tv_nsec = 0;
- if (timer_settime (*timerId, 0, &its, NULL) == -1)
- {
- ERR ("timer_settime error");
- }
- DEBUG ("call timer_settime reset timer done.");
- return;
- }
seekTimerTimeout函数,time out以后,销毁之前调用createTimer创建的timer,完成time out后要做的工作
- void seekTimerTimeout(union sigval sig)
- {
- GstPlayer *player = (GstPlayerplayer*)sig.sival_ptr;
- if (player->mSeekTimer != -1)
- {
- DEBUG("timeout, delete timer:Id = %d",
- player->mSeekTimer);
- timer_delete(player->mSeekTimer);
- player->mSeekTimer = -1;
- }
- // ... 完成time out后要做的工作
- }
prepareAsyncTimeout的time out函数:
- void prepareAsyncTimeout(union sigval sig)
- {
- GstStateChangeReturn state_return;
- GstPlayer *player = (GstPlayerplayer*)sig.sival_ptr;
- if (player->mPrepareAsyncTimer != -1)
- {
- DEBUG("timeout, delete timer:Id = %d",
- player->mPrepareAsyncTimer);
- timer_delete(player->mPrepareAsyncTimer);
- player->mPrepareAsyncTimer = -1;
- }
- // ...完成time out后要做的工作
- }
调用一:
- 创建timer,设定prepareAsyncTimeout
- 开始timer,timeout时间为500ms
- createTimer(&mPrepareAsyncTimer, prepareAsyncTimeout);
- setTimer(&mPrepareAsyncTimer, 500/*ms*/);
调用二:
- 创建timer,设定timeout回调函数。
- // create timer
- if (mSeekTimer == -1)
- {
- createTimer(&mSeekTimer, seekTimerTimeout);
- }
- 判断mSeekTimer是否有效,有效,计算到timeout的剩余时间,如果还没到timeout,重置timer,
- 开始新的计时。
- // if timer exist and not expire, reset timer.
- if (mSeekTimer != -1)
- {
- gulong remaining = 0; //us
- struct itimerspec its;
- timer_gettime(mSeekTimer, &its);
- remaining = its.it_value.tv_sec * 1000000
- its.it_value.tv_nsec / 1000;
- DEBUG ("-- remaining time = %lu us", remaining);
- if ((100/*ms*/ * 1000 - remaining) > 0)
- {
- setTimer(&mSeekTimer, 100/*ms*/);
- DEBUG ("the new seek interval < 100ms, return");
- mSeekCount = 1;
- return TRUE;
- }
- }
参考:
http://blog.163.com/zheng_he_xiang/blog/static/18650532620116311020390/
http://blog.csdn.net/leo9150285/article/details/8271910