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#include "stdinc.h"
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#include "dat.h"
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#include "fns.h"
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#include "error.h"
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struct Periodic {
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	VtLock *lk;
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	int die;		/* flag: quit if set */
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	void (*f)(void*);	/* call this each period */
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	void *a;		/* argument to f */
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	int msec;		/* period */
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};
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static void periodicThread(void *a);
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Periodic *
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periodicAlloc(void (*f)(void*), void *a, int msec)
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{
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	Periodic *p;
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	p = vtMemAllocZ(sizeof(Periodic));
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	p->lk = vtLockAlloc();
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	p->f = f;
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	p->a = a;
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	p->msec = msec;
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	if(p->msec < 10)
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		p->msec = 10;
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	vtThread(periodicThread, p);
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	return p;
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}
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void
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periodicKill(Periodic *p)
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{
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	if(p == nil)
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		return;
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	vtLock(p->lk);
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	p->die = 1;
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	vtUnlock(p->lk);
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}
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static void
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periodicFree(Periodic *p)
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{
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	vtLockFree(p->lk);
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	vtMemFree(p);
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}
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static void
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periodicThread(void *a)
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{
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	Periodic *p = a;
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	vlong t, ct, ts;		/* times in ms. */
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	vtThreadSetName("periodic");
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	ct = nsec() / 1000000;
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	t = ct + p->msec;		/* call p->f at or after this time */
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	for(;;){
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		ts = t - ct;		/* ms. to next cycle's start */
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		if(ts > 1000)
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			ts = 1000;	/* bound sleep duration */
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		if(ts > 0)
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			sleep(ts);	/* wait for cycle's start */
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		vtLock(p->lk);
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		if(p->die){
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			vtUnlock(p->lk);
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			break;
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		}
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		ct = nsec() / 1000000;
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		if(t <= ct){		/* due to call p->f? */
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			p->f(p->a);
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			ct = nsec() / 1000000;
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			while(t <= ct)	/* advance t to future cycle start */
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				t += p->msec;
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		}
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		vtUnlock(p->lk);
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	}
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	periodicFree(p);
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}
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