fossil: import from plan 9

R=rsc
https://codereview.appspot.com/7988047

1 files changed, 84 insertions, 0 deletions

diff --git a/src/cmd/fossil/periodic.c b/src/cmd/fossil/periodic.c
new file mode 100644
index 00000000..8a0c2084
--- /dev/null
+++ b/src/cmd/fossil/periodic.c
@@ -0,0 +1,84 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+#include "error.h"
+
+struct Periodic {
+	VtLock *lk;
+	int die;		/* flag: quit if set */
+	void (*f)(void*);	/* call this each period */
+	void *a;		/* argument to f */
+	int msec;		/* period */
+};
+
+static void periodicThread(void *a);
+
+Periodic *
+periodicAlloc(void (*f)(void*), void *a, int msec)
+{
+	Periodic *p;
+
+	p = vtMemAllocZ(sizeof(Periodic));
+	p->lk = vtLockAlloc();
+	p->f = f;
+	p->a = a;
+	p->msec = msec;
+	if(p->msec < 10)
+		p->msec = 10;
+
+	vtThread(periodicThread, p);
+	return p;
+}
+
+void
+periodicKill(Periodic *p)
+{
+	if(p == nil)
+		return;
+	vtLock(p->lk);
+	p->die = 1;
+	vtUnlock(p->lk);
+}
+
+static void
+periodicFree(Periodic *p)
+{
+	vtLockFree(p->lk);
+	vtMemFree(p);
+}
+
+static void
+periodicThread(void *a)
+{
+	Periodic *p = a;
+	vlong t, ct, ts;		/* times in ms. */
+
+	vtThreadSetName("periodic");
+
+	ct = nsec() / 1000000;
+	t = ct + p->msec;		/* call p->f at or after this time */
+
+	for(;;){
+		ts = t - ct;		/* ms. to next cycle's start */
+		if(ts > 1000)
+			ts = 1000;	/* bound sleep duration */
+		if(ts > 0)
+			sleep(ts);	/* wait for cycle's start */
+
+		vtLock(p->lk);
+		if(p->die){
+			vtUnlock(p->lk);
+			break;
+		}
+		ct = nsec() / 1000000;
+		if(t <= ct){		/* due to call p->f? */
+			p->f(p->a);
+			ct = nsec() / 1000000;
+			while(t <= ct)	/* advance t to future cycle start */
+				t += p->msec;
+		}
+		vtUnlock(p->lk);
+	}
+	periodicFree(p);
+}
+