time: timemono_add.

[ccan] / ccan / time / time.h

diff --git a/ccan/time/time.h b/ccan/time/time.h
index 7bb3547d6227630fb5eb682544dc7e2eb4c2e6aa..f2b335cf45de0af387c2b0a9e1cba09c73ceb86a 100644 (file)
--- a/ccan/time/time.h
+++ b/ccan/time/time.h
@@ -48,6 +48,28 @@ struct timeabs {
        struct timespec ts;
 };
 
+/**
+ * struct timemono - a monotonic time.
+ * @ts: the actual timespec value.
+ *
+ * This comes from the monotonic clock (if available), so it's useful
+ * for measuring intervals as it won't change even if the system clock
+ * is moved for some reason.
+ */
+struct timemono {
+       struct timespec ts;
+};
+
+/**
+ * TIME_HAVE_MONOTONIC - defined if we really have a monotonic clock.
+ *
+ * Otherwise time_mono() just refers to time_now().  Your code might
+ * test this if you really need a monotonic clock.
+ */
+#if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
+#define TIME_HAVE_MONOTONIC 1
+#endif
+
 struct timespec time_check_(struct timespec in, const char *abortstr);
 
 /**
@@ -99,6 +121,16 @@ struct timeabs timeabs_check(struct timeabs in, const char *abortstr);
  */
 struct timeabs time_now(void);
 
+/**
+ * time_mono - return the current monotonic time
+ *
+ * This value is only really useful for measuring time intervals.
+ *
+ * See also:
+ *     timemono_since()
+ */
+struct timemono time_mono(void);
+
 static inline bool time_greater_(struct timespec a, struct timespec b)
 {
        if (TIME_CHECK(a).tv_sec > TIME_CHECK(b).tv_sec)
@@ -217,7 +249,7 @@ static inline bool timeabs_eq(struct timeabs a, struct timeabs b)
  *                     exit(0);
  *             }
  *             wait(NULL);
- *             diff = time_between(start, time_now());
+ *             diff = time_between(time_now(), start);
  *             return timerel_eq(diff, zero);
  *     }
  */
@@ -272,6 +304,33 @@ static inline struct timerel time_between(struct timeabs recent, struct timeabs
        return t;
 }
 
+/**
+ * timemono_between - time between two monotonic times
+ * @recent: the larger time.
+ * @old: the smaller time.
+ *
+ * This returns a well formed struct timerel of @recent - @old.
+ */
+static inline struct timerel timemono_between(struct timemono recent,
+                                             struct timemono old)
+{
+       struct timerel t;
+
+       t.ts = time_sub_(recent.ts, old.ts);
+       return t;
+}
+
+/**
+ * timemono_since - elapsed monotonic time since @old
+ * @old: a monotonic time from the past.
+ */
+static inline struct timerel timemono_since(struct timemono old)
+{
+       struct timemono now = time_mono();
+
+       return timemono_between(now, old);
+}
+
 /**
  * timeabs_sub - subtract a relative time from an absolute time
  * @abs: the absolute time.
@@ -329,6 +388,28 @@ static inline struct timeabs timeabs_add(struct timeabs a, struct timerel b)
        return t;
 }
 
+/**
+ * timemono_add - add a relative to a monotonic time
+ * @a: the monotonic time.
+ * @b: a relative time.
+ *
+ * The times must not overflow, or the results are undefined.
+ *
+ * Example:
+ *     // We do one every second.
+ *     static struct timemono next_timem(void)
+ *     {
+ *             return timemono_add(time_mono(), time_from_msec(1000));
+ *     }
+ */
+static inline struct timemono timemono_add(struct timemono a, struct timerel b)
+{
+       struct timemono t;
+
+       t.ts = time_add_(a.ts, b.ts);
+       return t;
+}
+
 /**
  * timerel_add - add two relative times
  * @a: one relative time.