Move below_speed_limit() from vfd_swmr_bigset_writer.c to

vfd_swmr_common.c, document it, and fix a bug.

1 files changed, 37 insertions, 0 deletions

diff --git a/test/vfd_swmr_common.c b/test/vfd_swmr_common.c
index f09336e..b986b31 100644
--- a/test/vfd_swmr_common.c
+++ b/test/vfd_swmr_common.c
@@ -28,6 +28,43 @@ static const hid_t badhid = H5I_INVALID_HID;
 
 int verbosity = 2;
 
+/* Return true no more than once in any `ival` interval of time,
+ * as measured by the system's monotonically increasing timer, to
+ * help rate-limit activities.
+ *
+ * Read the system's current time and compare it with the time stored in
+ * `last`.  If the difference between `last` and the current time is
+ * greater than the duration `ival`, then record the current time at
+ * `last` and return true.  Otherwise, return false.
+ */
+bool
+below_speed_limit(struct timespec *last, const struct timespec *ival)
+{
+    struct timespec now;
+    bool result;
+
+    assert(0 <= last->tv_nsec && last->tv_nsec < 1000000000L);
+    assert(0 <= ival->tv_nsec && ival->tv_nsec < 1000000000L);
+
+    if (clock_gettime(CLOCK_MONOTONIC, &now) == -1)
+        err(EXIT_FAILURE, "%s: clock_gettime", __func__);
+
+    if (now.tv_sec - last->tv_sec > ival->tv_sec)
+        result = true;
+    else if (now.tv_sec - last->tv_sec < ival->tv_sec)
+        result = false;
+    else
+        result = (now.tv_nsec - last->tv_nsec >= ival->tv_nsec);
+
+    if (result)
+        *last = now;
+
+    return result;
+}
+
+/* Like vsnprintf(3), but abort the program with an error message on
+ * `stderr` if the buffer is too small or some other error occurs.
+ */
 void
 evsnprintf(char *buf, size_t bufsz, const char *fmt, va_list ap)
 {