Add amqp_time_tv_until() function.

2 files changed, 52 insertions, 0 deletions

diff --git a/librabbitmq/amqp_time.c b/librabbitmq/amqp_time.c
index 9bfbb16..86a992c 100644
--- a/librabbitmq/amqp_time.c
+++ b/librabbitmq/amqp_time.c
@@ -204,6 +204,43 @@ int amqp_time_ms_until(amqp_time_t time) {
   return left_ms;
 }
 
+int amqp_time_tv_until(amqp_time_t time, struct timeval *in,
+                       struct timeval **out) {
+  uint64_t now_ns;
+  uint64_t delta_ns;
+
+  assert(in != NULL);
+  if (UINT64_MAX == time.time_point_ns) {
+    *out = NULL;
+    return AMQP_STATUS_OK;
+  }
+  if (0 == time.time_point_ns) {
+    in->tv_sec = 0;
+    in->tv_usec = 0;
+    *out = in;
+    return AMQP_STATUS_OK;
+  }
+
+  now_ns = amqp_get_monotonic_timestamp();
+  if (0 == now_ns) {
+    return AMQP_STATUS_TIMER_FAILURE;
+  }
+
+  if (now_ns >= time.time_point_ns) {
+    in->tv_sec = 0;
+    in->tv_usec = 0;
+    *out = in;
+    return AMQP_STATUS_OK;
+  }
+
+  delta_ns = time.time_point_ns - now_ns;
+  in->tv_sec = (int)(delta_ns / AMQP_NS_PER_S);
+  in->tv_usec = (int)((delta_ns % AMQP_NS_PER_S) / AMQP_NS_PER_US);
+  *out = in;
+
+  return AMQP_STATUS_OK;
+}
+
 int amqp_time_has_past(amqp_time_t time) {
   uint64_t now_ns;
   if (UINT64_MAX == time.time_point_ns) {
diff --git a/librabbitmq/amqp_time.h b/librabbitmq/amqp_time.h
index 1bafd50..be939f1 100644
--- a/librabbitmq/amqp_time.h
+++ b/librabbitmq/amqp_time.h
@@ -100,6 +100,21 @@ amqp_time_t amqp_time_infinite(void);
  */
 int amqp_time_ms_until(amqp_time_t time);
 
+/* Gets a timeval filled in with the time until amqp_time_t. Suitable for the
+ * parameter in select().
+ *
+ * The in parameter specifies a storage location for *out.
+ * If time is an inf timeout, then *out = NULL.
+ * If time is a 0-timeout or the timer has expired, then *out = {0, 0}
+ * Otherwise *out is set to the time left on the time.
+ *
+ * AMQP_STATUS_OK will be returned if successfully filled.
+ * AMQP_STATUS_TIMER_FAILURE is returned when the underlying call to get the
+ * current timestamp fails.
+ */
+int amqp_time_tv_until(amqp_time_t time, struct timeval *in,
+                       struct timeval **out);
+
 /* Test whether current time is past the provided time.
  *
  * TODO: this isn't a great interface to use. Fix this.