[PATCH 2/2] rtems: Add more clock tick functions

[Sebastian Huber]

Add rtems_clock_ticks_later(), rtems_clock_ticks_later_us() and
rtems_clock_ticks_later_us().

FIXME: Patch is incomplete.  Documentation and tests are missing.  Just
for API review.
---
 cpukit/rtems/include/rtems/rtems/clock.h | 66 ++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/cpukit/rtems/include/rtems/rtems/clock.h b/cpukit/rtems/include/rtems/rtems/clock.h
index ff71665..cee930e 100644
--- a/cpukit/rtems/include/rtems/rtems/clock.h
+++ b/cpukit/rtems/include/rtems/rtems/clock.h
@@ -34,6 +34,7 @@
 #include <rtems/score/tod.h>
 #include <rtems/rtems/status.h>
 #include <rtems/rtems/types.h>
+#include <rtems/config.h>
 
 #include <sys/time.h> /* struct timeval */
 
@@ -160,6 +161,71 @@ RTEMS_INLINE_ROUTINE rtems_interval rtems_clock_get_ticks_since_boot(void)
 }
 
 /**
+ * @brief Returns the ticks counter value delta ticks in the future.
+ *
+ * @param[in] delta The ticks delta value.
+ *
+ * @return The tick counter value delta ticks in the future.
+ */
+RTEMS_INLINE_ROUTINE rtems_interval rtems_clock_ticks_later(
+  rtems_interval delta
+)
+{
+  return _Watchdog_Ticks_since_boot + delta;
+}
+
+/**
+ * @brief Returns the ticks counter value at least delta microseconds in the
+ * future.
+ *
+ * @param[in] delta The delta value in microseconds.
+ *
+ * @return The tick counter value at least delta microseconds in the future.
+ */
+RTEMS_INLINE_ROUTINE rtems_interval rtems_clock_ticks_later_us(
+  rtems_interval delta
+)
+{
+  rtems_interval us_per_tick = rtems_configuration_get_microseconds_per_tick();
+
+  return _Watchdog_Ticks_since_boot + (delta + us_per_tick - 1) / us_per_tick;
+}
+
+/**
+ * @brief Returns true if the current ticks counter value indicates a time
+ * before the time specified by the ticks value and false otherwise.
+ *
+ * @param[in] ticks The ticks value.
+ *
+ * This can be used to write busy loops with a timeout.
+ *
+ * @code
+ * status busy( void )
+ * {
+ *   rtems_interval timeout = rtems_clock_ticks_later_us( 10000 );
+ *
+ *   do {
+ *     if ( ok() ) {
+ *       return success;
+ *     }
+ *   } while ( rtems_clock_ticks_before( timeout ) );
+ *
+ *   return timeout;
+ * }
+ * @endcode
+ *
+ * @retval true The current ticks counter value indicates a time before the
+ * time specified by the ticks value.
+ * @retval false Otherwise.
+ */
+RTEMS_INLINE_ROUTINE bool rtems_clock_ticks_before(
+  rtems_interval ticks
+)
+{
+  return ( (int32_t) ticks - (int32_t) _Watchdog_Ticks_since_boot ) > 0;
+}
+
+/**
  * @brief Obtain Ticks Per Seconds
  *
  * This routine implements the rtems_clock_get_ticks_per_second
-- 
1.8.4.5