--- Gnu-Mach/include/mach/time_value.h	2020/09/02 04:36:57	1.1.1.1
+++ Gnu-Mach/include/mach/time_value.h	2020/09/02 04:50:22	1.1.1.2
@@ -45,29 +45,48 @@ typedef	struct time_value	time_value_t;
  */
 #define	TIME_MICROS_MAX	(1000000)
 
+#define time_value_assert(val)			\
+  assert(0 <= (val)->microseconds && (val)->microseconds < TIME_MICROS_MAX);
+
 #define	time_value_add_usec(val, micros)	{	\
+	time_value_assert(val);				\
 	if (((val)->microseconds += (micros))		\
 		>= TIME_MICROS_MAX) {			\
 	    (val)->microseconds -= TIME_MICROS_MAX;	\
 	    (val)->seconds++;				\
 	}						\
+	time_value_assert(val);				\
 }
 
-#define	time_value_add(result, addend)		{		\
-	(result)->microseconds += (addend)->microseconds;	\
-	(result)->seconds += (addend)->seconds;			\
-	if ((result)->microseconds >= TIME_MICROS_MAX) {	\
-	    (result)->microseconds -= TIME_MICROS_MAX;		\
-	    (result)->seconds++;				\
-	}							\
+#define	time_value_sub_usec(val, micros)	{	\
+	time_value_assert(val);				\
+	if (((val)->microseconds -= (micros)) < 0) {	\
+	    (val)->microseconds += TIME_MICROS_MAX;	\
+	    (val)->seconds--;				\
+	}						\
+	time_value_assert(val);				\
 }
 
+#define	time_value_add(result, addend) {			\
+    time_value_assert(addend);					\
+    (result)->seconds += (addend)->seconds;			\
+    time_value_add_usec(result, (addend)->microseconds);	\
+  }
+
+#define	time_value_sub(result, subtrahend) {			\
+    time_value_assert(subtrahend);				\
+    (result)->seconds -= (subtrahend)->seconds;			\
+    time_value_sub_usec(result, (subtrahend)->microseconds);	\
+  }
+
 /*
  *	Time value available through the mapped-time interface.
  *	Read this mapped value with
  *		do {
  *			secs = mtime->seconds;
+ *			__sync_synchronize();
  *			usecs = mtime->microseconds;
+ *			__sync_synchronize();
  *		} while (secs != mtime->check_seconds);
  */
 
@@ -77,4 +96,16 @@ typedef struct mapped_time_value {
 	integer_t check_seconds;
 } mapped_time_value_t;
 
+/* Macros for converting between struct timespec and time_value_t. */
+
+#define TIME_VALUE_TO_TIMESPEC(tv, ts) do {                             \
+        (ts)->tv_sec = (tv)->seconds;                                   \
+        (ts)->tv_nsec = (tv)->microseconds * 1000;                      \
+} while(0)
+
+#define TIMESPEC_TO_TIME_VALUE(tv, ts) do {                             \
+        (tv)->seconds = (ts)->tv_sec;                                   \
+        (tv)->microseconds = (ts)->tv_nsec / 1000;                      \
+} while(0)
+
 #endif	/* _MACH_TIME_VALUE_H_ */