reftable/system: add abstraction to retrieve time in milliseconds

We directly call gettimeofday(3p), which may not be available on some
platforms. Provide the infrastructure to let projects easily use their
own implementations of this function.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

reftable/stack.c

@@ -372,45 +372,26 @@ static int reftable_stack_reload_once(struct reftable_stack *st,
 	return err;
 }
 
-/* return negative if a before b. */
-static int tv_cmp(struct timeval *a, struct timeval *b)
-{
-	time_t diff = a->tv_sec - b->tv_sec;
-	int udiff = a->tv_usec - b->tv_usec;
-
-	if (diff != 0)
-		return diff;
-
-	return udiff;
-}
-
 static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st,
 					     int reuse_open)
 {
 	char **names = NULL, **names_after = NULL;
-	struct timeval deadline;
+	uint64_t deadline;
 	int64_t delay = 0;
 	int tries = 0, err;
 	int fd = -1;
 
-	err = gettimeofday(&deadline, NULL);
-	if (err < 0)
-		goto out;
-	deadline.tv_sec += 3;
+	deadline = reftable_time_ms() + 3000;
 
 	while (1) {
-		struct timeval now;
-
-		err = gettimeofday(&now, NULL);
-		if (err < 0)
-			goto out;
+		uint64_t now = reftable_time_ms();
 
 		/*
 		 * Only look at deadlines after the first few times. This
 		 * simplifies debugging in GDB.
 		 */
 		tries++;
-		if (tries > 3 && tv_cmp(&now, &deadline) >= 0)
+		if (tries > 3 && now >= deadline)
 			goto out;
 
 		fd = open(st->list_file, O_RDONLY);

reftable/system.c

@@ -4,6 +4,7 @@
 #include "basics.h"
 #include "reftable-error.h"
 #include "../lockfile.h"
+#include "../trace.h"
 #include "../tempfile.h"
 
 uint32_t reftable_rand(void)
@@ -131,3 +132,8 @@ int flock_commit(struct reftable_flock *l)
 
 	return 0;
 }
+
+uint64_t reftable_time_ms(void)
+{
+	return getnanotime() / 1000000;
+}

reftable/system.h

@@ -110,4 +110,7 @@ int flock_release(struct reftable_flock *l);
  */
 int flock_commit(struct reftable_flock *l);
 
+/* Report the time in milliseconds. */
+uint64_t reftable_time_ms(void);
+
 #endif