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timeval: clock_gettime() for Windows.

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QueryPerformanceCounter() retrieves the current value of the performance
counter, which is a high resolution (<1us) time stamp that can be used for
time-interval measurements. So, use it for MONOTONIC clock.

The GetSystemTimePreciseAsFileTime() function retrieves the current system date
and time with the highest possible level of precision (<1us). Use it for
real time clock. This function returns a counter representing the number of
100-nanosecond intervals since January 1, 1601. To make it compatible with
Linux CLOCK_REALTIME, we need to calculate the 100-nanoseconds counter value
till 01/01/1970.

An upcoming commit implements gettimeofday() using the same clock, so,
carve out a function.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Gurucharan Shetty
2014-03-03 13:27:35 -08:00
parent 5020f5f099
commit 48f8613f26
1 changed files with 74 additions and 0 deletions
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74
lib/timeval.c
View File

@@ -40,6 +40,21 @@
VLOG_DEFINE_THIS_MODULE(timeval);
#ifdef _WIN32
typedef unsigned int clockid_t;
#ifndef CLOCK_MONOTONIC
#define CLOCK_MONOTONIC 1
#endif
#ifndef CLOCK_REALTIME
#define CLOCK_REALTIME 2
#endif
/* Number of 100 ns intervals from January 1, 1601 till January 1, 1970. */
static ULARGE_INTEGER unix_epoch;
#endif /* _WIN32 */
struct clock {
clockid_t id; /* CLOCK_MONOTONIC or CLOCK_REALTIME. */
@@ -96,6 +111,16 @@ do_init_time(void)
{
struct timespec ts;
#ifdef _WIN32
/* Calculate number of 100-nanosecond intervals till 01/01/1970. */
SYSTEMTIME unix_epoch_st = { 1970, 1, 0, 1, 0, 0, 0, 0};
FILETIME unix_epoch_ft;
SystemTimeToFileTime(&unix_epoch_st, &unix_epoch_ft);
unix_epoch.LowPart = unix_epoch_ft.dwLowDateTime;
unix_epoch.HighPart = unix_epoch_ft.dwHighDateTime;
#endif
coverage_init();
init_clock(&monotonic_clock, (!clock_gettime(CLOCK_MONOTONIC, &ts)
@@ -325,6 +350,55 @@ time_boot_msec(void)
return boot_time;
}
#ifdef _WIN32
static ULARGE_INTEGER
xgetfiletime(void)
{
ULARGE_INTEGER current_time;
FILETIME current_time_ft;
/* Returns current time in UTC as a 64-bit value representing the number
* of 100-nanosecond intervals since January 1, 1601 . */
GetSystemTimePreciseAsFileTime(&current_time_ft);
current_time.LowPart = current_time_ft.dwLowDateTime;
current_time.HighPart = current_time_ft.dwHighDateTime;
return current_time;
}
static int
clock_gettime(clock_t id, struct timespec *ts)
{
if (id == CLOCK_MONOTONIC) {
static LARGE_INTEGER freq;
LARGE_INTEGER count;
long long int ns;
if (!freq.QuadPart) {
/* Number of counts per second. */
QueryPerformanceFrequency(&freq);
}
/* Total number of counts from a starting point. */
QueryPerformanceCounter(&count);
/* Total nano seconds from a starting point. */
ns = (double) count.QuadPart / freq.QuadPart * 1000000000;
ts->tv_sec = count.QuadPart / freq.QuadPart;
ts->tv_nsec = ns % 1000000000;
} else if (id == CLOCK_REALTIME) {
ULARGE_INTEGER current_time = xgetfiletime();
/* Time from Epoch to now. */
ts->tv_sec = (current_time.QuadPart - unix_epoch.QuadPart) / 10000000;
ts->tv_nsec = ((current_time.QuadPart - unix_epoch.QuadPart) %
10000000) * 100;
} else {
return -1;
}
}
#endif /* _WIN32 */
void
xgettimeofday(struct timeval *tv)
{