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Using timeGetTime to get the elapsed milliseconds after a baseline GetSystemTimeAsFileTime to emulate the Unix gettimeofday function at millisecond resolution on Windows.

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This commit is contained in:
skarg
2011-07-25 22:12:28 +00:00
parent 059a9e8471
commit 3c9c235d28
1 changed files with 33 additions and 50 deletions
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bacnet-stack/ports/win32/timer.c
+33 -50
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@@ -35,6 +35,8 @@
#include <MMSystem.h>
#include "timer.h"
/* Offset between Windows epoch 1/1/1601 and
Unix epoch 1/1/1970 in 100 nanosec units */
#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS)
#define DELTA_EPOCH_IN_MICROSECS 11644473600000000Ui64
#else
@@ -44,55 +46,51 @@
/* counter for the various timers */
static volatile uint32_t Millisecond_Counter[MAX_MILLISECOND_TIMERS];
/* Windows timer period */
/* Windows timer period - in milliseconds */
static uint32_t Timer_Period = 1;
/*************************************************************************
* Description: simulate the gettimeofday Linux function
* Returns: zero
* Note: The resolution of GetSystemTimeAsFileTime() is 15625 microseconds
* The resolution of _ftime() is 16 milliseconds
* The only way to get microseconds accuracy is to use QueryPerformanceCounter
* Note: The resolution of GetSystemTimeAsFileTime() is 15625 microseconds.
* The resolution of _ftime() is about 16 milliseconds.
* To get microseconds accuracy we need to use QueryPerformanceCounter or
* timeGetTime for the elapsed time.
*************************************************************************/
#if 0
int gettimeofday(
struct timeval *tp,
void *tzp)
{
/* QPC uses frequency and ticks */
LARGE_INTEGER tickPerSecond;
LARGE_INTEGER tick;
struct _timeb timebuffer;
tzp = tzp;
_ftime(&timebuffer);
QueryPerformanceFrequency(&tickPerSecond);
QueryPerformanceCounter(&tick);
tp->tv_usec = (tick.QuadPart % tickPerSecond.QuadPart);
tp->tv_sec = timebuffer.time;
return 0;
}
#elif 1
int gettimeofday(
struct timeval *tp,
void *tzp)
{
FILETIME ft;
unsigned __int64 tmpres = 0;
static int tzflag = 0;
struct timezone *tz;
/* start calendar time in microseconds */
static LONGLONG usec_timer = 0;
LONGLONG usec_elapsed = 0;
/* elapsed time in milliseconds */
static uint32_t time_start = 0;
/* semi-accurate time from File Timer */
FILETIME ft;
uint32_t elapsed_milliseconds = 0;
if (tp) {
tzp = tzp;
if (usec_timer == 0) {
/* a 64-bit value representing the number of
100-nanosecond intervals since January 1, 1601 (UTC). */
GetSystemTimeAsFileTime(&ft);
tmpres |= ft.dwHighDateTime;
tmpres <<= 32;
tmpres |= ft.dwLowDateTime;
/*converting file time to unix epoch*/
tmpres /= 10; /*convert into microseconds*/
tmpres -= DELTA_EPOCH_IN_MICROSECS;
tp->tv_sec = (long)(tmpres / 1000000UL);
tp->tv_usec = (long)(tmpres % 1000000UL);
usec_timer |= ft.dwHighDateTime;
usec_timer <<= 32;
usec_timer |= ft.dwLowDateTime;
/*converting file time to unix epoch 1970 */
usec_timer /= 10; /*convert into microseconds*/
usec_timer -= DELTA_EPOCH_IN_MICROSECS;
tp->tv_sec = (long)(usec_timer / 1000000UL);
tp->tv_usec = (long)(usec_timer % 1000000UL);
time_start = timeGetTime();
} else {
elapsed_milliseconds = timeGetTime() - time_start;
usec_elapsed = usec_timer + (elapsed_milliseconds * 1000UL);
tp->tv_sec = (long)(usec_elapsed / 1000000UL);
tp->tv_usec = (long)(usec_elapsed % 1000000UL);
}
if (tzp) {
if (!tzflag) {
@@ -106,21 +104,6 @@ int gettimeofday(
return 0;
}
#else
int gettimeofday(
struct timeval *tp,
void *tzp)
{
struct _timeb timebuffer;
tzp = tzp;
_ftime(&timebuffer);
tp->tv_sec = timebuffer.time;
tp->tv_usec = timebuffer.millitm * 1000;
return 0;
}
#endif
/*************************************************************************
* Description: returns the current millisecond count