Attempting to get better timestamp resolution on Win32. Added some functional tests for determining accuracy. The existing gettimeofday emulations only give 15ms to 16ms of resolution, so that needs fixed.

bacnet-stack/ports/win32/timer.c

@@ -26,6 +26,8 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
+#include <time.h>
 #define WIN32_LEAN_AND_MEAN
 #define STRICT 1
 #include <windows.h>
@@ -33,14 +35,57 @@
 #include <MMSystem.h>
 #include "timer.h"
 
+#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS)
+  #define DELTA_EPOCH_IN_MICROSECS  11644473600000000Ui64
+#else
+  #define DELTA_EPOCH_IN_MICROSECS  11644473600000000ULL
+#endif
+
 /* counter for the various timers */
 static volatile uint32_t Millisecond_Counter[MAX_MILLISECOND_TIMERS];
 
+/* Windows timer period */
+static uint32_t Timer_Period = 1;
+
 /*************************************************************************
 * Description: simulate the gettimeofday Linux function
-* Returns: none
-* Notes: none
+* Returns: zero
+* Note: The resolution of GetSystemTimeAsFileTime() is 15625 microseconds
 *************************************************************************/
+#if 1
+int gettimeofday(
+    struct timeval *tp,
+    void *tzp)
+{
+    FILETIME ft;
+    unsigned __int64 tmpres = 0;
+    static int tzflag = 0;
+    struct timezone *tz;
+
+    if (tp) {
+        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);
+    }
+    if (tzp) {
+        if (!tzflag) {
+            _tzset();
+            tzflag++;
+        }
+        tz = tzp;
+        tz->tz_minuteswest = _timezone / 60;
+        tz->tz_dsttime = _daylight;
+    }
+
+    return 0;
+}
+#else
 int gettimeofday(
     struct timeval *tp,
     void *tzp)
@@ -54,6 +99,7 @@ int gettimeofday(
 
     return 0;
 }
+#endif
 
 /*************************************************************************
 * Description: returns the current millisecond count
@@ -129,6 +175,17 @@ uint32_t timer_reset(
     return timer_value;
 }
 
+/*************************************************************************
+* Description: Shut down for timer
+* Returns: none
+* Notes: none
+*************************************************************************/
+static void timer_cleanup(
+    void)
+{
+    timeEndPeriod(Timer_Period);
+}
+
 /*************************************************************************
 * Description: Initialization for timer
 * Returns: none
@@ -138,13 +195,74 @@ void timer_init(
     void)
 {
     TIMECAPS tc;
-    uint32_t period;
 
     /* set timer resolution */
     if (timeGetDevCaps(&tc, sizeof(TIMECAPS)) != TIMERR_NOERROR) {
         fprintf(stderr, "Failed to get timer resolution parameters\n");
     }
     /* configure for 1ms resolution - if possible */
-    period = min(max(tc.wPeriodMin, 1), tc.wPeriodMax);
-    timeBeginPeriod(period);
+    Timer_Period = min(max(tc.wPeriodMin, 1L), tc.wPeriodMax);
+    if (Timer_Period != 1L) {
+        fprintf(stderr, "Failed to set timer to 1ms.  "
+          "Time period set to %ums\n", (unsigned)Timer_Period);
+    }
+    timeBeginPeriod(Timer_Period);
+    atexit(timer_cleanup);
 }
+
+#ifdef TEST_TIMER_WIN
+static uint32_t timeval_diff_ms(
+    struct timeval *old,
+    struct timeval *now)
+{
+    uint32_t ms = 0;
+
+    /* convert to milliseconds */
+    ms = (now->tv_sec - old->tv_sec) * 1000 + (now->tv_usec -
+        old->tv_usec) / 1000;
+
+    return ms;
+}
+
+int main(
+    int argc,
+    char *argv[])
+{
+    long now = 0, last = 0, delta = 0;
+    struct timeval tv;
+    struct timeval old_tv = {0};
+
+    timer_init();
+    printf("Testing granularity of timeGetTime()...\n");
+    timer_reset(0);
+    for (;;) {
+        now = timeGetTime();
+        delta = now - last;
+        if (delta) {
+            if (delta > 1) {
+                printf("Delta is %ld.\n", delta);
+            }
+            last = now;
+        }
+        if (timer_elapsed_milliseconds(0, 5000)) {
+            break;
+        }
+    }
+    printf("Testing granularity of gettimeofday()...\n");
+    for (;;) {
+        gettimeofday(&tv, NULL);
+        delta = timeval_diff_ms(&old_tv, &tv);
+        if (delta) {
+            if (delta > 1) {
+                printf("Delta is %ld.\n", delta);
+            }
+            old_tv.tv_sec = tv.tv_sec;
+            old_tv.tv_usec = tv.tv_usec;
+        }
+        if (timer_elapsed_milliseconds(0, 10000)) {
+            break;
+        }
+    }
+
+}
+#endif