usleep.c

#include <Windows.h>
#include <mmsystem.h>
#include <math.h>

static BOOL inited = FALSE;
static double dhz;

void usleep( long us )
{
    const double sleep_granularity = 2.0E-3;
    __int64 cnt, end;
    double diff;
    
    if (!inited) {
        __int64 hz;
        timeBeginPeriod(1);
        QueryPerformanceFrequency((LARGE_INTEGER*)&hz);
        dhz = (double)hz;
        inited = TRUE;
    }      
    
    QueryPerformanceCounter((LARGE_INTEGER*)&cnt);
    end = cnt + (__int64)ceil(1.0E-6 * (double)(us) * dhz);
    for (;;) {
        QueryPerformanceCounter((LARGE_INTEGER*)&cnt);
        if (cnt >= end) break;
        diff = (double)(end - cnt)/dhz;
        if (diff > sleep_granularity)
            Sleep((DWORD)floor(1000 * (diff - sleep_granularity)));
        else
            Sleep(0);  /* yields the cpu */
    }
}

Emulation of Unix usleep function in Windows.