High precision (nanoseconds) time for windows and linux

utime.h

#ifndef UTIME_INCLUDED
#define UTIME_INCLUDED

#include <stdint.h>

void
UT_Init(void);

int64_t
UT_Time(void);

#if defined(__linux__) || defined(__unix__)

#include <time.h>

static struct timespec UT__initial_time = {0};

void
UT_Init(void) {
	clock_gettime(CLOCK_MONOTONIC_RAW, &UT__initial_time);
}

int64_t
UT_Time(void) {
	const int64_t SECOND = 1000*1000*1000;
	struct timespec current;
	clock_gettime(CLOCK_MONOTONIC_RAW, &current);
	int64_t result = (current.tv_sec - UT__initial_time.tv_sec) * (1 * SECOND);
	result += current.tv_nsec - UT__initial_time.tv_nsec;
	return result;
}


#elif defined(_WIN32) || defined(WIN32)

#include <windows.h>

static LARGE_INTEGER UT__initial_time = {0};
static LARGE_INTEGER UT__time_freq = {0};

void
UT_Init(void) {
	QueryPerformanceFrequency(&UT__time_freq);
	QueryPerformanceCounter(&UT__initial_time);
}

int64_t
UT_Time(void) {
	const int64_t SECOND = 1000*1000*1000;

	LARGE_INTEGER qpc_t;
	QueryPerformanceCounter(&qpc_t);

	int64_t counter_diff = qpc_t.QuadPart - UT__initial_time.QuadPart;
	int64_t freq         = UT__time_freq.QuadPart;
	
	// This is to preserve the precission (from sokol time)
    int64_t q = counter_diff / freq;
    int64_t r = counter_diff % freq;

    int64_t result = q * SECOND + (r * SECOND) / freq;
	return result;
}

#elif defined (__wasm__)

#define UT__WA_JS(ret, name, args, ...) extern __attribute__((import_module("JS"), import_name(#name "|" #args "|" #__VA_ARGS__))) ret name args;

static int64_t UT__initial_time = 0;

UT__WA_JS(double, UT__JS_Get_time, (void), {
	return Date.now();
});

void
UT_Init(void) {
	UT__initial_time = (int64_t)UT__JS_Get_time();
}

int64_t
UT_Time(void) {
	int64_t MSECOND = 1000 * 1000;
	int64_t result = MSECOND*((int64_t)UT__JS_Get_time() - UT__initial_time);
	return result;
}

#endif

#endif // UTIME_INCLUDED