High precision timer/clock (Windows, Linux)

timer.c

#include <stdio.h>
#include <stdlib.h>

#ifdef _WIN32
#include <windows.h>
#else
#include <time.h>
#endif

static double timer_start = 0.0;

#ifdef _WIN32
static LARGE_INTEGER freq;
#endif

double TimerGetCurrentTime(void){
#ifdef _WIN32
    LARGE_INTEGER now;
    QueryPerformanceCounter(&now);
    return (double)now.QuadPart / (double)freq.QuadPart;
#else
    struct timespec now;
    clock_gettime(CLOCK_MONOTONIC, &now);
    return (double)now.tv_sec + (double)now.tv_nsec / 1e9;
#endif
}

void TimerInit(void) {
#ifdef _WIN32
    QueryPerformanceFrequency(&freq);
#endif
    timer_start = TimerGetCurrentTime();
}

double TimerGetTime(void) {
    double current = TimerGetCurrentTime();
    return (current - timer_start);
}