Timer function to provide time in nano seconds using C++

Question

I wish to calculate the time it took for an API to return a value. The time taken for such an action is in the space of nano seconds. As the API is a C++ class/function, I a

Answer 1

Using Brock Adams's method, with a simple class:

int get_cpu_ticks()
{
    LARGE_INTEGER ticks;
    QueryPerformanceFrequency(&ticks);
    return ticks.LowPart;
}

__int64 get_cpu_clocks()
{
    struct { int32 low, high; } counter;

    __asm cpuid
    __asm push EDX
    __asm rdtsc
    __asm mov counter.low, EAX
    __asm mov counter.high, EDX
    __asm pop EDX
    __asm pop EAX

    return *(__int64 *)(&counter);
}

class cbench
{
public:
    cbench(const char *desc_in) 
         : desc(strdup(desc_in)), start(get_cpu_clocks()) { }
    ~cbench()
    {
        printf("%s took: %.4f ms\n", desc, (float)(get_cpu_clocks()-start)/get_cpu_ticks());
        if(desc) free(desc);
    }
private:
    char *desc;
    __int64 start;
};

Usage Example:

int main()
{
    {
        cbench c("test");
        ... code ...
    }
    return 0;
}

Result:

test took: 0.0002 ms

Has some function call overhead, but should be still more than fast enough :)