Windows: sail.c uses CLOCK_REALTIME

[Timmmm]

This code doesn't compile with MSVC:

sail/lib/sail.c

Lines 1916 to 1923 in 277470b

	void get_time_ns(sail_int *rop, const unit u)
	{
	struct timespec t;
	clock_gettime(CLOCK_REALTIME, &t);
	mpz_set_si(*rop, t.tv_sec);
	mpz_mul_ui(*rop, *rop, 1000000000);
	mpz_add_ui(*rop, *rop, t.tv_nsec);
	}

ChatGPT suggested this which probably needs a bit of tweaking but looks pretty close:

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

void get_time_ns(sail_int *rop, const unit u)
{
#ifdef _WIN32
    static LARGE_INTEGER freq;
    static int freq_initialized = 0;
    LARGE_INTEGER counter;

    if (!freq_initialized) {
        QueryPerformanceFrequency(&freq);
        freq_initialized = 1;
    }

    QueryPerformanceCounter(&counter);

    // Convert to nanoseconds:
    // (counter * 1e9) / freq
    mpz_set_ui(*rop, counter.QuadPart);
    mpz_mul_ui(*rop, *rop, 1000000000ULL);
    mpz_tdiv_q_ui(*rop, *rop, freq.QuadPart);

#else
    struct timespec t;
    clock_gettime(CLOCK_MONOTONIC, &t);

    mpz_set_si(*rop, t.tv_sec);
    mpz_mul_ui(*rop, *rop, 1000000000);
    mpz_add_ui(*rop, *rop, t.tv_nsec);
#endif
}

[Alasdair]

Would have to check if CLOCK_MONOTONIC is supported on macOS. I think that might be the reason it's using CLOCK_REALTIME.

[Timmmm]

I think Windows doesn't have clock_gettime at all. I have a commit that uses QueryPerformanceCounter which is probably the best option. I'll make a PR later.