How do I port code calling QueryPerformanceFrequency to Rust? - windows

Question

I need to port this C code into Rust:
QueryPerformanceFrequency((unsigned long long int *) &frequency);
I didn't find a function that does that.
The Linux variant looks like:
struct timespec now;
if (clock_gettime(CLOCK_MONOTONIC, &now) == 0)
frequency = 1000000000;
Should I call std::time::Instant::now() and set the frequency to 1000000000?
This is the complete function:
// Initializes hi-resolution MONOTONIC timer
static void InitTimer(void)
{
srand(time(NULL)); // Initialize random seed
#if defined(_WIN32)
QueryPerformanceFrequency((unsigned long long int *) &frequency);
#endif
#if defined(__linux__)
struct timespec now;
if (clock_gettime(CLOCK_MONOTONIC, &now) == 0)
frequency = 1000000000;
#endif
#if defined(__APPLE__)
mach_timebase_info_data_t timebase;
mach_timebase_info(&timebase);
frequency = (timebase.denom*1e9)/timebase.numer;
#endif
baseTime = GetTimeCount(); // Get MONOTONIC clock time offset
startTime = GetCurrentTime(); // Get current time
}

Answer 1

The direct solution to accessing Windows APIs is to use the winapi crate. In this case, call QueryPerformanceFrequency:
use std::mem;
use winapi::um::profileapi::QueryPerformanceFrequency;
fn freq() -> u64 {
unsafe {
let mut freq = mem::zeroed();
QueryPerformanceFrequency(&mut freq);
*freq.QuadPart() as u64
}
}
fn main() {
println!("Hello, world!");
}
[dependencies]
winapi = { version = "0.3.8", features = ["profileapi"] }
hi-resolution MONOTONIC timer
I would use Instant as a monotonic timer and assume it's high-enough precision until proven otherwise.