Windows FILETIME to UNIX time epoch.

windows-FILETIME-to-unix-time-epoch.rs

use std::os::windows::fs::MetadataExt;

// Nanoseconds between [Jan 1 1601, Jan 1 1970]
const UNIX_EPOCH_OFFSET: u64 = 0x019d_b1de_d53e_8000;

// Panic if file_time is below Jan 1 1970
fn filetime_to_unix_ns(file_time: u64) -> u64 {
    (file_time - UNIX_EPOCH_OFFSET) * 100
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let md = std::fs::symlink_metadata(r#"C:\Users\nutstore\Desktop\hfs.exe"#)?;
    let last_access_filetime = md.last_access_time();
    println!("FILETIME: {}", last_access_filetime);

    let year1970 = windows::Win32::Foundation::SYSTEMTIME {
        wYear: 1970,
        wMonth: 1,
        /* Jan 1, 1970 is Thursday */
        wDayOfWeek: 4,
        wDay: 1,
        wHour: 0,
        wMinute: 0,
        wSecond: 0,
        wMilliseconds: 0,
    };

    let mut file_time = windows::Win32::Foundation::FILETIME::default();
    unsafe {
        windows::Win32::System::Time::SystemTimeToFileTime(
            std::ptr::addr_of!(year1970),
            std::ptr::addr_of_mut!(file_time),
        )?;
    }

    let t = (file_time.dwHighDateTime as u64) << 32 | file_time.dwLowDateTime as u64;
    println!("Year 1970 FILETIME: {:?}", file_time);
    println!("Year 1970 FILETIME: {:#x}", t);

    println!("FILETIME to unix epoch ns: {}", filetime_to_unix_ns(last_access_filetime));

    Ok(())
}

$ ./rust-test.exe
FILETIME: 133378730073603227
Year 1970 FILETIME: FILETIME { dwLowDateTime: 3577643008, dwHighDateTime: 27111902 }
Year 1970 FILETIME: 0x19db1ded53e8000
FILETIME to unix epoch ns: 1693399407360322700

1693399407360322700

GMT: Wednesday, August 30, 2023 12:43:27.360 PM
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