Rust + windows-rs: Get current logged-in users

get-current-logged-in-users.rs

const WTS_CONNECT_STATE_ACTIVE: i32 = 0;

// https://learn.microsoft.com/en-us/windows/win32/api/wtsapi32/ne-wtsapi32-wts_connectstate_class#syntax
fn wts_state_to_string(state: windows::Win32::System::RemoteDesktop::WTS_CONNECTSTATE_CLASS) -> String {
    match state.0 {
        0 => "Active".to_string(),
        1 => "Connected".to_string(),
        2 => "ConnectQuery".to_string(),
        3 => "Shadow".to_string(),
        4 => "Disconnected".to_string(),
        5 => "Idle".to_string(),
        6 => "Listen".to_string(),
        7 => "Reset".to_string(),
        8 => "Down".to_string(),
        9 => "Init".to_string(),
        _ => format!("Unknown({})", state.0),
    }
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let active_console_session_id = unsafe { windows::Win32::System::RemoteDesktop::WTSGetActiveConsoleSessionId() };
    println!("Active console session id: {}", active_console_session_id);

    let handle = windows::Win32::System::RemoteDesktop::WTS_CURRENT_SERVER_HANDLE;

    let mut session_info_ptr: *mut windows::Win32::System::RemoteDesktop::WTS_SESSION_INFOW = std::ptr::null_mut();
    let mut session_count = 0u32;
    unsafe {
        windows::Win32::System::RemoteDesktop::WTSEnumerateSessionsW(
            handle,
            0,
            1,
            &mut session_info_ptr,
            &mut session_count,
        )?;
    }

    for i in 0..session_count {
        let session_info = &unsafe { *session_info_ptr.add(i as usize) };
        let win_station_name = unsafe { session_info.pWinStationName.to_string()? };
        println!("> session_id: {} win_station_name: {} state: {}",
                 session_info.SessionId,
                 win_station_name,
                 wts_state_to_string(session_info.State),
        );

        if session_info.State.0 == WTS_CONNECT_STATE_ACTIVE {
            let mut username_buf = windows::core::PWSTR::null();
            let mut bytes_returned = 0u32;

            unsafe {
                windows::Win32::System::RemoteDesktop::WTSQuerySessionInformationW(
                    handle,
                    session_info.SessionId,
                    windows::Win32::System::RemoteDesktop::WTSUserName,
                    &mut username_buf,
                    &mut bytes_returned,
                )?;
            }

            assert!(!username_buf.is_null());
            let username = unsafe { username_buf.to_string()? };
            println!("\t username: {} bytes_returned: {}", username, bytes_returned);
        }
    }

    Ok(())
}

$ ./rust-test.exe
Active console session id: 1
> session_id: 0 win_station_name: Services state: Disconnected
> session_id: 1 win_station_name: Console state: Connected
> session_id: 2 win_station_name: RDP-Tcp#12 state: Active
         username: foobar bytes_returned: 14
> session_id: 65536 win_station_name: RDP-Tcp state: Listen