Repository: google/OpenSK
File: third_party/libtock-drivers/src/nfc.rs (Rust)

Code before:
    pub const RECEIVE: usize = 2;
}

pub struct NfcTag {}

impl NfcTag {
    pub fn enable_emulation() {
        NfcTag::emulate(true);
    }

    pub fn disable_emulation() {
        NfcTag::emulate(false);
    }

    pub fn emulate(enabled: bool) -> bool {
        let result_code =
            syscalls::command(DRIVER_NUMBER, command_nr::EMULATE, enabled as usize, 0);
        if result_code.is_err() {
            return false;
        }

        true
    }

    /// Subscribe to the tag being SELECTED callback.
    pub fn selected() -> bool {
        let is_selected = Cell::new(false);
        let mut is_selected_alarm = || is_selected.set(true);
        let subscription = syscalls::subscribe::<callback::Identity0Consumer, _>(
            DRIVER_NUMBER,
            subscribe_nr::SELECT,
            &mut is_selected_alarm,
        );
        if subscription.is_err() {
            return false;
        }

        util::yieldk_for(|| is_selected.get());
        true
    }

    /// Configure the tag type command.
    pub fn configure(tag_type: u8) -> bool {
        let result_code =
            syscalls::command(DRIVER_NUMBER, command_nr::CONFIGURE, tag_type as usize, 0);
        if result_code.is_err() {
            return false;
        }

        true
    }

Review comment (suggestion):
You could consider not returning `bool` everywhere, but just passing on the error code with a `Result<(), ErrorType>`. The you'd have access to the `?` operator below, like
`syscalls::subscribe(...)?;
instead of `is_err`.

Code after:
    pub const TRANSMIT: usize = 1;
    pub const RECEIVE: usize = 2;
}

#[allow(dead_code)]
#[derive(Clone, Copy)]
pub struct RecvOp {
    pub result_code: usize,
    pub recv_amount: usize,
}

pub struct NfcTag {}

impl NfcTag {
    /// Check the existence of an NFC driver.
    pub fn setup() -> bool {
        syscalls::command(DRIVER_NUMBER, command_nr::CHECK, 0, 0).is_ok()
    }

    pub fn enable_emulation() -> bool {
        NfcTag::emulate(true)
    }

    pub fn disable_emulation() -> bool {
        NfcTag::emulate(false)
    }

    fn emulate(enabled: bool) -> bool {
        syscalls::command(DRIVER_NUMBER, command_nr::EMULATE, enabled as usize, 0).is_ok()
    }

    /// Configure the tag type command.
    pub fn configure(tag_type: u8) -> bool {
        syscalls::command(DRIVER_NUMBER, command_nr::CONFIGURE, tag_type as usize, 0).is_ok()
    }

    /// 1. Share with the driver a buffer.
    /// 2. Subscribe to having a successful receive callback.
    /// 3. Issue the request for reception.
    pub fn receive(buf: &mut [u8; 256]) -> TockResult<RecvOp> {
        let result = syscalls::allow(DRIVER_NUMBER, allow_nr::RECEIVE, buf)?;
        // set callback with 2 arguments, to receive ReturnCode and RX Amount
        let recv_data = Cell::new(None);
        let mut callback = |result, amount| {
            recv_data.set(Some(RecvOp {
                result_code: result,
                recv_amount: amount,
            }))
        };
        let subscription = syscalls::subscribe::<callback::Identity2Consumer, _>(
            DRIVER_NUMBER,