nusb 0.2.3

Cross-platform low-level access to USB devices in pure Rust
Documentation 
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/// Transfer direction
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
#[repr(u8)]
pub enum Direction {
    /// Host to device
    Out = 0,

    /// Device to host
    In = 0x80,
}

impl Direction {
    pub(crate) fn from_address(addr: u8) -> Direction {
        match addr & Self::MASK {
            0 => Self::Out,
            _ => Self::In,
        }
    }
    pub(crate) const MASK: u8 = 0x80;
}

/// Specification defining the request.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
#[repr(u8)]
pub enum ControlType {
    /// Request defined by the USB standard.
    Standard = 0,

    /// Request defined by the standard USB class specification.
    Class = 1,

    /// Non-standard request.
    Vendor = 2,
}

/// Entity targeted by the request.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
#[repr(u8)]
pub enum Recipient {
    /// Request made to device as a whole.
    Device = 0,

    /// Request made to specific interface.
    Interface = 1,

    /// Request made to specific endpoint.
    Endpoint = 2,

    /// Other request.
    Other = 3,
}

/// SETUP packet and associated data to make an **OUT** request on a control endpoint.
#[derive(Debug, Clone, Copy)]
pub struct ControlOut<'a> {
    /// Request type used for the `bmRequestType` field sent in the SETUP packet.
    #[doc(alias = "bmRequestType")]
    pub control_type: ControlType,

    /// Recipient used for the `bmRequestType` field sent in the SETUP packet.
    #[doc(alias = "bmRequestType")]
    pub recipient: Recipient,

    /// `bRequest` field sent in the SETUP packet.
    #[doc(alias = "bRequest")]
    pub request: u8,

    /// `wValue` field sent in the SETUP packet.
    #[doc(alias = "wValue")]
    pub value: u16,

    /// `wIndex` field sent in the SETUP packet.
    ///
    /// For [`Recipient::Interface`] this is the interface number. For [`Recipient::Endpoint`] this is the endpoint number.
    #[doc(alias = "wIndex")]
    pub index: u16,

    /// Data to be sent in the data stage.
    #[doc(alias = "wLength")]
    pub data: &'a [u8],
}

impl<'a> ControlOut<'a> {
    #[allow(unused)]
    pub(crate) fn setup_packet(&self) -> [u8; SETUP_PACKET_SIZE] {
        pack_setup(
            Direction::Out,
            self.control_type,
            self.recipient,
            self.request,
            self.value,
            self.index,
            self.data.len().try_into().expect("length must fit in u16"),
        )
    }

    #[allow(unused)]
    pub(crate) fn request_type(&self) -> u8 {
        request_type(Direction::Out, self.control_type, self.recipient)
    }
}

/// SETUP packet to make an **IN** request on a control endpoint.
#[derive(Debug, Clone, Copy)]
pub struct ControlIn {
    /// Request type used for the `bmRequestType` field sent in the SETUP packet.
    #[doc(alias = "bmRequestType")]
    pub control_type: ControlType,

    /// Recipient used for the `bmRequestType` field sent in the SETUP packet.
    #[doc(alias = "bmRequestType")]
    pub recipient: Recipient,

    /// `bRequest` field sent in the SETUP packet.
    #[doc(alias = "bRequest")]
    pub request: u8,

    /// `wValue` field sent in the SETUP packet.
    #[doc(alias = "wValue")]
    pub value: u16,

    /// `wIndex` field sent in the SETUP packet.
    ///
    /// For [`Recipient::Interface`] this is the interface number. For [`Recipient::Endpoint`] this is the endpoint number.
    #[doc(alias = "wIndex")]
    pub index: u16,

    /// Number of bytes to be read in the data stage.
    #[doc(alias = "wLength")]
    pub length: u16,
}

impl ControlIn {
    #[allow(unused)]
    pub(crate) fn setup_packet(&self) -> [u8; SETUP_PACKET_SIZE] {
        pack_setup(
            Direction::In,
            self.control_type,
            self.recipient,
            self.request,
            self.value,
            self.index,
            self.length,
        )
    }

    #[allow(unused)]
    pub(crate) fn request_type(&self) -> u8 {
        request_type(Direction::In, self.control_type, self.recipient)
    }
}

pub(crate) const SETUP_PACKET_SIZE: usize = 8;

fn pack_setup(
    direction: Direction,
    control_type: ControlType,
    recipient: Recipient,
    request: u8,
    value: u16,
    index: u16,
    length: u16,
) -> [u8; SETUP_PACKET_SIZE] {
    let bmrequesttype = request_type(direction, control_type, recipient);

    [
        bmrequesttype,
        request,
        (value & 0xFF) as u8,
        (value >> 8) as u8,
        (index & 0xFF) as u8,
        (index >> 8) as u8,
        (length & 0xFF) as u8,
        (length >> 8) as u8,
    ]
}

pub(crate) fn request_type(
    direction: Direction,
    control_type: ControlType,
    recipient: Recipient,
) -> u8 {
    (direction as u8) | ((control_type as u8) << 5) | (recipient as u8)
}