wasefire 0.8.1

High-level Wasefire applet API
Documentation 
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// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Provides API for UART.

use sealed::sealed;
use wasefire_applet_api::uart as api;

use crate::serial::Event;
use crate::{Error, convert, convert_unit};

/// Returns the number of available UARTs on the board.
pub fn count() -> usize {
    convert(unsafe { api::count() }).unwrap_or(0)
}

/// Implements the [`Serial`](crate::serial::Serial) interface for UART.
///
/// The UART is stopped when dropped.
pub struct Uart(usize);

impl Uart {
    /// Builds and starts a UART with the default configuration.
    pub fn new(uart: usize) -> Result<Self, Error> {
        UartBuilder::new(uart).build()
    }
}

/// UART configuration.
pub struct UartBuilder {
    uart: usize,
    baudrate: Option<usize>,
}

impl UartBuilder {
    /// Creates a new UART configuration.
    pub fn new(uart: usize) -> Self {
        UartBuilder { uart, baudrate: None }
    }

    /// Sets the UART baudrate.
    pub fn set_baudrate(mut self, baudrate: usize) -> Self {
        self.baudrate = Some(baudrate);
        self
    }

    /// Builds and starts a UART with the given configuration.
    pub fn build(self) -> Result<Uart, Error> {
        let uart = self.uart;
        if let Some(baudrate) = self.baudrate {
            let params = api::set_baudrate::Params { uart, baudrate };
            convert_unit(unsafe { api::set_baudrate(params) })?;
        }
        let params = api::start::Params { uart };
        convert_unit(unsafe { api::start(params) })?;
        Ok(Uart(uart))
    }
}

impl Drop for Uart {
    fn drop(&mut self) {
        let params = api::stop::Params { uart: self.0 };
        convert_unit(unsafe { api::stop(params) }).unwrap();
    }
}

#[sealed]
impl crate::serial::Serial for Uart {
    fn read(&self, buffer: &mut [u8]) -> Result<usize, Error> {
        let params =
            api::read::Params { uart: self.0, ptr: buffer.as_mut_ptr(), len: buffer.len() };
        convert(unsafe { api::read(params) })
    }

    fn write(&self, buffer: &[u8]) -> Result<usize, Error> {
        let params = api::write::Params { uart: self.0, ptr: buffer.as_ptr(), len: buffer.len() };
        convert(unsafe { api::write(params) })
    }

    fn flush(&self) -> Result<(), Error> {
        Ok(())
    }

    unsafe fn register(
        &self, event: Event, func: extern "C" fn(*const u8), data: *const u8,
    ) -> Result<(), Error> {
        let params = api::register::Params {
            uart: self.0,
            event: convert_event(event) as usize,
            handler_func: func,
            handler_data: data,
        };
        convert_unit(unsafe { api::register(params) })
    }

    fn unregister(&self, event: Event) -> Result<(), Error> {
        let params = api::unregister::Params { uart: self.0, event: convert_event(event) as usize };
        convert_unit(unsafe { api::unregister(params) })
    }
}

fn convert_event(event: Event) -> api::Event {
    match event {
        Event::Read => api::Event::Read,
        Event::Write => api::Event::Write,
    }
}