Merge #9

9: Add serial::Read/Write implementation r=ryankurte a=rnestler

So this is just a quick PoC to implement #8.
@japaric Do you think it would be OK to implement it in that way? If yes I can finish it up.

Co-authored-by: Raphael Nestler <raphael.nestler@gmail.com>
Co-authored-by: Raphael Nestler <raphael.nestler@sensirion.com>
Co-authored-by: Danilo Bargen <mail@dbrgn.ch>

Cargo.toml

@@ -13,6 +13,12 @@ embedded-hal = { version = "0.2.0", features = ["unproven"] }
 i2cdev = "0.4.1"
 spidev = "0.3.0"
 sysfs_gpio = "0.5.1"
+serial-unix = "0.4.0"
+serial-core = "0.4.0"
+nb = "0.1.1"
+
+[dev-dependencies]
+openpty = "0.1.0"
 
 [dependencies.cast]
 # we don't need the `Error` implementation

src/lib.rs

@@ -17,6 +17,9 @@ extern crate embedded_hal as hal;
 pub extern crate i2cdev;
 pub extern crate spidev;
 pub extern crate sysfs_gpio;
+pub extern crate serial_unix;
+pub extern crate serial_core;
+pub extern crate nb;
 
 use std::io::{self, Write};
 use std::path::{Path, PathBuf};
@@ -27,6 +30,10 @@ use cast::{u32, u64};
 use i2cdev::core::I2CDevice;
 use spidev::SpidevTransfer;
 
+mod serial;
+
+pub use serial::Serial;
+
 /// Empty struct that provides delay functionality on top of `thread::sleep`
 pub struct Delay;
 

src/serial.rs

@@ -0,0 +1,97 @@
+//! Implementation of [`Serial`](https://docs.rs/embedded-hal/0.2.1/embedded_hal/serial/index.html)
+
+use std::io::{ErrorKind as IoErrorKind, Read, Write};
+use std::path::Path;
+
+use nb;
+
+use hal;
+use serial_core;
+use serial_unix::TTYPort;
+
+/// Newtype around [`serial_unix::TTYPort`] that implements
+/// the `embedded-hal` traits.
+pub struct Serial(pub TTYPort);
+
+impl Serial {
+    /// Wrapper for `serial_unix::TTYPort::open`
+    pub fn open(path: &Path) -> Result<Serial, serial_core::Error> {
+        Ok(Serial(TTYPort::open(path)?))
+    }
+}
+
+/// Helper to convert std::io::Error to the nb::Error
+fn translate_io_errors(err: std::io::Error) -> nb::Error<IoErrorKind> {
+    match err.kind() {
+        IoErrorKind::WouldBlock | IoErrorKind::TimedOut | IoErrorKind::Interrupted => {
+            nb::Error::WouldBlock
+        }
+        err => nb::Error::Other(err),
+    }
+}
+
+impl hal::serial::Read<u8> for Serial {
+    type Error = IoErrorKind;
+
+    fn read(&mut self) -> nb::Result<u8, Self::Error> {
+        let mut buffer = [0; 1];
+        let bytes_read = self.0.read(&mut buffer).map_err(translate_io_errors)?;
+        if bytes_read == 1 {
+            Ok(buffer[0])
+        } else {
+            Err(nb::Error::WouldBlock)
+        }
+    }
+}
+
+impl hal::serial::Write<u8> for Serial {
+    type Error = IoErrorKind;
+
+    fn write(&mut self, word: u8) -> nb::Result<(), Self::Error> {
+        self.0.write(&[word]).map_err(translate_io_errors)?;
+        Ok(())
+    }
+
+    fn flush(&mut self) -> nb::Result<(), Self::Error> {
+        self.0.flush().map_err(translate_io_errors)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::path::Path;
+
+    use hal::serial::{Read, Write};
+    use std::io::{Read as IoRead, Write as IoWrite};
+
+    use super::*;
+
+    fn create_pty_and_serial() -> (std::fs::File, Serial) {
+        let (master, _slave, name) =
+            openpty::openpty(None, None, None).expect("Creating pty failed");
+        let serial = Serial::open(Path::new(&name)).expect("Creating TTYPort failed");
+        (master, serial)
+    }
+
+    #[test]
+    fn test_empty_read() {
+        let (mut _master, mut serial) = create_pty_and_serial();
+        assert_eq!(Err(nb::Error::WouldBlock), serial.read());
+    }
+
+    #[test]
+    fn test_read() {
+        let (mut master, mut serial) = create_pty_and_serial();
+        master.write(&[1]).expect("Write failed");
+        assert_eq!(Ok(1), serial.read());
+    }
+
+    #[test]
+    fn test_write() {
+        let (mut master, mut serial) = create_pty_and_serial();
+        serial.write(2).expect("Write failed");
+        let mut buf = [0; 2];
+        assert_eq!(1, master.read(&mut buf).unwrap());
+        assert_eq!(buf, [2, 0]);
+    }
+}