embedded-error-chain

Easy error handling for embedded devices (no liballoc and no_std).

A rust library implementing easy error handling for embedded devices. An Error value is only a single u32 in size and supports up to 4 chained error codes. Each error code can have a value from 0 to 15 (4 bits). All error codes come from an enum that implements the ErrorCategory trait (a derive macro exists). This trait is also used to implement debug printing and equality for each error code.

This library was inspired by libraries such as error-chain and anyhow, though its goal is to work in no_std and no_alloc environments with very little memory overhead.

Example

use embedded_error_chain::prelude::*;

#[derive(Clone, Copy, ErrorCategory)]
#[repr(u8)]
enum SpiError {
    BusError,
    // ...
}

static LAST_GYRO_ACC_READOUT: usize = 200;

#[derive(Clone, Copy, ErrorCategory)]
#[error_category(links(SpiError))]
#[repr(u8)]
enum GyroAccError {
    InitFailed,

    #[error("{variant} (readout={})", LAST_GYRO_ACC_READOUT)]
    ReadoutFailed,

    /// Value must be in range [0, 256)
    #[error("{variant}: {summary}")]
    InvalidValue,
}

#[derive(Clone, Copy, ErrorCategory)]
#[error_category(links(GyroAccError))]
#[repr(u8)]
enum CalibrationError {
    Inner,
}

fn main() {
    if let Err(err) = calibrate() {
        // log the error
        println!("{:?}", err);
        // ...
    }

    let readout = match gyro_acc_readout() {
        Ok(val) => val,
        Err(err) => {
            if let Some(spi_error) = err.code_of_category::<SpiError>() {
                // try to fix it
                0
            }
            else {
                panic!("unfixable spi error");
            }
        }
    };
}

fn spi_init() -> Result<(), SpiError> {
    Err(SpiError::BusError)
}

fn gyro_acc_init() -> Result<(), Error<GyroAccError>> {
    spi_init().chain_err(GyroAccError::InitFailed)?;
    Ok(())
}

fn gyro_acc_readout() -> Result<u32, Error<GyroAccError>> {
    Err(SpiError::BusError.chain(GyroAccError::InvalidValue))
}

fn calibrate() -> Result<(), Error<CalibrationError>> {
    gyro_acc_init().chain_err(CalibrationError::Inner)?;
    Ok(())
}

License: MIT