Crate int_to_c_enum 

TryFromInt

A convenient derive macro for converting an integer to a C-like enum.

This crate provides a derive procedural macro named TryFromInt. This macro will automatically implement TryFrom trait for enums that meet the following requirements:

1. The enum must have a primitive repr, i.e., the enum should have attribute like #[repr(u8)], #[repr(u32)], etc. The type parameter of TryFrom will be the repr.
2. The enum must consist solely of unit variants, which is called units only enum. Each field should have an explicit discriminant.

Quick Start

To use this crate, first add this crate to your Cargo.toml.

[dependencies]
int-to-c-enum = "0.1.0"

Below is a simple example. We derive macro TryFromInt for an enum Color.

use int_to_c_enum::TryFromInt;

#[repr(u8)]
#[derive(TryFromInt, Debug, Eq, PartialEq)]
pub enum Color {
    Red = 1,
    Yellow = 2,
    Blue = 3,
}

// Then, we can use method `try_from` for `Color`.
let color = Color::try_from(1).unwrap();
assert!(color == Color::Red);

Macro Expansion

The TryFromInt macro will automatically implement trait TryFrom<u8> for Color. After macro expansion, the generated code looks like as follows:

impl TryFrom<u8> for Color {
    type Error = TryFromIntError;
    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            1 => Ok(Color::Red),
            2 => Ok(Color::Yellow),
            3 => Ok(Color::Blue),
            _ => Err(TryFromIntError::InvalidValue),
        }
    }
}

License

This project is licensed under MPL-2.0.

Enums

TryFromIntError

Error type for TryFromInt derive macro

Derive Macros

TryFromInt