bstringify!

类似于 stringify!，但生成字节字符串字面量。

由于在 strings 上 .as_bytes() 是一个 const fn，这个宏应该只用于创建用于 match 的字节字符串字面量

use ::bstringify::bstringify;

/// like FromStr but with [u8] instead
trait FromBytes : Sized {
    fn from_bytes (input: &'_ [u8])
      -> Option<Self>
    ;
}

macro_rules! derive_FromBytes {(
    $(#[$attr:meta])*
    $pub:vis
    enum $EnumName:ident {
        $(
            $Variant:ident
        ),* $(,)?
    }
) => (
    $(#[$attr])*
    $pub
    enum $EnumName {
        $(
            $Variant,
        )*
    }
    
    impl $crate::FromBytes
        for $EnumName
    {
        fn from_bytes (input: &'_ [u8])
          -> Option<Self>
        {
            match input {
            $(
                | bstringify!($Variant) => Some(Self::$Variant),
            )*
                | _ => None,
            }
        }
    }
)}

derive_FromBytes! {
    enum Example {
        Foo,
        Bar,
    }
}

fn main ()
{
    assert!(matches!(
        Example::from_bytes(b"Foo"), Some(Example::Foo)
    ));
    assert!(matches!(
        Example::from_bytes(b"Bar"), Some(Example::Bar)
    ));
    assert!(matches!(
        Example::from_bytes(b"Bad"), None
    ));
}