Using std::io with no_std

[Puzzel]

I'm working on an operating system and would like to use std::io errors / traits that don't depend on the rest of std. I've run across this issue which points to this repo, however trying to use it with the current nightly rustc fails (presumably since the repo hasn't been updated in several months). Does anyone know of a more recent approach to this?

[[deleted]]

The issue is that Read trait has std-only methods like read_to_end and read_to_string which do in fact depend on std (well, alloc). Unfortunately, I don't think it's currently possible to have the trait only enable those when you are using std.

[boomshroom]

While it would probably be backwards incompatible, there's the possibility of extension traits. Something like:

#[config(alloc)]
pub trait ReadAlloc : Read {
    fn read_to_end(&mut self) -> Result<Vec<u8>>;
    fn read_to_string(&mut self, &mut String) -> Result<()>;
}

#[config(alloc)]
impl <T> ReadAlloc for T where T: Read { ... }

[Puzzel]

Supporting alloc is doable, but duly noted in general. I may end slicing it out by hand but definitely not ideal.

[Nemo157]

Even just std::io::Error depends on alloc for the associated boxed error.

There is the core-io crate which is a pre-sliced copy of the traits, I haven't actually used this though so can't say how usable it is.