I/O adapters

This crate provides adapters to compose writeable traits in the standard library. The following conversions are available:

• fmt::Write -> io::Write
• io::Write -> hash::Hasher

Use case

Suppose you are writing a function which emits human-readable data in a zero-alloc way. The best interface looks something like this:

fn foo<Out: fmt::Write>(mut output: Out, ...) {
    // Do stuff
    writeln!(output, "My computation: {result}").unwrap();
}

Notice the use of fmt::Write: using this trait provides a type-system guarantee that the data written is valid UTF-8, hence why it should be preferred over io::Write.

Now users of this API can gather data into a String, provide their own fmt::Write implementation, etc. The problem you'll run into is if you'd like to send the output of this function to stdout: there is no built-in way to do so! That's where this crate comes in by providing an adapter, so you can write the following:

foo(&mut io::stdout().write_adapter());