Add read_adapter to avoid dynamic dispatch

[SUPERCILEX]

No description provided.

[SUPERCILEX]

I don't think there are any cases where you couldn't use the read_adapter?

[dhardy]

Can you give an example where this improves benchmark results?

[SUPERCILEX]

I forgot to mention that using dyn is also just plain annoying: &mut (&mut rand as &mut dyn RngCore).take(100_000) is just super ugly compared to &mut rand.read_adapter().take(100_000). Using dyn also defaults to a static lifetime which makes life more difficult when passing stuff around. So basically there are strong pros to the read_adapter approach beyond perf.

---

group.bench_function("dyn-on", |b| {
    b.iter_with_setup(
        || Xoshiro256PlusPlus::seed_from_u64(42),
        |mut rand| {
            io::copy(
                &mut (&mut rand as &mut dyn RngCore).take(100),
                &mut io::sink(),
            )
        },
    );
});
group.bench_function("dyn-off", |b| {
    b.iter_with_setup(
        || Xoshiro256PlusPlus::seed_from_u64(42),
        |mut rand| io::copy(&mut rand.read_adapter().take(100), &mut io::sink()),
    );
});

bytes_generate/dyn-on   time:   [49.346 ns 49.566 ns 49.829 ns]
bytes_generate/dyn-off  time:   [17.053 ns 17.096 ns 17.139 ns]

[dhardy]

Looks good to me, thanks!

[SUPERCILEX]

Thanks!