Tape storage re-use

[JosiahWhite]

Is it possible to reuse the storage that was allocated for the Tape Vec? Based on my digging it doesn't look to be possible in the current state.

If I am right about this not being possible at the moment, It feels like it isn't supported due to the tape type in this package being Peekable<IntoIter<>> but this looks like it could be solved by using a Peekable<Drain<>>?

Let me know if I am on the right track with this...

[Licenser]

That sounds reasonable, I like the idea:) definitely worth a try

[Licenser]

I think the reason this didn't happen is lifetimes. since the tape has a lifetime bound to it's elements the re-use would make the borrowchedker think the life times are related:

let a: &'a[u8] = b"42";
let mut reusable_tape = make_new_tape();;
parse(a, &mut reusable_tape);
// reusable_tape: Tape<'a>
do_stuff_with(reusable_tape);
reusable_tape.clear()
let a: &'b[u8] = b"43";
parse(b, &mut reusable_tape);
// reusable_tape: Tape<'b> <= lifetime conflict! 'a now needs to be 'b or wider

[JosiahWhite]

I was able to modify the library to support this by adding an additional lifetime on the tape, I'll open a PR with the changes shortly but it was pretty straightforward to implement. The tape type now looks like this:

pub type Tape<'tape, 'input> = Peekable<Drain<'tape, Node<'input>>>;
pub trait Deserialize<'input> {
    fn from_tape<'tape>(tape: &mut Tape<'tape, 'input>) -> simd_json::Result<Self>
    where
        Self: Sized + 'input;
/// etc...
}

This also required modifying every deserializer implementation to match the trait lifetime changes. After the changes I can reuse a tape like so (roughly):

simd_json::fill_tape(json_msg, buffers, tape)?;
let mut itr = tape.0.drain(..).peekable();
let item = MyStruct::from_tape(&mut itr);
println!("item: {:?}", item);
let tape = tape.reset();
simd_json::fill_tape(second_json_msg, buffers, tape)?;
let mut itr = tape.0.drain(..).peekable();
let item = MyStruct::from_tape(&mut itr);
println!("other item: {:?}", item);

The only downside of this is that any existing deserializer implementations need to be updated with the new type signatures