dfir_lang 0.16.0

Hydro's Dataflow Intermediate Representation (DFIR) implementation
Documentation 
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use quote::quote_spanned;

use super::{
    FloType, OperatorCategory, OperatorConstraints, OperatorWriteOutput, RANGE_0, RANGE_1,
    WriteContextArgs,
};

/// Given an _unbounded_ input stream, emits full prefixes of the input, of arbitrarily increasing length, in the same order.
///
/// Will cause additional loop iterations as long as new values arrive.
pub const PREFIX: OperatorConstraints = OperatorConstraints {
    name: "prefix",
    categories: &[OperatorCategory::Fold, OperatorCategory::Windowing],
    hard_range_inn: RANGE_1,
    soft_range_inn: RANGE_1,
    hard_range_out: &(0..=1),
    soft_range_out: &(0..=1),
    num_args: 0,
    persistence_args: RANGE_0,
    type_args: RANGE_0,
    is_external_input: false,
    has_singleton_output: true,
    flo_type: Some(FloType::Windowing),
    ports_inn: None,
    ports_out: None,
    input_delaytype_fn: |_| None,
    write_fn: |wc @ &WriteContextArgs {
                   root,
                   context,
                   df_ident,
                   op_span,
                   work_fn_async,
                   ident,
                   is_pull,
                   inputs,
                   singleton_output_ident,
                   ..
               },
               _diagnostics| {
        assert!(is_pull);

        let write_prologue = quote_spanned! {op_span=>
            #[allow(clippy::redundant_closure_call)]
            let #singleton_output_ident = #df_ident.add_state(
                ::std::cell::RefCell::new(::std::vec::Vec::new())
            );
        };

        let vec_ident = wc.make_ident("vec");

        let input = &inputs[0];
        let write_iterator = quote_spanned! {op_span=>
            let mut #vec_ident = unsafe {
                // SAFETY: handle from `#df_ident.add_state(..)`.
                #context.state_ref_unchecked(#singleton_output_ident)
            }.borrow_mut();

            // The same as `persist()`, except always replays.

            let #ident = {
                let fut = #root::dfir_pipes::pull::Pull::for_each(#input, |item| {
                    #vec_ident.push(item);
                });
                let () = #work_fn_async(fut).await;

                let iter = #vec_ident.iter().cloned();
                #root::dfir_pipes::pull::iter(iter)
            };
        };
        let write_iterator_after = quote_spanned! {op_span=>
            #context.allow_another_iteration();
        };

        Ok(OperatorWriteOutput {
            write_prologue,
            write_iterator,
            write_iterator_after,
            ..Default::default()
        })
    },
};