rustfst/fst_impls/const_fst/
iterators.rs

1use std::iter::{Enumerate, Map, Zip};
2use std::ops::Range;
3use std::sync::Arc;
4
5use itertools::Itertools;
6use itertools::{izip, repeat_n, RepeatN};
7
8use crate::fst_impls::const_fst::data_structure::ConstState;
9use crate::fst_impls::ConstFst;
10use crate::fst_traits::FstIterData;
11use crate::fst_traits::{FstIntoIterator, FstIterator, StateIterator};
12use crate::semirings::Semiring;
13use crate::Tr;
14use crate::{StateId, TrsConst};
15
16impl<W: Semiring> FstIntoIterator<W> for ConstFst<W>
17where
18    W: 'static,
19{
20    type TrsIter = std::vec::IntoIter<Tr<W>>;
21    // TODO: Change this to impl once the feature has been stabilized
22    // #![feature(type_alias_impl_trait)]
23    // https://github.com/rust-lang/rust/issues/63063)
24    type FstIter = Box<dyn Iterator<Item = FstIterData<W, Self::TrsIter>>>;
25
26    fn fst_into_iter(mut self) -> Self::FstIter {
27        // Here the contiguous trs are moved into multiple vectors in order to be able to create
28        // iterator for each states.
29        // TODO: Find a way to avoid this allocation.
30        let mut v_trs = Vec::with_capacity(self.states.len());
31        let trs = Arc::make_mut(&mut self.trs);
32        for const_state in &self.states {
33            v_trs.push(trs.drain(0..const_state.ntrs).collect_vec())
34        }
35
36        Box::new(
37            izip!(self.states.into_iter(), v_trs.into_iter())
38                .enumerate()
39                .map(|(state_id, (const_state, trs_from_state))| FstIterData {
40                    state_id: state_id as StateId,
41                    trs: trs_from_state.into_iter(),
42                    final_weight: const_state.final_weight,
43                    num_trs: const_state.ntrs,
44                }),
45        )
46    }
47}
48
49impl<'a, W> StateIterator<'a> for ConstFst<W> {
50    type Iter = Range<StateId>;
51    fn states_iter(&'a self) -> Self::Iter {
52        0..(self.states.len() as StateId)
53    }
54}
55
56type States<'a, W> =
57    Enumerate<Zip<std::slice::Iter<'a, ConstState<W>>, RepeatN<&'a Arc<Vec<Tr<W>>>>>>;
58type StateToData<'a, W, TRS> =
59    Box<dyn FnMut((usize, (&'a ConstState<W>, &'a Arc<Vec<Tr<W>>>))) -> FstIterData<W, TRS>>;
60
61impl<'a, W: Semiring + 'static> FstIterator<'a, W> for ConstFst<W> {
62    type FstIter = Map<States<'a, W>, StateToData<'a, W, Self::TRS>>;
63    fn fst_iter(&'a self) -> Self::FstIter {
64        let it = repeat_n(&self.trs, self.states.len());
65        izip!(self.states.iter(), it)
66            .enumerate()
67            .map(Box::new(|(state_id, (fst_state, trs))| FstIterData {
68                state_id: state_id as StateId,
69                trs: TrsConst {
70                    trs: Arc::clone(trs),
71                    pos: fst_state.pos,
72                    n: fst_state.ntrs,
73                },
74                final_weight: fst_state.final_weight.clone(),
75                num_trs: fst_state.ntrs,
76            }))
77    }
78}
rustfst/fst_impls/const_fst/iterators.rs

rustfst/fst_impls/const_fst/
iterators.rs
