lender/fallible_adapters/
cycle.rs

1use crate::{
2    Cycle, FallibleLend, FallibleLender, FallibleLending, FusedFallibleLender,
3    try_trait_v2::{FromResidual, Try},
4};
5use core::{num::NonZeroUsize, ops::ControlFlow};
6
7impl<L: Clone + FallibleLender> Cycle<L> {
8    #[inline]
9    pub(crate) fn new_fallible(lender: L) -> Cycle<L> {
10        let _ = L::__check_covariance(crate::CovariantProof::new());
11        Cycle {
12            orig: lender.clone(),
13            lender,
14        }
15    }
16}
17
18impl<'lend, L> FallibleLending<'lend> for Cycle<L>
19where
20    L: Clone + FallibleLender,
21{
22    type Lend = FallibleLend<'lend, L>;
23}
24
25impl<L> FallibleLender for Cycle<L>
26where
27    L: Clone + FallibleLender,
28{
29    type Error = L::Error;
30    // SAFETY: the lend is that of L
31    crate::unsafe_assume_covariance_fallible!();
32
33    #[inline]
34    fn next(&mut self) -> Result<Option<FallibleLend<'_, Self>>, Self::Error> {
35        // SAFETY: polonius return
36        #[allow(clippy::deref_addrof)]
37        let reborrow = unsafe { &mut *(&raw mut *self) };
38        if let x @ Some(_) = reborrow.lender.next()? {
39            return Ok(x);
40        }
41        self.lender = self.orig.clone();
42        self.lender.next()
43    }
44
45    #[inline]
46    fn size_hint(&self) -> (usize, Option<usize>) {
47        match self.orig.size_hint() {
48            h @ (0, Some(0)) => h,
49            (0, _) => (0, None),
50            _ => (usize::MAX, None),
51        }
52    }
53
54    #[inline]
55    fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> Result<R, Self::Error>
56    where
57        Self: Sized,
58        F: FnMut(B, FallibleLend<'_, Self>) -> Result<R, Self::Error>,
59        R: Try<Output = B>,
60    {
61        let mut acc = init;
62        acc = match self.lender.try_fold(acc, &mut f)?.branch() {
63            ControlFlow::Break(x) => return Ok(FromResidual::from_residual(x)),
64            ControlFlow::Continue(x) => x,
65        };
66        self.lender = self.orig.clone();
67        let mut empty = true;
68        acc = match self
69            .lender
70            .try_fold(acc, |acc, x| {
71                empty = false;
72                f(acc, x)
73            })?
74            .branch()
75        {
76            ControlFlow::Break(x) => return Ok(FromResidual::from_residual(x)),
77            ControlFlow::Continue(x) => x,
78        };
79        if empty {
80            return Ok(Try::from_output(acc));
81        }
82        loop {
83            self.lender = self.orig.clone();
84            acc = match self.lender.try_fold(acc, &mut f)?.branch() {
85                ControlFlow::Break(x) => return Ok(FromResidual::from_residual(x)),
86                ControlFlow::Continue(x) => x,
87            };
88        }
89    }
90
91    #[inline]
92    fn advance_by(&mut self, n: usize) -> Result<Result<(), NonZeroUsize>, Self::Error> {
93        let mut n = match self.lender.advance_by(n)? {
94            Ok(()) => return Ok(Ok(())),
95            Err(rem) => rem.get(),
96        };
97
98        while n > 0 {
99            self.lender = self.orig.clone();
100            n = match self.lender.advance_by(n)? {
101                Ok(()) => return Ok(Ok(())),
102                Err(rem) if rem.get() == n => return Ok(Err(rem)),
103                Err(rem) => rem.get(),
104            };
105        }
106
107        Ok(Ok(()))
108    }
109}
110
111impl<L> FusedFallibleLender for Cycle<L> where L: Clone + FallibleLender {}
lender/fallible_adapters/cycle.rs

lender/fallible_adapters/
cycle.rs
