1use self::ChainState::*;
2use crate::StdError;
3
4#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
5use alloc::vec::{self, Vec};
6
7#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
8pub(crate) use crate::Chain;
9
10#[cfg(all(not(feature = "std"), anyhow_no_core_error))]
11pub(crate) struct Chain<'a> {
12 state: ChainState<'a>,
13}
14
15#[derive(Clone)]
16pub(crate) enum ChainState<'a> {
17 Linked {
18 next: Option<&'a (dyn StdError + 'static)>,
19 },
20 #[cfg(any(feature = "std", not(anyhow_no_core_error)))]
21 Buffered {
22 rest: vec::IntoIter<&'a (dyn StdError + 'static)>,
23 },
24}
25
26impl<'a> Chain<'a> {
27 #[cold]
28 pub fn new(head: &'a (dyn StdError + 'static)) -> Self {
29 Chain {
30 state: ChainState::Linked { next: Some(head) },
31 }
32 }
33}
34
35impl<'a> Iterator for Chain<'a> {
36 type Item = &'a (dyn StdError + 'static);
37
38 fn next(&mut self) -> Option<Self::Item> {
39 match &mut self.state {
40 Linked { next: &mut Option<&(dyn Error + 'static)> } => {
41 let error: &dyn Error = (*next)?;
42 *next = error.source();
43 Some(error)
44 }
45 #[cfg(any(feature = "std", not(anyhow_no_core_error)))]
46 Buffered { rest: &mut IntoIter<&(dyn Error + 'static)> } => rest.next(),
47 }
48 }
49
50 fn size_hint(&self) -> (usize, Option<usize>) {
51 let len: usize = self.len();
52 (len, Some(len))
53 }
54}
55
56#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
57impl DoubleEndedIterator for Chain<'_> {
58 fn next_back(&mut self) -> Option<Self::Item> {
59 match &mut self.state {
60 Linked { mut next: Option<&(dyn Error + 'static)> } => {
61 let mut rest: Vec<&dyn Error> = Vec::new();
62 while let Some(cause: &dyn Error) = next {
63 next = cause.source();
64 rest.push(cause);
65 }
66 let mut rest: IntoIter<&dyn Error> = rest.into_iter();
67 let last: Option<&dyn Error> = rest.next_back();
68 self.state = Buffered { rest };
69 last
70 }
71 Buffered { rest: &mut IntoIter<&(dyn Error + 'static)> } => rest.next_back(),
72 }
73 }
74}
75
76impl ExactSizeIterator for Chain<'_> {
77 fn len(&self) -> usize {
78 match &self.state {
79 Linked { mut next: Option<&(dyn Error + 'static)> } => {
80 let mut len: usize = 0;
81 while let Some(cause: &dyn Error) = next {
82 next = cause.source();
83 len += 1;
84 }
85 len
86 }
87 #[cfg(any(feature = "std", not(anyhow_no_core_error)))]
88 Buffered { rest: &IntoIter<&(dyn Error + 'static)> } => rest.len(),
89 }
90 }
91}
92
93#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
94impl Default for Chain<'_> {
95 fn default() -> Self {
96 Chain {
97 state: ChainState::Buffered {
98 rest: Vec::new().into_iter(),
99 },
100 }
101 }
102}
103