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use self::ChainState::*;
use crate::StdError;
#[cfg(feature = "std")]
use std::vec;
#[cfg(feature = "std")]
pub(crate) use crate::Chain;
#[cfg(not(feature = "std"))]
pub(crate) struct Chain<'a> {
state: ChainState<'a>,
}
#[derive(Clone)]
pub(crate) enum ChainState<'a> {
Linked {
next: Option<&'a (dyn StdError + 'static)>,
},
#[cfg(feature = "std")]
Buffered {
rest: vec::IntoIter<&'a (dyn StdError + 'static)>,
},
}
impl<'a> Chain<'a> {
#[cold]
pub fn new(head: &'a (dyn StdError + 'static)) -> Self {
Chain {
state: ChainState::Linked { next: Some(head) },
}
}
}
impl<'a> Iterator for Chain<'a> {
type Item = &'a (dyn StdError + 'static);
fn next(&mut self) -> Option<Self::Item> {
match &mut self.state {
Linked { next } => {
let error = (*next)?;
*next = error.source();
Some(error)
}
#[cfg(feature = "std")]
Buffered { rest } => rest.next(),
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.len();
(len, Some(len))
}
}
#[cfg(feature = "std")]
impl DoubleEndedIterator for Chain<'_> {
fn next_back(&mut self) -> Option<Self::Item> {
match &mut self.state {
Linked { mut next } => {
let mut rest = Vec::new();
while let Some(cause) = next {
next = cause.source();
rest.push(cause);
}
let mut rest = rest.into_iter();
let last = rest.next_back();
self.state = Buffered { rest };
last
}
Buffered { rest } => rest.next_back(),
}
}
}
impl ExactSizeIterator for Chain<'_> {
fn len(&self) -> usize {
match &self.state {
Linked { mut next } => {
let mut len = 0;
while let Some(cause) = next {
next = cause.source();
len += 1;
}
len
}
#[cfg(feature = "std")]
Buffered { rest } => rest.len(),
}
}
}
#[cfg(feature = "std")]
impl Default for Chain<'_> {
fn default() -> Self {
Chain {
state: ChainState::Buffered {
rest: Vec::new().into_iter(),
},
}
}
}