126 lines
3.3 KiB
Rust
126 lines
3.3 KiB
Rust
#[cfg(feature = "use_std")]
|
|
use std::error::Error;
|
|
use std::fmt::{Debug, Display, Formatter, Result as FmtResult};
|
|
|
|
use std::iter::ExactSizeIterator;
|
|
|
|
use either::Either;
|
|
|
|
use crate::size_hint;
|
|
|
|
/// Iterator returned for the error case of `Itertools::exactly_one()`
|
|
/// This iterator yields exactly the same elements as the input iterator.
|
|
///
|
|
/// During the execution of `exactly_one` the iterator must be mutated. This wrapper
|
|
/// effectively "restores" the state of the input iterator when it's handed back.
|
|
///
|
|
/// This is very similar to `PutBackN` except this iterator only supports 0-2 elements and does not
|
|
/// use a `Vec`.
|
|
#[derive(Clone)]
|
|
pub struct ExactlyOneError<I>
|
|
where
|
|
I: Iterator,
|
|
{
|
|
first_two: Option<Either<[I::Item; 2], I::Item>>,
|
|
inner: I,
|
|
}
|
|
|
|
impl<I> ExactlyOneError<I>
|
|
where
|
|
I: Iterator,
|
|
{
|
|
/// Creates a new `ExactlyOneErr` iterator.
|
|
pub(crate) fn new(first_two: Option<Either<[I::Item; 2], I::Item>>, inner: I) -> Self {
|
|
Self { first_two, inner }
|
|
}
|
|
|
|
fn additional_len(&self) -> usize {
|
|
match self.first_two {
|
|
Some(Either::Left(_)) => 2,
|
|
Some(Either::Right(_)) => 1,
|
|
None => 0,
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<I> Iterator for ExactlyOneError<I>
|
|
where
|
|
I: Iterator,
|
|
{
|
|
type Item = I::Item;
|
|
|
|
fn next(&mut self) -> Option<Self::Item> {
|
|
match self.first_two.take() {
|
|
Some(Either::Left([first, second])) => {
|
|
self.first_two = Some(Either::Right(second));
|
|
Some(first)
|
|
}
|
|
Some(Either::Right(second)) => Some(second),
|
|
None => self.inner.next(),
|
|
}
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
size_hint::add_scalar(self.inner.size_hint(), self.additional_len())
|
|
}
|
|
|
|
fn fold<B, F>(self, mut init: B, mut f: F) -> B
|
|
where
|
|
F: FnMut(B, Self::Item) -> B,
|
|
{
|
|
match self.first_two {
|
|
Some(Either::Left([first, second])) => {
|
|
init = f(init, first);
|
|
init = f(init, second);
|
|
}
|
|
Some(Either::Right(second)) => init = f(init, second),
|
|
None => {}
|
|
}
|
|
self.inner.fold(init, f)
|
|
}
|
|
}
|
|
|
|
impl<I> ExactSizeIterator for ExactlyOneError<I> where I: ExactSizeIterator {}
|
|
|
|
impl<I> Display for ExactlyOneError<I>
|
|
where
|
|
I: Iterator,
|
|
{
|
|
fn fmt(&self, f: &mut Formatter) -> FmtResult {
|
|
let additional = self.additional_len();
|
|
if additional > 0 {
|
|
write!(f, "got at least 2 elements when exactly one was expected")
|
|
} else {
|
|
write!(f, "got zero elements when exactly one was expected")
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<I> Debug for ExactlyOneError<I>
|
|
where
|
|
I: Iterator + Debug,
|
|
I::Item: Debug,
|
|
{
|
|
fn fmt(&self, f: &mut Formatter) -> FmtResult {
|
|
let mut dbg = f.debug_struct("ExactlyOneError");
|
|
match &self.first_two {
|
|
Some(Either::Left([first, second])) => {
|
|
dbg.field("first", first).field("second", second);
|
|
}
|
|
Some(Either::Right(second)) => {
|
|
dbg.field("second", second);
|
|
}
|
|
None => {}
|
|
}
|
|
dbg.field("inner", &self.inner).finish()
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "use_std")]
|
|
impl<I> Error for ExactlyOneError<I>
|
|
where
|
|
I: Iterator + Debug,
|
|
I::Item: Debug,
|
|
{
|
|
}
|