use std::{cmp::Ordering, collections::BTreeMap};/// A counter for items that are in sequence, to be able to put them back into original order later.pub type SequenceId = usize;/// An iterator which olds iterated items with a **sequential** ID starting at 0 long enough to dispense them in order.pub struct InOrderIter<T, I> { /// The iterator yielding the out-of-order elements we are to yield in order. pub inner: I, store: BTreeMap<SequenceId, T>, next_chunk: SequenceId, is_done: bool,}impl<T, E, I> From<I> for InOrderIter<T, I>where I: Iterator<Item = Result<(SequenceId, T), E>>,{ fn from(iter: I) -> Self { InOrderIter { inner: iter, store: Default::default(), next_chunk: 0, is_done: false, } }}impl<T, E, I> Iterator for InOrderIter<T, I>where I: Iterator<Item = Result<(SequenceId, T), E>>,{ type Item = Result<T, E>; fn next(&mut self) -> Option<Self::Item> { if self.is_done { return None; } 'find_next_in_sequence: loop { match self.inner.next() { Some(Ok((c, v))) => match c.cmp(&self.next_chunk) { Ordering::Equal => { self.next_chunk += 1; return Some(Ok(v)); } Ordering::Less => { unreachable!("in a correctly ordered sequence we can never see keys again, got {}", c) } Ordering::Greater => { let previous = self.store.insert(c, v); assert!( previous.is_none(), "Chunks are returned only once, input is an invalid sequence" ); if let Some(v) = self.store.remove(&self.next_chunk) { self.next_chunk += 1; return Some(Ok(v)); } continue 'find_next_in_sequence; } }, Some(Err(e)) => { self.is_done = true; self.store.clear(); return Some(Err(e)); } None => match self.store.remove(&self.next_chunk) { Some(v) => { self.next_chunk += 1; return Some(Ok(v)); } None => { debug_assert!( self.store.is_empty(), "When iteration is done we should not have stored items left" ); return None; } }, } } }}
use std::{cmp::Ordering, collections::BTreeMap};
/// A counter for items that are in sequence, to be able to put them back into original order later.
pub type SequenceId = usize;
/// An iterator which olds iterated items with a **sequential** ID starting at 0 long enough to dispense them in order.
pub struct InOrderIter<T, I> {
/// The iterator yielding the out-of-order elements we are to yield in order.
pub inner: I,
store: BTreeMap<SequenceId, T>,
next_chunk: SequenceId,
is_done: bool,
}
impl<T, E, I> From<I> for InOrderIter<T, I>
where
I: Iterator<Item = Result<(SequenceId, T), E>>,
{
fn from(iter: I) -> Self {
InOrderIter {
inner: iter,
store: Default::default(),
next_chunk: 0,
is_done: false,
}
}
}
impl<T, E, I> Iterator for InOrderIter<T, I>
where
I: Iterator<Item = Result<(SequenceId, T), E>>,
{
type Item = Result<T, E>;
fn next(&mut self) -> Option<Self::Item> {
if self.is_done {
return None;
}
'find_next_in_sequence: loop {
match self.inner.next() {
Some(Ok((c, v))) => match c.cmp(&self.next_chunk) {
Ordering::Equal => {
self.next_chunk += 1;
return Some(Ok(v));
}
Ordering::Less => {
unreachable!("in a correctly ordered sequence we can never see keys again, got {}", c)
}
Ordering::Greater => {
let previous = self.store.insert(c, v);
assert!(
previous.is_none(),
"Chunks are returned only once, input is an invalid sequence"
);
if let Some(v) = self.store.remove(&self.next_chunk) {
self.next_chunk += 1;
return Some(Ok(v));
}
continue 'find_next_in_sequence;
}
},
Some(Err(e)) => {
self.is_done = true;
self.store.clear();
return Some(Err(e));
}
None => match self.store.remove(&self.next_chunk) {
Some(v) => {
self.next_chunk += 1;
return Some(Ok(v));
}
None => {
debug_assert!(
self.store.is_empty(),
"When iteration is done we should not have stored items left"
);
return None;
}
},
}
}
}
}