fn unmark_range()

in neqo-transport/src/send_stream.rs [398:457]
47 lines of code
10 McCabe index (conditional complexity)

    fn unmark_range(&mut self, off: u64, len: usize) {
        if len == 0 {
            qdebug!("unmark 0-length range at {off}");
            return;
        }

        self.first_unmarked = None;
        let len = u64::try_from(len).expect("usize fits in u64");
        let end_off = off + len;

        let mut to_remove = SmallVec::<[_; 8]>::new();
        let mut to_add = None;

        // Walk backwards through possibly affected existing ranges
        for (cur_off, (cur_len, cur_state)) in self.used.range_mut(..off + len).rev() {
            // Maybe fixup range preceding the removed range
            if *cur_off < off {
                // Check for overlap
                if *cur_off + *cur_len > off {
                    if *cur_state == RangeState::Acked {
                        qdebug!(
                            "Attempted to unmark Acked range {cur_off}-{cur_len} with unmark_range {off}-{}",
                            off + len
                        );
                    } else {
                        *cur_len = off - cur_off;
                    }
                }
                break;
            }

            if *cur_state == RangeState::Acked {
                qdebug!(
                    "Attempted to unmark Acked range {cur_off}-{cur_len} with unmark_range {off}-{}",
                    off + len
                );
                continue;
            }

            // Add a new range for old subrange extending beyond
            // to-be-unmarked range
            let cur_end_off = cur_off + *cur_len;
            if cur_end_off > end_off {
                let new_cur_off = off + len;
                let new_cur_len = cur_end_off - end_off;
                assert_eq!(to_add, None);
                to_add = Some((new_cur_off, new_cur_len, *cur_state));
            }

            to_remove.push(*cur_off);
        }

        for remove_off in to_remove {
            self.used.remove(&remove_off);
        }

        if let Some((new_cur_off, new_cur_len, cur_state)) = to_add {
            self.used.insert(new_cur_off, (new_cur_len, cur_state));
        }
    }