Function try_seek_using_offset_index

crates/commitlog/src/commitlog.rs:1009–1045

Try to advance `reader` to `offset` using the offset index. If successful, returns the offset index and the byte position of `reader`. `None` if the position of `reader` is unchanged.

(
    repo: &R,
    reader: &mut segment::Reader<R::SegmentReader>,
    offset: u64,
)

/// If successful, returns the offset index and the byte position of `reader`.
/// `None` if the position of `reader` is unchanged.
fn try_seek_using_offset_index<R: Repo>(
    repo: &R,
    reader: &mut segment::Reader<R::SegmentReader>,
    offset: u64,
) -> Option<(TxOffsetIndex, u64)> {
    let segment_offset = reader.min_tx_offset;
    let index = repo
        .get_offset_index(segment_offset)
        .inspect_err(|e| {
            if e.kind() == io::ErrorKind::NotFound {
                debug!("offset index does not exist segment={segment_offset}");
            } else {
                warn!(
                    "error opening offset index segment={segment_offset}: {e} {}",
                    source_chain(&e)
                );
            }
        })
        .ok()?;

    reader
        .seek_to_offset(&index, offset)
        .inspect_err(|e| match e {
            // Can happen if the segment is empty or small, so don't spam the logs.
            IndexError::KeyNotFound => {
                debug!("offset not found segment={segment_offset} offset={offset}");
            }
            e => {
                warn!(
                    "error reading index segment={segment_offset} offset={offset}: {e} {}",
                    source_chain(&e)
                );
            }
        })
        .ok()
        .map(|pos| (index, pos))
}

// `range_bounds_is_empty` https://github.com/rust-lang/rust/issues/137300
//