Function coalesce_runs 

pub fn coalesce_runs(
    sorted_missing_owned: &[u64],
    block_size: u64,
    max_coalesced_get_bytes: u64,
) -> Vec<Range<u64>>

Group sorted, deduplicated, owned missing block indices into maximal contiguous runs, splitting any run whose byte span would exceed max_coalesced_get_bytes at block boundaries. Each returned block-index range becomes one origin.get_range call.