Function assert_ranges_disjoint 

fn assert_ranges_disjoint(ranges: &[(usize, usize)])

Available on crate feature pager and Unix only.

Asserts that no two ranges share any byte position. Both backends assume disjoint ranges: the file backend coalesces adjacent ranges into a single pread and writes into a contiguous slice of dst, and the swap backend likewise concatenates into dst per range. Overlapping ranges would duplicate bytes in dst silently, which is almost certainly not what the caller meant; reject upfront so misuse fails loud.