Function data_regions 

pub fn data_regions(
    payloads: &[VirtioQueuePayload],
    writable: bool,
    skip_bytes: u64,
    data_len: u64,
) -> DataRegions<'_> 

Extract the data-carrying regions from a descriptor chain.

Returns an iterator that filters descriptors by direction (writable), skips skip_bytes (the request header for writes), and limits the total to data_len (which excludes the status byte for reads).