Function encode_range 

pub fn encode_range(
    output: &LayoutOutput,
    first: usize,
    count: usize,
) -> Result<Vec<u8>, WireError>

Encodes count pages starting at first, version first. A range past the end of the book is clamped rather than refused: an edit that shortens the book while a page past its new end is still being asked for gets back whatever is left, not a panic.

first and the book’s page count travel as u32, the same as every other count on the wire; a book past four billion pages is not one this format is sized for.