fn combine(curr: ElfRange, next: ElfRange) -> Result<(Option<PageRange>, Option<PageRange>, ElfRange)> {
    validate_order(&curr, &next)?;

    let curr_block = curr.memory;
    let curr_aligned_block = curr.memory.enclosing();

    let next_block = next.memory;
    let next_aligned_block = next.memory.enclosing();

    if curr_block.start_address() > next_block.start_address() {
        return Err(Error::InvalidArgument);
    }

    if curr_aligned_block.is_disjoint(next_aligned_block) {
        return Ok((Some(PageRange{flags:curr.flags, memory:curr_aligned_block}), None, ElfRange{file_range: 0..0, flags:next.flags, memory:next.memory}))
    }

    let intersection = curr_aligned_block.intersection(next_aligned_block);

    let mut curr_minus_next_range= None;

    if curr_aligned_block.ne(&intersection) {
        curr_minus_next_range = Some(PageRange{flags: curr.flags, memory: Block::<Page>::from_index(curr_aligned_block.start(), intersection.start())?});
    }

    if next.memory.end_address()? >= intersection.end_address()? {
        return Ok(
            (
                curr_minus_next_range,
                Some(PageRange{flags: combine_flags(curr.flags, next.flags), memory:intersection}),
                ElfRange{file_range: 0..0, flags: next.flags, memory: Block::new(intersection.end_address()?, next.memory.end_address()?)?}
            )
        )
    } else {
        return Ok(
            (
                curr_minus_next_range,
                None,
                ElfRange{file_range: 0..0, flags: combine_flags(curr.flags, next.flags), memory: Block::new(intersection.start_address(), next.memory.end_address()?)?}
            )
        )

    }
}