Struct Hooks 

pub struct Hooks<'a> {
    pub copied: &'a mut dyn FnMut(u8),
    pub progress: &'a mut dyn FnMut(u64, u64),
    pub needed: &'a mut dyn FnMut(u64, u64),
    pub consumed: &'a mut dyn FnMut(u64, u64),
    pub settle: &'a mut dyn FnMut(&mut dyn Write) -> Result<()>,
}

What assemble_with reports while it writes.

Fields

copied: &'a mut dyn FnMut(u8)

Called once each data section (a kind of DICT_DATA, INDEX_DATA, QUAD_DATA, LABEL_DATA, TEXT_DATA or PYRAMID) is in the output: the input bytes it came from are not read again.

progress: &'a mut dyn FnMut(u64, u64)

(data bytes written so far, data bytes in all), after each write.

needed: &'a mut dyn FnMut(u64, u64)

(input offset, length) of every payload range the copy will read, announced once before the first byte is written.

consumed: &'a mut dyn FnMut(u64, u64)

(input offset, length) of a payload range now in the output, whatever order the ranges come in. Once every announced range of a spill file has been consumed, nothing reads that file again.

settle: &'a mut dyn FnMut(&mut dyn Write) -> Result<()>

Called with the output after every copied run and every finished data section, once consumed / copied may have made spill files ready to go. The implementation flushes out, makes the bytes durable, and only then deletes: a file must never be removed while its bytes are still in a buffer or an unsynced page.