Method new_iter

Create an iterator for the specified `file_number` (the corresponding file length must be exactly `file_size` bytes). The table referenced by returning Iterator will be released after the Iterator is dropped. Entry format: key: internal key value: value of user key

(
        &self,
        cmp: TC,
        options: ReadOptions,
        file_number: u64,
        file_size: u64,
    )