1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

use std::path::PathBuf;

use super::FileMmap;

const U32_SIZE: usize = std::mem::size_of::<u32>();

pub struct RowFragment {
    filemmap: FileMmap,
}
impl RowFragment {
    pub fn new(path: PathBuf) -> Self {
        let mut filemmap = FileMmap::new(path).unwrap();
        if filemmap.len() == 0 {
            filemmap.set_len(U32_SIZE as u64).unwrap();
        }
        Self { filemmap }
    }
    fn blank_count(&self) -> u64 {
        self.filemmap.len() / U32_SIZE as u64 - 1
    }
    pub fn insert_blank(&mut self, row: u32) -> u64 {
        self.filemmap.append(&row.to_ne_bytes()).unwrap()
    }
    pub fn pop(&mut self) -> Option<u32> {
        let count = self.blank_count();
        if count > 0 {
            let last = unsafe { *(self.filemmap.as_ptr() as *mut u32).offset(count as isize) };
            self.filemmap.set_len(count * U32_SIZE as u64).unwrap();
            Some(last)
        } else {
            None
        }
    }
    pub fn serial_increment(&mut self) -> u32 {
        let blank_list = unsafe { &mut *(self.filemmap.as_ptr() as *mut u32) };
        *blank_list += 1;
        *blank_list
    }
}