virtual_fs/
zero_file.rs

1//! Used for /dev/zero - infinitely returns zero
2//! which is useful for commands like `dd if=/dev/zero of=bigfile.img size=1G`
3
4use std::{
5    io::{self, IoSlice, SeekFrom},
6    iter,
7    pin::Pin,
8    task::{Context, Poll},
9};
10
11use tokio::io::{AsyncRead, AsyncSeek, AsyncWrite};
12
13use crate::VirtualFile;
14
15#[derive(Debug, Default)]
16pub struct ZeroFile {}
17
18impl AsyncSeek for ZeroFile {
19    fn start_seek(self: Pin<&mut Self>, _position: SeekFrom) -> io::Result<()> {
20        Ok(())
21    }
22    fn poll_complete(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<u64>> {
23        Poll::Ready(Ok(0))
24    }
25}
26
27impl AsyncWrite for ZeroFile {
28    fn poll_write(
29        self: Pin<&mut Self>,
30        _cx: &mut Context<'_>,
31        buf: &[u8],
32    ) -> Poll<io::Result<usize>> {
33        Poll::Ready(Ok(buf.len()))
34    }
35    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
36        Poll::Ready(Ok(()))
37    }
38    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
39        Poll::Ready(Ok(()))
40    }
41    fn poll_write_vectored(
42        self: Pin<&mut Self>,
43        _cx: &mut Context<'_>,
44        bufs: &[IoSlice<'_>],
45    ) -> Poll<io::Result<usize>> {
46        Poll::Ready(Ok(bufs.len()))
47    }
48    fn is_write_vectored(&self) -> bool {
49        false
50    }
51}
52
53impl AsyncRead for ZeroFile {
54    fn poll_read(
55        self: Pin<&mut Self>,
56        _cx: &mut Context<'_>,
57        buf: &mut tokio::io::ReadBuf<'_>,
58    ) -> Poll<io::Result<()>> {
59        let zeros: Vec<u8> = iter::repeat_n(0, buf.remaining()).collect();
60        buf.put_slice(&zeros[..]);
61        Poll::Ready(Ok(()))
62    }
63}
64
65impl VirtualFile for ZeroFile {
66    fn last_accessed(&self) -> u64 {
67        0
68    }
69    fn last_modified(&self) -> u64 {
70        0
71    }
72    fn created_time(&self) -> u64 {
73        0
74    }
75    fn size(&self) -> u64 {
76        0
77    }
78    fn set_len(&mut self, _new_size: u64) -> crate::Result<()> {
79        Ok(())
80    }
81    fn unlink(&mut self) -> crate::Result<()> {
82        Ok(())
83    }
84    fn poll_read_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
85        Poll::Ready(Ok(0))
86    }
87    fn poll_write_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
88        Poll::Ready(Ok(0))
89    }
90}
virtual_fs/zero_file.rs

virtual_fs/
zero_file.rs
