tokio/fs/
write.rs

1use crate::{fs::asyncify, util::as_ref::OwnedBuf};
2
3use std::{io, path::Path};
4
5/// Creates a future that will open a file for writing and write the entire
6/// contents of `contents` to it.
7///
8/// This is the async equivalent of [`std::fs::write`][std].
9///
10/// This operation is implemented by running the equivalent blocking operation
11/// on a separate thread pool using [`spawn_blocking`].
12///
13/// [`spawn_blocking`]: crate::task::spawn_blocking
14/// [std]: fn@std::fs::write
15///
16/// # Examples
17///
18/// ```no_run
19/// use tokio::fs;
20///
21/// # async fn dox() -> std::io::Result<()> {
22/// fs::write("foo.txt", b"Hello world!").await?;
23/// # Ok(())
24/// # }
25/// ```
26pub async fn write(path: impl AsRef<Path>, contents: impl AsRef<[u8]>) -> io::Result<()> {
27    let path = path.as_ref();
28    let contents = crate::util::as_ref::upgrade(contents);
29
30    #[cfg(all(
31        tokio_unstable,
32        feature = "io-uring",
33        feature = "rt",
34        feature = "fs",
35        target_os = "linux"
36    ))]
37    {
38        let handle = crate::runtime::Handle::current();
39        let driver_handle = handle.inner.driver().io();
40        if driver_handle.check_and_init()? {
41            return write_uring(path, contents).await;
42        }
43    }
44
45    write_spawn_blocking(path, contents).await
46}
47
48#[cfg(all(
49    tokio_unstable,
50    feature = "io-uring",
51    feature = "rt",
52    feature = "fs",
53    target_os = "linux"
54))]
55async fn write_uring(path: &Path, mut buf: OwnedBuf) -> io::Result<()> {
56    use crate::{fs::OpenOptions, runtime::driver::op::Op};
57    use std::os::fd::OwnedFd;
58
59    let file = OpenOptions::new()
60        .write(true)
61        .create(true)
62        .truncate(true)
63        .open(path)
64        .await?;
65
66    let mut fd: OwnedFd = file
67        .try_into_std()
68        .expect("unexpected in-flight operation detected")
69        .into();
70
71    let total: usize = buf.as_ref().len();
72    let mut buf_offset: usize = 0;
73    let mut file_offset: u64 = 0;
74    while buf_offset < total {
75        let (n, _buf, _fd) = Op::write_at(fd, buf, buf_offset, file_offset)?.await?;
76        if n == 0 {
77            return Err(io::ErrorKind::WriteZero.into());
78        }
79
80        buf = _buf;
81        fd = _fd;
82        buf_offset += n as usize;
83        file_offset += n as u64;
84    }
85
86    Ok(())
87}
88
89async fn write_spawn_blocking(path: &Path, contents: OwnedBuf) -> io::Result<()> {
90    let path = path.to_owned();
91    asyncify(move || std::fs::write(path, contents)).await
92}
tokio/fs/write.rs

tokio/fs/
write.rs
