Method write_all_at

src/fs/file_io_ext.rs:196–208

Attempts to write an entire buffer starting from a given offset. This is similar to [`std::os::unix::fs::FileExt::write_all_at`], except it takes `self` by immutable reference since the entire side effect is I/O, and it's supported on non-Unix platforms including Windows. A write past the end of the file extends the file with zero bytes until the point where the write starts. Contrary to POSIX,

(&self, mut buf: &[u8], mut offset: u64)

    ///
    /// [`std::os::unix::fs::FileExt::write_all_at`]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#tymethod.write_all_at
    fn write_all_at(&self, mut buf: &[u8], mut offset: u64) -> io::Result<()> {
        while !buf.is_empty() {
            match self.write_at(buf, offset) {
                Ok(nwritten) => {
                    buf = &buf[nwritten..];
                    offset += nwritten as u64;
                }
                Err(ref e) if e.kind() == io::ErrorKind::Interrupted => (),
                Err(e) => return Err(e),
            }
        }
        Ok(())
    }

    /// Is to `write_vectored` what `write_at` is to `write`.
    fn write_vectored_at(&self, bufs: &[IoSlice], offset: u64) -> io::Result<usize> {