Method append

src/fs/file_io_ext.rs:527–558

(&self, buf: &[u8])

    }

    fn append(&self, buf: &[u8]) -> io::Result<usize> {
        use rustix::fs::{fcntl_getfl, fcntl_setfl, seek, OFlags, SeekFrom};
        use rustix::io::write;

        // On Linux, use `pwritev2`.
        #[cfg(any(target_os = "android", target_os = "linux"))]
        {
            use rustix::io::{pwritev2, Errno, ReadWriteFlags};

            let iovs = [IoSlice::new(buf)];
            match pwritev2(self, &iovs, 0, ReadWriteFlags::APPEND) {
                Err(Errno::NOSYS) | Err(Errno::NOTSUP) => {}
                otherwise => return Ok(otherwise?),
            }
        }

        // Otherwise use `F_SETFL` to switch the file description to append
        // mode, do the write, and switch back. This is not atomic with
        // respect to other users of the file description, but this is
        // possibility is documented in the trait.
        //
        // Optimization idea: some users don't care about the current position,
        // changing, so perhaps we could add a `append_relaxed` etc. API which
        // doesn't preserve positions.
        let old_flags = fcntl_getfl(self)?;
        let old_pos = tell(self)?;
        fcntl_setfl(self, old_flags | OFlags::APPEND)?;
        let result = write(self, buf);
        fcntl_setfl(self, old_flags).unwrap();
        seek(self, SeekFrom::Start(old_pos)).unwrap();
        Ok(result?)
    }

    fn append_vectored(&self, bufs: &[IoSlice]) -> io::Result<usize> {
        use rustix::fs::{fcntl_getfl, fcntl_setfl, seek, OFlags, SeekFrom};