fuser 0.17.0

Filesystem in Userspace (FUSE) for Rust
Documentation 
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use std::ffi::CString;
use std::fs::File;
use std::io;
use std::os::unix::prelude::FromRawFd;
use std::os::unix::prelude::OsStrExt;
use std::path::Path;
use std::sync::Arc;

use crate::SessionACL;
use crate::dev_fuse::DevFuse;
use crate::mnt::MountOption;
use crate::mnt::fuse2_sys::*;
use crate::mnt::with_fuse_args;

/// Ensures that an os error is never 0/Success
fn ensure_last_os_error() -> io::Error {
    let err = io::Error::last_os_error();
    match err.raw_os_error() {
        Some(0) => io::Error::new(io::ErrorKind::Other, "Unspecified Error"),
        _ => err,
    }
}

#[derive(Debug)]
pub(crate) struct MountImpl {
    mountpoint: CString,
}
impl MountImpl {
    pub(crate) fn new(
        mountpoint: &Path,
        options: &[MountOption],
        acl: SessionACL,
    ) -> io::Result<(Arc<DevFuse>, MountImpl)> {
        let mountpoint = CString::new(mountpoint.as_os_str().as_bytes()).unwrap();
        with_fuse_args(options, acl, |args| {
            let fd = unsafe { fuse_mount_compat25(mountpoint.as_ptr(), args) };
            if fd < 0 {
                Err(ensure_last_os_error())
            } else {
                let file = unsafe { File::from_raw_fd(fd) };
                Ok((Arc::new(DevFuse(file)), MountImpl { mountpoint }))
            }
        })
    }

    pub(crate) fn umount_impl(&mut self) -> io::Result<()> {
        // fuse_unmount_compat22 unfortunately doesn't return a status. Additionally,
        // it attempts to call realpath, which in turn calls into the filesystem. So
        // if the filesystem returns an error, the unmount does not take place, with
        // no indication of the error available to the caller. So we call unmount
        // directly, which is what osxfuse does anyway, since we already converted
        // to the real path when we first mounted.
        if let Err(err) = crate::mnt::libc_umount(&self.mountpoint) {
            // Linux always returns EPERM for non-root users.  We have to let the
            // library go through the setuid-root "fusermount -u" to unmount.
            if err == nix::errno::Errno::EPERM {
                #[cfg(not(any(
                    target_os = "macos",
                    target_os = "freebsd",
                    target_os = "dragonfly",
                    target_os = "openbsd",
                    target_os = "netbsd"
                )))]
                unsafe {
                    fuse_unmount_compat22(self.mountpoint.as_ptr());
                    return Ok(());
                }
            }
            return Err(err.into());
        }
        Ok(())
    }
}