//! FUSE userspace library implementation
//!
//! This is an improved rewrite of the FUSE userspace library (lowlevel interface) to fully take
//! advantage of Rust's architecture. The only thing we rely on in the real libfuse are mount
//! and unmount calls which are needed to establish a fd to talk to the kernel driver.

#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]

use libc::{c_int, ENOSYS};
use mnt::mount_options::parse_options_from_args;
#[cfg(feature = "serializable")]
use serde::{Deserialize, Serialize};
use std::ffi::OsStr;
use std::io;
use std::path::Path;
#[cfg(feature = "abi-7-23")]
use std::time::Duration;
use std::time::SystemTime;
use std::{convert::AsRef, io::ErrorKind};

use crate::ll::fuse_abi::consts::*;
pub use crate::ll::fuse_abi::FUSE_ROOT_ID;
pub use crate::ll::{fuse_abi::consts, TimeOrNow};
use crate::mnt::mount_options::check_option_conflicts;
use crate::session::MAX_WRITE_SIZE;
#[cfg(feature = "abi-7-16")]
pub use ll::fuse_abi::fuse_forget_one;
pub use mnt::mount_options::MountOption;
#[cfg(target_os = "macos")]
pub use reply::ReplyXTimes;
pub use reply::ReplyXattr;
pub use reply::{Reply, ReplyAttr, ReplyData, ReplyEmpty, ReplyEntry, ReplyOpen};
pub use reply::{
    ReplyBmap, ReplyCreate, ReplyDirectory, ReplyDirectoryPlus, ReplyIoctl, ReplyLock, ReplyLseek,
    ReplyStatfs, ReplyWrite,
};
pub use request::Request;
pub use session::{BackgroundSession, Session};
#[cfg(feature = "abi-7-28")]
use std::cmp::max;
#[cfg(feature = "abi-7-13")]
use std::cmp::min;

mod channel;
mod ll;
mod mnt;
mod reply;
mod request;
mod session;

/// We generally support async reads
#[cfg(all(not(target_os = "macos"), not(feature = "abi-7-10")))]
const INIT_FLAGS: u32 = FUSE_ASYNC_READ;
#[cfg(all(not(target_os = "macos"), feature = "abi-7-10"))]
const INIT_FLAGS: u32 = FUSE_ASYNC_READ | FUSE_BIG_WRITES;
// TODO: Add FUSE_EXPORT_SUPPORT

/// On macOS, we additionally support case insensitiveness, volume renames and xtimes
/// TODO: we should eventually let the filesystem implementation decide which flags to set
#[cfg(target_os = "macos")]
const INIT_FLAGS: u32 = FUSE_ASYNC_READ | FUSE_CASE_INSENSITIVE | FUSE_VOL_RENAME | FUSE_XTIMES;
// TODO: Add FUSE_EXPORT_SUPPORT and FUSE_BIG_WRITES (requires ABI 7.10)

const fn default_init_flags(#[allow(unused_variables)] capabilities: u32) -> u32 {
    #[cfg(not(feature = "abi-7-28"))]
    {
        INIT_FLAGS
    }

    #[cfg(feature = "abi-7-28")]
    {
        let mut flags = INIT_FLAGS;
        if capabilities & FUSE_MAX_PAGES != 0 {
            flags |= FUSE_MAX_PAGES;
        }
        flags
    }
}

/// File types
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
#[cfg_attr(feature = "serializable", derive(Serialize, Deserialize))]
pub enum FileType {
    /// Named pipe (S_IFIFO)
    NamedPipe,
    /// Character device (S_IFCHR)
    CharDevice,
    /// Block device (S_IFBLK)
    BlockDevice,
    /// Directory (S_IFDIR)
    Directory,
    /// Regular file (S_IFREG)
    RegularFile,
    /// Symbolic link (S_IFLNK)
    Symlink,
    /// Unix domain socket (S_IFSOCK)
    Socket,
}

/// File attributes
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "serializable", derive(Serialize, Deserialize))]
pub struct FileAttr {
    /// Inode number
    pub ino: u64,
    /// Size in bytes
    pub size: u64,
    /// Size in blocks
    pub blocks: u64,
    /// Time of last access
    pub atime: SystemTime,
    /// Time of last modification
    pub mtime: SystemTime,
    /// Time of last change
    pub ctime: SystemTime,
    /// Time of creation (macOS only)
    pub crtime: SystemTime,
    /// Kind of file (directory, file, pipe, etc)
    pub kind: FileType,
    /// Permissions
    pub perm: u16,
    /// Number of hard links
    pub nlink: u32,
    /// User id
    pub uid: u32,
    /// Group id
    pub gid: u32,
    /// Rdev
    pub rdev: u32,
    /// Block size
    pub blksize: u32,
    /// Flags (macOS only, see chflags(2))
    pub flags: u32,
}

/// Configuration of the fuse kernel module connection
#[derive(Debug)]
pub struct KernelConfig {
    capabilities: u32,
    requested: u32,
    max_readahead: u32,
    max_max_readahead: u32,
    #[cfg(feature = "abi-7-13")]
    max_background: u16,
    #[cfg(feature = "abi-7-13")]
    congestion_threshold: Option<u16>,
    max_write: u32,
    #[cfg(feature = "abi-7-23")]
    time_gran: Duration,
}

impl KernelConfig {
    fn new(capabilities: u32, max_readahead: u32) -> Self {
        Self {
            capabilities,
            requested: default_init_flags(capabilities),
            max_readahead,
            max_max_readahead: max_readahead,
            #[cfg(feature = "abi-7-13")]
            max_background: 16,
            #[cfg(feature = "abi-7-13")]
            congestion_threshold: None,
            // use a max write size that fits into the session's buffer
            max_write: MAX_WRITE_SIZE as u32,
            // 1ns means nano-second granularity.
            #[cfg(feature = "abi-7-23")]
            time_gran: Duration::new(0, 1),
        }
    }

    /// Set the timestamp granularity
    ///
    /// Must be a power of 10 nanoseconds. i.e. 1s, 0.1s, 0.01s, 1ms, 0.1ms...etc
    ///
    /// On success returns the previous value. On error returns the nearest value which will succeed
    #[cfg(feature = "abi-7-23")]
    pub fn set_time_granularity(&mut self, value: Duration) -> Result<Duration, Duration> {
        if value.as_nanos() == 0 {
            return Err(Duration::new(0, 1));
        }
        if value.as_secs() > 1 || (value.as_secs() == 1 && value.subsec_nanos() > 0) {
            return Err(Duration::new(1, 0));
        }
        let mut power_of_10 = 1;
        while power_of_10 < value.as_nanos() {
            if value.as_nanos() < power_of_10 * 10 {
                // value must not be a power of ten, since power_of_10 < value < power_of_10 * 10
                return Err(Duration::new(0, power_of_10 as u32));
            }
            power_of_10 *= 10;
        }
        let previous = self.time_gran;
        self.time_gran = value;
        Ok(previous)
    }

    /// Set the maximum write size for a single request
    ///
    /// On success returns the previous value. On error returns the nearest value which will succeed
    pub fn set_max_write(&mut self, value: u32) -> Result<u32, u32> {
        if value == 0 {
            return Err(1);
        }
        if value > MAX_WRITE_SIZE as u32 {
            return Err(MAX_WRITE_SIZE as u32);
        }
        let previous = self.max_write;
        self.max_write = value;
        Ok(previous)
    }

    /// Set the maximum readahead size
    ///
    /// On success returns the previous value. On error returns the nearest value which will succeed
    pub fn set_max_readahead(&mut self, value: u32) -> Result<u32, u32> {
        if value == 0 {
            return Err(1);
        }
        if value > self.max_max_readahead {
            return Err(self.max_max_readahead);
        }
        let previous = self.max_readahead;
        self.max_readahead = value;
        Ok(previous)
    }

    /// Add a set of capabilities.
    ///
    /// On success returns Ok, else return bits of capabilities not supported when capabilities you provided are not all supported by kernel.
    pub fn add_capabilities(&mut self, capabilities_to_add: u32) -> Result<(), u32> {
        if capabilities_to_add & self.capabilities != capabilities_to_add {
            return Err(capabilities_to_add - (capabilities_to_add & self.capabilities));
        }
        self.requested |= capabilities_to_add;
        Ok(())
    }

    /// Set the maximum number of pending background requests. Such as readahead requests.
    ///
    /// On success returns the previous value. On error returns the nearest value which will succeed
    #[cfg(feature = "abi-7-13")]
    pub fn set_max_background(&mut self, value: u16) -> Result<u16, u16> {
        if value == 0 {
            return Err(1);
        }
        let previous = self.max_background;
        self.max_background = value;
        Ok(previous)
    }

    /// Set the threshold of background requests at which the kernel will consider the filesystem
    /// request queue congested. (it may then switch to sleeping instead of spin-waiting, for example)
    ///
    /// On success returns the previous value. On error returns the nearest value which will succeed
    #[cfg(feature = "abi-7-13")]
    pub fn set_congestion_threshold(&mut self, value: u16) -> Result<u16, u16> {
        if value == 0 {
            return Err(1);
        }
        let previous = self.congestion_threshold();
        self.congestion_threshold = Some(value);
        Ok(previous)
    }

    #[cfg(feature = "abi-7-13")]
    fn congestion_threshold(&self) -> u16 {
        match self.congestion_threshold {
            // Default to a threshold of 3/4 of the max background threads
            None => (self.max_background as u32 * 3 / 4) as u16,
            Some(value) => min(value, self.max_background),
        }
    }

    #[cfg(feature = "abi-7-28")]
    fn max_pages(&self) -> u16 {
        ((max(self.max_write, self.max_readahead) - 1) / page_size::get() as u32) as u16 + 1
    }
}

/// Filesystem trait.
///
/// This trait must be implemented to provide a userspace filesystem via FUSE.
/// These methods correspond to fuse_lowlevel_ops in libfuse. Reasonable default
/// implementations are provided here to get a mountable filesystem that does
/// nothing.
#[allow(clippy::too_many_arguments)]
pub trait Filesystem {
    /// Initialize filesystem.
    /// Called before any other filesystem method.
    /// The kernel module connection can be configured using the KernelConfig object
    fn init(&mut self, _req: &Request<'_>, _config: &mut KernelConfig) -> Result<(), c_int> {
        Ok(())
    }

    /// Clean up filesystem.
    /// Called on filesystem exit.
    fn destroy(&mut self) {}

    /// Look up a directory entry by name and get its attributes.
    fn lookup(&mut self, _req: &Request<'_>, _parent: u64, _name: &OsStr, reply: ReplyEntry) {
        reply.error(ENOSYS);
    }

    /// Forget about an inode.
    /// The nlookup parameter indicates the number of lookups previously performed on
    /// this inode. If the filesystem implements inode lifetimes, it is recommended that
    /// inodes acquire a single reference on each lookup, and lose nlookup references on
    /// each forget. The filesystem may ignore forget calls, if the inodes don't need to
    /// have a limited lifetime. On unmount it is not guaranteed, that all referenced
    /// inodes will receive a forget message.
    fn forget(&mut self, _req: &Request<'_>, _ino: u64, _nlookup: u64) {}

    /// Like forget, but take multiple forget requests at once for performance. The default
    /// implementation will fallback to forget.
    #[cfg(feature = "abi-7-16")]
    fn batch_forget(&mut self, req: &Request<'_>, nodes: &[fuse_forget_one]) {
        for node in nodes {
            self.forget(req, node.nodeid, node.nlookup);
        }
    }

    /// Get file attributes.
    fn getattr(&mut self, _req: &Request<'_>, _ino: u64, reply: ReplyAttr) {
        reply.error(ENOSYS);
    }

    /// Set file attributes.
    fn setattr(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _mode: Option<u32>,
        _uid: Option<u32>,
        _gid: Option<u32>,
        _size: Option<u64>,
        _atime: Option<TimeOrNow>,
        _mtime: Option<TimeOrNow>,
        _ctime: Option<SystemTime>,
        _fh: Option<u64>,
        _crtime: Option<SystemTime>,
        _chgtime: Option<SystemTime>,
        _bkuptime: Option<SystemTime>,
        _flags: Option<u32>,
        reply: ReplyAttr,
    ) {
        reply.error(ENOSYS);
    }

    /// Read symbolic link.
    fn readlink(&mut self, _req: &Request<'_>, _ino: u64, reply: ReplyData) {
        reply.error(ENOSYS);
    }

    /// Create file node.
    /// Create a regular file, character device, block device, fifo or socket node.
    fn mknod(
        &mut self,
        _req: &Request<'_>,
        _parent: u64,
        _name: &OsStr,
        _mode: u32,
        _umask: u32,
        _rdev: u32,
        reply: ReplyEntry,
    ) {
        reply.error(ENOSYS);
    }

    /// Create a directory.
    fn mkdir(
        &mut self,
        _req: &Request<'_>,
        _parent: u64,
        _name: &OsStr,
        _mode: u32,
        _umask: u32,
        reply: ReplyEntry,
    ) {
        reply.error(ENOSYS);
    }

    /// Remove a file.
    fn unlink(&mut self, _req: &Request<'_>, _parent: u64, _name: &OsStr, reply: ReplyEmpty) {
        reply.error(ENOSYS);
    }

    /// Remove a directory.
    fn rmdir(&mut self, _req: &Request<'_>, _parent: u64, _name: &OsStr, reply: ReplyEmpty) {
        reply.error(ENOSYS);
    }

    /// Create a symbolic link.
    fn symlink(
        &mut self,
        _req: &Request<'_>,
        _parent: u64,
        _name: &OsStr,
        _link: &Path,
        reply: ReplyEntry,
    ) {
        reply.error(ENOSYS);
    }

    /// Rename a file.
    fn rename(
        &mut self,
        _req: &Request<'_>,
        _parent: u64,
        _name: &OsStr,
        _newparent: u64,
        _newname: &OsStr,
        _flags: u32,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Create a hard link.
    fn link(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _newparent: u64,
        _newname: &OsStr,
        reply: ReplyEntry,
    ) {
        reply.error(ENOSYS);
    }

    /// Open a file.
    /// Open flags (with the exception of O_CREAT, O_EXCL, O_NOCTTY and O_TRUNC) are
    /// available in flags. Filesystem may store an arbitrary file handle (pointer, index,
    /// etc) in fh, and use this in other all other file operations (read, write, flush,
    /// release, fsync). Filesystem may also implement stateless file I/O and not store
    /// anything in fh. There are also some flags (direct_io, keep_cache) which the
    /// filesystem may set, to change the way the file is opened. See fuse_file_info
    /// structure in <fuse_common.h> for more details.
    fn open(&mut self, _req: &Request<'_>, _ino: u64, _flags: i32, reply: ReplyOpen) {
        reply.opened(0, 0);
    }

    /// Read data.
    /// Read should send exactly the number of bytes requested except on EOF or error,
    /// otherwise the rest of the data will be substituted with zeroes. An exception to
    /// this is when the file has been opened in 'direct_io' mode, in which case the
    /// return value of the read system call will reflect the return value of this
    /// operation. fh will contain the value set by the open method, or will be undefined
    /// if the open method didn't set any value.
    ///
    /// flags: these are the file flags, such as O_SYNC. Only supported with ABI >= 7.9
    /// lock_owner: only supported with ABI >= 7.9
    fn read(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _offset: i64,
        _size: u32,
        _flags: i32,
        _lock_owner: Option<u64>,
        reply: ReplyData,
    ) {
        reply.error(ENOSYS);
    }

    /// Write data.
    /// Write should return exactly the number of bytes requested except on error. An
    /// exception to this is when the file has been opened in 'direct_io' mode, in
    /// which case the return value of the write system call will reflect the return
    /// value of this operation. fh will contain the value set by the open method, or
    /// will be undefined if the open method didn't set any value.
    ///
    /// write_flags: will contain FUSE_WRITE_CACHE, if this write is from the page cache. If set,
    /// the pid, uid, gid, and fh may not match the value that would have been sent if write cachin
    /// is disabled
    /// flags: these are the file flags, such as O_SYNC. Only supported with ABI >= 7.9
    /// lock_owner: only supported with ABI >= 7.9
    fn write(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _offset: i64,
        _data: &[u8],
        _write_flags: u32,
        _flags: i32,
        _lock_owner: Option<u64>,
        reply: ReplyWrite,
    ) {
        reply.error(ENOSYS);
    }

    /// Flush method.
    /// This is called on each close() of the opened file. Since file descriptors can
    /// be duplicated (dup, dup2, fork), for one open call there may be many flush
    /// calls. Filesystems shouldn't assume that flush will always be called after some
    /// writes, or that if will be called at all. fh will contain the value set by the
    /// open method, or will be undefined if the open method didn't set any value.
    /// NOTE: the name of the method is misleading, since (unlike fsync) the filesystem
    /// is not forced to flush pending writes. One reason to flush data, is if the
    /// filesystem wants to return write errors. If the filesystem supports file locking
    /// operations (setlk, getlk) it should remove all locks belonging to 'lock_owner'.
    fn flush(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _lock_owner: u64,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Release an open file.
    /// Release is called when there are no more references to an open file: all file
    /// descriptors are closed and all memory mappings are unmapped. For every open
    /// call there will be exactly one release call. The filesystem may reply with an
    /// error, but error values are not returned to close() or munmap() which triggered
    /// the release. fh will contain the value set by the open method, or will be undefined
    /// if the open method didn't set any value. flags will contain the same flags as for
    /// open.
    fn release(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _flags: i32,
        _lock_owner: Option<u64>,
        _flush: bool,
        reply: ReplyEmpty,
    ) {
        reply.ok();
    }

    /// Synchronize file contents.
    /// If the datasync parameter is non-zero, then only the user data should be flushed,
    /// not the meta data.
    fn fsync(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _datasync: bool,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Open a directory.
    /// Filesystem may store an arbitrary file handle (pointer, index, etc) in fh, and
    /// use this in other all other directory stream operations (readdir, releasedir,
    /// fsyncdir). Filesystem may also implement stateless directory I/O and not store
    /// anything in fh, though that makes it impossible to implement standard conforming
    /// directory stream operations in case the contents of the directory can change
    /// between opendir and releasedir.
    fn opendir(&mut self, _req: &Request<'_>, _ino: u64, _flags: i32, reply: ReplyOpen) {
        reply.opened(0, 0);
    }

    /// Read directory.
    /// Send a buffer filled using buffer.fill(), with size not exceeding the
    /// requested size. Send an empty buffer on end of stream. fh will contain the
    /// value set by the opendir method, or will be undefined if the opendir method
    /// didn't set any value.
    fn readdir(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _offset: i64,
        reply: ReplyDirectory,
    ) {
        reply.error(ENOSYS);
    }

    /// Read directory.
    /// Send a buffer filled using buffer.fill(), with size not exceeding the
    /// requested size. Send an empty buffer on end of stream. fh will contain the
    /// value set by the opendir method, or will be undefined if the opendir method
    /// didn't set any value.
    fn readdirplus(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _offset: i64,
        reply: ReplyDirectoryPlus,
    ) {
        reply.error(ENOSYS);
    }

    /// Release an open directory.
    /// For every opendir call there will be exactly one releasedir call. fh will
    /// contain the value set by the opendir method, or will be undefined if the
    /// opendir method didn't set any value.
    fn releasedir(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _flags: i32,
        reply: ReplyEmpty,
    ) {
        reply.ok();
    }

    /// Synchronize directory contents.
    /// If the datasync parameter is set, then only the directory contents should
    /// be flushed, not the meta data. fh will contain the value set by the opendir
    /// method, or will be undefined if the opendir method didn't set any value.
    fn fsyncdir(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _datasync: bool,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Get file system statistics.
    fn statfs(&mut self, _req: &Request<'_>, _ino: u64, reply: ReplyStatfs) {
        reply.statfs(0, 0, 0, 0, 0, 512, 255, 0);
    }

    /// Set an extended attribute.
    fn setxattr(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _name: &OsStr,
        _value: &[u8],
        _flags: i32,
        _position: u32,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Get an extended attribute.
    /// If `size` is 0, the size of the value should be sent with `reply.size()`.
    /// If `size` is not 0, and the value fits, send it with `reply.data()`, or
    /// `reply.error(ERANGE)` if it doesn't.
    fn getxattr(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _name: &OsStr,
        _size: u32,
        reply: ReplyXattr,
    ) {
        reply.error(ENOSYS);
    }

    /// List extended attribute names.
    /// If `size` is 0, the size of the value should be sent with `reply.size()`.
    /// If `size` is not 0, and the value fits, send it with `reply.data()`, or
    /// `reply.error(ERANGE)` if it doesn't.
    fn listxattr(&mut self, _req: &Request<'_>, _ino: u64, _size: u32, reply: ReplyXattr) {
        reply.error(ENOSYS);
    }

    /// Remove an extended attribute.
    fn removexattr(&mut self, _req: &Request<'_>, _ino: u64, _name: &OsStr, reply: ReplyEmpty) {
        reply.error(ENOSYS);
    }

    /// Check file access permissions.
    /// This will be called for the access() system call. If the 'default_permissions'
    /// mount option is given, this method is not called. This method is not called
    /// under Linux kernel versions 2.4.x
    fn access(&mut self, _req: &Request<'_>, _ino: u64, _mask: i32, reply: ReplyEmpty) {
        reply.error(ENOSYS);
    }

    /// Create and open a file.
    /// If the file does not exist, first create it with the specified mode, and then
    /// open it. Open flags (with the exception of O_NOCTTY) are available in flags.
    /// Filesystem may store an arbitrary file handle (pointer, index, etc) in fh,
    /// and use this in other all other file operations (read, write, flush, release,
    /// fsync). There are also some flags (direct_io, keep_cache) which the
    /// filesystem may set, to change the way the file is opened. See fuse_file_info
    /// structure in <fuse_common.h> for more details. If this method is not
    /// implemented or under Linux kernel versions earlier than 2.6.15, the mknod()
    /// and open() methods will be called instead.
    fn create(
        &mut self,
        _req: &Request<'_>,
        _parent: u64,
        _name: &OsStr,
        _mode: u32,
        _umask: u32,
        _flags: i32,
        reply: ReplyCreate,
    ) {
        reply.error(ENOSYS);
    }

    /// Test for a POSIX file lock.
    fn getlk(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _lock_owner: u64,
        _start: u64,
        _end: u64,
        _typ: i32,
        _pid: u32,
        reply: ReplyLock,
    ) {
        reply.error(ENOSYS);
    }

    /// Acquire, modify or release a POSIX file lock.
    /// For POSIX threads (NPTL) there's a 1-1 relation between pid and owner, but
    /// otherwise this is not always the case.  For checking lock ownership,
    /// 'fi->owner' must be used. The l_pid field in 'struct flock' should only be
    /// used to fill in this field in getlk(). Note: if the locking methods are not
    /// implemented, the kernel will still allow file locking to work locally.
    /// Hence these are only interesting for network filesystems and similar.
    fn setlk(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _lock_owner: u64,
        _start: u64,
        _end: u64,
        _typ: i32,
        _pid: u32,
        _sleep: bool,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Map block index within file to block index within device.
    /// Note: This makes sense only for block device backed filesystems mounted
    /// with the 'blkdev' option
    fn bmap(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _blocksize: u32,
        _idx: u64,
        reply: ReplyBmap,
    ) {
        reply.error(ENOSYS);
    }

    /// control device
    fn ioctl(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _flags: u32,
        _cmd: u32,
        _in_data: &[u8],
        _out_size: u32,
        reply: ReplyIoctl,
    ) {
        reply.error(ENOSYS);
    }

    /// Preallocate or deallocate space to a file
    fn fallocate(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _offset: i64,
        _length: i64,
        _mode: i32,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// Reposition read/write file offset
    fn lseek(
        &mut self,
        _req: &Request<'_>,
        _ino: u64,
        _fh: u64,
        _offset: i64,
        _whence: i32,
        reply: ReplyLseek,
    ) {
        reply.error(ENOSYS);
    }

    /// Copy the specified range from the source inode to the destination inode
    fn copy_file_range(
        &mut self,
        _req: &Request<'_>,
        _ino_in: u64,
        _fh_in: u64,
        _offset_in: i64,
        _ino_out: u64,
        _fh_out: u64,
        _offset_out: i64,
        _len: u64,
        _flags: u32,
        reply: ReplyWrite,
    ) {
        reply.error(ENOSYS);
    }

    /// macOS only: Rename the volume. Set fuse_init_out.flags during init to
    /// FUSE_VOL_RENAME to enable
    #[cfg(target_os = "macos")]
    fn setvolname(&mut self, _req: &Request<'_>, _name: &OsStr, reply: ReplyEmpty) {
        reply.error(ENOSYS);
    }

    /// macOS only (undocumented)
    #[cfg(target_os = "macos")]
    fn exchange(
        &mut self,
        _req: &Request<'_>,
        _parent: u64,
        _name: &OsStr,
        _newparent: u64,
        _newname: &OsStr,
        _options: u64,
        reply: ReplyEmpty,
    ) {
        reply.error(ENOSYS);
    }

    /// macOS only: Query extended times (bkuptime and crtime). Set fuse_init_out.flags
    /// during init to FUSE_XTIMES to enable
    #[cfg(target_os = "macos")]
    fn getxtimes(&mut self, _req: &Request<'_>, _ino: u64, reply: ReplyXTimes) {
        reply.error(ENOSYS);
    }
}

/// Mount the given filesystem to the given mountpoint. This function will
/// not return until the filesystem is unmounted.
///
/// Note that you need to lead each option with a separate `"-o"` string. See
/// `examples/hello.rs`.
#[deprecated(note = "use mount2() instead")]
pub fn mount<FS: Filesystem, P: AsRef<Path>>(
    filesystem: FS,
    mountpoint: P,
    options: &[&OsStr],
) -> io::Result<()> {
    let options = parse_options_from_args(options)?;
    mount2(filesystem, mountpoint, options.as_ref())
}

/// Mount the given filesystem to the given mountpoint. This function will
/// not return until the filesystem is unmounted.
///
/// NOTE: This will eventually replace mount(), once the API is stable
pub fn mount2<FS: Filesystem, P: AsRef<Path>>(
    filesystem: FS,
    mountpoint: P,
    options: &[MountOption],
) -> io::Result<()> {
    check_option_conflicts(options)?;
    Session::new(filesystem, mountpoint.as_ref(), options).and_then(|mut se| se.run())
}

/// Mount the given filesystem to the given mountpoint. This function spawns
/// a background thread to handle filesystem operations while being mounted
/// and therefore returns immediately. The returned handle should be stored
/// to reference the mounted filesystem. If it's dropped, the filesystem will
/// be unmounted.
///
/// # Safety
///
/// This interface is inherently unsafe if the BackgroundSession is allowed to leak without being
/// dropped. See rust-lang/rust#24292 for more details.
pub fn spawn_mount<'a, FS: Filesystem + Send + 'static + 'a, P: AsRef<Path>>(
    filesystem: FS,
    mountpoint: P,
    options: &[&OsStr],
) -> io::Result<BackgroundSession> {
    let options: Option<Vec<_>> = options
        .iter()
        .map(|x| Some(MountOption::from_str(x.to_str()?)))
        .collect();
    let options = options.ok_or(ErrorKind::InvalidData)?;
    Session::new(filesystem, mountpoint.as_ref(), options.as_ref()).and_then(|se| se.spawn())
}