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Implement InotifyReader for raw inotify event iteration (#1113)
* Implement InotifyReader for raw inotify event iteration Signed-off-by: Alex Saveau <[email protected]> * Add inotify test Signed-off-by: Alex Saveau <[email protected]> --------- Signed-off-by: Alex Saveau <[email protected]>
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‎src/backend/libc/fs/inotify.rs

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@@ -76,3 +76,49 @@ bitflags! {
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const _ = !0;
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}
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}
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bitflags! {
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/// `IN*` for use with [`InotifyReader`].
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///
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/// [`InotifyReader`]: crate::fs::inotify::InotifyReader
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#[repr(transparent)]
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#[derive(Default, Copy, Clone, Eq, PartialEq, Hash, Debug)]
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pub struct ReadFlags: u32 {
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/// `IN_ACCESS`
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const ACCESS = c::IN_ACCESS;
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/// `IN_ATTRIB`
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const ATTRIB = c::IN_ATTRIB;
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/// `IN_CLOSE_NOWRITE`
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const CLOSE_NOWRITE = c::IN_CLOSE_NOWRITE;
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/// `IN_CLOSE_WRITE`
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const CLOSE_WRITE = c::IN_CLOSE_WRITE;
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/// `IN_CREATE`
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const CREATE = c::IN_CREATE;
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/// `IN_DELETE`
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const DELETE = c::IN_DELETE;
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/// `IN_DELETE_SELF`
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const DELETE_SELF = c::IN_DELETE_SELF;
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/// `IN_MODIFY`
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const MODIFY = c::IN_MODIFY;
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/// `IN_MOVE_SELF`
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const MOVE_SELF = c::IN_MOVE_SELF;
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/// `IN_MOVED_FROM`
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const MOVED_FROM = c::IN_MOVED_FROM;
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/// `IN_MOVED_TO`
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const MOVED_TO = c::IN_MOVED_TO;
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/// `IN_OPEN`
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const OPEN = c::IN_OPEN;
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/// `IN_IGNORED`
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const IGNORED = c::IN_IGNORED;
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/// `IN_ISDIR`
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const ISDIR = c::IN_ISDIR;
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/// `IN_Q_OVERFLOW`
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const QUEUE_OVERFLOW = c::IN_Q_OVERFLOW;
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/// `IN_UNMOUNT`
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const UNMOUNT = c::IN_UNMOUNT;
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/// <https://docs.rs/bitflags/*/bitflags/#externally-defined-flags>
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const _ = !0;
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}
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}

‎src/backend/linux_raw/fs/inotify.rs

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@@ -76,3 +76,49 @@ bitflags! {
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const _ = !0;
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}
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}
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bitflags! {
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/// `IN*` for use with [`InotifyReader`].
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///
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/// [`InotifyReader`]: crate::fs::inotify::InotifyReader
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#[repr(transparent)]
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#[derive(Default, Copy, Clone, Eq, PartialEq, Hash, Debug)]
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pub struct ReadFlags: c::c_uint {
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/// `IN_ACCESS`
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const ACCESS = linux_raw_sys::general::IN_ACCESS;
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/// `IN_ATTRIB`
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const ATTRIB = linux_raw_sys::general::IN_ATTRIB;
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/// `IN_CLOSE_NOWRITE`
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const CLOSE_NOWRITE = linux_raw_sys::general::IN_CLOSE_NOWRITE;
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/// `IN_CLOSE_WRITE`
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const CLOSE_WRITE = linux_raw_sys::general::IN_CLOSE_WRITE;
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/// `IN_CREATE`
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const CREATE = linux_raw_sys::general::IN_CREATE;
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/// `IN_DELETE`
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const DELETE = linux_raw_sys::general::IN_DELETE;
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/// `IN_DELETE_SELF`
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const DELETE_SELF = linux_raw_sys::general::IN_DELETE_SELF;
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/// `IN_MODIFY`
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const MODIFY = linux_raw_sys::general::IN_MODIFY;
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/// `IN_MOVE_SELF`
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const MOVE_SELF = linux_raw_sys::general::IN_MOVE_SELF;
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/// `IN_MOVED_FROM`
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const MOVED_FROM = linux_raw_sys::general::IN_MOVED_FROM;
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/// `IN_MOVED_TO`
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const MOVED_TO = linux_raw_sys::general::IN_MOVED_TO;
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/// `IN_OPEN`
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const OPEN = linux_raw_sys::general::IN_OPEN;
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/// `IN_IGNORED`
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const IGNORED = linux_raw_sys::general::IN_IGNORED;
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/// `IN_ISDIR`
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const ISDIR = linux_raw_sys::general::IN_ISDIR;
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/// `IN_Q_OVERFLOW`
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const QUEUE_OVERFLOW = linux_raw_sys::general::IN_Q_OVERFLOW;
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/// `IN_UNMOUNT`
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const UNMOUNT = linux_raw_sys::general::IN_UNMOUNT;
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/// <https://docs.rs/bitflags/*/bitflags/#externally-defined-flags>
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const _ = !0;
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}
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}

‎src/fs/inotify.rs

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@@ -1,9 +1,13 @@
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//! inotify support for working with inotifies
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3-
pub use crate::backend::fs::inotify::{CreateFlags, WatchFlags};
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pub use crate::backend::fs::inotify::{CreateFlags, ReadFlags, WatchFlags};
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use crate::backend::fs::syscalls;
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use crate::fd::{AsFd, OwnedFd};
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use crate::ffi::CStr;
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use crate::io;
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use crate::io::{read_uninit, Errno};
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use core::mem::{align_of, size_of, MaybeUninit};
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use linux_raw_sys::general::inotify_event;
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/// `inotify_init1(flags)`—Creates a new inotify object.
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///
@@ -41,3 +45,118 @@ pub fn inotify_add_watch<P: crate::path::Arg>(
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pub fn inotify_remove_watch(inot: impl AsFd, wd: i32) -> io::Result<()> {
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syscalls::inotify_rm_watch(inot.as_fd(), wd)
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}
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/// An inotify event iterator implemented with the read syscall.
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///
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/// See the [`RawDir`] API for more details and usage examples as this API is
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/// based on it.
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///
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/// [`RawDir`]: crate::fs::raw_dir::RawDir
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pub struct InotifyReader<'buf, Fd: AsFd> {
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fd: Fd,
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buf: &'buf mut [MaybeUninit<u8>],
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initialized: usize,
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offset: usize,
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}
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impl<'buf, Fd: AsFd> InotifyReader<'buf, Fd> {
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/// Create a new iterator from the given file descriptor and buffer.
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pub fn new(fd: Fd, buf: &'buf mut [MaybeUninit<u8>]) -> Self {
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Self {
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fd,
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buf: {
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let offset = buf.as_ptr().align_offset(align_of::<inotify_event>());
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if offset < buf.len() {
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&mut buf[offset..]
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} else {
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&mut []
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}
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},
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initialized: 0,
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offset: 0,
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}
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}
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}
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/// An inotify event.
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#[derive(Debug)]
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pub struct InotifyEvent<'a> {
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wd: i32,
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events: ReadFlags,
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cookie: u32,
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file_name: Option<&'a CStr>,
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}
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impl<'a> InotifyEvent<'a> {
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/// Returns the watch for which this event occurs.
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#[inline]
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pub fn wd(&self) -> i32 {
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self.wd
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}
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/// Returns a description of the events.
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#[inline]
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#[doc(alias = "mask")]
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pub fn events(&self) -> ReadFlags {
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self.events
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}
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/// Returns the unique cookie associating related events.
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#[inline]
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pub fn cookie(&self) -> u32 {
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self.cookie
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}
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/// Returns the file name of this event, if any.
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#[inline]
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pub fn file_name(&self) -> Option<&CStr> {
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self.file_name
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}
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}
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impl<'buf, Fd: AsFd> InotifyReader<'buf, Fd> {
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/// Read the next inotify event.
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#[allow(unsafe_code)]
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pub fn next(&mut self) -> io::Result<InotifyEvent> {
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if self.is_buffer_empty() {
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match read_uninit(self.fd.as_fd(), self.buf).map(|(init, _)| init.len()) {
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Ok(0) => return Err(Errno::INVAL),
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Ok(bytes_read) => {
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self.initialized = bytes_read;
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self.offset = 0;
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}
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Err(e) => return Err(e),
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}
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}
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let ptr = self.buf[self.offset..].as_ptr();
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// SAFETY:
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// - This data is initialized by the check above.
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// - Assumption: the kernel will not give us partial structs.
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// - Assumption: the kernel uses proper alignment between structs.
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// - The starting pointer is aligned (performed in RawDir::new)
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let event = unsafe { &*ptr.cast::<inotify_event>() };
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self.offset += size_of::<inotify_event>() + usize::try_from(event.len).unwrap();
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Ok(InotifyEvent {
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wd: event.wd,
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events: ReadFlags::from_bits_retain(event.mask),
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cookie: event.cookie,
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file_name: if event.len > 0 {
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// SAFETY: The kernel guarantees a NUL-terminated string.
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Some(unsafe { CStr::from_ptr(event.name.as_ptr().cast()) })
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} else {
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None
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},
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})
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}
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/// Returns true if the internal buffer is empty and will be refilled when
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/// calling [`next`]. This is useful to avoid further blocking reads.
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///
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/// [`next`]: Self::next
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pub fn is_buffer_empty(&self) -> bool {
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self.offset >= self.initialized
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}
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}

‎tests/fs/inotify.rs

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@@ -0,0 +1,109 @@
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use rustix::fs::inotify::{
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inotify_add_watch, inotify_init, CreateFlags, InotifyReader, WatchFlags,
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};
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use rustix::io::Errno;
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use std::fmt::Write;
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use std::fs::{create_dir_all, remove_file, rename, File};
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use std::mem::MaybeUninit;
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#[test]
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fn test_inotify_iter() {
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let inotify = inotify_init(CreateFlags::NONBLOCK).unwrap();
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create_dir_all("/tmp/.rustix-inotify-test").unwrap();
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inotify_add_watch(
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&inotify,
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"/tmp/.rustix-inotify-test",
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WatchFlags::ALL_EVENTS,
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)
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.unwrap();
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File::create("/tmp/.rustix-inotify-test/foo").unwrap();
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rename(
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"/tmp/.rustix-inotify-test/foo",
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"/tmp/.rustix-inotify-test/bar",
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)
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.unwrap();
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remove_file("/tmp/.rustix-inotify-test/bar").unwrap();
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let mut output = String::new();
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let mut cookie = 0;
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let mut buf = [MaybeUninit::uninit(); 512];
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let mut iter = InotifyReader::new(inotify, &mut buf);
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loop {
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let e = match iter.next() {
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Err(Errno::WOULDBLOCK) => break,
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r => r.unwrap(),
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};
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writeln!(output, "{e:#?}").unwrap();
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if e.cookie() != 0 {
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cookie = e.cookie();
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}
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}
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let expected = format!(
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r#"InotifyEvent {{
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wd: 1,
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events: ReadFlags(
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CREATE,
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),
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cookie: 0,
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file_name: Some(
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"foo",
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),
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}}
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InotifyEvent {{
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wd: 1,
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events: ReadFlags(
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OPEN,
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),
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cookie: 0,
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file_name: Some(
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"foo",
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),
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}}
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InotifyEvent {{
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wd: 1,
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events: ReadFlags(
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CLOSE_WRITE,
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),
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cookie: 0,
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file_name: Some(
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"foo",
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),
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}}
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InotifyEvent {{
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wd: 1,
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events: ReadFlags(
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MOVED_FROM,
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),
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cookie: {cookie},
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file_name: Some(
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"foo",
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),
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}}
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InotifyEvent {{
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wd: 1,
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events: ReadFlags(
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MOVED_TO,
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),
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cookie: {cookie},
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file_name: Some(
93+
"bar",
94+
),
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}}
96+
InotifyEvent {{
97+
wd: 1,
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events: ReadFlags(
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DELETE,
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),
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cookie: 0,
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file_name: Some(
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"bar",
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),
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}}
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"#
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);
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assert_eq!(expected, output);
109+
}

‎tests/fs/main.rs

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@@ -20,6 +20,8 @@ mod file;
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#[cfg(not(target_os = "wasi"))]
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mod flock;
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mod futimens;
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#[cfg(linux_kernel)]
24+
mod inotify;
2325
mod invalid_offset;
2426
#[cfg(not(target_os = "redox"))]
2527
mod ioctl;

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