Struct FileHandle 

pub struct FileHandle(pub u64);

A newtype for file handles

This corresponds to a single file description in a client program. These are generated by the filesystem implementation in replies to Open, OpenDir and Create requests. It’s used as a correlation id across Read, Write, FSync, IoCtl, Poll, FAllocate, ReadDir, FSyncDir, GetLk, SetLk, SetLkW, ReadDirPlus, Lseek and CopyFileRange requests.

A filesystem implementation may store arbitrary data as the FileHandle, as long as it fits into 64-bits and doesn’t need to change for over the lifetime of the FileHandle. Typically this might consist of an index into an array of FileHandles that the filesystem implementation maintains.

Filesystems may instead implement stateless file I/O and use 0 as the FileHandle - although this makes it impossible to correctly implement resumable ReadDir in the presence of mutable directories (see OpenDir).

Lifecycle

A FileHandle is owned by one or more file-descriptors (or memory mappings) in the client program. Multiple file descriptors can point to the same FileHandle, just as a single INode can have multiple FileHandles open at one time. Every time a single file-descriptor is closed a Flush request is made. This gives filesystem implementations an opportunity to return an error message from that close() call. After all the file-descriptors are closed that own a given FileHandle the Release/ReleaseDir request will be made. This is an opportunity for the filesystem implementation to free any internal per-FileHandle data structures it has allocated.

Tuple Fields

0: u64

Trait Implementations

impl Clone for FileHandle

fn clone(&self) -> FileHandle

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FileHandle

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for FileHandle

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl From<FileHandle> for u64

fn from(fh: FileHandle) -> Self

Converts to this type from the input type.

impl Hash for FileHandle

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for FileHandle

fn cmp(&self, other: &FileHandle) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for FileHandle

fn eq(&self, other: &FileHandle) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for FileHandle

fn partial_cmp(&self, other: &FileHandle) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for FileHandle

impl Eq for FileHandle

impl StructuralPartialEq for FileHandle