Struct linux_io::fd::File

#[repr(transparent)]
pub struct File { /* private fields */ }

An encapsulated Linux file descriptor.

The methods of File are largely just thin wrappers around Linux system calls that work with file descriptors. Aside from type conversions to make the API safer and more ergonomic there are no additional userspace abstractions such as buffering.

When the std crate feature is enabled, a File also implements the std:io traits Read, Write, and Seek.

Implementations

impl File

pub fn open(path: &CStr, options: OpenOptions<OpenWithoutMode>) -> Result<Self>

Open an existing file.

Use this function for OpenOptions that don’t require a mode. If you set the “create” option then you will need to use Self::open_with_mode instead, to specify the mode of the new file.

pub fn open_with_mode( path: &CStr, options: OpenOptions<OpenWithMode>, mode: mode_t ) -> Result<Self>

Open a file, creating it if necessary using the given file mode.

Use this function only for OpenOptions that require a mode. For most options you can use Self::open instead.

pub fn open_raw(path: &CStr, flags: int, mode: mode_t) -> Result<Self>

Open a file using the open system call.

This function exposes the raw flags and mode arguments from the underlying system call, which the caller must populate appropriately.

pub fn create_raw(path: &CStr, mode: mode_t) -> Result<Self>

Create a new file using the creat system call.

This function exposes the raw mode argument from the underlying system call, which the caller must populate appropriately.

pub fn socket(domain: sa_family_t, typ: sock_type, protocol: int) -> Result<Self>

pub unsafe fn from_raw_fd(fd: int) -> Self

Wrap an existing raw file descriptor into a File.

Safety:

• The given file descriptor must not belong to an active standard library file or any similar wrapping abstraction.
• The file descriptor must remain open and valid for the full lifetime of the File object.
• The same file descriptor must not be wrapped in instances of File, because the first one to be dropped will close the file descriptor.

pub fn duplicate(&self) -> Result<Self>

Creates a new file descriptor referring to the same underlying file description as self.

Note that the read/write position of a file is a property of its file description rather than its descriptor, and so modifying the position (and some other aspects) of the new file will also affect the original.

pub fn into_raw_fd(self) -> int

Consumes the file object and returns the underlying file descriptor without closing it.

pub fn close(self) -> Result<()>

Consumes the file object and closes the underlying file descriptor.

If close fails then the file descriptor is always leaked, because there is no way to recover it once consumed.

pub unsafe fn close_mut(&mut self) -> Result<()>

Closes the underlying file descriptor without consuming it.

Safety:

• Callers must pass the file to core::mem::forget immediately after calling this function to prevent the implicit close in the Drop implementation.
• Callers must not use the file object again after calling this method; file descriptor will either be dangling or will be referring to some other unrelated file.

pub fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Read some bytes from the file into the given buffer, returning the number of bytes that were read.

pub unsafe fn read_raw(&mut self, buf: *mut void, count: size_t) -> Result<size_t>

A thin wrapper around the raw read system call against this file’s file descriptor.

Use File::read as a safe alternative.

pub fn seek(&mut self, pos: impl Into<SeekFrom>) -> Result<u64>

Change the current read/write position of the file.

pub fn sync(&mut self) -> Result<()>

Tell the kernel to flush any in-memory buffers and caches for the file.

pub fn write(&mut self, buf: &[u8]) -> Result<usize>

Write bytes from the given buffer to the file, returning how many bytes were written.

pub unsafe fn write_raw( &mut self, buf: *const void, count: size_t ) -> Result<size_t>

A thin wrapper around the raw write system call against this file’s file descriptor.

Use File::write as a safe alternative.

pub fn fcntl<'a, Cmd: FcntlCmd<'a>>( &'a mut self, cmd: Cmd, arg: Cmd::ExtArg ) -> Result<Cmd::Result>

Safe wrapper for the fcntl system call.

The safety of this wrapper relies on being passed only correct implementations of fcntl::FcntlCmd, some of which are predefined as constants in the fcntl module.

The type of the argument depends on which cmd you choose.

pub unsafe fn fcntl_raw(&mut self, cmd: int, arg: impl AsRawV) -> Result<int>

Direct wrapper around the raw fcntl system call.

This system call is particularly unsafe because it interprets its last argument differently depending on the value of cmd. Self::fcntl provides a slightly safer abstraction around this operation.

pub fn bind(&mut self, addr: impl SockAddr) -> Result<()>

Bind an address to a socket.

pub unsafe fn bind_raw( &mut self, addr: *const void, addrlen: socklen_t ) -> Result<()>

Bind an address to a socket using a raw pointer.

pub fn connect(&mut self, addr: impl SockAddr) -> Result<()>

Initiate a connection on a socket.

pub unsafe fn connect_raw( &mut self, addr: *const void, addrlen: socklen_t ) -> Result<()>

Initiate a connection on a socket using a raw pointer.

pub fn listen(&mut self, backlog: int) -> Result<()>

Listen for incoming connections on this socket.

pub fn getsockopt<'a, O: GetSockOpt<'a>>(&self, opt: O) -> Result<O::Result>

Get a socket option for a file descriptor representing a socket.

The value for opt is typically a constant defined elsewhere in this crate, or possibly in another crate, which describes both the level and optname for the underlying call and the type of the result.

pub unsafe fn getsockopt_raw( &self, level: int, optname: int, optval: *mut void, optlen: *mut socklen_t ) -> Result<int>

Get a socket option for a file descriptor representing a socket using the raw arguments to the getsockopt system call.

pub fn setsockopt<'a, O: SetSockOpt<'a>>( &mut self, opt: O, arg: O::ExtArg ) -> Result<O::Result>

Set a socket option for a file descriptor representing a socket.

The value for opt is typically a constant defined elsewhere in this crate, or possibly in another crate, which describes both the level and optname for the underlying call and the type of the argument.

pub unsafe fn setsockopt_raw( &mut self, level: int, optname: int, optval: *const void, optlen: socklen_t ) -> Result<int>

Set a socket option for a file descriptor representing a socket using the raw arguments to the setsockopt system call.

Trait Implementations

impl Drop for File

fn drop(&mut self)

Attempts to close the file when it’s no longer in scope.

This implicit close ignores errors, which might cause data loss if the final commit of data to disk fails. Use File::close explicitly if you need to detect errors.

impl From<OwnedFd> for File

Available on crate feature std only.

fn from(value: OwnedFd) -> Self

Converts to this type from the input type.

impl FromFcntlResult for File

unsafe fn prepare_result(raw: int) -> Self

impl FromRawFd for File

Available on crate feature std only.

unsafe fn from_raw_fd(fd: RawFd) -> Self

Constructs a new instance of Self from the given raw file descriptor.

impl IntoRawFd for File

Available on crate feature std only.

fn into_raw_fd(self) -> RawFd

Consumes this object, returning the raw underlying file descriptor.

impl Read for File

Available on crate feature std only.

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8, Global>) -> Result<usize, Error>

Read all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Read all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Read the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Read the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Selfwhere Self: Sized,

Creates a “by reference” adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

impl Seek for File

Available on crate feature std only.

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

impl Write for File

File implements core::fmt::Write by passing UTF-8 encoded bytes directly to the write method.

fn write_str(&mut self, s: &str) -> Result

Writes a string slice into this writer, returning whether the write succeeded.

fn write_char(&mut self, c: char) -> Result<(), Error>

Writes a char into this writer, returning whether the write succeeded.

fn write_fmt(&mut self, args: Arguments<'_>) -> Result<(), Error>

Glue for usage of the write! macro with implementors of this trait.

impl Write for File

Available on crate feature std only.

fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Selfwhere Self: Sized,

Creates a “by reference” adapter for this instance of Write.