1.0.0[−][src]Struct tract_nnef::internal::tract_downcast_rs::__std::fs::File
A reference to an open file on the filesystem.
An instance of a File
can be read and/or written depending on what options
it was opened with. Files also implement Seek
to alter the logical cursor
that the file contains internally.
Files are automatically closed when they go out of scope. Errors detected
on closing are ignored by the implementation of Drop
. Use the method
sync_all
if these errors must be manually handled.
Examples
Creates a new file and write bytes to it (you can also use write()
):
use std::fs::File; use std::io::prelude::*; fn main() -> std::io::Result<()> { let mut file = File::create("foo.txt")?; file.write_all(b"Hello, world!")?; Ok(()) }
Read the contents of a file into a String
(you can also use read
):
use std::fs::File; use std::io::prelude::*; fn main() -> std::io::Result<()> { let mut file = File::open("foo.txt")?; let mut contents = String::new(); file.read_to_string(&mut contents)?; assert_eq!(contents, "Hello, world!"); Ok(()) }
It can be more efficient to read the contents of a file with a buffered
Read
er. This can be accomplished with BufReader<R>
:
use std::fs::File; use std::io::BufReader; use std::io::prelude::*; fn main() -> std::io::Result<()> { let file = File::open("foo.txt")?; let mut buf_reader = BufReader::new(file); let mut contents = String::new(); buf_reader.read_to_string(&mut contents)?; assert_eq!(contents, "Hello, world!"); Ok(()) }
Note that, although read and write methods require a &mut File
, because
of the interfaces for Read
and Write
, the holder of a &File
can
still modify the file, either through methods that take &File
or by
retrieving the underlying OS object and modifying the file that way.
Additionally, many operating systems allow concurrent modification of files
by different processes. Avoid assuming that holding a &File
means that the
file will not change.
Implementations
impl File
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pub fn open<P>(path: P) -> Result<File, Error> where
P: AsRef<Path>,
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P: AsRef<Path>,
Attempts to open a file in read-only mode.
See the OpenOptions::open
method for more details.
Errors
This function will return an error if path
does not already exist.
Other errors may also be returned according to OpenOptions::open
.
Examples
use std::fs::File; fn main() -> std::io::Result<()> { let mut f = File::open("foo.txt")?; Ok(()) }
pub fn create<P>(path: P) -> Result<File, Error> where
P: AsRef<Path>,
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P: AsRef<Path>,
Opens a file in write-only mode.
This function will create a file if it does not exist, and will truncate it if it does.
See the OpenOptions::open
function for more details.
Examples
use std::fs::File; fn main() -> std::io::Result<()> { let mut f = File::create("foo.txt")?; Ok(()) }
pub fn with_options() -> OpenOptions
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with_options
)Returns a new OpenOptions object.
This function returns a new OpenOptions object that you can use to
open or create a file with specific options if open()
or create()
are not appropriate.
It is equivalent to OpenOptions::new()
but allows you to write more
readable code. Instead of OpenOptions::new().read(true).open("foo.txt")
you can write File::with_options().read(true).open("foo.txt")
. This
also avoids the need to import OpenOptions
.
See the OpenOptions::new
function for more details.
Examples
#![feature(with_options)] use std::fs::File; fn main() -> std::io::Result<()> { let mut f = File::with_options().read(true).open("foo.txt")?; Ok(()) }
pub fn sync_all(&self) -> Result<(), Error>
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Attempts to sync all OS-internal metadata to disk.
This function will attempt to ensure that all in-memory data reaches the filesystem before returning.
This can be used to handle errors that would otherwise only be caught
when the File
is closed. Dropping a file will ignore errors in
synchronizing this in-memory data.
Examples
use std::fs::File; use std::io::prelude::*; fn main() -> std::io::Result<()> { let mut f = File::create("foo.txt")?; f.write_all(b"Hello, world!")?; f.sync_all()?; Ok(()) }
pub fn sync_data(&self) -> Result<(), Error>
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This function is similar to sync_all
, except that it may not
synchronize file metadata to the filesystem.
This is intended for use cases that must synchronize content, but don't need the metadata on disk. The goal of this method is to reduce disk operations.
Note that some platforms may simply implement this in terms of
sync_all
.
Examples
use std::fs::File; use std::io::prelude::*; fn main() -> std::io::Result<()> { let mut f = File::create("foo.txt")?; f.write_all(b"Hello, world!")?; f.sync_data()?; Ok(()) }
pub fn set_len(&self, size: u64) -> Result<(), Error>
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Truncates or extends the underlying file, updating the size of
this file to become size
.
If the size
is less than the current file's size, then the file will
be shrunk. If it is greater than the current file's size, then the file
will be extended to size
and have all of the intermediate data filled
in with 0s.
The file's cursor isn't changed. In particular, if the cursor was at the end and the file is shrunk using this operation, the cursor will now be past the end.
Errors
This function will return an error if the file is not opened for writing. Also, std::io::ErrorKind::InvalidInput will be returned if the desired length would cause an overflow due to the implementation specifics.
Examples
use std::fs::File; fn main() -> std::io::Result<()> { let mut f = File::create("foo.txt")?; f.set_len(10)?; Ok(()) }
Note that this method alters the content of the underlying file, even
though it takes &self
rather than &mut self
.
pub fn metadata(&self) -> Result<Metadata, Error>
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Queries metadata about the underlying file.
Examples
use std::fs::File; fn main() -> std::io::Result<()> { let mut f = File::open("foo.txt")?; let metadata = f.metadata()?; Ok(()) }
pub fn try_clone(&self) -> Result<File, Error>
1.9.0[src]
Creates a new File
instance that shares the same underlying file handle
as the existing File
instance. Reads, writes, and seeks will affect
both File
instances simultaneously.
Examples
Creates two handles for a file named foo.txt
:
use std::fs::File; fn main() -> std::io::Result<()> { let mut file = File::open("foo.txt")?; let file_copy = file.try_clone()?; Ok(()) }
Assuming there’s a file named foo.txt
with contents abcdef\n
, create
two handles, seek one of them, and read the remaining bytes from the
other handle:
use std::fs::File; use std::io::SeekFrom; use std::io::prelude::*; fn main() -> std::io::Result<()> { let mut file = File::open("foo.txt")?; let mut file_copy = file.try_clone()?; file.seek(SeekFrom::Start(3))?; let mut contents = vec![]; file_copy.read_to_end(&mut contents)?; assert_eq!(contents, b"def\n"); Ok(()) }
pub fn set_permissions(&self, perm: Permissions) -> Result<(), Error>
1.16.0[src]
Changes the permissions on the underlying file.
Platform-specific behavior
This function currently corresponds to the fchmod
function on Unix and
the SetFileInformationByHandle
function on Windows. Note that, this
may change in the future.
Errors
This function will return an error if the user lacks permission change attributes on the underlying file. It may also return an error in other os-specific unspecified cases.
Examples
fn main() -> std::io::Result<()> { use std::fs::File; let file = File::open("foo.txt")?; let mut perms = file.metadata()?.permissions(); perms.set_readonly(true); file.set_permissions(perms)?; Ok(()) }
Note that this method alters the permissions of the underlying file,
even though it takes &self
rather than &mut self
.
Trait Implementations
impl AsRawFd for File
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impl Debug for File
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impl FileExt for File
1.15.0[src]
fn read_at(&self, buf: &mut [u8], offset: u64) -> Result<usize, Error>
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fn write_at(&self, buf: &[u8], offset: u64) -> Result<usize, Error>
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fn read_exact_at(&self, buf: &mut [u8], offset: u64) -> Result<(), Error>
1.33.0[src]
fn write_all_at(&self, buf: &[u8], offset: u64) -> Result<(), Error>
1.33.0[src]
impl FileExt for File
fn get_xattr<N>(&self, name: N) -> Result<Option<Vec<u8>>, Error> where
N: AsRef<OsStr>,
N: AsRef<OsStr>,
fn set_xattr<N>(&self, name: N, value: &[u8]) -> Result<(), Error> where
N: AsRef<OsStr>,
N: AsRef<OsStr>,
fn remove_xattr<N>(&self, name: N) -> Result<(), Error> where
N: AsRef<OsStr>,
N: AsRef<OsStr>,
fn list_xattr(&self) -> Result<XAttrs, Error>
impl From<File> for Stdio
1.20.0[src]
fn from(file: File) -> Stdio
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Converts a File
into a Stdio
Examples
File
will be converted to Stdio
using Stdio::from
under the hood.
use std::fs::File; use std::process::Command; // With the `foo.txt` file containing `Hello, world!" let file = File::open("foo.txt").unwrap(); let reverse = Command::new("rev") .stdin(file) // Implicit File conversion into a Stdio .output() .expect("failed reverse command"); assert_eq!(reverse.stdout, b"!dlrow ,olleH");
impl FromRawFd for File
1.1.0[src]
unsafe fn from_raw_fd(fd: i32) -> Fileⓘ
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impl IntoRawFd for File
1.4.0[src]
fn into_raw_fd(self) -> i32
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impl Read for File
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fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>
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fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>
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fn is_read_vectored(&self) -> bool
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unsafe fn initializer(&self) -> Initializer
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fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>
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fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>
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fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>
1.6.0[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
fn bytes(self) -> Bytes<Self>ⓘ
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fn chain<R>(self, next: R) -> Chain<Self, R>ⓘ where
R: Read,
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R: Read,
fn take(self, limit: u64) -> Take<Self>ⓘ
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impl<'_> Read for &'_ File
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fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>
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fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>
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fn is_read_vectored(&self) -> bool
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unsafe fn initializer(&self) -> Initializer
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fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>
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fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>
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fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>
1.6.0[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
fn bytes(self) -> Bytes<Self>ⓘ
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fn chain<R>(self, next: R) -> Chain<Self, R>ⓘ where
R: Read,
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R: Read,
fn take(self, limit: u64) -> Take<Self>ⓘ
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impl<'_> Seek for &'_ File
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fn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>
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fn stream_len(&mut self) -> Result<u64, Error>
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fn stream_position(&mut self) -> Result<u64, Error>
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impl Seek for File
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fn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>
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fn stream_len(&mut self) -> Result<u64, Error>
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fn stream_position(&mut self) -> Result<u64, Error>
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impl Write for File
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fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
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fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>
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fn is_write_vectored(&self) -> bool
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fn flush(&mut self) -> Result<(), Error>
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fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
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fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>
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fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>
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fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
impl<'_> Write for &'_ File
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fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
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fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>
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fn is_write_vectored(&self) -> bool
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fn flush(&mut self) -> Result<(), Error>
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fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
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fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>
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fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>
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fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
Auto Trait Implementations
impl RefUnwindSafe for File
impl Send for File
impl Sync for File
impl Unpin for File
impl UnwindSafe for File
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow(&self) -> &TⓘNotable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
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Notable traits for &'_ mut W
impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;
impl<T> Downcast for T where
T: Any,
T: Any,
fn into_any(self: Box<T>) -> Box<dyn Any + 'static>ⓘNotable traits for Box<W>
impl<W> Write for Box<W> where
W: Write + ?Sized, impl<R> Read for Box<R> where
R: Read + ?Sized, impl<F> Future for Box<F> where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
Notable traits for Box<W>
impl<W> Write for Box<W> where
W: Write + ?Sized, impl<R> Read for Box<R> where
R: Read + ?Sized, impl<F> Future for Box<F> where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn as_any(&self) -> &(dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
impl<T> DowncastSync for T where
T: Send + Sync + Any,
T: Send + Sync + Any,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,