[−][src]Struct reopen::Reopen
A Read
/Write
proxy that can reopen the underlying object.
It is constructed with a function that can open a new instance of the object. If it is signaled
to reopen it (though handle
), it drops the old instance and uses the
function to create a new one at the next IO operation.
Error handling
The reopening is performed lazily, on the first operation done to the object. Opening a new
instance can fail with an error. If this happens, the error is returned as part of the
operation being performed ‒ therefore, you can get an error like File not found
while
performing read
.
If an error happens, the operation is aborted. Next time an operation is performed, another attempt to open the object is made (which in turn can fail again).
Scheduling of a reopen
The implementation tries to ensure whole operations happen on the same FD. For example, even if
multiple read
calls need to be performed as part of
read_exact
, the Reopen
will check for reopening flags only once
before the whole operation and then will keep the same FD.
If this is not enough, the Reopen
can be locked to bundle multiple
operations without reopening.
Handling of ends
Certain operations make ordinary file descriptors „finished“ ‒ for example,
read_to_end
. Usually, further calls to any read operations would produce
EOF from then on.
While this reaches the end of the currently opened FD and further read operations would still
produce EOF, reopening the FD may lead to it being readable again. Therefore, reaching EOF is
not necessarily final for Reopen
.
Implementations
impl<FD> Reopen<FD>
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pub fn new(
constructor: Box<dyn Fn() -> Result<FD, Error> + Send>
) -> Result<Self, Error>
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constructor: Box<dyn Fn() -> Result<FD, Error> + Send>
) -> Result<Self, Error>
Creates a new instance.
pub fn with_handle(
handle: Handle,
constructor: Box<dyn Fn() -> Result<FD, Error> + Send>
) -> Result<Self, Error>
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handle: Handle,
constructor: Box<dyn Fn() -> Result<FD, Error> + Send>
) -> Result<Self, Error>
Creates a new instance from the given handle.
This might come useful if you want to create the handle beforehand with
Handle::stub
(eg. in
once_cell
).
Note that using the same handle for multiple Reopen
s will not work as expected (the first
one to be used resets the signal and the others don't reopen).
Examples
// Something that implements `Write`, for example. struct Writer; let handle = Handle::stub(); let reopen = Reopen::with_handle(handle.clone(), Box::new(|| Ok(Writer))); handle.reopen();
pub fn handle(&self) -> Handle
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Returns a handle to signal this Reopen
to perform the reopening.
pub fn lock(&mut self) -> Result<&mut FD, Error>
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Lock the Reopen
against reopening in the middle of operation.
In case of needing to perform multiple operations without reopening in the middle, it can be locked by this method. This provides access to the inner FD.
Errors
This can result in an error in case the FD needs to be reopened (or wasn't opened previously) and the reopening results in an error.
Examples
let mut writer = Reopen::new(Box::new(|| { // Vec::<u8> is an in-memory writer Ok(Vec::new()) }))?; let handle = writer.handle(); let mut lock = writer.lock()?; write!(&mut lock, "Hello ")?; // Request reopening. But as we locked, it won't happen until we are done with it. handle.reopen(); write!(&mut lock, "world")?; // See? Both writes are here now. assert_eq!(b"Hello world", &lock[..]); // But when we return to using the writer directly (and drop the lock by that), it gets // reopened and we get a whole new Vec to play with. write!(&mut writer, "Another message")?; assert_eq!(b"Another message", &writer.lock()?[..]);
Trait Implementations
impl<FD: Debug> Debug for Reopen<FD>
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impl<FD: Read> Read for Reopen<FD>
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pub fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>
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pub fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>
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pub fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>
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pub fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>
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pub fn read_vectored(
&mut self,
bufs: &mut [IoSliceMut<'_>]
) -> Result<usize, Error>
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&mut self,
bufs: &mut [IoSliceMut<'_>]
) -> Result<usize, Error>
pub fn is_read_vectored(&self) -> bool
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pub unsafe fn initializer(&self) -> Initializer
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pub fn by_ref(&mut self) -> &mut Self
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pub fn bytes(self) -> Bytes<Self>
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pub fn chain<R>(self, next: R) -> Chain<Self, R> where
R: Read,
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R: Read,
pub fn take(self, limit: u64) -> Take<Self>
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impl<FD: Write> Write for Reopen<FD>
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pub fn flush(&mut self) -> Result<(), Error>
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pub fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
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pub fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
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pub fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>
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pub fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>
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pub fn is_write_vectored(&self) -> bool
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pub fn write_all_vectored(
&mut self,
bufs: &mut [IoSlice<'_>]
) -> Result<(), Error>
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&mut self,
bufs: &mut [IoSlice<'_>]
) -> Result<(), Error>
pub fn by_ref(&mut self) -> &mut Self
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Auto Trait Implementations
impl<FD> !RefUnwindSafe for Reopen<FD>
impl<FD> Send for Reopen<FD> where
FD: Send,
FD: Send,
impl<FD> !Sync for Reopen<FD>
impl<FD> Unpin for Reopen<FD> where
FD: Unpin,
FD: Unpin,
impl<FD> !UnwindSafe for Reopen<FD>
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,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow_mut(&mut self) -> &mut T
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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.
pub 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>,