# Struct HandleOrInvalid

1.63.0 · Source

    pub struct HandleOrInvalid(/* private fields */);

Available on Windows only.
Expand description

FFI type for handles in return values or out parameters, where `INVALID_HANDLE_VALUE` is used as a sentry value to indicate errors, such as in the return value of `CreateFileW`. This uses `repr(transparent)` and has the representation of a host handle, so that it can be used in such FFI declarations.

The only thing you can usefully do with a `HandleOrInvalid` is to convert it into an `OwnedHandle` using its `TryFrom` implementation; this conversion takes care of the check for `INVALID_HANDLE_VALUE`. This ensures that such FFI calls cannot start using the handle without checking for `INVALID_HANDLE_VALUE` first.

This type may hold any handle value that `OwnedHandle` may hold, except that when it holds `-1`, that value is interpreted to mean `INVALID_HANDLE_VALUE`.

If holds a handle other than `INVALID_HANDLE_VALUE`, it will close the handle on drop.

## Implementations§

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### impl HandleOrInvalid

1.63.0 · Source

#### pub unsafe fn from_raw_handle(handle: RawHandle) -> Self

Constructs a new instance of `Self` from the given `RawHandle` returned from a Windows API that uses `INVALID_HANDLE_VALUE` to indicate failure, such as `CreateFileW`.

Use `HandleOrNull` instead of `HandleOrInvalid` for APIs that use null to indicate failure.

##### §Safety

The passed `handle` value must either satisfy the safety requirements of `FromRawHandle::from_raw_handle`, or be `INVALID_HANDLE_VALUE` (-1). Note that not all Windows APIs use `INVALID_HANDLE_VALUE` for errors; see here for the full story.

## Trait Implementations§

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### impl Debug for HandleOrInvalid

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

Formats the value using the given formatter. Read more
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### impl Drop for HandleOrInvalid

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#### fn drop(&mut self)

Executes the destructor for this type. Read more
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### impl TryFrom<HandleOrInvalid> for OwnedHandle

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#### type Error = InvalidHandleError

The type returned in the event of a conversion error.
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#### fn try_from( handle_or_invalid: HandleOrInvalid, ) -> Result<Self, InvalidHandleError>

Performs the conversion.
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### impl Send for HandleOrInvalid

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### impl Sync for HandleOrInvalid

## Auto Trait Implementations§

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### impl Freeze for HandleOrInvalid

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### impl RefUnwindSafe for HandleOrInvalid

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### impl Unpin for HandleOrInvalid

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### impl UnwindSafe for HandleOrInvalid

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.