#[repr(transparent)]
pub struct HandleOrInvalid(_);
🔬 This is a nightly-only experimental API. (io_safety #87074)
This is supported 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 concerns any value other than INVALID_HANDLE_VALUE to be valid, including NULL. This is because APIs that use INVALID_HANDLE_VALUE as their sentry value may return NULL under windows_subsystem = "windows" or other situations where I/O devices are detached.

If this holds a valid handle, it will close the handle on drop.

Implementations

🔬 This is a nightly-only experimental API. (io_safety #87074)

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

Formats the value using the given formatter. Read more

The type returned in the event of a conversion error.

Performs the conversion.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.