#[repr(transparent)]pub struct HandleOrNull(_);Expand description
FFI type for handles in return values or out parameters, where NULL is used
as a sentry value to indicate errors, such as in the return value of CreateThread. 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 HandleOrNull is to convert it into an
OwnedHandle using its TryFrom implementation; this conversion takes care of the check for
NULL. This ensures that such FFI calls cannot start using the handle without
checking for NULL first.
This type concerns any value other than NULL to be valid, including INVALID_HANDLE_VALUE.
This is because APIs that use NULL as their sentry value don’t treat INVALID_HANDLE_VALUE
as special.
If this holds a valid handle, it will close the handle on drop.
Trait Implementations
Constructs a new instance of Self from the given RawHandle returned
from a Windows API that uses null to indicate failure, such as
CreateThread.
Use HandleOrInvalid instead of HandleOrNull for APIs that
use INVALID_HANDLE_VALUE to indicate failure.
Safety
The resource pointed to by handle must be either open and otherwise
unowned, or null. Note that not all Windows APIs use null for errors;
see here for the full story.