pub struct HandleOrNull(/* private fields */);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 may hold any handle value that OwnedHandle may hold. As with OwnedHandle, when
it holds -1, that value is interpreted as a valid handle value, such as
the current process handle, and not INVALID_HANDLE_VALUE.
If this holds a non-null handle, it will close the handle on drop.
Implementations§
source§impl HandleOrNull
impl HandleOrNull
sourcepub unsafe fn from_raw_handle(handle: RawHandle) -> Self
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 null to indicate failure, such as
CreateThread.
Use HandleOrInvalid instead of HandleOrNull for APIs that
use INVALID_HANDLE_VALUE to indicate failure.
Safety
The passed handle value must either satisfy the safety requirements
of FromRawHandle::from_raw_handle, or be null. Note that not all
Windows APIs use null for errors; see here for the full story.