HandleOrNull in std::os::windows::io - Rust (original) (raw)
Struct HandleOrNull
1.63.0 · Source
pub struct HandleOrNull(/* private fields */);Available on Windows only.
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 usesrepr(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 anOwnedHandle using its TryFrom implementation; this conversion takes care of the check forNULL. 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 asthe current process handle, and not INVALID_HANDLE_VALUE.
If this holds a non-null handle, it will close the handle on drop.
1.63.0 · Source
Constructs a new instance of Self from the given RawHandle returned from a Windows API that uses null to indicate failure, such asCreateThread.
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.