Struct std::os::windows::io::HandleOrInvalid

#[repr(transparent)]
pub struct HandleOrInvalid(_);

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

This is supported on Windows only.

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.

Trait Implementations

impl Debug for HandleOrInvalid

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

Formats the value using the given formatter.

impl FromRawHandle for HandleOrInvalid

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 resource pointed to by handle must be either open and otherwise unowned, null, or equal to INVALID_HANDLE_VALUE (-1). Note that not all Windows APIs use INVALID_HANDLE_VALUE for errors; see here for the full story.

impl TryFrom<HandleOrInvalid> for OwnedHandle

type Error = ()

The type returned in the event of a conversion error.

fn try_from(handle_or_invalid: HandleOrInvalid) -> Result<Self, ()>

Performs the conversion.

impl Send for HandleOrInvalid

impl Sync for HandleOrInvalid