Trait bytemuck::AnyBitPattern [−][src]
Expand description
Marker trait for “plain old data” types that are valid for any bit pattern.
The requirements for this is very similar to Pod,
except that it doesn’t require that the type contains no uninit (or padding) bytes.
This limits what you can do with a type of this kind, but also broadens the
included types to repr(C) structs that contain padding as well as unions. Notably, you can only cast
immutable references and owned values into AnyBitPattern types, not
mutable references.
Pod is a subset of AnyBitPattern, meaning that any T: Pod is also
AnyBitPattern but any T: AnyBitPattern is not necessarily Pod.
AnyBitPattern is a subset of Zeroable, meaning that any T: AnyBitPattern
is also Zeroable, but any T: Zeroable is not necessarily `AnyBitPattern
Derive
A #[derive(AnyBitPattern)] macro is provided under the derive feature flag which will
automatically validate the requirements of this trait and implement the
trait for you for both structs and enums. This is the recommended method for
implementing the trait, however it’s also possible to do manually. If you
implement it manually, you must carefully follow the below safety rules.
- *NOTE: even
C-style, fieldless enums are intentionally excluded from this trait, since it is unsound for an enum to have a discriminant value that is not one of its defined variants.
Safety
Similar to Pod except we disregard the rule about it must not contain uninit bytes.
Still, this is a quite strong guarantee about a type, so be careful when
implementing it manually.
- The type must be inhabited (eg: no Infallible).
- The type must be valid for any bit pattern of its backing memory.
- Structs need to have all fields also be
AnyBitPattern. - There’s probably more, don’t mess it up (I mean it).