Struct holochain_types::prelude::dependencies::holochain_integrity_types::prelude::dependencies::subtle::Choice

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pub struct Choice(_);
Expand description

The Choice struct represents a choice for use in conditional assignment.

It is a wrapper around a u8, which should have the value either 1 (true) or 0 (false).

The conversion from u8 to Choice passes the value through an optimization barrier, as a best-effort attempt to prevent the compiler from inferring that the Choice value is a boolean. This strategy is based on Tim Maclean’s work on rust-timing-shield, which attempts to provide a more comprehensive approach for preventing software side-channels in Rust code.

The Choice struct implements operators for AND, OR, XOR, and NOT, to allow combining Choice values. These operations do not short-circuit.

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impl Choice

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pub fn unwrap_u8(&self) -> u8

Unwrap the Choice wrapper to reveal the underlying u8.

Note

This function only exists as an escape hatch for the rare case where it’s not possible to use one of the subtle-provided trait impls.

To convert a Choice to a bool, use the From implementation instead.

Trait Implementations§

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impl BitAnd<Choice> for Choice

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type Output = Choice

The resulting type after applying the & operator.
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fn bitand(self, rhs: Choice) -> Choice

Performs the & operation. Read more
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impl BitAndAssign<Choice> for Choice

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fn bitand_assign(&mut self, rhs: Choice)

Performs the &= operation. Read more
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impl BitOr<Choice> for Choice

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type Output = Choice

The resulting type after applying the | operator.
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fn bitor(self, rhs: Choice) -> Choice

Performs the | operation. Read more
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impl BitOrAssign<Choice> for Choice

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fn bitor_assign(&mut self, rhs: Choice)

Performs the |= operation. Read more
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impl BitXor<Choice> for Choice

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type Output = Choice

The resulting type after applying the ^ operator.
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fn bitxor(self, rhs: Choice) -> Choice

Performs the ^ operation. Read more
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impl BitXorAssign<Choice> for Choice

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fn bitxor_assign(&mut self, rhs: Choice)

Performs the ^= operation. Read more
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impl Clone for Choice

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fn clone(&self) -> Choice

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl ConditionallySelectable for Choice

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fn conditional_select(a: &Choice, b: &Choice, choice: Choice) -> Choice

Select a or b according to choice. Read more
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fn conditional_assign(&mut self, other: &Self, choice: Choice)

Conditionally assign other to self, according to choice. Read more
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fn conditional_swap(a: &mut Self, b: &mut Self, choice: Choice)

Conditionally swap self and other if choice == 1; otherwise, reassign both unto themselves. Read more
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impl ConstantTimeEq for Choice

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fn ct_eq(&self, rhs: &Choice) -> Choice

Determine if two items are equal. Read more
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fn ct_ne(&self, other: &Self) -> Choice

Determine if two items are NOT equal. Read more
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impl Debug for Choice

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

Formats the value using the given formatter. Read more
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impl From<u8> for Choice

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fn from(input: u8) -> Choice

Converts to this type from the input type.
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impl Not for Choice

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type Output = Choice

The resulting type after applying the ! operator.
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fn not(self) -> Choice

Performs the unary ! operation. Read more
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impl Copy for Choice

Auto Trait Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> ArchivePointee for T

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type ArchivedMetadata = ()

The archived version of the pointer metadata for this type.
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fn pointer_metadata( _: &<T as ArchivePointee>::ArchivedMetadata ) -> <T as Pointee>::Metadata

Converts some archived metadata to the pointer metadata for itself.
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<F, W, T, D> Deserialize<With<T, W>, D> for Fwhere W: DeserializeWith<F, T, D>, D: Fallible + ?Sized, F: ?Sized,

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fn deserialize( &self, deserializer: &mut D ) -> Result<With<T, W>, <D as Fallible>::Error>

Deserializes using the given deserializer
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> FutureExt for T

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fn with_context(self, otel_cx: Context) -> WithContext<Self>

Attaches the provided Context to this type, returning a WithContext wrapper. Read more
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fn with_current_context(self) -> WithContext<Self>

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Pointable for T

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const ALIGN: usize = mem::align_of::<T>()

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> Pointee for T

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type Metadata = ()

The type for metadata in pointers and references to Self.
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impl<T> Same<T> for T

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type Output = T

Should always be Self
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impl<SS, SP> SupersetOf<SS> for SPwhere SS: SubsetOf<SP>,

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fn to_subset(&self) -> Option<SS>

The inverse inclusion map: attempts to construct self from the equivalent element of its superset. Read more
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fn is_in_subset(&self) -> bool

Checks if self is actually part of its subset T (and can be converted to it).
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fn to_subset_unchecked(&self) -> SS

Use with care! Same as self.to_subset but without any property checks. Always succeeds.
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fn from_subset(element: &SS) -> SP

The inclusion map: converts self to the equivalent element of its superset.
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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> Upcastable for Twhere T: Any + Send + Sync + 'static,

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fn upcast_any_ref(&self) -> &(dyn Any + 'static)

upcast ref
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fn upcast_any_mut(&mut self) -> &mut (dyn Any + 'static)

upcast mut ref
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fn upcast_any_box(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>

upcast boxed dyn
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impl<V, T> VZip<V> for Twhere V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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