[][src]Struct subtle::CtOption

pub struct CtOption<T> { /* fields omitted */ }

The CtOption<T> type represents an optional value similar to the Option<T> type but is intended for use in constant time APIs.

Any given CtOption<T> is either Some or None, but unlike Option<T> these variants are not exposed. The is_some() method is used to determine if the value is Some, and unwrap_or() and unwrap_or_else() methods are provided to access the underlying value. The value can also be obtained with unwrap() but this will panic if it is None.

Functions that are intended to be constant time may not produce valid results for all inputs, such as square root and inversion operations in finite field arithmetic. Returning an Option<T> from these functions makes it difficult for the caller to reason about the result in constant time, and returning an incorrect value burdens the caller and increases the chance of bugs.

Methods

impl<T> CtOption<T>[src]

pub fn new(value: T, is_some: Choice) -> CtOption<T>[src]

This method is used to construct a new CtOption<T> and takes a value of type T, and a Choice that determines whether the optional value should be Some or not. If is_some is false, the value will still be stored but its value is never exposed.

pub fn unwrap(self) -> T[src]

This returns the underlying value but panics if it is not Some.

pub fn unwrap_or(self, def: T) -> T where
    T: ConditionallySelectable
[src]

This returns the underlying value if it is Some or the provided value otherwise.

pub fn unwrap_or_else<F>(self, f: F) -> T where
    T: ConditionallySelectable,
    F: FnOnce() -> T, 
[src]

This returns the underlying value if it is Some or the value produced by the provided closure otherwise.

pub fn is_some(&self) -> Choice[src]

Returns a true Choice if this value is Some.

pub fn is_none(&self) -> Choice[src]

Returns a true Choice if this value is None.

pub fn map<U, F>(self, f: F) -> CtOption<U> where
    T: Default + ConditionallySelectable,
    F: FnOnce(T) -> U, 
[src]

Returns a None value if the option is None, otherwise returns a CtOption enclosing the value of the provided closure. The closure is given the enclosed value or, if the option is None, it is provided a dummy value computed using Default::default().

This operates in constant time, because the provided closure is always called.

pub fn and_then<U, F>(self, f: F) -> CtOption<U> where
    T: Default + ConditionallySelectable,
    F: FnOnce(T) -> CtOption<U>, 
[src]

Returns a None value if the option is None, otherwise returns the result of the provided closure. The closure is given the enclosed value or, if the option is None, it is provided a dummy value computed using Default::default().

This operates in constant time, because the provided closure is always called.

pub fn or_else<F>(self, f: F) -> CtOption<T> where
    T: ConditionallySelectable,
    F: FnOnce() -> CtOption<T>, 
[src]

Returns self if it contains a value, and otherwise returns the result of calling f. The provided function f is always called.

Trait Implementations

impl<T: Clone> Clone for CtOption<T>[src]

impl<T: ConditionallySelectable> ConditionallySelectable for CtOption<T>[src]

impl<T: ConstantTimeEq> ConstantTimeEq for CtOption<T>[src]

fn ct_eq(&self, rhs: &CtOption<T>) -> Choice[src]

Two CtOption<T>s are equal if they are both Some and their values are equal, or both None.

impl<T: Copy> Copy for CtOption<T>[src]

impl<T: Debug> Debug for CtOption<T>[src]

Auto Trait Implementations

impl<T> RefUnwindSafe for CtOption<T> where
    T: RefUnwindSafe

impl<T> Send for CtOption<T> where
    T: Send

impl<T> Sync for CtOption<T> where
    T: Sync

impl<T> Unpin for CtOption<T> where
    T: Unpin

impl<T> UnwindSafe for CtOption<T> where
    T: UnwindSafe

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = !

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

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

The type returned in the event of a conversion error.