pub struct Resource<P> { /* private fields */ }Expand description
Interface for PCM / Resource Algebra ghost state.
RA-based ghost state is a well-established theory that is especially useful for verifying concurrent code. An introduction to the concept can be found in Iris: Monoids and Invariants as an Orthogonal Basis for Concurrent Reasoning or Iris from the ground up.
To embed the concept into Verus, we:
- Use a trait,
PCM, to embed the well-formedness laws of a resource algebra - use a “tracked ghost” object,
Resource<P>(this page) to represent ownership of a resource.
Most operations are fairly standard, just “translated” from the usual CSL presentation into Verus.
allocto allocate a resource.jointo combine two resources viaP::op, andsplit, its inverse.validateto assert the validity of any held resource.updateorupdate_nondeterministicto perform a frame-preserving update.
The interface also includes a nontrivial extension for working with shared references to resources.
Shared resources do not compose in a “separating” way via P::op, but rather, in a “potentially overlapping” way (join_shared). Shared resources can also be used to “help” perform frame-preserving updates, as long as they themselves do not change (update_with_shared).
§Examples
See:
- Any of the examples in this directory
- The source code for the fractional resource library
§See also
The “storage protocol” formalism is an even more significant extension with additional capabilities for interacting with shared resources.
VerusSync provides a higher-level “swiss army knife” for building useful ghost resources.
Implementations§
Source§impl<P: PCM> Resource<P>
impl<P: PCM> Resource<P>
Sourcepub proof fn alloc(value: P) -> tracked out : Self
pub proof fn alloc(value: P) -> tracked out : Self
value.valid(),out.value() == value,Sourcepub proof fn join(tracked self, tracked other: Self) -> tracked out : Self
pub proof fn join(tracked self, tracked other: Self) -> tracked out : Self
self.loc() == other.loc(),out.loc() == self.loc(),out.value() == P::op(self.value(), other.value()),Sourcepub proof fn split(tracked self, left: P, right: P) -> tracked out : (Self, Self)
pub proof fn split(tracked self, left: P, right: P) -> tracked out : (Self, Self)
self.value() == P::op(left, right),out.0.loc() == self.loc(),out.1.loc() == self.loc(),out.0.value() == left,out.1.value() == right,Sourcepub proof fn create_unit(loc: Loc) -> tracked out : Self
pub proof fn create_unit(loc: Loc) -> tracked out : Self
out.value() == P::unit(),out.loc() == loc,Sourcepub proof fn update(tracked self, new_value: P) -> tracked out : Self
pub proof fn update(tracked self, new_value: P) -> tracked out : Self
frame_preserving_update(self.value(), new_value),out.loc() == self.loc(),out.value() == new_value,Sourcepub proof fn update_nondeterministic(tracked self, new_values: Set<P>) -> tracked out : Self
pub proof fn update_nondeterministic(tracked self, new_values: Set<P>) -> tracked out : Self
frame_preserving_update_nondeterministic(self.value(), new_values),out.loc() == self.loc(),new_values.contains(out.value()),self.loc() == other.loc(),out.loc() == self.loc(),incl(self.value(), out.value()),incl(other.value(), out.value()),This is useful when you have two (or more) shared resources and want to learn
that they agree, as you can combine this validate, e.g., x.join_shared(y).validate().
self.loc() == other.loc(),conjunct_shared(self.value(), other.value(), target),out.loc() == self.loc(),out.value() == target,Sourcepub proof fn weaken<'a>(tracked &'a self, target: P) -> tracked out : &'a Self
pub proof fn weaken<'a>(tracked &'a self, target: P) -> tracked out : &'a Self
incl(target, self.value()),out.loc() == self.loc(),out.value() == target,Sourcepub proof fn validate_2(tracked &mut self, tracked other: &Self)
pub proof fn validate_2(tracked &mut self, tracked other: &Self)
old(self).loc() == other.loc(),*self == *old(self),P::op(self.value(), other.value()).valid(),self.loc() == other.loc(),frame_preserving_update(
P::op(self.value(), other.value()),
P::op(new_value, other.value()),
),out.loc() == self.loc(),out.value() == new_value,If x · y --> x · z is a frame-perserving update, and we have a shared reference to x,
we can update the y resource to z.
self.loc() == other.loc(),frame_preserving_update_nondeterministic(
P::op(self.value(), other.value()),
set_op(new_values, other.value()),
),out.loc() == self.loc(),new_values.contains(out.value()),