Struct CountGhostResource 

pub struct CountGhostResource<T, const TOTAL: usize> { /* private fields */ }

A struct that stores and dispatches CountGhost<T>. Unlike CountGhost, it provides an empty state: after all fractions have been split out, it still remembers the resource value inside the carrier, mirroring CountResource.

Implementations

impl<T, const TOTAL: usize> CountGhostResource<T, TOTAL>

pub closed spec fn type_inv(self) -> bool

pub open spec fn wf(self) -> bool

{
    &&& TOTAL > 0
    &&& 0 <= self.frac() <= TOTAL
    &&& self.type_inv()

}

Type invariant.

pub open spec fn is_empty(self) -> bool

{ self.frac() == 0 }

Whether this CountGhostResource is empty, i.e., has no fraction.

pub open spec fn not_empty(self) -> bool

{ !self.is_empty() }

Whether the fraction stored in this CountGhostResource is less than TOTAL.

pub open spec fn is_full(self) -> bool

{ self.frac() == TOTAL }

Whether this CountGhostResource has the full fraction, i.e., TOTAL.

pub closed spec fn view(self) -> T

Returns the value of type T stored in this CountGhostResource.

pub closed spec fn frac(self) -> int

The fractions stored in this CountGhostResource.

pub closed spec fn id(self) -> Loc

Returns the unique identifier.

pub proof fn arbitrary() -> tracked res : Self

requires

TOTAL > 0,

Create an arbitrary CountGhostResource. Useful as a placeholder.

pub proof fn alloc(value: T) -> tracked res : Self

requires

TOTAL > 0,

ensures

res.not_empty(),

res.is_full(),

res@ == value,

res.wf(),

Allocates a new CountGhostResource with the full fraction and the given value.

pub proof fn split_one(tracked &mut self) -> tracked res : CountGhost<T, TOTAL>

requires

old(self).not_empty(),

ensures

final(self).id() == old(self).id(),

final(self).frac() + 1 == old(self).frac(),

final(self)@ == old(self)@,

res.frac() == 1,

res.id() == final(self).id(),

res@ == final(self)@,

!res.has_authority(),

old(self).frac() == 1 ==> final(self).is_empty(),

final(self).wf(),

Splits a CountGhost with fraction 1.

pub proof fn split(tracked &mut self, n: int) -> tracked res : CountGhost<T, TOTAL>

requires

1 <= n <= old(self).frac(),

ensures

final(self).id() == old(self).id(),

final(self).frac() + n == old(self).frac(),

final(self)@ == old(self)@,

res.frac() == n,

res.id() == final(self).id(),

res@ == final(self)@,

!res.has_authority(),

old(self).frac() == n ==> final(self).is_empty(),

final(self).wf(),

Splits a CountGhost with the given fraction.

pub proof fn combine(tracked &mut self, tracked other: CountGhost<T, TOTAL>)

requires

old(self).id() == other.id(),

ensures

old(self).frac() + other.frac() > TOTAL ==> false,

old(self).frac() + other.frac() <= TOTAL
    ==> {
        &&& final(self).id() == old(self).id()
        &&& final(self)@ == old(self)@
        &&& final(self)@ == other@
        &&& final(self).frac() == old(self).frac() + other.frac()
        &&& final(self).wf()

    },

Combines a CountGhost.

pub proof fn validate(tracked &self)

ensures

self.wf(),

CountGhostResource satisfies the type invariant.

pub proof fn validate_with_frac(tracked &self, tracked frac: &CountGhost<T, TOTAL>)

requires

self.id() == frac.id(),

ensures

self@ == frac@,

A CountGhostResource and a CountGhost with the same id agree on the value.

Unlike CountGhost::agree, this works even when the resource is empty (all fractions split out).

pub proof fn update(tracked &mut self, value: T)

requires

old(self).is_full(),

ensures

final(self).is_full(),

final(self)@ == value,

final(self).id() == old(self).id(),

final(self).wf(),

Updates the value stored in this CountGhostResource. The fraction must be full before the update.