Safe HaskellSafe-Infered



Implementation of lock allocation.



data OwnerState Source

Data type describing the way a lock can be owned.




Eq OwnerState 
Ord OwnerState 
Show OwnerState 
Arbitrary OwnerState 
JSON OwnerState

Serializaiton of Lock Allocations

To serialize a lock allocation, we only remember which owner holds which locks at which level (shared or exclusive). From this information, everything else can be reconstructed, simply using updateLocks.

type IndirectOwners a b = Map (a, b) OwnerStateSource

data AllocationState a b Source


Exclusive b (IndirectOwners a b) 
Shared (Set b) (IndirectOwners a b) 


(Eq a, Eq b) => Eq (AllocationState a b) 
(Show a, Show b) => Show (AllocationState a b) 

indirectOwners :: (Ord a, Ord b) => Map (a, b) OwnerState -> Set bSource

indirectExclusives :: (Ord a, Ord b) => Map (a, b) OwnerState -> Set bSource

data LockAllocation a b Source

Representation of a Lock allocation

To keep queries for locks efficient, we keep two associations, with the invariant that they fit together: the association from locks to their allocation state, and the association from an owner to the set of locks owned. As we do not export the constructor, the problem of keeping this invariant reduces to only exporting functions that keep the invariant.




laLocks :: Map a (AllocationState a b)
laOwned :: Map b (Map a OwnerState)


(Eq a, Eq b) => Eq (LockAllocation a b) 
(Show a, Show b) => Show (LockAllocation a b) 
(Arbitrary a, Lock a, Arbitrary b, Ord b, Show b) => Arbitrary (LockAllocation a b) 
(Lock a, JSON a, Ord b, JSON b, Show b) => JSON (LockAllocation a b) 

emptyAllocation :: (Ord a, Ord b) => LockAllocation a bSource

A state with all locks being free.

lockOwners :: Ord b => LockAllocation a b -> [b]Source

Obtain the list of all owners holding at least a single lock.

listLocks :: Ord b => b -> LockAllocation a b -> Map a OwnerStateSource

Obtain the locks held by a given owner. The locks are reported as a map from the owned locks to the form of ownership (OwnShared or OwnExclusive).

listAllLocks :: Ord b => LockAllocation a b -> [a]Source

List all locks currently (directly or indirectly) owned by someone.

listAllLocksOwners :: LockAllocation a b -> [(a, [(b, OwnerState)])]Source

List all locks currently (directly of indirectly) in use together with the direct owners.

holdsLock :: (Ord a, Ord b) => b -> a -> OwnerState -> LockAllocation a b -> BoolSource

Returns True if the given owner holds the given lock at the given ownership level or higher. This means that querying for a shared lock returns True of the owner holds the lock in shared or exlusive mode.

data LockRequest a Source

Data Type describing a change request on a single lock.




lockAffected :: a
lockRequestType :: Maybe OwnerState


Eq a => Eq (LockRequest a) 
Ord a => Ord (LockRequest a) 
Show a => Show (LockRequest a) 
Arbitrary a => Arbitrary (LockRequest a) 
JSON a => JSON (LockRequest a) 

requestExclusive :: a -> LockRequest aSource

Lock request for an exclusive lock.

requestShared :: a -> LockRequest aSource

Lock request for a shared lock.

requestRelease :: a -> LockRequest aSource

Request to release a lock.

updateAllocState :: (Ord a, Ord b) => (Maybe (AllocationState a b) -> AllocationState a b) -> LockAllocation a b -> a -> LockAllocation a bSource

updateLock :: (Ord a, Ord b) => b -> LockAllocation a b -> LockRequest a -> LockAllocation a bSource

updateIndirectSet :: (Ord a, Ord b) => (IndirectOwners a b -> IndirectOwners a b) -> LockAllocation a b -> a -> LockAllocation a bSource

updateLocks :: (Lock a, Ord b) => b -> [LockRequest a] -> LockAllocation a b -> (LockAllocation a b, Result (Set b))Source

Update the locks of an owner according to the given request. Return the pair of the new state and the result of the operation, which is the the set of owners on which the operation was blocked on. so an empty set is success, and the state is updated if, and only if, the returned set is emtpy. In that way, it can be used in atomicModifyIORef.

manipulateLocksPredicate :: (Lock a, Ord b) => (a -> LockRequest a) -> (a -> Bool) -> b -> LockAllocation a b -> LockAllocation a bSource

freeLocksPredicate :: (Lock a, Ord b) => (a -> Bool) -> LockAllocation a b -> b -> LockAllocation a bSource

freeLocks :: (Lock a, Ord b) => LockAllocation a b -> b -> LockAllocation a bSource

Compute the state after an onwer releases all its locks.

readLockOwnerstate :: JSON a => JSValue -> Result (a, OwnerState)Source

readOwnerLock :: (JSON a, JSON b) => JSValue -> Result (b, [(a, OwnerState)])Source

allocationFromOwners :: (Lock a, Ord b, Show b) => [(b, [(a, OwnerState)])] -> Result (LockAllocation a b)Source