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fix: add a single element cache

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Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>
This commit is contained in:
Dr. Carsten Leue
2023-12-21 14:10:46 +01:00
parent 3aa55c74d4
commit 5ac47440a1
5 changed files with 76 additions and 5 deletions
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46
function/generic/cache.go
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@@ -28,7 +28,7 @@ func Memoize[F ~func(K) T, K comparable, T any](f F) F {
// ContramapMemoize converts a unary function into a unary function that caches the value depending on the parameter
func ContramapMemoize[F ~func(A) T, KF func(A) K, A any, K comparable, T any](kf KF) func(F) F {
return CacheCallback[F](kf, getOrCreate[K, T]())
return CacheCallback[func(F) F, func() func() T](kf, getOrCreate[K, T]())
}
// getOrCreate is a naive implementation of a cache, without bounds
@@ -50,13 +50,51 @@ func getOrCreate[K comparable, T any]() func(K, func() func() T) func() T {
}
}
// SingleElementCache is a cache with a capacity of a single element
func SingleElementCache[
LLT ~func() LT, // generator of the generator
K comparable, // key into the cache
LT ~func() T, // generator of a value
T any, // the cached data type
]() func(K, LLT) LT {
var l sync.Mutex
var key K
var value LT
hasKey := false
return func(k K, gen LLT) LT {
l.Lock()
existing := value
if !hasKey || key != k {
existing = gen()
// update state
key = k
value = existing
hasKey = true
}
l.Unlock()
return existing
}
}
// CacheCallback converts a unary function into a unary function that caches the value depending on the parameter
func CacheCallback[F ~func(A) T, KF func(A) K, C ~func(K, func() func() T) func() T, A any, K comparable, T any](kf KF, getOrCreate C) func(F) F {
func CacheCallback[
EM ~func(F) F, // endomorphism of the function
LLT ~func() LT, // generator of the generator
LT ~func() T, // generator of a value
F ~func(A) T, // function to actually cache
KF func(A) K, // extracts the cache key from the input
C ~func(K, LLT) LT, // the cache callback function
A any, K comparable, T any](kf KF, getOrCreate C) EM {
return func(f F) F {
return func(a A) T {
// cache entry
return getOrCreate(kf(a), func() func() T {
return L.Memoize[func() T](func() T {
return getOrCreate(kf(a), func() LT {
return L.Memoize[LT](func() T {
return f(a)
})
})()