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package moe.nea.firmament.util
fun <K, V> mutableMapWithMaxSize(maxSize: Int): MutableMap<K, V> = object : LinkedHashMap<K, V>() {
override fun removeEldestEntry(eldest: MutableMap.MutableEntry<K, V>): Boolean {
return size > maxSize
}
}
fun <T, R> ((T) -> R).memoizeIdentity(maxCacheSize: Int): (T) -> R {
val memoized = { it: IdentityCharacteristics<T> ->
this(it.value)
}.memoize(maxCacheSize)
return { memoized(IdentityCharacteristics(it)) }
}
@PublishedApi
internal val SENTINEL_NULL = java.lang.Object()
/**
* Requires the map to only contain values of type [R] or [SENTINEL_NULL]. This is ensured if the map is only ever
* accessed via this function.
*/
inline fun <T, R> MutableMap<T, Any>.computeNullableFunction(key: T, crossinline func: () -> R): R {
val value = this.getOrPut(key) {
func() ?: SENTINEL_NULL
}
@Suppress("UNCHECKED_CAST")
return if (value === SENTINEL_NULL) null as R
else value as R
}
fun <T, R> ((T) -> R).memoize(maxCacheSize: Int): (T) -> R {
val map = mutableMapWithMaxSize<T, Any>(maxCacheSize)
return {
map.computeNullableFunction(it) { this@memoize(it) }
}
}
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