sbt.inc.FileValueCache.scala Maven / Gradle / Ivy
package sbt
package inc
import java.io.File
import java.util.concurrent.ConcurrentHashMap
sealed trait FileValueCache[T] {
def clear(): Unit
def get: File => T
}
private[this] final class FileValueCache0[T](getStamp: File => Stamp, make: File => T)(implicit equiv: Equiv[Stamp]) extends FileValueCache[T] {
private[this] val backing = new ConcurrentHashMap[File, FileCache]
def clear(): Unit = backing.clear()
def get = file => {
val ifAbsent = new FileCache(file)
val cache = backing.putIfAbsent(file, ifAbsent)
(if (cache eq null) ifAbsent else cache).get()
}
private[this] final class FileCache(file: File) {
private[this] var stampedValue: Option[(Stamp, T)] = None
def get(): T = synchronized {
val latest = getStamp(file)
stampedValue match {
case Some((stamp, value)) if (equiv.equiv(latest, stamp)) => value
case _ => update(latest)
}
}
private[this] def update(stamp: Stamp): T =
{
val value = make(file)
stampedValue = Some((stamp, value))
value
}
}
}
object FileValueCache {
def apply[T](f: File => T): FileValueCache[T] = make(Stamp.lastModified)(f)
def make[T](stamp: File => Stamp)(f: File => T): FileValueCache[T] = new FileValueCache0[T](stamp, f)
}