java.lang.ref.WeakReference Scala Examples

The following examples show how to use java.lang.ref.WeakReference. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example.
Example 1
Source File: Symbol.scala    From perf_tester   with Apache License 2.0 5 votes vote down vote up 
package scala


private[scala] abstract class UniquenessCache[K, V >: Null]
{
  import java.lang.ref.WeakReference
  import java.util.WeakHashMap
  import java.util.concurrent.locks.ReentrantReadWriteLock

  private val rwl = new ReentrantReadWriteLock()
  private val rlock = rwl.readLock
  private val wlock = rwl.writeLock
  private val map = new WeakHashMap[K, WeakReference[V]]

  protected def valueFromKey(k: K): V
  protected def keyFromValue(v: V): Option[K]

  def apply(name: K): V = {
    def cached(): V = {
      rlock.lock
      try {
        val reference = map get name
        if (reference == null) null
        else reference.get  // will be null if we were gc-ed
      }
      finally rlock.unlock
    }
    def updateCache(): V = {
      wlock.lock
      try {
        val res = cached()
        if (res != null) res
        else {
          // If we don't remove the old String key from the map, we can
          // wind up with one String as the key and a different String as
          // the name field in the Symbol, which can lead to surprising GC
          // behavior and duplicate Symbols. See scala/bug#6706.
          map remove name
          val sym = valueFromKey(name)
          map.put(name, new WeakReference(sym))
          sym
        }
      }
      finally wlock.unlock
    }

    val res = cached()
    if (res == null) updateCache()
    else res
  }
  def unapply(other: V): Option[K] = keyFromValue(other)
}
Example 2
Source File: UniquenessCache.scala    From incubator-daffodil   with Apache License 2.0 5 votes vote down vote up 
package org.apache.daffodil.util


abstract class UniquenessCache[K, V >: Null]
{
  import java.lang.ref.WeakReference
  import java.util.WeakHashMap
  import java.util.concurrent.locks.ReentrantReadWriteLock

  private[this] val rwl = new ReentrantReadWriteLock()
  private[this] val rlock = rwl.readLock
  private[this] val wlock = rwl.writeLock
  private[this] val map = new WeakHashMap[K, WeakReference[V]]

  protected def valueFromKey(k: K): V
  protected def keyFromValue(v: V): Option[K]

  def apply(name: K): V = {
    def cached(): V = {
      rlock.lock
      try {
        val reference = map get name
        if (reference == null) null
        else reference.get  // will be null if we were gc-ed
      }
      finally rlock.unlock
    }
    def updateCache(): V = {
      wlock.lock
      try {
        val res = cached()
        if (res != null) res
        else {
          // If we don't remove the old String key from the map, we can
          // wind up with one String as the key and a different String as
          // the name field in the Symbol, which can lead to surprising GC
          // behavior and duplicate Symbols. See scala/bug#6706.
          map remove name
          val sym = valueFromKey(name)
          map.put(name, new WeakReference(sym))
          sym
        }
      }
      finally wlock.unlock
    }

    val res = cached()
    if (res == null) updateCache()
    else res
  }
  def unapply(other: V): Option[K] = keyFromValue(other)
}
Example 3
Source File: cache.scala    From libisabelle   with Apache License 2.0 5 votes vote down vote up 
package isabelle


import java.util.{Collections, WeakHashMap}
import java.lang.ref.WeakReference


class Cache(initial_size: Int = 131071, max_string: Int = 100)
{
  private val table =
    Collections.synchronizedMap(new WeakHashMap[Any, WeakReference[Any]](initial_size))

  def size: Int = table.size

  override def toString: String = "Cache(" + size + ")"

  protected def lookup[A](x: A): Option[A] =
  {
    val ref = table.get(x)
    if (ref == null) None
    else {
      val y = ref.asInstanceOf[WeakReference[A]].get
      if (y == null) None
      else Some(y)
    }
  }

  protected def store[A](x: A): A =
  {
    table.put(x, new WeakReference[Any](x))
    x
  }

  protected def cache_int(x: Int): Int =
    lookup(x) getOrElse store(x)

  protected def cache_string(x: String): String =
  {
    if (x == "") ""
    else if (x == "true") "true"
    else if (x == "false") "false"
    else if (x == "0.0") "0.0"
    else if (Library.is_small_int(x)) Library.signed_string_of_int(Integer.parseInt(x))
    else {
      lookup(x) match {
        case Some(y) => y
        case None =>
          val z = Library.isolate_substring(x)
          if (z.length > max_string) z else store(z)
      }
    }
  }

  // main methods
  def int(x: Int): Int = synchronized { cache_int(x) }
  def string(x: String): String = synchronized { cache_string(x) }
}
Example 4
Source File: cache.scala    From libisabelle   with Apache License 2.0 5 votes vote down vote up 
package isabelle


import java.util.{Collections, WeakHashMap}
import java.lang.ref.WeakReference


class Cache(initial_size: Int = 131071, max_string: Int = 100)
{
  private val table =
    Collections.synchronizedMap(new WeakHashMap[Any, WeakReference[Any]](initial_size))

  def size: Int = table.size

  override def toString: String = "Cache(" + size + ")"

  protected def lookup[A](x: A): Option[A] =
  {
    val ref = table.get(x)
    if (ref == null) None
    else {
      val y = ref.asInstanceOf[WeakReference[A]].get
      if (y == null) None
      else Some(y)
    }
  }

  protected def store[A](x: A): A =
  {
    table.put(x, new WeakReference[Any](x))
    x
  }

  protected def cache_int(x: Int): Int =
    lookup(x) getOrElse store(x)

  protected def cache_string(x: String): String =
  {
    if (x == "") ""
    else if (x == "true") "true"
    else if (x == "false") "false"
    else if (x == "0.0") "0.0"
    else if (Library.is_small_int(x)) Library.signed_string_of_int(Integer.parseInt(x))
    else {
      lookup(x) match {
        case Some(y) => y
        case None =>
          val z = Library.isolate_substring(x)
          if (z.length > max_string) z else store(z)
      }
    }
  }

  // main methods
  def int(x: Int): Int = synchronized { cache_int(x) }
  def string(x: String): String = synchronized { cache_string(x) }
}