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/* TODO: Reintegrate
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2008-2009, David MacIver **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id: $
package scala.collection.immutable
object TreeHashMap {
private[TreeHashMap] val _empty = new TreeHashMap[Any, Nothing](IntMap.empty[Nothing]);
def empty[Key, Value] : TreeHashMap[Key, Value] = _empty.asInstanceOf[TreeHashMap[Key, Value]];
def apply[Key, Value](elems : (Key, Value)*) : TreeHashMap[Key, Value] = fromIterable(elems)
def fromIterable[Key, Value](elems : Iterable[(Key, Value)]) : TreeHashMap[Key, Value] =
elems.foldLeft(TreeHashMap.empty[Key, Value])((m, entry) => m.update(entry._1, entry._2))
private def apply[Key, Value](underlying : IntMap[AssocMap[Key, Value]]) = new TreeHashMap(underlying);
}
/**
* An immutable Map which is based on an IntMap mapping hash codes to lists of (Key, Value) pairs with the
* same hashCode.
*
* Unlike the usual immutable.HashMap it is truly immutable behind the scenes. Consequently it is entirely
* safe to share between multiple threads and should achieve a much greater degree of sharing between instances.
*
* Performancewise, get and update seem to be somewhat slower than with a traditional hash map, but bulk operations
* such as filter, foreach and transform appear to get something of a speedup.
*
* @author David MacIver
*/
class TreeHashMap[Key, +Value] private (private val underlying : IntMap[AssocMap[Key, Value]]) extends scala.collection.immutable.Map[Key, Value]{
def elements : Iterator[(Key, Value)] = new Iterator[(Key, Value)]{
val assocIt = new AssocMapIterator(AssocMap.empty[Key, Value]);
val intIterator = underlying.values;
def hasNext = assocIt.hasNext || intIterator.hasNext;
def next = {
if (!assocIt.hasNext) assocIt.it = intIterator.next;
assocIt.next
}
}
def empty[V] = TreeHashMap.empty[Key, V]
private def hash(key : Key) = {
var h = key.hashCode;
h ^= ((h >>> 20) ^ (h >>> 12));
h ^ (h >>> 7) ^ (h >>> 4);
}
override def stringPrefix = "TreeHashMap"
override lazy val size = underlying.values.foldLeft(0)((x, y) => x + y.size);
// todo: probably drop to make conform with general equals/hashcode policy
override def equals(that : Any) = that match {
case (that : TreeHashMap[_, _]) =>
if (this eq that) true
else if (this.size != that.size) false;
else this.underlying == that.underlying;
case _ => false
}
// todo: probably drop to make conform with general equals/hashcode policy
override def hashCode = underlying.hashCode
override def foreach[U](f : ((Key, Value)) => U) = underlying.foreachValue(_.foreach(f));
override def toList : List[(Key, Value)] = {
val buffer = new scala.collection.mutable.ListBuffer[(Key, Value)];
foreach(buffer += _);
buffer.toList;
}
override def apply(key : Key) =
underlying.get(hash(key)) match {
case None => default(key);
case Some(table) => table.getOrElse(key, default(key));
}
override def isEmpty = underlying.isEmpty;
override def filter(f : ((Key, Value)) => Boolean) : TreeHashMap[Key, Value]= {
val newunderlying = underlying.modifyOrRemove(
(key, x) => {
val newtable = x.filter(f);
if (newtable.isEmpty) None;
else Some(newtable);
}
)
if (newunderlying eq underlying) this;
else TreeHashMap(newunderlying);
}
override def transform[C](f : (Key, Value) => C) = {
val newunderlying = underlying.transform(
(key, value) => value.transform(f)
)
if (underlying eq newunderlying) this.asInstanceOf[TreeHashMap[Key, C]];
else TreeHashMap(newunderlying);
}
def get(key : Key) = underlying.get(hash(key)).flatMap(_.get(key));
def update[S >: Value](key : Key, value : S) : TreeHashMap[Key, S] = TreeHashMap(
underlying.updateWith[AssocMap[Key, S]](hash(key), AssocMap.singleton[Key, S](key, value), (x, y) => y.merge(x))
)
def minus(key : Key) : TreeHashMap[Key, Value] = {
val h = hash(key);
underlying.get(h) match {
case None => this;
case Some(table) => {
val newtable = table - key;
if (table eq newtable) this;
else if (newtable.isEmpty) TreeHashMap(underlying - h)
else TreeHashMap(underlying.update(h, newtable));
}
}
}
override def ++[V >: Value](that : Iterable[(Key, V)]) : TreeHashMap[Key, V] = that match {
case (that : TreeHashMap[_, _]) => this ++ TreeHashMap.fromIterable(that.asInstanceOf[TreeHashMap[Key, V]])
case that => that.foldLeft(this : TreeHashMap[Key, V])((m, e) => m.update(e._1, e._2));
}
def ++[V >: Value](that : TreeHashMap[Key, V]) : TreeHashMap[Key, V] =
TreeHashMap(this.underlying.unionWith[AssocMap[Key, V]](that.underlying, (key, x, y) => x ++ y));
}
private [collection] object AssocMap {
val _empty = Nil[Any]
def empty[Key, Value] : AssocMap[Key, Value] = _empty.asInstanceOf[AssocMap[Key, Value]]
def singleton[Key, Value](key : Key, value : Value) = Cons(key, value, empty);
def apply[Key, Value](maps : (Key, Value)*) =
maps.foldLeft(empty[Key, Value])((x, y) => x.update(y._1, y._2));
private[collection] case class Nil[Key]() extends AssocMap[Key, Nothing]
private[collection] case class Cons[S, +T](key: S, value: T, tail: AssocMap[S, T]) extends AssocMap[S, T]
}
import AssocMap._
// AssocMap is very similar to ListMap. I don't want to patch ListMap right
// now, so I've got a separate implementation here to make tweaks to. Long
// term any of these changes should be merged into ListMap
// Short term it doesn't really matter because there are almost no viable
// use cases for ListMap compared to one of the alternatives.
private[collection] sealed abstract class AssocMap[Key, +Value] extends immutable.Map[Key, Value]{
def empty[V] = AssocMap.empty[Key, V]
final def get(key : Key) : Option[Value] = this match {
case Nil() => None;
case Cons(key2, value, tail) => if (key == key2) Some(value)
else tail.get(key);
}
override final def getOrElse[V >: Value](key : Key, default : =>V) : V = this match {
case Nil() => default;
case Cons(key2, value, tail) => if (key == key2) value
else tail.getOrElse(key, default);
}
override final def apply(key : Key) : Value = getOrElse(key, default(key));
override def filter(f : ((Key, Value)) => Boolean) : AssocMap[Key, Value] = this match {
case Cons(key, value, tail) => {
val filteredtail = tail.filter(f);
if (f((key, value))) {
if (tail eq filteredtail) this;
else Cons(key, value, filteredtail);
} else filteredtail;
}
case Nil() => AssocMap.empty;
}
def elements : Iterator[(Key, Value)] = new AssocMapIterator(this);
override final def foreach[U](f : ((Key, Value)) => U) = this match {
case Cons(key, value, tail) => { f((key, value)); tail.foreach(f); }
case Nil() => {}
}
def size = this match {
case Nil() => 0;
case Cons(_, _, tail) => 1 + tail.size;
}
override def isEmpty = this match {
case Nil() => true;
case _ => false;
}
private def removeKeyValue(key : Any, value : Any) : Option[AssocMap[Key, Value]] = this match {
case Nil() => None;
case Cons(key2, value2, tail) =>
if (key == key2){
if (value == value2) Some(tail);
else None;
} else tail.removeKeyValue(key, value) match {
case None => None;
case Some(x) => Some(Cons(key2, value2, x));
}
}
private def sameMappings(that : AssocMap[_, _]) : Boolean = (this, that) match {
case (Nil(), Nil()) => true;
case (Nil(), _) => false;
case (_, Nil()) => false;
case (Cons(key, value, tail), that) => that.removeKeyValue(key, value) match {
case None => false;
case Some(x) => tail.sameMappings(x);
}
}
override def equals(that : Any) =
if (this eq that.asInstanceOf[AnyRef]) true;
else that match {
case (that : AssocMap[_, _]) =>
if (this.size != that.size) false;
else this.sameMappings(that);
case _ => false;
}
final def merge[S >: Value](that : AssocMap[Key, S]) : AssocMap[Key, S] = (this, that) match {
case (Nil(), that) => that;
case (_, Nil()) => this;
case (Cons(key, value, tail), that) =>
tail.merge[S](that).update(key, value);
}
def update[S >: Value](key : Key, value : S) : AssocMap[Key, S] = this match {
case Nil() => Cons(key, value, empty);
case Cons(key2, value2, tail) =>
if (key2 == key) Cons(key, value, tail)
else Cons(key2, value2, tail.update(key, value));
}
override def transform[C](f: (Key, Value) => C): AssocMap[Key, C] = this match {
case Nil() =>
AssocMap.empty[Key, C]
case Cons(key, value, tail) =>
val newtail = tail.transform(f)
val newval = f(key, value)
if ((tail eq newtail) && (value.asInstanceOf[AnyRef] eq newval.asInstanceOf[AnyRef])) this.asInstanceOf[AssocMap[Key, C]];
else Cons(key, newval, newtail);
}
def minus(key : Key) : AssocMap[Key, Value]= this match {
case Nil() => this;
case Cons(key2, value, tail) =>
if (key == key2) tail;
else {
val newtail = tail - key;
if (tail eq newtail) this;
else Cons(key2, value, newtail);
}
}
final def ++[V >: Value](that : AssocMap[Key, V]) : AssocMap[Key, V] = (this, that) match {
case (Nil(), that) => that;
case (_, Nil()) => this;
case (t1, Cons(key, value, tail)) => t1.update(key, value.asInstanceOf[Value] /* evil hack to work around bug 1140 */) ++ tail;
}
}
private[collection] class AssocMapIterator[Key, Value](var it : AssocMap[Key, Value]) extends Iterator[(Key, Value)]{
def hasNext = it match {
case Nil() => false;
case _ => true;
}
def next = {
val Cons(key, value, next) = it;
it = next;
(key, value);
}
}
*/
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