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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection
package immutable
import generic._
import annotation.unchecked.uncheckedVariance
/** This class implements immutable maps using a hash trie.
*
* <b>Note:</b> the builder of a hash map returns specialized representations EmptyMap,Map1,..., Map4
* for maps of size <= 4.
*
* @tparam A the type of the keys contained in this hash map.
* @tparam B the type of the values associated with the keys.
*
* @author Martin Odersky
* @author Tiark Rompf
* @version 2.8
* @since 2.3
* @define Coll immutable.HashMap
* @define coll immutable hash map
* @define mayNotTerminateInf
* @define willNotTerminateInf
*/
@serializable @SerialVersionUID(2L)
class HashMap[A, +B] extends Map[A,B] with MapLike[A, B, HashMap[A, B]] {
override def size: Int = 0
override def empty = HashMap.empty[A, B]
def iterator: Iterator[(A,B)] = Iterator.empty
override def foreach[U](f: ((A, B)) => U): Unit = { }
def get(key: A): Option[B] =
get0(key, computeHash(key), 0)
override def updated [B1 >: B] (key: A, value: B1): HashMap[A, B1] =
updated0(key, computeHash(key), 0, value, null)
override def + [B1 >: B] (kv: (A, B1)): HashMap[A, B1] =
updated0(kv._1, computeHash(kv._1), 0, kv._2, kv)
override def + [B1 >: B] (elem1: (A, B1), elem2: (A, B1), elems: (A, B1) *): HashMap[A, B1] =
this + elem1 + elem2 ++ elems
// TODO: optimize (might be able to use mutable updates)
def - (key: A): HashMap[A, B] =
removed0(key, computeHash(key), 0)
protected def elemHashCode(key: A) = if (key == null) 0 else key.hashCode()
protected final def improve(hcode: Int) = {
var h: Int = hcode + ~(hcode << 9)
h = h ^ (h >>> 14)
h = h + (h << 4)
h ^ (h >>> 10)
}
protected def computeHash(key: A) = improve(elemHashCode(key))
protected def get0(key: A, hash: Int, level: Int): Option[B] = None
protected def updated0[B1 >: B](key: A, hash: Int, level: Int, value: B1, kv: (A, B1)): HashMap[A, B1] =
new HashMap.HashMap1(key, hash, value, kv)
protected def removed0(key: A, hash: Int, level: Int): HashMap[A, B] = this
}
/** $factoryInfo
* @define Coll immutable.HashMap
* @define coll immutable hash map
*
* @author Tiark Rompf
* @since 2.3
*/
object HashMap extends ImmutableMapFactory[HashMap] {
implicit def canBuildFrom[A, B]: CanBuildFrom[Coll, (A, B), HashMap[A, B]] = new MapCanBuildFrom[A, B]
def empty[A, B]: HashMap[A, B] = EmptyHashMap.asInstanceOf[HashMap[A, B]]
private object EmptyHashMap extends HashMap[Any,Nothing] {
}
// TODO: add HashMap2, HashMap3, ...
class HashMap1[A,+B](private var key: A, private[HashMap] var hash: Int, private var value: (B @uncheckedVariance), private var kv: (A,B @uncheckedVariance)) extends HashMap[A,B] {
override def size = 1
override def get0(key: A, hash: Int, level: Int): Option[B] =
if (hash == this.hash && key == this.key) Some(value) else None
override def updated0[B1 >: B](key: A, hash: Int, level: Int, value: B1, kv: (A, B1)): HashMap[A, B1] =
if (hash == this.hash && key == this.key) new HashMap1(key, hash, value, kv)
else {
if (hash != this.hash) {
//new HashTrieMap[A,B1](level+5, this, new HashMap1(key, hash, value, kv))
val m = new HashTrieMap[A,B1](0,new Array[HashMap[A,B1]](0),0) // TODO: could save array alloc
m.updated0(this.key, this.hash, level, this.value, this.kv).updated0(key, hash, level, value, kv)
} else {
// 32-bit hash collision (rare, but not impossible)
// wrap this in a HashTrieMap if called with level == 0 (otherwise serialization won't work)
if (level == 0) {
val elems = new Array[HashMap[A,B1]](1)
elems(0) = new HashMapCollision1(hash, ListMap.empty.updated(this.key,this.value).updated(key,value))
new HashTrieMap[A,B1](1 << ((hash >>> level) & 0x1f), elems, 2)
} else {
new HashMapCollision1(hash, ListMap.empty.updated(this.key,this.value).updated(key,value))
}
}
}
override def removed0(key: A, hash: Int, level: Int): HashMap[A, B] =
if (hash == this.hash && key == this.key) HashMap.empty[A,B] else this
override def iterator: Iterator[(A,B)] = Iterator(ensurePair)
override def foreach[U](f: ((A, B)) => U): Unit = f(ensurePair)
private[HashMap] def ensurePair: (A,B) = if (kv ne null) kv else { kv = (key, value); kv }
private def writeObject(out: java.io.ObjectOutputStream) {
out.writeObject(key)
out.writeObject(value)
}
private def readObject(in: java.io.ObjectInputStream) {
key = in.readObject().asInstanceOf[A]
value = in.readObject().asInstanceOf[B]
hash = computeHash(key)
}
}
private class HashMapCollision1[A,+B](private[HashMap] var hash: Int, var kvs: ListMap[A,B @uncheckedVariance]) extends HashMap[A,B] {
override def size = kvs.size
override def get0(key: A, hash: Int, level: Int): Option[B] =
if (hash == this.hash) kvs.get(key) else None
override def updated0[B1 >: B](key: A, hash: Int, level: Int, value: B1, kv: (A, B1)): HashMap[A, B1] =
if (hash == this.hash) new HashMapCollision1(hash, kvs.updated(key, value))
else {
var m: HashMap[A,B1] = new HashTrieMap[A,B1](0,new Array[HashMap[A,B1]](0),0)
// might be able to save some ops here, but it doesn't seem to be worth it
for ((k,v) <- kvs)
m = m.updated0(k, this.hash, level, v, null)
m.updated0(key, hash, level, value, kv)
}
override def removed0(key: A, hash: Int, level: Int): HashMap[A, B] =
if (hash == this.hash) {
val kvs1 = kvs - key
if (!kvs1.isEmpty)
new HashMapCollision1(hash, kvs1)
else
HashMap.empty[A,B]
} else this
override def iterator: Iterator[(A,B)] = kvs.iterator
override def foreach[U](f: ((A, B)) => U): Unit = kvs.foreach(f)
private def writeObject(out: java.io.ObjectOutputStream) {
// this cannot work - reading things in might produce different
// hash codes and remove the collision. however this is never called
// because no references to this class are ever handed out to client code
// and HashTrieMap serialization takes care of the situation
error("cannot serialize an immutable.HashMap where all items have the same 32-bit hash code")
//out.writeObject(kvs)
}
private def readObject(in: java.io.ObjectInputStream) {
error("cannot deserialize an immutable.HashMap where all items have the same 32-bit hash code")
//kvs = in.readObject().asInstanceOf[ListMap[A,B]]
//hash = computeHash(kvs.)
}
}
class HashTrieMap[A,+B](private var bitmap: Int, private var elems: Array[HashMap[A,B @uncheckedVariance]],
private var size0: Int) extends HashMap[A,B] {
/*
def this (level: Int, m1: HashMap1[A,B], m2: HashMap1[A,B]) = {
this(((m1.hash >>> level) & 0x1f) | ((m2.hash >>> level) & 0x1f), {
val idx1 = (m1.hash >>> level) & 0x1f
val idx2 = (m2.hash >>> level) & 0x1f
assert(idx1 != idx2, m1.hash + "==" + m2.hash + " at level " + level) // TODO
val elems = new Array[HashMap[A,B]](2)
if (idx1 < idx2) {
elems(0) = m1
elems(1) = m2
} else {
elems(0) = m2
elems(1) = m1
}
elems
}, 2)
}
*/
override def size = size0
override def get0(key: A, hash: Int, level: Int): Option[B] = {
val index = (hash >>> level) & 0x1f
val mask = (1 << index)
if (bitmap == - 1) {
elems(index & 0x1f).get0(key, hash, level + 5)
} else if ((bitmap & mask) != 0) {
val offset = Integer.bitCount(bitmap & (mask-1))
// TODO: might be worth checking if sub is HashTrieMap (-> monomorphic call site)
elems(offset).get0(key, hash, level + 5)
} else
None
}
override def updated0[B1 >: B](key: A, hash: Int, level: Int, value: B1, kv: (A, B1)): HashMap[A, B1] = {
val index = (hash >>> level) & 0x1f
val mask = (1 << index)
val offset = Integer.bitCount(bitmap & (mask-1))
if ((bitmap & mask) != 0) {
val elemsNew = new Array[HashMap[A,B1]](elems.length)
Array.copy(elems, 0, elemsNew, 0, elems.length)
val sub = elems(offset)
// TODO: might be worth checking if sub is HashTrieMap (-> monomorphic call site)
val subNew = sub.updated0(key, hash, level + 5, value, kv)
elemsNew(offset) = subNew
new HashTrieMap(bitmap, elemsNew, size + (subNew.size - sub.size))
} else {
val elemsNew = new Array[HashMap[A,B1]](elems.length + 1)
Array.copy(elems, 0, elemsNew, 0, offset)
elemsNew(offset) = new HashMap1(key, hash, value, kv)
Array.copy(elems, offset, elemsNew, offset + 1, elems.length - offset)
val bitmapNew = bitmap | mask
new HashTrieMap(bitmapNew, elemsNew, size + 1)
}
}
override def removed0(key: A, hash: Int, level: Int): HashMap[A, B] = {
val index = (hash >>> level) & 0x1f
val mask = (1 << index)
val offset = Integer.bitCount(bitmap & (mask-1))
if (((bitmap >>> index) & 1) == 1) {
val elemsNew = new Array[HashMap[A,B]](elems.length)
Array.copy(elems, 0, elemsNew, 0, elems.length)
val sub = elems(offset)
// TODO: might be worth checking if sub is HashTrieMap (-> monomorphic call site)
val subNew = sub.removed0(key, hash, level + 5)
elemsNew(offset) = subNew
// TODO: handle shrinking
val sizeNew = size + (subNew.size - sub.size)
if (sizeNew > 0)
new HashTrieMap(bitmap, elemsNew, size + (subNew.size - sub.size))
else
HashMap.empty[A,B]
} else {
this
}
}
/*
override def iterator = { // TODO: optimize (use a stack to keep track of pos)
def iter(m: HashTrieMap[A,B], k: => Stream[(A,B)]): Stream[(A,B)] = {
def horiz(elems: Array[HashMap[A,B]], i: Int, k: => Stream[(A,B)]): Stream[(A,B)] = {
if (i < elems.length) {
elems(i) match {
case m: HashTrieMap[A,B] => iter(m, horiz(elems, i+1, k))
case m: HashMap1[A,B] => new Stream.Cons(m.ensurePair, horiz(elems, i+1, k))
}
} else k
}
horiz(m.elems, 0, k)
}
iter(this, Stream.empty).iterator
}
*/
override def iterator = new Iterator[(A,B)] {
private[this] var depth = 0
private[this] var arrayStack = new Array[Array[HashMap[A,B]]](6)
private[this] var posStack = new Array[Int](6)
private[this] var arrayD = elems
private[this] var posD = 0
private[this] var subIter: Iterator[(A,B)] = null // to traverse collision nodes
def hasNext = (subIter ne null) || depth >= 0
def next: (A,B) = {
if (subIter ne null) {
val el = subIter.next
if (!subIter.hasNext)
subIter = null
el
} else
next0(arrayD, posD)
}
@scala.annotation.tailrec private[this] def next0(elems: Array[HashMap[A,B]], i: Int): (A,B) = {
if (i == elems.length-1) { // reached end of level, pop stack
depth -= 1
if (depth >= 0) {
arrayD = arrayStack(depth)
posD = posStack(depth)
arrayStack(depth) = null
} else {
arrayD = null
posD = 0
}
} else
posD += 1
elems(i) match {
case m: HashTrieMap[A,B] => // push current pos onto stack and descend
if (depth >= 0) {
arrayStack(depth) = arrayD
posStack(depth) = posD
}
depth += 1
arrayD = m.elems
posD = 0
next0(m.elems, 0)
case m: HashMap1[A,B] => m.ensurePair
case m =>
subIter = m.iterator
subIter.next
}
}
}
/*
import collection.immutable._
def time(block: =>Unit) = { val t0 = System.nanoTime; block; println("elapsed: " + (System.nanoTime - t0)/1000000.0) }
var mOld = OldHashMap.empty[Int,Int]
var mNew = HashMap.empty[Int,Int]
time { for (i <- 0 until 100000) mOld = mOld.updated(i,i) }
time { for (i <- 0 until 100000) mOld = mOld.updated(i,i) }
time { for (i <- 0 until 100000) mOld = mOld.updated(i,i) }
time { for (i <- 0 until 100000) mNew = mNew.updated(i,i) }
time { for (i <- 0 until 100000) mNew = mNew.updated(i,i) }
time { for (i <- 0 until 100000) mNew = mNew.updated(i,i) }
time { mOld.iterator.foreach( p => ()) }
time { mOld.iterator.foreach( p => ()) }
time { mOld.iterator.foreach( p => ()) }
time { mNew.iterator.foreach( p => ()) }
time { mNew.iterator.foreach( p => ()) }
time { mNew.iterator.foreach( p => ()) }
*/
override def foreach[U](f: ((A, B)) => U): Unit = {
var i = 0;
while (i < elems.length) {
elems(i).foreach(f)
i += 1
}
}
private def writeObject(out: java.io.ObjectOutputStream) {
// no out.defaultWriteObject()
out.writeInt(size)
foreach { p =>
out.writeObject(p._1)
out.writeObject(p._2)
}
}
private def readObject(in: java.io.ObjectInputStream) {
val size = in.readInt
var index = 0
var m = HashMap.empty[A,B]
while (index < size) {
// TODO: optimize (use unsafe mutable update)
m = m + ((in.readObject.asInstanceOf[A], in.readObject.asInstanceOf[B]))
index += 1
}
var tm = m.asInstanceOf[HashTrieMap[A,B]]
bitmap = tm.bitmap
elems = tm.elems
size0 = tm.size0
}
}
}
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