/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
package mutable
/** An implementation class backing a `HashSet`.
*
* This trait is used internally. It can be mixed in with various collections relying on
* hash table as an implementation.
*
* @since 2.3
*
* @tparam A the type of the elements contained in the flat hash table.
*/
trait FlatHashTable[A] extends FlatHashTable.HashUtils[A] {
import FlatHashTable._
private final val tableDebug = false
@transient private[collection] var _loadFactor = defaultLoadFactor
/** The actual hash table.
*/
@transient protected var table: Array[AnyRef] = new Array(initialCapacity)
/** The number of mappings contained in this hash table.
*/
@transient protected var tableSize = 0
/** The next size value at which to resize (capacity * load factor).
*/
@transient protected var threshold: Int = newThreshold(_loadFactor, initialCapacity)
/** The array keeping track of number of elements in 32 element blocks.
*/
@transient protected var sizemap: Array[Int] = null
import HashTable.powerOfTwo
protected def capacity(expectedSize: Int) = if (expectedSize == 0) 1 else powerOfTwo(expectedSize)
private def initialCapacity = capacity(initialSize)
/**
* Initializes the collection from the input stream. `f` will be called for each element
* read from the input stream in the order determined by the stream. This is useful for
* structures where iteration order is important (e.g. LinkedHashSet).
*
* The serialization format expected is the one produced by `serializeTo`.
*/
private[collection] def init(in: java.io.ObjectInputStream, f: A => Unit) {
in.defaultReadObject
_loadFactor = in.readInt
assert(_loadFactor > 0)
val size = in.readInt
tableSize = 0
assert(size >= 0)
table = new Array(capacity(sizeForThreshold(size, _loadFactor)))
threshold = newThreshold(_loadFactor, table.size)
val smDefined = in.readBoolean
if (smDefined) sizeMapInit(table.length)
var index = 0
while (index < size) {
val elem = in.readObject.asInstanceOf[A]
f(elem)
addEntry(elem)
index += 1
}
}
/**
* Serializes the collection to the output stream by saving the load factor, collection
* size and collection elements. `foreach` determines the order in which the elements are saved
* to the stream. To deserialize, `init` should be used.
*/
private[collection] def serializeTo(out: java.io.ObjectOutputStream) {
out.defaultWriteObject
out.writeInt(_loadFactor)
out.writeInt(tableSize)
out.writeBoolean(isSizeMapDefined)
iterator.foreach(out.writeObject)
}
/** Finds an entry in the hash table if such an element exists. */
def findEntry(elem: A): Option[A] = {
var h = index(elemHashCode(elem))
var entry = table(h)
while (null != entry && entry != elem) {
h = (h + 1) % table.length
entry = table(h)
}
if (null == entry) None else Some(entry.asInstanceOf[A])
}
/** Checks whether an element is contained in the hash table. */
def containsEntry(elem: A): Boolean = {
var h = index(elemHashCode(elem))
var entry = table(h)
while (null != entry && entry != elem) {
h = (h + 1) % table.length
entry = table(h)
}
null != entry
}
/** Add entry if not yet in table.
* @return Returns `true` if a new entry was added, `false` otherwise.
*/
def addEntry(elem: A) : Boolean = {
var h = index(elemHashCode(elem))
var entry = table(h)
while (null != entry) {
if (entry == elem) return false
h = (h + 1) % table.length
entry = table(h)
}
table(h) = elem.asInstanceOf[AnyRef]
tableSize = tableSize + 1
nnSizeMapAdd(h)
if (tableSize >= threshold) growTable()
true
}
/** Removes an entry from the hash table, returning an option value with the element, or `None` if it didn't exist. */
def removeEntry(elem: A) : Option[A] = {
if (tableDebug) checkConsistent()
def precedes(i: Int, j: Int) = {
val d = table.length >> 1
if (i <= j) j - i < d
else i - j > d
}
var h = index(elemHashCode(elem))
var entry = table(h)
while (null != entry) {
if (entry == elem) {
var h0 = h
var h1 = (h0 + 1) % table.length
while (null != table(h1)) {
val h2 = index(elemHashCode(table(h1).asInstanceOf[A]))
//Console.println("shift at "+h1+":"+table(h1)+" with h2 = "+h2+"? "+(h2 != h1)+precedes(h2, h0)+table.length)
if (h2 != h1 && precedes(h2, h0)) {
//Console.println("shift "+h1+" to "+h0+"!")
table(h0) = table(h1)
h0 = h1
}
h1 = (h1 + 1) % table.length
}
table(h0) = null
tableSize -= 1
nnSizeMapRemove(h0)
if (tableDebug) checkConsistent()
return Some(entry.asInstanceOf[A])
}
h = (h + 1) % table.length
entry = table(h)
}
None
}
def iterator = new Iterator[A] {
private var i = 0
def hasNext: Boolean = {
while (i < table.length && (null == table(i))) i += 1
i < table.length
}
def next(): A =
if (hasNext) { i += 1; table(i - 1).asInstanceOf[A] }
else Iterator.empty.next
}
private def growTable() {
val oldtable = table
table = new Array[AnyRef](table.length * 2)
tableSize = 0
nnSizeMapReset(table.length)
threshold = newThreshold(_loadFactor, table.length)
var i = 0
while (i < oldtable.length) {
val entry = oldtable(i)
if (null != entry) addEntry(entry.asInstanceOf[A])
i += 1
}
if (tableDebug) checkConsistent()
}
private def checkConsistent() {
for (i <- 0 until table.length)
if (table(i) != null && !containsEntry(table(i).asInstanceOf[A]))
assert(false, i+" "+table(i)+" "+table.mkString)
}
/* Size map handling code */
/*
* The following three methods (nn*) modify a size map only if it has been
* initialized, that is, if it's not set to null.
*
* The size map logically divides the hash table into `sizeMapBucketSize` element buckets
* by keeping an integer entry for each such bucket. Each integer entry simply denotes
* the number of elements in the corresponding bucket.
* Best understood through an example, see:
* table = [/, 1, /, 6, 90, /, -3, 5] (8 entries)
* sizemap = [ 2 | 3 ] (2 entries)
* where sizeMapBucketSize == 4.
*
*/
protected def nnSizeMapAdd(h: Int) = if (sizemap ne null) {
val p = h >> sizeMapBucketBitSize
sizemap(p) += 1
}
protected def nnSizeMapRemove(h: Int) = if (sizemap ne null) {
sizemap(h >> sizeMapBucketBitSize) -= 1
}
protected def nnSizeMapReset(tableLength: Int) = if (sizemap ne null) {
val nsize = calcSizeMapSize(tableLength)
if (sizemap.length != nsize) sizemap = new Array[Int](nsize)
else java.util.Arrays.fill(sizemap, 0)
}
private[collection] final def totalSizeMapBuckets = if (sizeMapBucketSize < table.length) 1 else table.length / sizeMapBucketSize
protected def calcSizeMapSize(tableLength: Int) = (tableLength >> sizeMapBucketBitSize) + 1
// discards the previous sizemap and only allocates a new one
protected def sizeMapInit(tableLength: Int) {
sizemap = new Array[Int](calcSizeMapSize(tableLength))
}
// discards the previous sizemap and populates the new one
protected def sizeMapInitAndRebuild {
// first allocate
sizeMapInit(table.length)
// rebuild
val totalbuckets = totalSizeMapBuckets
var bucketidx = 0
var tableidx = 0
var tbl = table
var tableuntil = sizeMapBucketSize min tbl.length
while (bucketidx < totalbuckets) {
var currbucketsz = 0
while (tableidx < tableuntil) {
if (tbl(tableidx) ne null) currbucketsz += 1
tableidx += 1
}
sizemap(bucketidx) = currbucketsz
tableuntil += sizeMapBucketSize
bucketidx += 1
}
}
private[collection] def printSizeMap {
println(sizemap.toList)
}
protected def sizeMapDisable = sizemap = null
protected def isSizeMapDefined = sizemap ne null
protected def alwaysInitSizeMap = false
/* End of size map handling code */
protected final def index(hcode: Int) = {
// improve(hcode) & (table.length - 1)
val improved = improve(hcode)
val ones = table.length - 1
(improved >> (32 - java.lang.Integer.bitCount(ones))) & ones
}
protected def clearTable() {
var i = table.length - 1
while (i >= 0) { table(i) = null; i -= 1 }
tableSize = 0
nnSizeMapReset(table.length)
}
private[collection] def hashTableContents = new FlatHashTable.Contents[A](
_loadFactor,
table,
tableSize,
threshold,
sizemap
)
protected def initWithContents(c: FlatHashTable.Contents[A]) = {
if (c != null) {
_loadFactor = c.loadFactor
table = c.table
tableSize = c.tableSize
threshold = c.threshold
sizemap = c.sizemap
}
if (alwaysInitSizeMap && sizemap == null) sizeMapInitAndRebuild
}
}
private[collection] object FlatHashTable {
/** The load factor for the hash table; must be < 500 (0.5)
*/
private[collection] def defaultLoadFactor: Int = 450
private[collection] final def loadFactorDenum = 1000
/** The initial size of the hash table.
*/
private[collection] def initialSize: Int = 16
private[collection] def sizeForThreshold(size: Int, _loadFactor: Int) = size * loadFactorDenum / _loadFactor
private[collection] def newThreshold(_loadFactor: Int, size: Int) = {
val lf = _loadFactor
assert(lf < (loadFactorDenum / 2), "loadFactor too large; must be < 0.5")
(size.toLong * lf / loadFactorDenum ).toInt
}
class Contents[A](
val loadFactor: Int,
val table: Array[AnyRef],
val tableSize: Int,
val threshold: Int,
val sizemap: Array[Int]
)
trait HashUtils[A] {
protected final def sizeMapBucketBitSize = 5
// so that:
protected final def sizeMapBucketSize = 1 << sizeMapBucketBitSize
protected def elemHashCode(elem: A) = if (elem == null) 0 else elem.hashCode()
protected final def improve(hcode: Int) = {
// var h: Int = hcode + ~(hcode << 9)
// h = h ^ (h >>> 14)
// h = h + (h << 4)
// h ^ (h >>> 10)
var i = hcode * 0x9e3775cd
i = java.lang.Integer.reverseBytes(i)
i * 0x9e3775cd
}
}
}
