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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection.mutable
import Predef._
trait FlatHashTable[A] {
/** The load factor for the hash table; must be < 500 (0.5)
*/
protected def loadFactor: Int = 450
protected final def loadFactorDenum = 1000
/** The initial size of the hash table.
*/
protected def initialSize: Int = 16
private final val tableDebug = false
/** The actual hash table.
*/
protected var table: Array[AnyRef] =
if (initialSize == 0) null else new Array(initialSize)
/** The number of mappings contained in this hash table.
*/
protected var tableSize = 0
/** The next size value at which to resize (capacity * load factor).
*/
protected var threshold: Int = newThreshold(initialSize)
/** Returns the number of entires in this hash table.
*/
def size: Int = tableSize
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])
}
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
}
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
if (tableSize >= threshold) growTable()
true
}
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
if (tableDebug) checkConsistent()
return Some(entry.asInstanceOf[A])
}
h = (h + 1) % table.length
entry = table(h)
}
None
}
def elements = 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
threshold = newThreshold(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.toString)
}
protected def elemHashCode(elem: A) = 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)
}
protected final def index(hcode: Int) = improve(hcode) & (table.length - 1)
private def newThreshold(size: Int) = {
val lf = loadFactor
assert(lf < (loadFactorDenum / 2), "loadFactor too large; must be < 0.5")
(size.toLong * lf / loadFactorDenum ).toInt
}
protected def clear() {
var i = table.length - 1
while (i >= 0) { table(i) = null; i -= 1 }
tableSize = 0
}
}
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