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/**
* Copyright (C) 2009-2011 Scalable Solutions AB <http://scalablesolutions.se>
*/
package akka.util
import java.lang.reflect.{ Array => JArray }
import java.lang.{ Float => JFloat, Double => JDouble }
/**
* Set of methods which allow easy implementation of <code>hashCode</code>.
*
* Example:
* <pre>
* override def hashCode: Int = {
* var result = HashCode.SEED
* //collect the contributions of various fields
* result = HashCode.hash(result, fPrimitive)
* result = HashCode.hash(result, fObject)
* result = HashCode.hash(result, fArray)
* result
* }
* </pre>
*
* @author <a href="http://jonasboner.com">Jonas Bonér</a>
*/
object HashCode {
val SEED = 23
def hash(seed: Int, any: Any): Int = any match {
case value: Boolean => hash(seed, value)
case value: Char => hash(seed, value)
case value: Short => hash(seed, value)
case value: Int => hash(seed, value)
case value: Long => hash(seed, value)
case value: Float => hash(seed, value)
case value: Double => hash(seed, value)
case value: Byte => hash(seed, value)
case value: AnyRef =>
var result = seed
if (value eq null) result = hash(result, 0)
else if (!isArray(value)) result = hash(result, value.hashCode())
else for (id ← 0 until JArray.getLength(value)) result = hash(result, JArray.get(value, id)) // is an array
result
}
def hash(seed: Int, value: Boolean): Int = firstTerm(seed) + (if (value) 1 else 0)
def hash(seed: Int, value: Char): Int = firstTerm(seed) + value.asInstanceOf[Int]
def hash(seed: Int, value: Int): Int = firstTerm(seed) + value
def hash(seed: Int, value: Long): Int = firstTerm(seed) + (value ^ (value >>> 32)).asInstanceOf[Int]
def hash(seed: Int, value: Float): Int = hash(seed, JFloat.floatToIntBits(value))
def hash(seed: Int, value: Double): Int = hash(seed, JDouble.doubleToLongBits(value))
private def firstTerm(seed: Int): Int = PRIME * seed
private def isArray(anyRef: AnyRef): Boolean = anyRef.getClass.isArray
private val PRIME = 37
}
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