chore: add all the files in scala.util.hashing

Author: hamzaremmal

library/src/scala/util/hashing/ByteswapHashing.scala

@@ -0,0 +1,40 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc. dba Akka
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala
+package util.hashing
+
+
+
+
+
+
+/** A fast multiplicative hash by Phil Bagwell.
+ */
+final class ByteswapHashing[T] extends Hashing[T] {
+
+  def hash(v: T) = byteswap32(v.##)
+
+}
+
+
+object ByteswapHashing {
+
+  private class Chained[T](h: Hashing[T]) extends Hashing[T] {
+    def hash(v: T) = byteswap32(h.hash(v))
+  }
+
+  /** Composes another `Hashing` with the Byteswap hash.
+   */
+  def chain[T](h: Hashing[T]): Hashing[T] = new Chained(h)
+
+}

library/src/scala/util/hashing/Hashing.scala

@@ -0,0 +1,42 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc. dba Akka
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala
+package util.hashing
+
+import scala.annotation.implicitNotFound
+
+/** `Hashing` is a trait whose instances each represent a strategy for hashing
+  * instances of a type.
+  *
+  * `Hashing`'s companion object defines a default hashing strategy for all
+  * objects - it calls their `##` method.
+  *
+  * Note: when using a custom `Hashing`, make sure to use it with the `Equiv`
+  * such that if any two objects are equal, then their hash codes must be equal.
+  */
+@implicitNotFound(msg = "No implicit Hashing defined for ${T}.")
+trait Hashing[T] extends Serializable {
+  def hash(x: T): Int
+}
+
+object Hashing {
+  final class Default[T] extends Hashing[T] {
+    def hash(x: T) = x.##
+  }
+
+  implicit def default[T]: Default[T] = new Default[T]
+
+  def fromFunction[T](f: T => Int) = new Hashing[T] {
+    def hash(x: T) = f(x)
+  }
+}