Packages

  • package root

    This is the documentation for the Scala standard library.

    This is the documentation for the Scala standard library.

    Package structure

    The scala package contains core types like Int, Float, Array or Option which are accessible in all Scala compilation units without explicit qualification or imports.

    Notable packages include:

    Other packages exist. See the complete list on the right.

    Additional parts of the standard library are shipped as separate libraries. These include:

    • scala.reflect - Scala's reflection API (scala-reflect.jar)
    • scala.xml - XML parsing, manipulation, and serialization (scala-xml.jar)
    • scala.collection.parallel - Parallel collections (scala-parallel-collections.jar)
    • scala.util.parsing - Parser combinators (scala-parser-combinators.jar)
    • scala.swing - A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)

    Automatic imports

    Identifiers in the scala package and the scala.Predef object are always in scope by default.

    Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example, List is an alias for scala.collection.immutable.List.

    Other aliases refer to classes provided by the underlying platform. For example, on the JVM, String is an alias for java.lang.String.

    Definition Classes
    root
  • package scala

    Core Scala types.

    Core Scala types. They are always available without an explicit import.

    Definition Classes
    root
  • package util
    Definition Classes
    scala
  • package hashing
    Definition Classes
    util
  • ByteswapHashing
  • Hashing
  • MurmurHash3
o

scala.util.hashing

MurmurHash3

object MurmurHash3 extends MurmurHash3

An implementation of Austin Appleby's MurmurHash 3 algorithm (MurmurHash3_x86_32). This object contains methods that hash values of various types as well as means to construct Hashing objects.

This algorithm is designed to generate well-distributed non-cryptographic hashes. It is designed to hash data in 32 bit chunks (ints).

The mix method needs to be called at each step to update the intermediate hash value. For the last chunk to incorporate into the hash mixLast may be used instead, which is slightly faster. Finally finalizeHash needs to be called to compute the final hash value.

This is based on the earlier MurmurHash3 code by Rex Kerr, but the MurmurHash3 algorithm was since changed by its creator Austin Appleby to remedy some weaknesses and improve performance. This represents the latest and supposedly final version of the algorithm (revision 136).

Source
MurmurHash3.scala
See also

https://github.com/aappleby/smhasher

Linear Supertypes
MurmurHash3, AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. MurmurHash3
  2. MurmurHash3
  3. AnyRef
  4. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. All

Type Members

  1. class ArrayHashing[T] extends Hashing[Array[T]]

Value Members

  1. def arrayHash[T](a: Array[T]): Int
  2. final def arrayHash[T](a: Array[T], seed: Int): Int

    Compute the hash of an array.

    Compute the hash of an array. Potential range hashes are recognized to produce a hash that is compatible with rangeHash.

    Definition Classes
    MurmurHash3
  3. def arrayHashing[T]: ArrayHashing[T]
  4. final val arraySeed: Int(1007110753)
  5. def bytesHash(data: Array[Byte]): Int
  6. final def bytesHash(data: Array[Byte], seed: Int): Int

    Compute the hash of a byte array.

    Compute the hash of a byte array. Faster than arrayHash, because it hashes 4 bytes at once. Note that the result is not compatible with arrayHash!

    Definition Classes
    MurmurHash3
  7. def bytesHashing: Hashing[Array[Byte]]
  8. final def finalizeHash(hash: Int, length: Int): Int

    Finalize a hash to incorporate the length and make sure all bits avalanche.

    Finalize a hash to incorporate the length and make sure all bits avalanche.

    Definition Classes
    MurmurHash3
  9. final def indexedSeqHash(a: collection.IndexedSeq[Any], seed: Int): Int

    Compute the hash of an IndexedSeq.

    Compute the hash of an IndexedSeq. Potential range hashes are recognized to produce a hash that is compatible with rangeHash.

    Definition Classes
    MurmurHash3
  10. final def listHash(xs: collection.immutable.List[_], seed: Int): Int

    Compute the hash of a List.

    Compute the hash of a List. Potential range hashes are recognized to produce a hash that is compatible with rangeHash.

    Definition Classes
    MurmurHash3
  11. def mapHash(xs: Map[_, _]): Int
  12. final val mapSeed: Int
  13. final def mix(hash: Int, data: Int): Int

    Mix in a block of data into an intermediate hash value.

    Mix in a block of data into an intermediate hash value.

    Definition Classes
    MurmurHash3
  14. final def mixLast(hash: Int, data: Int): Int

    May optionally be used as the last mixing step.

    May optionally be used as the last mixing step. Is a little bit faster than mix, as it does no further mixing of the resulting hash. For the last element this is not necessary as the hash is thoroughly mixed during finalization anyway.

    Definition Classes
    MurmurHash3
  15. def orderedHash(xs: IterableOnce[Any]): Int
  16. final def orderedHash(xs: IterableOnce[Any], seed: Int): Int

    Compute a hash that depends on the order of its arguments.

    Compute a hash that depends on the order of its arguments. Potential range hashes are recognized to produce a hash that is compatible with rangeHash.

    Definition Classes
    MurmurHash3
  17. def orderedHashing: Hashing[IterableOnce[Any]]
  18. def productHash(x: Product): Int
  19. final def productHash(x: Product, seed: Int, ignorePrefix: Boolean = false): Int

    Compute the hash of a product

    Compute the hash of a product

    Definition Classes
    MurmurHash3
  20. def productHashing: Hashing[Product]
  21. final val productSeed: Int(-889275714)
  22. def rangeHash(start: Int, step: Int, last: Int): Int
  23. final def rangeHash(start: Int, step: Int, last: Int, seed: Int): Int

    Compute the hash of a Range with at least 2 elements.

    Compute the hash of a Range with at least 2 elements. Ranges with fewer elements need to use seqHash instead. The last parameter must be the actual last element produced by a Range, not the nominal end.

    Definition Classes
    MurmurHash3
  24. def seqHash(xs: collection.Seq[_]): Int

    To offer some potential for optimization.

  25. final val seqSeed: Int
  26. def setHash(xs: Set[_]): Int
  27. final val setSeed: Int
  28. def stringHash(x: String): Int
  29. final def stringHash(str: String, seed: Int): Int

    Compute the hash of a string

    Compute the hash of a string

    Definition Classes
    MurmurHash3
  30. def stringHashing: Hashing[String]
  31. final val stringSeed: Int(-137723950)
  32. final val symmetricSeed: Int(-1248659538)
  33. final val traversableSeed: Int(-415593707)
  34. def unorderedHash(xs: IterableOnce[Any]): Int
  35. final def unorderedHash(xs: IterableOnce[Any], seed: Int): Int

    Compute a hash that is symmetric in its arguments - that is a hash where the order of appearance of elements does not matter.

    Compute a hash that is symmetric in its arguments - that is a hash where the order of appearance of elements does not matter. This is useful for hashing sets, for example.

    Definition Classes
    MurmurHash3
  36. def unorderedHashing: Hashing[IterableOnce[Any]]