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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). Even so, test the generated hashes in between Scala versions, even for point releases, as fast, non-cryptographic hashing algorithms evolve rapidly.

Source
MurmurHash3.scala
See also

https://github.com/aappleby/smhasher

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MurmurHash3, AnyRef, Any
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Type Members

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

Value Members

  1. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

    true if !(this == that), false otherwise.

    Definition Classes
    AnyRef → Any
  2. final def ##: Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  4. def arrayHash[T](a: Array[T]): Int
  5. 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
  6. def arrayHashing[T]: ArrayHashing[T]
  7. final val arraySeed: Int(1007110753)
  8. final def asInstanceOf[T0]: T0

    Cast the receiver object to be of type T0.

    Cast the receiver object to be of type T0.

    Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

    returns

    the receiver object.

    Definition Classes
    Any
    Exceptions thrown

    ClassCastException if the receiver object is not an instance of the erasure of type T0.

  9. def bytesHash(data: Array[Byte]): Int
  10. 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
  11. def bytesHashing: Hashing[Array[Byte]]
  12. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  13. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (that) is a reference to the receiver object (this).

    Tests whether the argument (that) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  14. def equals(arg0: AnyRef): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  15. def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
    Note

    not specified by SLS as a member of AnyRef

  16. 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
  17. final def getClass(): Class[_ <: AnyRef]

    Returns the runtime class representation of the object.

    Returns the runtime class representation of the object.

    returns

    a class object corresponding to the runtime type of the receiver.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  18. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  19. 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
  20. final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is T0.

    Test whether the dynamic type of the receiver object is T0.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any
  21. 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
  22. def mapHash(xs: Map[_, _]): Int
  23. final val mapSeed: Int
  24. 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
  25. 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
  26. final def ne(arg0: AnyRef): Boolean

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  27. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  28. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  29. def orderedHash(xs: IterableOnce[Any]): Int
  30. 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
  31. def orderedHashing: Hashing[IterableOnce[Any]]
  32. def productHash(x: Product): Int
  33. 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
  34. def productHashing: Hashing[Product]
  35. final val productSeed: Int(-889275714)
  36. def rangeHash(start: Int, step: Int, last: Int): Int
  37. 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
  38. def seqHash(xs: collection.Seq[_]): Int

    To offer some potential for optimization.

  39. final val seqSeed: Int
  40. def setHash(xs: Set[_]): Int
  41. final val setSeed: Int
  42. def stringHash(x: String): Int
  43. final def stringHash(str: String, seed: Int): Int

    Compute the hash of a string

    Compute the hash of a string

    Definition Classes
    MurmurHash3
  44. def stringHashing: Hashing[String]
  45. final val stringSeed: Int(-137723950)
  46. final val symmetricSeed: Int(-1248659538)
  47. final def synchronized[T0](arg0: => T0): T0

    Executes the code in body with an exclusive lock on this.

    Executes the code in body with an exclusive lock on this.

    returns

    the result of body

    Definition Classes
    AnyRef
  48. def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

    a String representation of the object.

    Definition Classes
    AnyRef → Any
  49. final val traversableSeed: Int(-415593707)
  50. def unorderedHash(xs: IterableOnce[Any]): Int
  51. 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
  52. def unorderedHashing: Hashing[IterableOnce[Any]]
  53. final def wait(): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
    Note

    not specified by SLS as a member of AnyRef

  54. final def wait(arg0: Long, arg1: Int): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
    Note

    not specified by SLS as a member of AnyRef

  55. final def wait(arg0: Long): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

Inherited from MurmurHash3

Inherited from AnyRef

Inherited from Any

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