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
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- MurmurHash3
- MurmurHash3
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Type Members
- class ArrayHashing[T] extends Hashing[Array[T]]
Value Members
- final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
trueif !(this == that), false otherwise.
- Definition Classes
- AnyRef → Any
- final def ##: Int
Equivalent to
x.hashCodeexcept for boxed numeric types andnull.Equivalent to
x.hashCodeexcept for boxed numeric types andnull. 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. Fornullreturns a hashcode wherenull.hashCodethrows aNullPointerException.- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
- final def ==(arg0: Any): Boolean
The expression
x == thatis equivalent toif (x eq null) that eq null else x.equals(that).The expression
x == thatis equivalent toif (x eq null) that eq null else x.equals(that).- returns
trueif the receiver object is equivalent to the argument;falseotherwise.
- Definition Classes
- AnyRef → Any
- def arrayHash[T](a: Array[T]): Int
- 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
- def arrayHashing[T]: ArrayHashing[T]
- final val arraySeed: Int(1007110753)
- final def asInstanceOf[T0]: T0
Forces the compiler to treat the receiver object as having type
T0, even though doing so may violate type safety.Forces the compiler to treat the receiver object as having type
T0, even though doing so may violate type safety.This method is useful when you believe you have type information the compiler doesn't, and it also isn't possible to check the type at runtime. In such situations, skipping type safety is the only option.
It is platform dependent whether
asInstanceOfhas any effect at runtime. It might do a runtime type test on the erasure ofT0, insert a conversion (such as boxing/unboxing), fill in a default value, or do nothing at all.In particular,
asInstanceOfis not a type test. It does **not** mean:this match { case x: T0 => x case _ => throw ClassCastException("...")
Use pattern matching or isInstanceOf for type testing instead.
Situations where
asInstanceOfis useful:- when flow analysis fails to deduce
T0automatically - when down-casting a type parameter or an abstract type member (which cannot be checked at runtime due to type erasure) If there is any doubt and you are able to type test instead, you should do so.
Be careful of using
asInstanceOfwhenT0is a primitive type. WhenT0is primitive,asInstanceOfmay insert a conversion instead of a type test. If your intent is to convert, use atoTmethod (x.toChar,x.toByte, etc.).- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastExceptionif the receiver is not an instance of the erasure ofT0, if that can be checked on this platform
- when flow analysis fails to deduce
- def bytesHash(data: Array[Byte]): Int
- 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
- def bytesHashing: Hashing[Array[Byte]]
- def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the
clonemethod is platform dependent.- returns
a copy of the receiver object.
- 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
eqmethod implements an equivalence relation on non-null instances ofAnyRef, and has three additional properties:- It is consistent: for any non-null instances
xandyof typeAnyRef, multiple invocations ofx.eq(y)consistently returnstrueor consistently returnsfalse. - For any non-null instance
xof typeAnyRef,x.eq(null)andnull.eq(x)returnsfalse. null.eq(null)returnstrue.
When overriding the
equalsorhashCodemethods, 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
trueif the argument is a reference to the receiver object;falseotherwise.
- Definition Classes
- AnyRef
- It is consistent: for any non-null instances
- def equals(arg0: AnyRef): Boolean
The equality method for reference types.
- 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
finalizemethod is invoked, as well as the interaction betweenfinalizeand 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
- 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
- final def getClass(): Class[_ <: AnyRef]
Returns the runtime class representation of the object.
- def hashCode(): Int
The hashCode method for reference types.
- 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
- final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object has the same erasure as
T0.Test whether the dynamic type of the receiver object has the same erasure as
T0.Depending on what
T0is, the test is done in one of the below ways:T0is a non-parameterized class type, e.g.BigDecimal: this method returnstrueif the value of the receiver object is aBigDecimalor a subtype ofBigDecimal.T0is a parameterized class type, e.g.List[Int]: this method returnstrueif the value of the receiver object is someList[X]for anyX. For example,List(1, 2, 3).isInstanceOf[List[String]]will return true.T0is some singleton typex.typeor literalx: this method returnsthis.eq(x). For example,x.isInstanceOf[1]is equivalent tox.eq(1)T0is an intersectionX with YorX & Y: this method is equivalent tox.isInstanceOf[X] && x.isInstanceOf[Y]T0is a unionX | Y: this method is equivalent tox.isInstanceOf[X] || x.isInstanceOf[Y]T0is a type parameter or an abstract type member: this method is equivalent toisInstanceOf[U]whereUisT0's upper bound,AnyifT0is unbounded. For example,x.isInstanceOf[A]whereAis an unbounded type parameter will return true for any value ofx.
This is exactly equivalent to the type pattern
_: T0- returns
trueif the receiver object is an instance of erasure of typeT0;falseotherwise.
- Definition Classes
- Any
- Note
due to the unexpectedness of
List(1, 2, 3).isInstanceOf[List[String]]returning true andx.isInstanceOf[A]whereAis a type parameter or abstract member returning true, these forms issue a warning.
- 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
- def mapHash(xs: Map[_, _]): Int
- final val mapSeed: Int
- 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
- 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
- final def ne(arg0: AnyRef): Boolean
Equivalent to
!(this eq that).Equivalent to
!(this eq that).- returns
trueif the argument is not a reference to the receiver object;falseotherwise.
- Definition Classes
- AnyRef
- 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
- 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
- def orderedHash(xs: IterableOnce[Any]): Int
- 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
- def orderedHashing: Hashing[IterableOnce[Any]]
- def productHash(x: Product): Int
- 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
- def productHashing: Hashing[Product]
- final val productSeed: Int(-889275714)
- def rangeHash(start: Int, step: Int, last: Int): Int
- 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
lastparameter must be the actual last element produced by a Range, not the nominalend.- Definition Classes
- MurmurHash3
- def seqHash(xs: collection.Seq[_]): Int
To offer some potential for optimization.
- final val seqSeed: Int
- def setHash(xs: Set[_]): Int
- final val setSeed: Int
- def stringHash(x: String): Int
- final def stringHash(str: String, seed: Int): Int
Compute the hash of a string
Compute the hash of a string
- Definition Classes
- MurmurHash3
- def stringHashing: Hashing[String]
- final val stringSeed: Int(-137723950)
- final val symmetricSeed: Int(-1248659538)
- final def synchronized[T0](arg0: => T0): T0
Executes the code in
bodywith an exclusive lock onthis.Executes the code in
bodywith an exclusive lock onthis.- returns
the result of
body
- Definition Classes
- AnyRef
- 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
- final val traversableSeed: Int(-415593707)
- def unorderedHash(xs: IterableOnce[Any]): Int
- 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
- def unorderedHashing: Hashing[IterableOnce[Any]]
- 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
- 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
- final def wait(arg0: Long): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.
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