Package org.apache.pekko.routing
Class MurmurHash
- java.lang.Object
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- org.apache.pekko.routing.MurmurHash
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public class MurmurHash extends java.lang.Object
An object designed to generate well-distributed non-cryptographic hashes. It is designed to hash a collection of integers; along with the integers to hash, it generates two magic streams of integers to increase the distribution of repetitive input sequences. Thus, three methods need to be called at each step (to start and to incorporate a new integer) to update the values. Only one method needs to be called to finalize the hash.
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Constructor Summary
Constructors Constructor Description MurmurHash()
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static <T> int
arrayHash(java.lang.Object a)
Compute a high-quality hash of an arraystatic int
extendHash(int hash, int value, int magicA, int magicB)
Incorporates a new value into an existing hash.static int
finalizeHash(int hash)
Once all hashes have been incorporated, this performs a final mixingstatic int
nextMagicA(int magicA)
Given a magic integer from the first stream, compute the nextstatic int
nextMagicB(int magicB)
Given a magic integer from the second stream, compute the nextstatic int
startHash(int seed)
Begin a new hash with a seed value.static int
startMagicA()
The initial magic integers in the first stream.static int
startMagicB()
The initial magic integer in the second stream.static int
stringHash(java.lang.String s)
Compute a high-quality hash of a stringstatic <T> int
symmetricHash(scala.collection.IterableOnce<T> xs, int seed)
Compute a hash that is symmetric in its arguments--that is, where the order of appearance of elements does not matter.
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Method Detail
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startHash
public static int startHash(int seed)
Begin a new hash with a seed value.
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startMagicA
public static int startMagicA()
The initial magic integers in the first stream.
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startMagicB
public static int startMagicB()
The initial magic integer in the second stream.
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extendHash
public static int extendHash(int hash, int value, int magicA, int magicB)
Incorporates a new value into an existing hash.- Parameters:
hash
- the prior hash valuevalue
- the new value to incorporatemagicA
- a magic integer from the streammagicB
- a magic integer from a different stream- Returns:
- the updated hash value
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nextMagicA
public static int nextMagicA(int magicA)
Given a magic integer from the first stream, compute the next
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nextMagicB
public static int nextMagicB(int magicB)
Given a magic integer from the second stream, compute the next
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finalizeHash
public static int finalizeHash(int hash)
Once all hashes have been incorporated, this performs a final mixing
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arrayHash
public static <T> int arrayHash(java.lang.Object a)
Compute a high-quality hash of an array
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stringHash
public static int stringHash(java.lang.String s)
Compute a high-quality hash of a string
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symmetricHash
public static <T> int symmetricHash(scala.collection.IterableOnce<T> xs, int seed)
Compute a hash that is symmetric in its arguments--that is, where the order of appearance of elements does not matter. This is useful for hashing sets, for example.
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