Package org.apache.arrow.memory.util.hash

Class SimpleHasher

java.lang.Object

org.apache.arrow.memory.util.hash.SimpleHasher

All Implemented Interfaces:

ArrowBufHasher

public class SimpleHasher
extends Object
implements ArrowBufHasher

A simple hasher that calculates the hash code of integers as is, and does not perform any finalization. So the computation is extremely efficient.

This algorithm only provides the most basic semantics for the hash code. That is, if two objects are equal, they must have equal hash code. However, the quality of the produced hash code may not be good. In other words, the generated hash codes are far from being uniformly distributed in the universe.

Therefore, this algorithm is suitable only for scenarios where the most basic semantics of the hash code is required (e.g. in scenarios that require fast and proactive data pruning)

An object of this class is stateless, so it can be shared between threads.

Field Summary

Fields

Modifier and Type	Field	Description
static SimpleHasher	INSTANCE

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SimpleHasher()

Method Summary

Modifier and Type	Method	Description
protected int	combineHashCode(int currentHashCode, int newHashCode)
boolean	equals(@Nullable Object obj)
protected int	finalizeHashCode(int hashCode)
protected int	getLongHashCode(long longValue)
int	hashCode()
int	hashCode(long address, long length)	Calculates the hash code for a memory region.
int	hashCode(ArrowBuf buf, long offset, long length)	Calculates the hash code for a memory region.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Details

INSTANCE

public static SimpleHasher INSTANCE

Constructor Details

SimpleHasher

protected SimpleHasher()

Method Details

hashCode

public int hashCode(long address,
 long length)

Calculates the hash code for a memory region.

Specified by:

hashCode in interface ArrowBufHasher

Parameters:

address - start address of the memory region.

length - length of the memory region.

Returns:

the hash code.

hashCode

public int hashCode(ArrowBuf buf,
 long offset,
 long length)

Calculates the hash code for a memory region.

Specified by:

hashCode in interface ArrowBufHasher

Parameters:

buf - the buffer for the memory region.

offset - offset within the buffer for the memory region.

length - length of the memory region.

Returns:

the hash code.

combineHashCode

protected int combineHashCode(int currentHashCode,
 int newHashCode)

getLongHashCode

protected int getLongHashCode(long longValue)

finalizeHashCode

protected int finalizeHashCode(int hashCode)

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(@Nullable Object obj)

Overrides:

equals in class Object