LongHashFunction (Zero-allocation Hashing 0.7 API)

java.lang.Object
- net.openhft.hashing.LongHashFunction

All Implemented Interfaces:

Serializable
```
public abstract class LongHashFunction
extends Object
implements Serializable
```
Hash function producing long-valued result from byte sequences of any length and a plenty of different sources which "feels like byte sequences". Except hashBytes(byte[]), hashBytes(ByteBuffer) (with their "sliced" versions) and hashMemory(long, long) methods, which actually accept byte sequences, notion of byte sequence is defined as follows:
- For methods accepting arrays of Java primitives, Strings and StringBuilders, byte sequence is how the input's bytes are actually lay in memory.
- For methods accepting single primitive values, byte sequence is how this primitive would be put into memory with native byte order, or equivalently, hashXxx(primitive) has always the same result as hashXxxs(new xxx[] {primitive}), where "xxx" is any Java primitive type name.
- For hash(Object, Access, long, long) method byte sequence abstraction is defined by the given Access strategy to the given object.
Hash function implementation could either produce equal results for equal input on platforms with different ByteOrder, favoring one byte order in terms of performance, or different results, but performing equally good. This choice should be explicitly documented for all LongHashFunction implementations.
Subclassing
To implement a specific hash function algorithm, this class should be subclassed. Only methods that accept single primitives, hashVoid() and hash(Object, Access, long, long) should be implemented; other have default implementations which in the end delegate to hash(Object, Access, long, long) abstract method.
Notes about how exactly methods with default implementations are implemented in doc comments are given for information and could be changed at any moment. However, it could hardly cause any issues with subclassing, except probably little performance degradation. Methods documented as "shortcuts" could either delegate to the referenced method or delegate directly to the method to which the referenced method delegates.
LongHashFunction implementations shouldn't assume that Access strategies do defensive checks, and access only bytes within the requested range.
See Also:

Serialized Form

Constructor Summary

Constructors
Modifier Constructor and Description

protected LongHashFunction()
Constructor for use in subclasses.

Constructors
Modifier	Constructor and Description
`protected`	`LongHashFunction()` Constructor for use in subclasses.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`static LongHashFunction`	`city_1_1()` Returns a hash function implementing CityHash64 algorithm, version 1.1 without seed values.
`static LongHashFunction`	`city_1_1(long seed)` Returns a hash function implementing CityHash64 algorithm, version 1.1 using the given seed value.
`static LongHashFunction`	`city_1_1(long seed0, long seed1)` Returns a hash function implementing CityHash64 algorithm, version 1.1 using the two given seed values.
`static LongHashFunction`	`farmNa()` Returns a hash function implementing so-called farmhashna algorithm, without seed values.
`static LongHashFunction`	`farmNa(long seed)` Returns a hash function implementing so-called farmhashna algorithm, using the given seed value.
`static LongHashFunction`	`farmNa(long seed0, long seed1)` Returns a hash function implementing so-called farmhashna algorithm, using the two given seed values.
`static LongHashFunction`	`farmUo()` Returns a hash function implementing so-called farmhashuo algorithm without seed values.
`static LongHashFunction`	`farmUo(long seed)` Returns a hash function implementing so-called farmhashuo algorithm with the given seed value.
`static LongHashFunction`	`farmUo(long seed0, long seed1)` Returns a hash function implementing so-called farmhashuo algorithm with the two given seed values.
`abstract <T> long`	`hash(T input, Access<T> access, long off, long len)` Returns the hash code for `len` continuous bytes of the given `input` object, starting from the given offset.
`long`	`hashBoolean(boolean input)` Shortcut for `hashBooleans(new boolean[] {input})`.
`long`	`hashBooleans(boolean[] input)` Shortcut for `hashBooleans(input, 0, input.length)`.
`long`	`hashBooleans(boolean[] input, int off, int len)` Returns the hash code for the specified subsequence of the given `boolean` array.
`abstract long`	`hashByte(byte input)` Returns the hash code for the given `byte` value.
`long`	`hashBytes(byte[] input)` Shortcut for `hashBytes(input, 0, input.length)`.
`long`	`hashBytes(byte[] input, int off, int len)` Returns the hash code for the specified subsequence of the given `byte` array.
`long`	`hashBytes(ByteBuffer input)` Shortcut for `hashBytes(input, input.position(), input.remaining())`.
`long`	`hashBytes(ByteBuffer input, int off, int len)` Returns the hash code for the specified subsequence of the given `ByteBuffer`.
`abstract long`	`hashChar(char input)` Returns the hash code for the given `char` value; this method is consistent with `LongHashFunction` methods that accept sequences of bytes, assuming the `input` value is interpreted in native byte order.
`long`	`hashChars(char[] input)` Shortcut for `hashChars(input, 0, input.length)`.
`long`	`hashChars(char[] input, int off, int len)` Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given `char` array.
`long`	`hashChars(String input)` Shortcut for `hashChars(input, 0, input.length())`.
`long`	`hashChars(StringBuilder input)` Shortcut for `hashChars(input, 0, input.length())`.
`long`	`hashChars(StringBuilder input, int off, int len)` Returns the hash code for bytes of the specified subsequence of the given `StringBuilder`'s underlying `char` array.
`long`	`hashChars(String input, int off, int len)` Returns the hash code for bytes of the specified subsequence of the given `String`'s underlying `char` array.
`abstract long`	`hashInt(int input)` Returns the hash code for the given `int` value; this method is consistent with `LongHashFunction` methods that accept sequences of bytes, assuming the `input` value is interpreted in native byte order.
`long`	`hashInts(int[] input)` Shortcut for `hashInts(input, 0, input.length)`.
`long`	`hashInts(int[] input, int off, int len)` Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given `int` array.
`abstract long`	`hashLong(long input)` Returns the hash code for the given `long` value; this method is consistent with `LongHashFunction` methods that accept sequences of bytes, assuming the `input` value is interpreted in native byte order.
`long`	`hashLongs(long[] input)` Shortcut for `hashLongs(input, 0, input.length)`.
`long`	`hashLongs(long[] input, int off, int len)` Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given `long` array.
`long`	`hashMemory(long address, long len)` Returns the hash code of bytes of the wild memory from the given address.
`abstract long`	`hashShort(short input)` Returns the hash code for the given `short` value; this method is consistent with `LongHashFunction` methods that accept sequences of bytes, assuming the `input` value is interpreted in native byte order.
`long`	`hashShorts(short[] input)` Shortcut for `hashShorts(input, 0, input.length)`.
`long`	`hashShorts(short[] input, int off, int len)` Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given `short` array.
`abstract long`	`hashVoid()` Returns the hash code for the empty (zero-length) bytes sequence, for example `hashBytes(new byte[0])`.
`static LongHashFunction`	`murmur_3()` Returns a hash function implementing MurmurHash3 algorithm without seed values.
`static LongHashFunction`	`murmur_3(long seed)` Returns a hash function implementing MurmurHash3 algorithm with the given seed value.
`static LongHashFunction`	`xx_r39()` Returns a hash function implementing xxHash algorithm, release 39 without seed value (0 is used as default seed value).
`static LongHashFunction`	`xx_r39(long seed)` Returns a hash function implementing xxHash algorithm, release 39 with the given seed value.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - LongHashFunction
```
protected LongHashFunction()
```
    Constructor for use in subclasses.
- Method Detail
  - city_1_1
```
public static LongHashFunction city_1_1()
```
    Returns a hash function implementing CityHash64 algorithm, version 1.1 without seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    
    See Also:
    
    city_1_1(long), city_1_1(long, long)
  - city_1_1
```
public static LongHashFunction city_1_1(long seed)
```
    Returns a hash function implementing CityHash64 algorithm, version 1.1 using the given seed value. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    
    See Also:
    
    city_1_1(), city_1_1(long, long)
  - city_1_1
```
public static LongHashFunction city_1_1(long seed0,
                                        long seed1)
```
    Returns a hash function implementing CityHash64 algorithm, version 1.1 using the two given seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    
    See Also:
    
    city_1_1(), city_1_1(long)
  - farmNa
```
public static LongHashFunction farmNa()
```
    Returns a hash function implementing so-called farmhashna algorithm, without seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    farmhashna was introduced in FarmHash 1.0. For inputs shorter than 32 bytes it's output is equivalent to city_1_1() output.
    
    See Also:
    
    farmNa(long), farmNa(long, long)
  - farmNa
```
public static LongHashFunction farmNa(long seed)
```
    Returns a hash function implementing so-called farmhashna algorithm, using the given seed value. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    farmhashna was introduced in FarmHash 1.0. For inputs shorter than 32 bytes it's output is equivalent to city_1_1(long) output.
    
    See Also:
    
    farmNa(), farmNa(long, long)
  - farmNa
```
public static LongHashFunction farmNa(long seed0,
                                      long seed1)
```
    Returns a hash function implementing so-called farmhashna algorithm, using the two given seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    farmhashna was introduced in FarmHash 1.0. For inputs shorter than 32 bytes it's output is equivalent to city_1_1(long, long) output.
    
    See Also:
    
    farmNa(), farmNa(long)
  - farmUo
```
public static LongHashFunction farmUo()
```
    Returns a hash function implementing so-called farmhashuo algorithm without seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    farmhashuo was introduced in FarmHash 1.1.
    
    See Also:
    
    farmUo(long), farmUo(long, long)
  - farmUo
```
public static LongHashFunction farmUo(long seed)
```
    Returns a hash function implementing so-called farmhashuo algorithm with the given seed value. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    farmhashuo was introduced in FarmHash 1.1.
    
    See Also:
    
    farmUo(), farmUo(long, long)
  - farmUo
```
public static LongHashFunction farmUo(long seed0,
                                      long seed1)
```
    Returns a hash function implementing so-called farmhashuo algorithm with the two given seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    farmhashuo was introduced in FarmHash 1.1.
    
    See Also:
    
    farmUo(), farmUo(long)
  - murmur_3
```
public static LongHashFunction murmur_3()
```
    Returns a hash function implementing MurmurHash3 algorithm without seed values. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    
    See Also:
    
    murmur_3(long)
  - murmur_3
```
public static LongHashFunction murmur_3(long seed)
```
    Returns a hash function implementing MurmurHash3 algorithm with the given seed value. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    
    See Also:
    
    murmur_3()
  - xx_r39
```
public static LongHashFunction xx_r39()
```
    Returns a hash function implementing xxHash algorithm, release 39 without seed value (0 is used as default seed value). This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    Note: implementation is fully compatible with xxHash releases at least up to r42.
    
    See Also:
    
    xx_r39(long)
  - xx_r39
```
public static LongHashFunction xx_r39(long seed)
```
    Returns a hash function implementing xxHash algorithm, release 39 with the given seed value. This implementation produce equal results for equal input on platforms with different ByteOrder, but is slower on big-endian platforms than on little-endian.
    Note: implementation is fully compatible with xxHash releases at least up to r42.
    
    See Also:
    
    xx_r39()
  - hashLong
```
public abstract long hashLong(long input)
```
    Returns the hash code for the given long value; this method is consistent with LongHashFunction methods that accept sequences of bytes, assuming the input value is interpreted in native byte order. For example, the result of hashLong(v) call is identical to the result of hashLongs(new long[] {v}) call for any long value.
  - hashInt
```
public abstract long hashInt(int input)
```
    Returns the hash code for the given int value; this method is consistent with LongHashFunction methods that accept sequences of bytes, assuming the input value is interpreted in native byte order. For example, the result of hashInt(v) call is identical to the result of hashInts(new int[] {v}) call for any int value.
  - hashShort
```
public abstract long hashShort(short input)
```
    Returns the hash code for the given short value; this method is consistent with LongHashFunction methods that accept sequences of bytes, assuming the input value is interpreted in native byte order. For example, the result of hashShort(v) call is identical to the result of hashShorts(new short[] {v}) call for any short value. As a consequence, hashShort(v) call produce always the same result as hashChar((char) v).
  - hashChar
```
public abstract long hashChar(char input)
```
    Returns the hash code for the given char value; this method is consistent with LongHashFunction methods that accept sequences of bytes, assuming the input value is interpreted in native byte order. For example, the result of hashChar(v) call is identical to the result of hashChars(new char[] {v}) call for any char value. As a consequence, hashChar(v) call produce always the same result as hashShort((short) v).
  - hashByte
```
public abstract long hashByte(byte input)
```
    Returns the hash code for the given byte value. This method is consistent with LongHashFunction methods that accept sequences of bytes. For example, the result of hashByte(v) call is identical to the result of hashBytes(new byte[] {v}) call for any byte value.
  - hashVoid
```
public abstract long hashVoid()
```
    Returns the hash code for the empty (zero-length) bytes sequence, for example hashBytes(new byte[0]).
  - hash
```
public abstract <T> long hash(T input,
                              Access<T> access,
                              long off,
                              long len)
```
    Returns the hash code for len continuous bytes of the given input object, starting from the given offset. The abstraction of input as ordered byte sequence and "offset within the input" is defined by the given access strategy.
    This method doesn't promise to throw a RuntimeException if [off, off + len - 1] subsequence exceeds the bounds of the bytes sequence, defined by access strategy for the given input, so use this method with caution.
    
    Type Parameters:
    
    T - the type of the input
    
    Parameters:
    
    input - the object to read bytes from
    
    access - access which defines the abstraction of the given input as ordered byte sequence
    
    off - offset to the first byte of the subsequence to hash
    
    len - length of the subsequence to hash
    
    Returns:
    
    hash code for the specified bytes subsequence
  - hashBoolean
```
public long hashBoolean(boolean input)
```
    Shortcut for hashBooleans(new boolean[] {input}). Note that this is not necessarily equal to hashByte(input ? (byte) 1 : (byte) 0), because booleans could be stored differently in this JVM.
  - hashBooleans
```
public long hashBooleans(@NotNull
                         boolean[] input)
```
    Shortcut for hashBooleans(input, 0, input.length).
  - hashBooleans
```
public long hashBooleans(@NotNull
                         boolean[] input,
                         int off,
                         int len)
```
    Returns the hash code for the specified subsequence of the given boolean array.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    input - the array to read data from
    
    off - index of the first boolean in the subsequence to hash
    
    len - length of the subsequence to hash
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length or len < 0
  - hashBytes
```
public long hashBytes(@NotNull
                      byte[] input)
```
    Shortcut for hashBytes(input, 0, input.length).
  - hashBytes
```
public long hashBytes(@NotNull
                      byte[] input,
                      int off,
                      int len)
```
    Returns the hash code for the specified subsequence of the given byte array.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    input - the array to read bytes from
    
    off - index of the first byte in the subsequence to hash
    
    len - length of the subsequence to hash
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length or len < 0
  - hashBytes
```
public long hashBytes(ByteBuffer input)
```
    Shortcut for hashBytes(input, input.position(), input.remaining()).
  - hashBytes
```
public long hashBytes(@NotNull
                      ByteBuffer input,
                      int off,
                      int len)
```
    Returns the hash code for the specified subsequence of the given ByteBuffer.
    This method doesn't alter the state (mark, position, limit or order) of the given ByteBuffer.
    Default implementation delegates to hash(Object, Access, long, long) method using Access.toByteBuffer().
    
    Parameters:
    
    input - the buffer to read bytes from
    
    off - index of the first byte in the subsequence to hash
    
    len - length of the subsequence to hash
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.capacity() or len < 0
  - hashMemory
```
public long hashMemory(long address,
                       long len)
```
    Returns the hash code of bytes of the wild memory from the given address. Use with caution.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    address - the address of the first byte to hash
    
    len - length of the byte sequence to hash
    
    Returns:
    
    hash code for the specified byte sequence
  - hashChars
```
public long hashChars(@NotNull
                      char[] input)
```
    Shortcut for hashChars(input, 0, input.length).
  - hashChars
```
public long hashChars(@NotNull
                      char[] input,
                      int off,
                      int len)
```
    Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given char array.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    input - the array to read data from
    
    off - index of the first char in the subsequence to hash
    
    len - length of the subsequence to hash, in chars (i. e. the length of the bytes sequence to hash is len * 2L)
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length or len < 0
  - hashChars
```
public long hashChars(@NotNull
                      String input)
```
    Shortcut for hashChars(input, 0, input.length()).
  - hashChars
```
public long hashChars(@NotNull
                      String input,
                      int off,
                      int len)
```
    Returns the hash code for bytes of the specified subsequence of the given String's underlying char array.
    Default implementation could either delegate to hash(Object, Access, long, long) using Access.toNativeCharSequence(), or to hashChars(char[], int, int).
    
    Parameters:
    
    input - the string which bytes to hash
    
    off - index of the first char in the subsequence to hash
    
    len - length of the subsequence to hash, in chars (i. e. the length of the bytes sequence to hash is len * 2L)
    
    Returns:
    
    the hash code of the given String's bytes
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length() or len < 0
  - hashChars
```
public long hashChars(@NotNull
                      StringBuilder input)
```
    Shortcut for hashChars(input, 0, input.length()).
  - hashChars
```
public long hashChars(@NotNull
                      StringBuilder input,
                      int off,
                      int len)
```
    Returns the hash code for bytes of the specified subsequence of the given StringBuilder's underlying char array.
    Default implementation could either delegate to hash(Object, Access, long, long) using Access.toNativeCharSequence(), or to hashChars(char[], int, int).
    
    Parameters:
    
    input - the string builder which bytes to hash
    
    off - index of the first char in the subsequence to hash
    
    len - length of the subsequence to hash, in chars (i. e. the length of the bytes sequence to hash is len * 2L)
    
    Returns:
    
    the hash code of the given String's bytes
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length() or len < 0
  - hashShorts
```
public long hashShorts(@NotNull
                       short[] input)
```
    Shortcut for hashShorts(input, 0, input.length).
  - hashShorts
```
public long hashShorts(@NotNull
                       short[] input,
                       int off,
                       int len)
```
    Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given short array.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    input - the array to read data from
    
    off - index of the first short in the subsequence to hash
    
    len - length of the subsequence to hash, in shorts (i. e. the length of the bytes sequence to hash is len * 2L)
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length or len < 0
  - hashInts
```
public long hashInts(@NotNull
                     int[] input)
```
    Shortcut for hashInts(input, 0, input.length).
  - hashInts
```
public long hashInts(@NotNull
                     int[] input,
                     int off,
                     int len)
```
    Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given int array.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    input - the array to read data from
    
    off - index of the first int in the subsequence to hash
    
    len - length of the subsequence to hash, in ints (i. e. the length of the bytes sequence to hash is len * 4L)
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length or len < 0
  - hashLongs
```
public long hashLongs(@NotNull
                      long[] input)
```
    Shortcut for hashLongs(input, 0, input.length).
  - hashLongs
```
public long hashLongs(@NotNull
                      long[] input,
                      int off,
                      int len)
```
    Returns the hash code for bytes, as they lay in memory, of the specified subsequence of the given long array.
    Default implementation delegates to hash(Object, Access, long, long) method using unsafe Access.
    
    Parameters:
    
    input - the array to read data from
    
    off - index of the first long in the subsequence to hash
    
    len - length of the subsequence to hash, in longs (i. e. the length of the bytes sequence to hash is len * 8L)
    
    Returns:
    
    hash code for the specified subsequence
    
    Throws:
    
    IndexOutOfBoundsException - if off < 0 or off + len > input.length or len < 0

Class LongHashFunction

Subclassing

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

LongHashFunction

Method Detail

city_1_1

city_1_1

city_1_1

farmNa

farmNa

farmNa

farmUo

farmUo

farmUo

murmur_3

murmur_3

xx_r39

xx_r39

hashLong

hashInt

hashShort

hashChar

hashByte

hashVoid

hash

hashBoolean

hashBooleans

hashBooleans

hashBytes

hashBytes

hashBytes

hashBytes

hashMemory

hashChars

hashChars

hashChars

hashChars

hashChars

hashChars

hashShorts

hashShorts

hashInts

hashInts

hashLongs

hashLongs