Package com.landawn.abacus.guava.hash

Interface Hasher

public interface Hasher
Note: It's copied from Google Guava under Apache License 2.0 and modified. Each hasher should translate all multibyte values (put(int), put(long), etc) to bytes in little-endian order.

Warning: The result of calling any methods after calling hash() is undefined.

Warning: Using a specific character encoding when hashing a CharSequence with put(CharSequence, Charset) is generally only useful for cross-language compatibility (otherwise prefer #putUnencodedChars). However, the character encodings must be identical across languages. Also beware that Charset definitions may occasionally change between Java releases.

Warning: Chunks of data that are put into the Hasher are not delimited. The resulting HashCode is dependent only on the bytes inserted, and the order in which they were inserted, not how those bytes were chunked into discrete put() operations. For example, the following three expressions all generate colliding hash codes: 

   

   newHasher().putByte(b1).putByte(b2).putByte(b3).hash()
   newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash()
   newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()

If you wish to avoid this, you should either prepend or append the size of each chunk. Keep in mind that when dealing with char sequences, the encoded form of two concatenated char sequences is not equivalent to the concatenation of their encoded form. Therefore, put(CharSequence, Charset) should only be used consistently with complete sequences and not broken into chunks.

Since:
11.0
Author:
Kevin Bourrillion

  • Method Summary

    Modifier and Type
    Method
    Description
    com.google.common.hash.HashCode
    hash()
    Computes a hash code based on the data that have been provided to this hasher.
    Hasher
    put(boolean b)
    Equivalent to putByte(b ? (byte) 1 : (byte) 0).
    Hasher
    put(byte b)
     
    Hasher
    put(byte[] bytes)
     
    Hasher
    put(byte[] bytes, int off, int len)
     
    Hasher
    put(char c)
     
    Hasher
    put(char[] chars)
     
    Hasher
    put(char[] chars, int off, int len)
     
    Hasher
    put(double d)
    Equivalent to putLong(Double.doubleToRawLongBits(d)).
    Hasher
    put(float f)
    Equivalent to putInt(Float.floatToRawIntBits(f)).
    Hasher
    put(int i)
     
    Hasher
    put(long l)
     
    Hasher
    put(short s)
     
    Hasher
    put(CharSequence charSequence)
    Equivalent to processing each char value in the CharSequence, in order.
    Hasher
    put(CharSequence charSequence, Charset charset)
    Equivalent to putBytes(charSequence.toString().getBytes(charset)).
    Hasher
    put(ByteBuffer bytes)
     
    <T> Hasher
    put(T instance, com.google.common.hash.Funnel<? super T> funnel)
    A simple convenience for funnel.funnel(object, this).

  • Method Details

    • put

      Hasher put(byte b)
      Parameters:
      b -
      Returns:

    • put

      Hasher put(byte[] bytes)
      Parameters:
      bytes -
      Returns:

    • put

      Hasher put(byte[] bytes, int off, int len)
      Parameters:
      bytes -
      off -
      len -
      Returns:

    • put

      Hasher put(ByteBuffer bytes)
      Parameters:
      bytes -
      Returns:

    • put

      Hasher put(short s)
      Parameters:
      s -
      Returns:

    • put

      Hasher put(int i)
      Parameters:
      i -
      Returns:

    • put

      Hasher put(long l)
      Parameters:
      l -
      Returns:

    • put

      Hasher put(float f)
      Equivalent to putInt(Float.floatToRawIntBits(f)).
      Parameters:
      f -
      Returns:

    • put

      Hasher put(double d)
      Equivalent to putLong(Double.doubleToRawLongBits(d)).
      Parameters:
      d -
      Returns:

    • put

      Hasher put(boolean b)
      Equivalent to putByte(b ? (byte) 1 : (byte) 0).
      Parameters:
      b -
      Returns:

    • put

      Hasher put(char c)
      Parameters:
      c -
      Returns:

    • put

      Hasher put(char[] chars)
      Parameters:
      chars -
      Returns:

    • put

      Hasher put(char[] chars, int off, int len)
      Parameters:
      chars -
      off -
      len -
      Returns:

    • put

      Hasher put(CharSequence charSequence)
      Equivalent to processing each char value in the CharSequence, in order. In other words, no character encoding is performed; the low byte and high byte of each char are hashed directly (in that order). The input must not be updated while this method is in progress.

      Warning: This method will produce different output than most other languages do when running the same hash function on the equivalent input. For cross-language compatibility, use #putString, usually with a charset of UTF-8. For other use cases, use putUnencodedChars.

      Parameters:
      charSequence -
      Returns:
      Since:
      15.0 (since 11.0 as putString(CharSequence)).

    • put

      Hasher put(CharSequence charSequence, Charset charset)
      Equivalent to putBytes(charSequence.toString().getBytes(charset)).

      Warning: This method, which reencodes the input before hashing it, is useful only for cross-language compatibility. For other use cases, prefer #putUnencodedChars, which is faster, produces the same output across Java releases, and hashes every char in the input, even if some are invalid.

      Parameters:
      charSequence -
      charset -
      Returns:

    • put

      <T> Hasher put(T instance, com.google.common.hash.Funnel<? super T> funnel)
      A simple convenience for funnel.funnel(object, this).
      Type Parameters:
      T -
      Parameters:
      instance -
      funnel -
      Returns:

    • hash

      com.google.common.hash.HashCode hash()
      Computes a hash code based on the data that have been provided to this hasher. The result is unspecified if this method is called more than once on the same instance.
      Returns: