Package com.google.common.hash

Interface Hasher

  • All Superinterfaces:
    PrimitiveSink
    @Beta
public interface Hasher
extends PrimitiveSink
    A PrimitiveSink that can compute a hash code after reading the input. Each hasher should translate all multibyte values (putInt(int), putLong(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 putString(CharSequence, Charset) is generally only useful for cross-language compatibility (otherwise prefer putUnencodedChars(java.lang.CharSequence)). 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, putString(CharSequence, Charset) should only be used consistently with complete sequences and not broken into chunks.

    Since:
    11.0
    Author:
    Kevin Bourrillion

    • Method Summary

      All Methods Instance Methods Abstract Methods Deprecated Methods 
      Modifier and Type Method Description
      HashCode hash()
      Computes a hash code based on the data that have been provided to this hasher.
      int hashCode()
      Deprecated.
      This returns Object.hashCode(); you almost certainly mean to call hash().asInt().
      Hasher putBoolean​(boolean b)
      Equivalent to putByte(b ? (byte) 1 : (byte) 0).
      Hasher putByte​(byte b)
      Puts a byte into this sink.
      Hasher putBytes​(byte[] bytes)
      Puts an array of bytes into this sink.
      Hasher putBytes​(byte[] bytes, int off, int len)
      Puts a chunk of an array of bytes into this sink.
      Hasher putBytes​(java.nio.ByteBuffer bytes)
      Puts the remaining bytes of a byte buffer into this sink.
      Hasher putChar​(char c)
      Puts a character into this sink.
      Hasher putDouble​(double d)
      Equivalent to putLong(Double.doubleToRawLongBits(d)).
      Hasher putFloat​(float f)
      Equivalent to putInt(Float.floatToRawIntBits(f)).
      Hasher putInt​(int i)
      Puts an int into this sink.
      Hasher putLong​(long l)
      Puts a long into this sink.
      <T extends @Nullable java.lang.Object>
      Hasher      		 putObject​(T instance, Funnel<? super T> funnel)
      A simple convenience for funnel.funnel(object, this).
      Hasher putShort​(short s)
      Puts a short into this sink.
      Hasher putString​(java.lang.CharSequence charSequence, java.nio.charset.Charset charset)
      Equivalent to putBytes(charSequence.toString().getBytes(charset)).
      Hasher putUnencodedChars​(java.lang.CharSequence charSequence)
      Equivalent to processing each char value in the CharSequence, in order.