Package com.exonum.binding.common.hash

Class HashCode

java.lang.Object
com.exonum.binding.common.hash.HashCode
public abstract class HashCode
extends java.lang.Object
An immutable hash code of arbitrary bit length.
Since:
11.0
Author:
Dimitris Andreou, Kurt Alfred Kluever

  • Method Summary

    Modifier and Type Method Description
    abstract byte[] asBytes()
    Returns the value of this hash code as a byte array.
    abstract int asInt()
    Returns the first four bytes of this hashcode's bytes, converted to an int value in little-endian order.
    abstract long asLong()
    Returns the first eight bytes of this hashcode's bytes, converted to a long value in little-endian order.
    abstract int bits()
    Returns the number of bits in this hash code; a positive multiple of 8.
    boolean equals​(java.lang.Object object)
    Returns true if object is a HashCode instance with the identical byte representation to this hash code.
    static HashCode fromBytes​(byte[] bytes)
    Creates a HashCode from a byte array.
    static HashCode fromInt​(int hash)
    Creates a 32-bit HashCode representation of the given int value.
    static HashCode fromLong​(long hash)
    Creates a 64-bit HashCode representation of the given long value.
    static HashCode fromString​(java.lang.String string)
    Creates a HashCode from a hexadecimal (base 16) encoded string.
    int hashCode()
    Returns a "Java hash code" for this HashCode instance; this is well-defined (so, for example, you can safely put HashCode instances into a HashSet) but is otherwise probably not what you want to use.
    abstract long padToLong()
    If this hashcode has enough bits, returns asLong(), otherwise returns a long value with asBytes() as the least-significant bytes and 0x00 as the remaining most-significant bytes.
    java.lang.String toString()
    Returns a string containing each byte of asBytes(), in order, as a two-digit unsigned hexadecimal number in lower case.
    int writeBytesTo​(byte[] dest, int offset, int maxLength)
    Copies bytes from this hash code into dest.

    Methods inherited from class java.lang.Object

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

  • Method Details

    • bits

      public abstract int bits()
      Returns the number of bits in this hash code; a positive multiple of 8.

    • asInt

      public abstract int asInt()
      Returns the first four bytes of this hashcode's bytes, converted to an int value in little-endian order.
      Throws:
      java.lang.IllegalStateException - if bits() < 32

    • asLong

      public abstract long asLong()
      Returns the first eight bytes of this hashcode's bytes, converted to a long value in little-endian order.
      Throws:
      java.lang.IllegalStateException - if bits() < 64

    • padToLong

      public abstract long padToLong()
      If this hashcode has enough bits, returns asLong(), otherwise returns a long value with asBytes() as the least-significant bytes and 0x00 as the remaining most-significant bytes.
      Since:
      14.0 (since 11.0 as Hashing.padToLong(HashCode))

    • asBytes

      public abstract byte[] asBytes()
      Returns the value of this hash code as a byte array. The caller may modify the byte array; changes to it will not be reflected in this HashCode object or any other arrays returned by this method.

    • writeBytesTo

      @CanIgnoreReturnValue public int writeBytesTo​(byte[] dest, int offset, int maxLength)
      Copies bytes from this hash code into dest.
      Parameters:
      dest - the byte array into which the hash code will be written
      offset - the start offset in the data
      maxLength - the maximum number of bytes to write
      Returns:
      the number of bytes written to dest
      Throws:
      java.lang.IndexOutOfBoundsException - if there is not enough room in dest

    • fromInt

      public static HashCode fromInt​(int hash)
      Creates a 32-bit HashCode representation of the given int value. The underlying bytes are interpreted in little endian order.
      Since:
      15.0 (since 12.0 in HashCodes)

    • fromLong

      public static HashCode fromLong​(long hash)
      Creates a 64-bit HashCode representation of the given long value. The underlying bytes are interpreted in little endian order.
      Since:
      15.0 (since 12.0 in HashCodes)

    • fromBytes

      public static HashCode fromBytes​(byte[] bytes)
      Creates a HashCode from a byte array. The array is defensively copied to preserve the immutability contract of HashCode. The array cannot be empty.
      Since:
      15.0 (since 12.0 in HashCodes)

    • fromString

      public static HashCode fromString​(java.lang.String string)
      Creates a HashCode from a hexadecimal (base 16) encoded string. The string must be at least 2 characters long, and contain only valid, lower-cased hexadecimal characters.

      This method accepts the exact format generated by toString(). If you require more lenient base 16 decoding, please use BaseEncoding.decode(java.lang.CharSequence) (and pass the result to fromBytes(byte[])).

      Since:
      15.0

    • equals

      public final boolean equals​(@Nullable java.lang.Object object)
      Returns true if object is a HashCode instance with the identical byte representation to this hash code.

      Security note: this method uses a constant-time (not short-circuiting) implementation to protect against timing attacks.

      Overrides:
      equals in class java.lang.Object

    • hashCode

      public final int hashCode()
      Returns a "Java hash code" for this HashCode instance; this is well-defined (so, for example, you can safely put HashCode instances into a HashSet) but is otherwise probably not what you want to use.
      Overrides:
      hashCode in class java.lang.Object

    • toString

      public final java.lang.String toString()
      Returns a string containing each byte of asBytes(), in order, as a two-digit unsigned hexadecimal number in lower case.

      Note that if the output is considered to be a single hexadecimal number, this hash code's bytes are the big-endian representation of that number. This may be surprising since everything else in the hashing API uniformly treats multibyte values as little-endian. But this format conveniently matches that of utilities such as the UNIX md5sum command.

      To create a HashCode from its string representation, see fromString(java.lang.String).

      Overrides:
      toString in class java.lang.Object