Hash

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jsdsi
Class Hash

java.lang.Object
  jsdsi.Obj
      jsdsi.Hash

public class Hash
extends Obj

A cryptographic hash value. Specifies the hash algorithm, the value to hash, and an optional set of URIs that specify where the hashed object is located.

Version:: $Revision: 1.3 $ $Date: 2003/08/02 18:35:48 $

Field Summary

private java.lang.String algo
          Name of the hash algorithm used.

private byte[] data
          Hash value.

private java.net.URL[] urls
          URLs assigned to this Hash (may be null).

Constructor Summary

Hash(java.lang.String a, byte[] d)
          Creates a new Hash from an algorithm name and a byte array that contains a hash value.

Hash(java.lang.String a, byte[] d, java.net.URL[] u)
          Creates a new Hash from a given algorithm name, a value to hash, and an array of URLs.

Hash(java.lang.String a, Obj o)
          Creates a new Hash from an algorithm name and an object.

Hash(java.lang.String a, Obj o, java.net.URL[] u)
          Creates a new Hash from a given algorithm name, object to hash, and an array of URLs.

Method Summary

boolean equals(java.lang.Object o)
          Determine whether this Object is semantically equal to another Object.

java.lang.String getAlgorithm()
          Returns the name of the algorithm used.

byte[] getData()
          Returns the hash value as a byte array.

java.net.URL[] getURLs()
          Returns an array of URLs assigned to this Hash.

int hashCode()
          Get a value that represents this Object, as uniquely as possible within the confines of an int.

static Hash parseHash(SexpList l)
          Parses an SexpList that holds a Hash and returns a Hash of this.

SexpList toSexp()
          Returns an SexpList that holds this Hash.

Methods inherited from class jsdsi.Obj

parseObj, toByteArray, toString

Methods inherited from class java.lang.Object

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

Field Detail

algo

private final java.lang.String algo

Name of the hash algorithm used.

data

private final byte[] data

Hash value.

urls

private final java.net.URL[] urls

URLs assigned to this Hash (may be null).

Constructor Detail

Hash

public Hash(java.lang.String a,
            byte[] d,
            java.net.URL[] u)

Creates a new Hash from a given algorithm name, a value to hash, and an array of URLs.

Hash

public Hash(java.lang.String a,
            Obj o,
            java.net.URL[] u)

Creates a new Hash from a given algorithm name, object to hash, and an array of URLs.

Hash

public Hash(java.lang.String a,
            byte[] d)

Creates a new Hash from an algorithm name and a byte array that contains a hash value.

Hash

public Hash(java.lang.String a,
            Obj o)

Creates a new Hash from an algorithm name and an object.

Method Detail

getAlgorithm

public java.lang.String getAlgorithm()

Returns the name of the algorithm used.

getData

public byte[] getData()

Returns the hash value as a byte array.

getURLs

public java.net.URL[] getURLs()

Returns an array of URLs assigned to this Hash.

equals

public boolean equals(java.lang.Object o)

Description copied from class: java.lang.Object

Determine whether this Object is semantically equal to another Object.

There are some fairly strict requirements on this method which subclasses must follow:

It must be transitive. If a.equals(b) and b.equals(c), then a.equals(c) must be true as well.
It must be symmetric. a.equals(b) and b.equals(a) must have the same value.
It must be reflexive. a.equals(a) must always be true.
It must be consistent. Whichever value a.equals(b) returns on the first invocation must be the value returned on all later invocations.
a.equals(null) must be false.
It must be consistent with hashCode(). That is, a.equals(b) must imply a.hashCode() == b.hashCode(). The reverse is not true; two objects that are not equal may have the same hashcode, but that has the potential to harm hashing performance.

This is typically overridden to throw a java.lang.ClassCastException if the argument is not comparable to the class performing the comparison, but that is not a requirement. It is legal for a.equals(b) to be true even though a.getClass() != b.getClass(). Also, it is typical to never cause a java.lang.NullPointerException.

In general, the Collections API (java.util) use the equals method rather than the == operator to compare objects. However, java.util.IdentityHashMap is an exception to this rule, for its own good reasons.

The default implementation returns this == o.

Specified by:: equals in class Obj

hashCode

public int hashCode()

Description copied from class: java.lang.Object

Get a value that represents this Object, as uniquely as possible within the confines of an int.

There are some requirements on this method which subclasses must follow:

Semantic equality implies identical hashcodes. In other words, if a.equals(b) is true, then a.hashCode() == b.hashCode() must be as well. However, the reverse is not necessarily true, and two objects may have the same hashcode without being equal.
It must be consistent. Whichever value o.hashCode() returns on the first invocation must be the value returned on all later invocations as long as the object exists. Notice, however, that the result of hashCode may change between separate executions of a Virtual Machine, because it is not invoked on the same object.

Notice that since hashCode is used in java.util.Hashtable and other hashing classes, a poor implementation will degrade the performance of hashing (so don't blindly implement it as returning a constant!). Also, if calculating the hash is time-consuming, a class may consider caching the results.

The default implementation returns System.identityHashCode(this)

Specified by:: hashCode in class Obj

toSexp

public SexpList toSexp()

Returns an SexpList that holds this Hash.

Specified by:: toSexp in class Obj

parseHash

public static Hash parseHash(SexpList l)
                      throws SexpParseException

Parses an SexpList that holds a Hash and returns a Hash of this.

Overview

Package

Class

Use

Deprecated

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Field Summary
`private java.lang.String`	`algo` Name of the hash algorithm used.
`private byte[]`	`data` Hash value.
`private java.net.URL[]`	`urls` URLs assigned to this `Hash` (may be `null`).

Constructor Summary
`Hash(java.lang.String a, byte[] d)` Creates a new `Hash` from an algorithm name and a byte array that contains a hash value.
`Hash(java.lang.String a, byte[] d, java.net.URL[] u)` Creates a new `Hash` from a given algorithm name, a value to hash, and an array of URLs.
`Hash(java.lang.String a, Obj o)` Creates a new `Hash` from an algorithm name and an object.
`Hash(java.lang.String a, Obj o, java.net.URL[] u)` Creates a new `Hash` from a given algorithm name, object to hash, and an array of URLs.

Method Summary
`boolean`	`equals(java.lang.Object o)` Determine whether this Object is semantically equal to another Object.
`java.lang.String`	`getAlgorithm()` Returns the name of the algorithm used.
`byte[]`	`getData()` Returns the hash value as a byte array.
`java.net.URL[]`	`getURLs()` Returns an array of URLs assigned to this `Hash`.
`int`	`hashCode()` Get a value that represents this Object, as uniquely as possible within the confines of an int.
`static Hash`	`parseHash(SexpList l)` Parses an `SexpList` that holds a `Hash` and returns a `Hash` of this.
`SexpList`	`toSexp()` Returns an `SexpList` that holds this `Hash`.

jsdsi Class Hash

algo

data

urls

Hash

Hash

Hash

Hash

getAlgorithm

getData

getURLs

equals

hashCode

toSexp

parseHash

jsdsi
Class Hash