<?php
/**
* Message digest implementation.
*
* @author Marius Zadara <marius@zadara.org>
* @category org.zadara.marius.messagedigester.classes
* @copyright (C) 2008, Marius Zadara <marius@zadara.org>
* @license GNU GPL
* @package org.zadara.marius.messagedigester
*
* @final
*/
final class MessageDigest
{
/**
* The choosen digest algorithm.
*
* @var String
* @access private
* @see getInstance()
*/
private $hashAlgorithm;
/**
* The text to digest
*
* @var String
* @access private
* @see update()
*/
private $textToDigest;
/**
* Default constructor.
* It will initialize the hash algorithm and text to digest
* will NULL values.
*
* @access public
*/
public function __construct()
{
// set to null the hash algorithm and text to digest
$this->hashAlgorithm = null;
$this->textToDigest = null;
}
/**
* Get an instance of a hash algorithm.
* The hash algorithm must have been defined.
*
* @param String $hashAlgorithmName The name of the hash algorithm
* @access public
*/
public function getInstance($hashAlgorithmName)
{
// search for the hash algorithm class
if (!class_exists($hashAlgorithmName))
throw new MessageDigestException(sprintf("'%s' license algorithm not found", $hashAlgorithmName));
// set the algorithm
$this->hashAlgorithm = new $hashAlgorithmName;
// the class algorithm must implement the specific interface
// if not, error
if (!in_array("IHashAlgorithm", class_implements($this->hashAlgorithm)))
{
$this->hashAlgorithm = null;
throw new MessageDigestException(sprintf("'%s' license is not correctly defined", $hashAlgorithmName));
}
}
/**
* Reset the message digest data.
* @access public
*/
public function reset()
{
if (!is_null($this->hashAlgorithm))
{
// reset to default values
$this->hashAlgorithm = null;
$this->textToDigest = null;
}
}
/**
* Function to set the text for digest.
* Also will check the algorithm to see if has been set
*
* @param String $text The text to digest later
*/
public function update($text)
{
// check the hash algorithm
if (is_null($this->hashAlgorithm))
throw new MessageDigestException("Hash algorithm not set yet");
// check the length of the string
if (strlen($text) == 0)
throw new MessageDigestException("Empty text to digest");
// set the text
$this->textToDigest = $text;
}
/**
* Digest function.
* This function will digest the text set before.
*
* @return string The text digested
* @see IHashAlgorithm::hash()
*/
public function digest()
{
// check the hash algorithm
if (is_null($this->hashAlgorithm))
throw new MessageDigestException("Hash algorithm not set yet");
// check the text to digest
if (is_null(($this->textToDigest)))
throw new MessageDigestException("Text to hash not set yet");
// set the default return string
$hashedText = "";
try
{
// try to call the hash method from the algorithm
$hashedText = $this->hashAlgorithm->hash($this->textToDigest);
}
catch (HashAlgorithmException $hashAlgorithmException)
{
// throw the exception further
throw new MessageDigestException
(
sprintf
(
"Failed to hash the text '%s' using the '%s' algorithm: %s",
$this->textToDigest,
$this->hashAlgorithm,
$hashAlgorithmException->getMessage()
)
);
}
catch (Exception $generalException)
{
// throw the exception further
throw new MessageDigestException
(
sprintf
(
"Failed to hash the text '%s' using the '%s' algorithm: %s",
$this->textToDigest,
$this->hashAlgorithm,
$hashAlgorithmException->getMessage()
)
);
}
// return the hashed text
return $hashedText;
}
}
?>
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