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<?php |
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/** |
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* The libsodium Random Number Source |
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* |
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* This uses the libsodium secure generator to generate high strength numbers |
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* |
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* PHP version 5.3 |
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* |
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* @category PHPCryptLib |
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* @package Random |
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* @subpackage Source |
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* @author Anthony Ferrara <[email protected]> |
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* @author Ben Ramsey <[email protected]> |
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* @copyright 2011 The Authors |
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* @license http://www.opensource.org/licenses/mit-license.html MIT License |
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* @version Build @@version@@ |
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* @link https://paragonie.com/book/pecl-libsodium |
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* @link http://pecl.php.net/package/libsodium |
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*/ |
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namespace RandomLib\Source; |
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use SecurityLib\Strength; |
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/** |
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* The libsodium Random Number Source |
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* |
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* This uses the libsodium secure generator to generate high strength numbers |
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* |
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* @category PHPCryptLib |
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* @package Random |
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* @subpackage Source |
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* @author Anthony Ferrara <[email protected]> |
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* @author Ben Ramsey <[email protected]> |
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*/ |
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class Sodium implements \RandomLib\Source { |
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/** |
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* A property that may be forcibly set to `false` in the constructor, for |
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* the purpose of testing this source |
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* |
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* @var bool |
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*/ |
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private $hasLibsodium = false; |
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/** |
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* Constructs a libsodium Random Number Source |
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* |
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* @param bool $useLibsodium May be set to `false` to disable libsodium for |
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* testing purposes |
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*/ |
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public function __construct($useLibsodium = true) { |
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if ($useLibsodium && extension_loaded('libsodium')) { |
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$this->hasLibsodium = true; |
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} |
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} |
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/** |
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* Return an instance of Strength indicating the strength of the source |
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* |
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* @return Strength An instance of one of the strength classes |
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*/ |
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public static function getStrength() { |
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return new Strength(Strength::HIGH); |
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} |
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/** |
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* Generate a random string of the specified size |
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* |
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* @param int $size The size of the requested random string |
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* |
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* @return string A string of the requested size |
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*/ |
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public function generate($size) { |
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if (!$this->hasLibsodium || $size < 1) { |
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return str_repeat(chr(0), $size); |
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} |
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return \Sodium\randombytes_buf($size); |
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} |
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} |
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.