Bitmask Example Read/Write/Execute/Delete

BitMaskPermission.php

<?php
/*                                                                        *
 * This script belongs to the TYPO3 Flow framework.                       *
 *                                                                        *
 * It is free software; you can redistribute it and/or modify it under    *
 * the terms of the GNU Lesser General Public License, either version 3   *
 * of the License, or (at your option) any later version.                 *
 *                                                                        *
 * The TYPO3 project - inspiring people to share!                         *
 *                                                                        */


/**
 * Class BitMaskPermission
 *
 * @author Carsten Bleicker
 */
class BitMaskPermission {

	/**
	 * Bitmasks as decimal values
	 * 1 =   00000001
	 * 2 =   00000010
	 * 4 =   00000100
	 * 8 =   00001000
	 * 16 =  00010000
	 * 32 =  00100000
	 * 64 =  01000000
	 * 128 = 10000000
	 */
	const READ = 1, WRITE = 2, EXECUTE = 4, DELETE = 8;

	/**
	 * The current permission storage
	 *
	 * @var integer
	 */
	private $storage;

	/**
	 * Basicaly the Permission is 0
	 *
	 * @return void
	 */
	public function __construct() {
		$this->storage = 0;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function grantRead() {
		$this->addPermission(self::READ);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function denyRead() {
		$this->removePermission(self::READ);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function grantWrite() {
		$this->addPermission(self::WRITE);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function denyWrite() {
		$this->removePermission(self::WRITE);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function grantExecute() {
		$this->addPermission(self::EXECUTE);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function denyExecute() {
		$this->removePermission(self::EXECUTE);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function grantDelete() {
		$this->addPermission(self::DELETE);
		return $this;
	}

	/**
	 * @return BitmaskPermission $this
	 */
	public function denyDelete() {
		$this->removePermission(self::DELETE);
		return $this;
	}

	/**
	 * Adding a Permission
	 *
	 * @see http://php.net/manual/de/language.operators.bitwise.php
	 * @example The permission is actualy set to READ permission wich is representated by decimalvalue: 1 (see constants of BitMaskPermission::READ)
	 * and we want also want to add WRITE permission wich is a decimalvalue 2
	 * 1 is in Binary 00000001
	 * 2 is in Binary 00000010
	 * What happens here is that we merge them together to the decimalvalue 3 by simply enable the 7th + 8th bit to:
	 * 3 is in Binary 00000011 wich is our for read+write access
	 * @param integer $bitmask
	 */
	private function addPermission($bitMaskAsDecimal) {
		$this->storage |= $bitMaskAsDecimal;
	}

	/**
	 * Removing a Permission
	 *
	 * @see http://php.net/manual/de/language.operators.bitwise.php
	 * @example The permission is actualy set to READ + WRITE permission wich is the decimalvalue 3 (BitMaskPermission::READ + BitMaskPermission::WRITE) (1 + 2)
	 * and we want also want to remove WRITE permission wich is a decimalvalue 2
	 * 3 is in Binary 00000001
	 * 2 is in Binary 00000010
	 * What happens here is that we disable the 7th digit of decimalvalue 2 in our storage:
	 * 1 is in Binary 00000001 wich is our bitmask for read access
	 * @param integer $bitmask
	 */
	private function removePermission($bitMaskAsDecimal) {
		$this->storage &= ~$bitMaskAsDecimal;
	}
}


$permission = new BitMaskPermission();

print_r($permission->grantDelete());
print_r($permission->grantRead());
print_r($permission->grantWrite());
print_r($permission->denyExecute());
print_r($permission->denyRead());
print_r($permission->grantExecute());


?>

##### OUTPUT ####

BitMaskPermission Object
(
[storage:BitMaskPermission:private] => 8
)
BitMaskPermission Object
(
[storage:BitMaskPermission:private] => 9
)
BitMaskPermission Object
(
[storage:BitMaskPermission:private] => 11
)
BitMaskPermission Object
(
[storage:BitMaskPermission:private] => 11
)
BitMaskPermission Object
(
[storage:BitMaskPermission:private] => 10
)
BitMaskPermission Object
(
[storage:BitMaskPermission:private] => 14
)