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<?php |
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namespace Riimu\Kit\SecureRandom\Generator; |
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use Riimu\Kit\SecureRandom\GeneratorException; |
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/** |
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* A random number generator that wraps the given byte generator for generating integers. |
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* |
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* @author Riikka Kalliomäki <[email protected]> |
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* @copyright Copyright (c) 2017 Riikka Kalliomäki |
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* @license http://opensource.org/licenses/mit-license.php MIT License |
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*/ |
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class ByteNumberGenerator implements NumberGenerator |
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{ |
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/** @var string[] Formats for different numbers of bytes */ |
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const BYTE_FORMATS = ['Ca', 'na', 'Cb/na', 'Na', 'Cc/Na', 'nc/Na', 'Cd/nc/Na', 'Ja']; |
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/** @var int[] Default values for byte format values */ |
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const BYTE_DEFAULTS = ['a' => 0, 'b' => 0, 'c' => 0, 'd' => 0]; |
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/** @var Generator The underlying byte generator */ |
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private $byteGenerator; |
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/** |
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* NumberByteGenerator constructor. |
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* @param Generator $generator The underlying byte generator used to generate random bytes |
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*/ |
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public function __construct(Generator $generator) |
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{ |
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$this->byteGenerator = $generator; |
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} |
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/** |
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* Tells if the underlying byte generator is supported by the system. |
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* @return bool True if the generator is supported, false if not |
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*/ |
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public function isSupported() |
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{ |
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return $this->byteGenerator->isSupported(); |
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} |
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/** |
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* Returns bytes read from the provided byte generator. |
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* @param int $count The number of bytes to read |
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* @return string A string of bytes |
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* @throws GeneratorException If there was an error generating the bytes |
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*/ |
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public function getBytes($count) |
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{ |
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return $this->byteGenerator->getBytes($count); |
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} |
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/** |
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* Returns a random integer between given minimum and maximum. |
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* @param int $min The minimum possible value to return |
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* @param int $max The maximum possible value to return |
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* @return int A random number between the lower and upper limit (inclusive) |
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* @throws \InvalidArgumentException If the provided values are invalid |
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* @throws GeneratorException If an error occurs generating the number |
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*/ |
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public function getNumber($min, $max) |
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{ |
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$min = (int) $min; |
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$max = (int) $max; |
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if ($min > $max) { |
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throw new \InvalidArgumentException('Invalid minimum and maximum value'); |
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} |
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if ($min === $max) { |
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return $min; |
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} |
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$difference = $max - $min; |
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if (!is_int($difference)) { |
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throw new GeneratorException('Too large difference between minimum and maximum'); |
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} |
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return $min + $this->getByteNumber($difference); |
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} |
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/** |
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* Returns a random number generated using the random byte generator. |
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* @param int $limit Maximum value for the random number |
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* @return int The generated random number between 0 and the limit |
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* @throws GeneratorException If error occurs generating the random number |
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*/ |
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private function getByteNumber($limit) |
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{ |
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$bits = 1; |
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$mask = 1; |
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while ($limit >> $bits > 0) { |
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$mask |= 1 << $bits; |
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$bits++; |
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} |
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$bytes = (int) ceil($bits / 8); |
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do { |
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$result = $this->readByteNumber($bytes) & $mask; |
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} while ($result > $limit); |
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return $result; |
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} |
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/** |
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* Returns a number from byte generator based on given number of bytes. |
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* @param int $bytes The number of bytes to read |
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* @return int A random number read from the bytes of the byte generator |
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* @throws GeneratorException If the errors occurs generating the bytes for the number |
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*/ |
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private function readByteNumber($bytes) |
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{ |
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$values = unpack(self::BYTE_FORMATS[$bytes - 1], $this->byteGenerator->getBytes($bytes)) + self::BYTE_DEFAULTS; |
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return $values['a'] | $values['b'] << 16 | $values['c'] << 32 | $values['d'] << 48; |
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} |
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} |
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Riimu /
Kit-SecureRandom
