* * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */ class MWP_Stream_Base64EncodedStream extends MWP_Stream_Decorator { /** @var MWP_Stream_Interface */ private $buffer; const BASE64_BLOCK_SIZE = 4; const ORIGIN_BLOCK_SIZE = 3; public function __construct(MWP_Stream_Interface $stream) { parent::__construct($stream); $this->buffer = new MWP_Stream_Buffer(); } public function eof() { return $this->buffer->eof() && $this->getStream()->eof(); } public function read($length) { $readFromBuffer = $this->buffer->read($length); if (strlen($readFromBuffer) === $length) { return $readFromBuffer; } $remaining = $length - strlen($readFromBuffer); // Calculate the approximate length required to read so that the base64 encoded stream does not have padding. // base64 is calculated for blocks of 3 input characters resulting in 4 output characters. // strlen(base64_encode($str)) ==> strlen($str) * 4 / 3 // // This leads to: // // strlen($str) ==> strlen(base64_encode($str)) * 3 / 4 // // Meaning, to read $length characters from the base64 encoded string, read 3/4 of $length from the original stream. // $length is first rounded to the first larger number divisible by 4 since base64 encoded strings come in blocks of 4 characters. $closestGroupLength = $remaining + (self::BASE64_BLOCK_SIZE - $remaining % self::BASE64_BLOCK_SIZE); $read = $closestGroupLength * self::ORIGIN_BLOCK_SIZE / self::BASE64_BLOCK_SIZE; $this->buffer->write(base64_encode($this->getStream()->read($read))); return $readFromBuffer.$this->buffer->read($remaining); } }