Php.php

<?php

namespace Drupal\Component\Uuid;


/**
 * Generates a UUID v4 (RFC 4122 section 4.4) using PHP code.
 *
 * @see http://www.rfc-editor.org/rfc/rfc4122.txt
 * @see http://www.rfc-editor.org/errata_search.php?rfc=4122&eid=3546
 */
class Php implements UuidInterface {
    
    /**
     * {@inheritdoc}
     */
    public function generate() {
        // Obtain a random string of 32 hex characters.
        $hex = bin2hex(random_bytes(16));
        // The variable names $time_low, $time_mid, $time_hi_and_version,
        // $clock_seq_hi_and_reserved, $clock_seq_low, and $node correlate to
        // the fields defined in RFC 4122 section 4.1.2.
        //
        // Use characters 0-11 to generate 32-bit $time_low and 16-bit $time_mid.
        $time_low = substr($hex, 0, 8);
        $time_mid = substr($hex, 8, 4);
        // Use characters 12-15 to generate 16-bit $time_hi_and_version.
        // The 4 most significant bits are the version number (0100 == 0x4).
        // We simply skip character 12 from $hex, and concatenate the strings.
        $time_hi_and_version = '4' . substr($hex, 13, 3);
        // Use characters 16-17 to generate 8-bit $clock_seq_hi_and_reserved.
        // The 2 most significant bits are set to one and zero respectively.
        $clock_seq_hi_and_reserved = base_convert(substr($hex, 16, 2), 16, 10);
        $clock_seq_hi_and_reserved &= 0b111111;
        $clock_seq_hi_and_reserved |= 0b10000000;
        // Use characters 18-19 to generate 8-bit $clock_seq_low.
        $clock_seq_low = substr($hex, 18, 2);
        // Use characters 20-31 to generate 48-bit $node.
        $node = substr($hex, 20);
        // Re-combine as a UUID. $clock_seq_hi_and_reserved is still an integer.
        $uuid = sprintf('%s-%s-%s-%02x%s-%s', $time_low, $time_mid, $time_hi_and_version, $clock_seq_hi_and_reserved, $clock_seq_low, $node);
        return $uuid;
    }

}