nodeId32 = wfBaseConvert( substr( sha1( $nodeId ), 0, 8 ), 16, 2, 32 ); $this->nodeId48 = wfBaseConvert( $nodeId, 16, 2, 48 ); // If different processes run as different users, they may have different temp dirs. // This is dealt with by initializing the clock sequence number and counters randomly. $this->lockFile88 = wfTempDir() . '/mw-' . __CLASS__ . '-UID-88'; $this->lockFile128 = wfTempDir() . '/mw-' . __CLASS__ . '-UID-128'; } /** * @return UIDGenerator */ protected static function singleton() { if ( self::$instance === null ) { self::$instance = new self(); } return self::$instance; } /** * Get a statistically unique 88-bit unsigned integer ID string. * The bits of the UID are prefixed with the time (down to the millisecond). * * These IDs are suitable as values for the shard key of distributed data. * If a column uses these as values, it should be declared UNIQUE to handle collisions. * New rows almost always have higher UIDs, which makes B-TREE updates on INSERT fast. * They can also be stored "DECIMAL(27) UNSIGNED" or BINARY(11) in MySQL. * * UID generation is serialized on each server (as the node ID is for the whole machine). * * @param $base integer Specifies a base other than 10 * @return string Number * @throws MWException */ public static function newTimestampedUID88( $base = 10 ) { if ( !is_integer( $base ) || $base > 36 || $base < 2 ) { throw new MWException( "Base must an integer be between 2 and 36" ); } $gen = self::singleton(); $time = $gen->getTimestampAndDelay( 'lockFile88', 1, 1024 ); return wfBaseConvert( $gen->getTimestampedID88( $time ), 2, $base ); } /** * @param array $time (UIDGenerator::millitime(), clock sequence) * @return string 88 bits */ protected function getTimestampedID88( array $info ) { list( $time, $counter ) = $info; // Take the 46 MSBs of "milliseconds since epoch" $id_bin = $this->millisecondsSinceEpochBinary( $time ); // Add a 10 bit counter resulting in 56 bits total $id_bin .= str_pad( decbin( $counter ), 10, '0', STR_PAD_LEFT ); // Add the 32 bit node ID resulting in 88 bits total $id_bin .= $this->nodeId32; // Convert to a 1-27 digit integer string if ( strlen( $id_bin ) !== 88 ) { throw new MWException( "Detected overflow for millisecond timestamp." ); } return $id_bin; } /** * Get a statistically unique 128-bit unsigned integer ID string. * The bits of the UID are prefixed with the time (down to the millisecond). * * These IDs are suitable as globally unique IDs, without any enforced uniqueness. * New rows almost always have higher UIDs, which makes B-TREE updates on INSERT fast. * They can also be stored as "DECIMAL(39) UNSIGNED" or BINARY(16) in MySQL. * * UID generation is serialized on each server (as the node ID is for the whole machine). * * @param $base integer Specifies a base other than 10 * @return string Number * @throws MWException */ public static function newTimestampedUID128( $base = 10 ) { if ( !is_integer( $base ) || $base > 36 || $base < 2 ) { throw new MWException( "Base must be an integer between 2 and 36" ); } $gen = self::singleton(); $time = $gen->getTimestampAndDelay( 'lockFile128', 16384, 1048576 ); return wfBaseConvert( $gen->getTimestampedID128( $time ), 2, $base ); } /** * @param array $info (UIDGenerator::millitime(), counter, clock sequence) * @return string 128 bits */ protected function getTimestampedID128( array $info ) { list( $time, $counter, $clkSeq ) = $info; // Take the 46 MSBs of "milliseconds since epoch" $id_bin = $this->millisecondsSinceEpochBinary( $time ); // Add a 20 bit counter resulting in 66 bits total $id_bin .= str_pad( decbin( $counter ), 20, '0', STR_PAD_LEFT ); // Add a 14 bit clock sequence number resulting in 80 bits total $id_bin .= str_pad( decbin( $clkSeq ), 14, '0', STR_PAD_LEFT ); // Add the 48 bit node ID resulting in 128 bits total $id_bin .= $this->nodeId48; // Convert to a 1-39 digit integer string if ( strlen( $id_bin ) !== 128 ) { throw new MWException( "Detected overflow for millisecond timestamp." ); } return $id_bin; } /** * Return an RFC4122 compliant v4 UUID * * @param $flags integer Bitfield (supports UIDGenerator::QUICK_RAND) * @return string * @throws MWException */ public static function newUUIDv4( $flags = 0 ) { $hex = ( $flags & self::QUICK_RAND ) ? wfRandomString( 31 ) : MWCryptRand::generateHex( 31 ); return sprintf( '%s-%s-%s-%s-%s', // "time_low" (32 bits) substr( $hex, 0, 8 ), // "time_mid" (16 bits) substr( $hex, 8, 4 ), // "time_hi_and_version" (16 bits) '4' . substr( $hex, 12, 3 ), // "clk_seq_hi_res (8 bits, variant is binary 10x) and "clk_seq_low" (8 bits) dechex( 0x8 | ( hexdec( $hex[15] ) & 0x3 ) ) . $hex[16] . substr( $hex, 17, 2 ), // "node" (48 bits) substr( $hex, 19, 12 ) ); } /** * Return an RFC4122 compliant v4 UUID * * @param $flags integer Bitfield (supports UIDGenerator::QUICK_RAND) * @return string 32 hex characters with no hyphens * @throws MWException */ public static function newRawUUIDv4( $flags = 0 ) { return str_replace( '-', '', self::newUUIDv4( $flags ) ); } /** * Get a (time,counter,clock sequence) where (time,counter) is higher * than any previous (time,counter) value for the given clock sequence. * This is useful for making UIDs sequential on a per-node bases. * * @param string $lockFile Name of a local lock file * @param $clockSeqSize integer The number of possible clock sequence values * @param $counterSize integer The number of possible counter values * @return Array (result of UIDGenerator::millitime(), counter, clock sequence) * @throws MWException */ protected function getTimestampAndDelay( $lockFile, $clockSeqSize, $counterSize ) { // Get the UID lock file handle if ( isset( $this->fileHandles[$lockFile] ) ) { $handle = $this->fileHandles[$lockFile]; } else { $handle = fopen( $this->$lockFile, 'cb+' ); $this->fileHandles[$lockFile] = $handle ?: null; // cache } // Acquire the UID lock file if ( $handle === false ) { throw new MWException( "Could not open '{$this->$lockFile}'." ); } elseif ( !flock( $handle, LOCK_EX ) ) { throw new MWException( "Could not acquire '{$this->$lockFile}'." ); } // Get the current timestamp, clock sequence number, last time, and counter rewind( $handle ); $data = explode( ' ', fgets( $handle ) ); // " " $clockChanged = false; // clock set back significantly? if ( count( $data ) == 5 ) { // last UID info already initialized $clkSeq = (int)$data[0] % $clockSeqSize; $prevTime = array( (int)$data[1], (int)$data[2] ); $offset = (int)$data[4] % $counterSize; // random counter offset $counter = 0; // counter for UIDs with the same timestamp // Delay until the clock reaches the time of the last ID. // This detects any microtime() drift among processes. $time = $this->timeWaitUntil( $prevTime ); if ( !$time ) { // too long to delay? $clockChanged = true; // bump clock sequence number $time = self::millitime(); } elseif ( $time == $prevTime ) { // Bump the counter if there are timestamp collisions $counter = (int)$data[3] % $counterSize; if ( ++$counter >= $counterSize ) { // sanity (starts at 0) flock( $handle, LOCK_UN ); // abort throw new MWException( "Counter overflow for timestamp value." ); } } } else { // last UID info not initialized $clkSeq = mt_rand( 0, $clockSeqSize - 1 ); $counter = 0; $offset = mt_rand( 0, $counterSize - 1 ); $time = self::millitime(); } // microtime() and gettimeofday() can drift from time() at least on Windows. // The drift is immediate for processes running while the system clock changes. // time() does not have this problem. See https://bugs.php.net/bug.php?id=42659. if ( abs( time() - $time[0] ) >= 2 ) { // We don't want processes using too high or low timestamps to avoid duplicate // UIDs and clock sequence number churn. This process should just be restarted. flock( $handle, LOCK_UN ); // abort throw new MWException( "Process clock is outdated or drifted." ); } // If microtime() is synced and a clock change was detected, then the clock went back if ( $clockChanged ) { // Bump the clock sequence number and also randomize the counter offset, // which is useful for UIDs that do not include the clock sequence number. $clkSeq = ( $clkSeq + 1 ) % $clockSeqSize; $offset = mt_rand( 0, $counterSize - 1 ); trigger_error( "Clock was set back; sequence number incremented." ); } // Update the (clock sequence number, timestamp, counter) ftruncate( $handle, 0 ); rewind( $handle ); fwrite( $handle, "{$clkSeq} {$time[0]} {$time[1]} {$counter} {$offset}" ); fflush( $handle ); // Release the UID lock file flock( $handle, LOCK_UN ); return array( $time, ( $counter + $offset ) % $counterSize, $clkSeq ); } /** * Wait till the current timestamp reaches $time and return the current * timestamp. This returns false if it would have to wait more than 10ms. * * @param array $time Result of UIDGenerator::millitime() * @return Array|bool UIDGenerator::millitime() result or false */ protected function timeWaitUntil( array $time ) { do { $ct = self::millitime(); if ( $ct >= $time ) { // http://php.net/manual/en/language.operators.comparison.php return $ct; // current timestamp is higher than $time } } while ( ( ( $time[0] - $ct[0] ) * 1000 + ( $time[1] - $ct[1] ) ) <= 10 ); return false; } /** * @param array $time Result of UIDGenerator::millitime() * @return string 46 MSBs of "milliseconds since epoch" in binary (rolls over in 4201) */ protected function millisecondsSinceEpochBinary( array $time ) { list( $sec, $msec ) = $time; $ts = 1000 * $sec + $msec; if ( $ts > pow( 2, 52 ) ) { throw new MWException( __METHOD__ . ': sorry, this function doesn\'t work after the year 144680' ); } return substr( wfBaseConvert( $ts, 10, 2, 46 ), -46 ); } /** * @return Array (current time in seconds, milliseconds since then) */ protected static function millitime() { list( $msec, $sec ) = explode( ' ', microtime() ); return array( (int)$sec, (int)( $msec * 1000 ) ); } function __destruct() { array_map( 'fclose', $this->fileHandles ); } }