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+<?php
+/**
+ * This file deals with UID generation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @author Aaron Schulz
+ */
+
+/**
+ * Class for getting statistically unique IDs
+ *
+ * @since 1.21
+ */
+class UIDGenerator {
+ /** @var UIDGenerator */
+ protected static $instance = null;
+
+ protected $nodeIdFile; // string; local file path
+ protected $nodeId32; // string; node ID in binary (32 bits)
+ protected $nodeId48; // string; node ID in binary (48 bits)
+
+ protected $lockFile88; // string; local file path
+ protected $lockFile128; // string; local file path
+
+ /** @var array */
+ protected $fileHandles = array(); // cache file handles
+
+ const QUICK_RAND = 1; // get randomness from fast and insecure sources
+ const QUICK_VOLATILE = 2; // use an APC like in-memory counter if available
+
+ protected function __construct() {
+ $this->nodeIdFile = wfTempDir() . '/mw-' . __CLASS__ . '-UID-nodeid';
+ $nodeId = '';
+ if ( is_file( $this->nodeIdFile ) ) {
+ $nodeId = file_get_contents( $this->nodeIdFile );
+ }
+ // Try to get some ID that uniquely identifies this machine (RFC 4122)...
+ if ( !preg_match( '/^[0-9a-f]{12}$/i', $nodeId ) ) {
+ wfSuppressWarnings();
+ if ( wfIsWindows() ) {
+ // http://technet.microsoft.com/en-us/library/bb490913.aspx
+ $csv = trim( wfShellExec( 'getmac /NH /FO CSV' ) );
+ $line = substr( $csv, 0, strcspn( $csv, "\n" ) );
+ $info = str_getcsv( $line );
+ $nodeId = isset( $info[0] ) ? str_replace( '-', '', $info[0] ) : '';
+ } elseif ( is_executable( '/sbin/ifconfig' ) ) { // Linux/BSD/Solaris/OS X
+ // See http://linux.die.net/man/8/ifconfig
+ $m = array();
+ preg_match( '/\s([0-9a-f]{2}(:[0-9a-f]{2}){5})\s/',
+ wfShellExec( '/sbin/ifconfig -a' ), $m );
+ $nodeId = isset( $m[1] ) ? str_replace( ':', '', $m[1] ) : '';
+ }
+ wfRestoreWarnings();
+ if ( !preg_match( '/^[0-9a-f]{12}$/i', $nodeId ) ) {
+ $nodeId = MWCryptRand::generateHex( 12, true );
+ $nodeId[1] = dechex( hexdec( $nodeId[1] ) | 0x1 ); // set multicast bit
+ }
+ file_put_contents( $this->nodeIdFile, $nodeId ); // cache
+ }
+ $this->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 int $base 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 $info (UIDGenerator::millitime(), counter, 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 int $base 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 int $flags 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 int $flags 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 ) );
+ }
+
+ /**
+ * Return an ID that is sequential *only* for this node and bucket
+ *
+ * These IDs are suitable for per-host sequence numbers, e.g. for some packet protocols.
+ * If UIDGenerator::QUICK_VOLATILE is used the counter might reset on server restart.
+ *
+ * @param string $bucket Arbitrary bucket name (should be ASCII)
+ * @param int $bits Bit size (<=48) of resulting numbers before wrap-around
+ * @param int $flags (supports UIDGenerator::QUICK_VOLATILE)
+ * @return float Integer value as float
+ * @since 1.23
+ */
+ public static function newSequentialPerNodeID( $bucket, $bits = 48, $flags = 0 ) {
+ return current( self::newSequentialPerNodeIDs( $bucket, $bits, 1, $flags ) );
+ }
+
+ /**
+ * Return IDs that are sequential *only* for this node and bucket
+ *
+ * @see UIDGenerator::newSequentialPerNodeID()
+ * @param string $bucket Arbitrary bucket name (should be ASCII)
+ * @param int $bits Bit size (16 to 48) of resulting numbers before wrap-around
+ * @param int $count Number of IDs to return (1 to 10000)
+ * @param int $flags (supports UIDGenerator::QUICK_VOLATILE)
+ * @return array Ordered list of float integer values
+ * @since 1.23
+ */
+ public static function newSequentialPerNodeIDs( $bucket, $bits, $count, $flags = 0 ) {
+ $gen = self::singleton();
+ return $gen->getSequentialPerNodeIDs( $bucket, $bits, $count, $flags );
+ }
+
+ /**
+ * Return IDs that are sequential *only* for this node and bucket
+ *
+ * @see UIDGenerator::newSequentialPerNodeID()
+ * @param string $bucket Arbitrary bucket name (should be ASCII)
+ * @param int $bits Bit size (16 to 48) of resulting numbers before wrap-around
+ * @param int $count Number of IDs to return (1 to 10000)
+ * @param int $flags (supports UIDGenerator::QUICK_VOLATILE)
+ * @return array Ordered list of float integer values
+ */
+ protected function getSequentialPerNodeIDs( $bucket, $bits, $count, $flags ) {
+ if ( $count <= 0 ) {
+ return array(); // nothing to do
+ } elseif ( $count > 10000 ) {
+ throw new MWException( "Number of requested IDs ($count) is too high." );
+ } elseif ( $bits < 16 || $bits > 48 ) {
+ throw new MWException( "Requested bit size ($bits) is out of range." );
+ }
+
+ $counter = null; // post-increment persistent counter value
+
+ // Use APC/eAccelerator/xcache if requested, available, and not in CLI mode;
+ // Counter values would not survive accross script instances in CLI mode.
+ $cache = null;
+ if ( ( $flags & self::QUICK_VOLATILE ) && PHP_SAPI !== 'cli' ) {
+ try {
+ $cache = ObjectCache::newAccelerator( array() );
+ } catch ( MWException $e ) {
+ // not supported
+ }
+ }
+ if ( $cache ) {
+ $counter = $cache->incr( $bucket, $count );
+ if ( $counter === false ) {
+ if ( !$cache->add( $bucket, (int)$count ) ) {
+ throw new MWException( 'Unable to set value to ' . get_class( $cache ) );
+ }
+ $counter = $count;
+ }
+ }
+
+ // Note: use of fmod() avoids "division by zero" on 32 bit machines
+ if ( $counter === null ) {
+ $path = wfTempDir() . '/mw-' . __CLASS__ . '-' . rawurlencode( $bucket ) . '-48';
+ // Get the UID lock file handle
+ if ( isset( $this->fileHandles[$path] ) ) {
+ $handle = $this->fileHandles[$path];
+ } else {
+ $handle = fopen( $path, 'cb+' );
+ $this->fileHandles[$path] = $handle ?: null; // cache
+ }
+ // Acquire the UID lock file
+ if ( $handle === false ) {
+ throw new MWException( "Could not open '{$path}'." );
+ } elseif ( !flock( $handle, LOCK_EX ) ) {
+ fclose( $handle );
+ throw new MWException( "Could not acquire '{$path}'." );
+ }
+ // Fetch the counter value and increment it...
+ rewind( $handle );
+ $counter = floor( trim( fgets( $handle ) ) ) + $count; // fetch as float
+ // Write back the new counter value
+ ftruncate( $handle, 0 );
+ rewind( $handle );
+ fwrite( $handle, fmod( $counter, pow( 2, 48 ) ) ); // warp-around as needed
+ fflush( $handle );
+ // Release the UID lock file
+ flock( $handle, LOCK_UN );
+ }
+
+ $ids = array();
+ $divisor = pow( 2, $bits );
+ $currentId = floor( $counter - $count ); // pre-increment counter value
+ for ( $i = 0; $i < $count; ++$i ) {
+ $ids[] = fmod( ++$currentId, $divisor );
+ }
+
+ return $ids;
+ }
+
+ /**
+ * 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 int $clockSeqSize The number of possible clock sequence values
+ * @param int $counterSize 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
+ $path = $this->$lockFile;
+ if ( isset( $this->fileHandles[$path] ) ) {
+ $handle = $this->fileHandles[$path];
+ } else {
+ $handle = fopen( $path, 'cb+' );
+ $this->fileHandles[$path] = $handle ?: null; // cache
+ }
+ // Acquire the UID lock file
+ if ( $handle === false ) {
+ throw new MWException( "Could not open '{$this->$lockFile}'." );
+ } elseif ( !flock( $handle, LOCK_EX ) ) {
+ fclose( $handle );
+ throw new MWException( "Could not acquire '{$this->$lockFile}'." );
+ }
+ // Get the current timestamp, clock sequence number, last time, and counter
+ rewind( $handle );
+ $data = explode( ' ', fgets( $handle ) ); // "<clk seq> <sec> <msec> <counter> <offset>"
+ $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 ) );
+ }
+
+ /**
+ * Delete all cache files that have been created.
+ *
+ * This is a cleanup method primarily meant to be used from unit tests to
+ * avoid poluting the local filesystem. If used outside of a unit test
+ * environment it should be used with caution as it may destroy state saved
+ * in the files.
+ *
+ * @see unitTestTearDown
+ * @since 1.23
+ */
+ protected function deleteCacheFiles() {
+ // Bug: 44850
+ foreach ( $this->fileHandles as $path => $handle ) {
+ if ( $handle !== null ) {
+ fclose( $handle );
+ }
+ if ( is_file( $path ) ) {
+ unlink( $path );
+ }
+ unset( $this->fileHandles[$path] );
+ }
+ if ( is_file( $this->nodeIdFile ) ) {
+ unlink( $this->nodeIdFile );
+ }
+ }
+
+ /**
+ * Cleanup resources when tearing down after a unit test.
+ *
+ * This is a cleanup method primarily meant to be used from unit tests to
+ * avoid poluting the local filesystem. If used outside of a unit test
+ * environment it should be used with caution as it may destroy state saved
+ * in the files.
+ *
+ * @see deleteCacheFiles
+ * @since 1.23
+ */
+ public static function unitTestTearDown() {
+ // Bug: 44850
+ $gen = self::singleton();
+ $gen->deleteCacheFiles();
+ }
+
+ function __destruct() {
+ array_map( 'fclose', array_filter( $this->fileHandles ) );
+ }
+}
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