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[mediawiki.git] / includes / libs / objectcache / MemcachedClient.php

<?php
// @codingStandardsIgnoreFile It's an external lib and it isn't. Let's not bother.
/**
 * Memcached client for PHP.
 *
 * +---------------------------------------------------------------------------+
 * | memcached client, PHP                                                     |
 * +---------------------------------------------------------------------------+
 * | Copyright (c) 2003 Ryan T. Dean <rtdean@cytherianage.net>                 |
 * | All rights reserved.                                                      |
 * |                                                                           |
 * | Redistribution and use in source and binary forms, with or without        |
 * | modification, are permitted provided that the following conditions        |
 * | are met:                                                                  |
 * |                                                                           |
 * | 1. Redistributions of source code must retain the above copyright         |
 * |    notice, this list of conditions and the following disclaimer.          |
 * | 2. Redistributions in binary form must reproduce the above copyright      |
 * |    notice, this list of conditions and the following disclaimer in the    |
 * |    documentation and/or other materials provided with the distribution.   |
 * |                                                                           |
 * | THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR      |
 * | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
 * | OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.   |
 * | IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,          |
 * | INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT  |
 * | NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
 * | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY     |
 * | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT       |
 * | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF  |
 * | THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.         |
 * +---------------------------------------------------------------------------+
 * | Author: Ryan T. Dean <rtdean@cytherianage.net>                            |
 * | Heavily influenced by the Perl memcached client by Brad Fitzpatrick.      |
 * |   Permission granted by Brad Fitzpatrick for relicense of ported Perl     |
 * |   client logic under 2-clause BSD license.                                |
 * +---------------------------------------------------------------------------+
 *
 * @file
 * $TCAnet$
 */

/**
 * This is a PHP client for memcached - a distributed memory cache daemon.
 *
 * More information is available at http://www.danga.com/memcached/
 *
 * Usage example:
 *
 *     $mc = new MemcachedClient(array(
 *         'servers' => array(
 *             '127.0.0.1:10000',
 *             array( '192.0.0.1:10010', 2 ),
 *             '127.0.0.1:10020'
 *         ),
 *         'debug'   => false,
 *         'compress_threshold' => 10240,
 *         'persistent' => true
 *     ));
 *
 *     $mc->add( 'key', array( 'some', 'array' ) );
 *     $mc->replace( 'key', 'some random string' );
 *     $val = $mc->get( 'key' );
 *
 * @author Ryan T. Dean <rtdean@cytherianage.net>
 * @version 0.1.2
 */

use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;

// {{{ class MemcachedClient
/**
 * memcached client class implemented using (p)fsockopen()
 *
 * @author  Ryan T. Dean <rtdean@cytherianage.net>
 * @ingroup Cache
 */
class MemcachedClient {
        // {{{ properties
        // {{{ public

        // {{{ constants
        // {{{ flags

        /**
         * Flag: indicates data is serialized
         */
        const SERIALIZED = 1;

        /**
         * Flag: indicates data is compressed
         */
        const COMPRESSED = 2;

        /**
         * Flag: indicates data is an integer
         */
        const INTVAL = 4;

        // }}}

        /**
         * Minimum savings to store data compressed
         */
        const COMPRESSION_SAVINGS = 0.20;

        // }}}

        /**
         * Command statistics
         *
         * @var array
         * @access public
         */
        public $stats;

        // }}}
        // {{{ private

        /**
         * Cached Sockets that are connected
         *
         * @var array
         * @access private
         */
        public $_cache_sock;

        /**
         * Current debug status; 0 - none to 9 - profiling
         *
         * @var bool
         * @access private
         */
        public $_debug;

        /**
         * Dead hosts, assoc array, 'host'=>'unixtime when ok to check again'
         *
         * @var array
         * @access private
         */
        public $_host_dead;

        /**
         * Is compression available?
         *
         * @var bool
         * @access private
         */
        public $_have_zlib;

        /**
         * Do we want to use compression?
         *
         * @var bool
         * @access private
         */
        public $_compress_enable;

        /**
         * At how many bytes should we compress?
         *
         * @var int
         * @access private
         */
        public $_compress_threshold;

        /**
         * Are we using persistent links?
         *
         * @var bool
         * @access private
         */
        public $_persistent;

        /**
         * If only using one server; contains ip:port to connect to
         *
         * @var string
         * @access private
         */
        public $_single_sock;

        /**
         * Array containing ip:port or array(ip:port, weight)
         *
         * @var array
         * @access private
         */
        public $_servers;

        /**
         * Our bit buckets
         *
         * @var array
         * @access private
         */
        public $_buckets;

        /**
         * Total # of bit buckets we have
         *
         * @var int
         * @access private
         */
        public $_bucketcount;

        /**
         * # of total servers we have
         *
         * @var int
         * @access private
         */
        public $_active;

        /**
         * Stream timeout in seconds. Applies for example to fread()
         *
         * @var int
         * @access private
         */
        public $_timeout_seconds;

        /**
         * Stream timeout in microseconds
         *
         * @var int
         * @access private
         */
        public $_timeout_microseconds;

        /**
         * Connect timeout in seconds
         */
        public $_connect_timeout;

        /**
         * Number of connection attempts for each server
         */
        public $_connect_attempts;

        /**
         * @var LoggerInterface
         */
        private $_logger;

        // }}}
        // }}}
        // {{{ methods
        // {{{ public functions
        // {{{ memcached()

        /**
         * Memcache initializer
         *
         * @param array $args Associative array of settings
         *
         * @return mixed
         */
        public function __construct( $args ) {
                $this->set_servers( isset( $args['servers'] ) ? $args['servers'] : array() );
                $this->_debug = isset( $args['debug'] ) ? $args['debug'] : false;
                $this->stats = array();
                $this->_compress_threshold = isset( $args['compress_threshold'] ) ? $args['compress_threshold'] : 0;
                $this->_persistent = isset( $args['persistent'] ) ? $args['persistent'] : false;
                $this->_compress_enable = true;
                $this->_have_zlib = function_exists( 'gzcompress' );

                $this->_cache_sock = array();
                $this->_host_dead = array();

                $this->_timeout_seconds = 0;
                $this->_timeout_microseconds = isset( $args['timeout'] ) ? $args['timeout'] : 500000;

                $this->_connect_timeout = isset( $args['connect_timeout'] ) ? $args['connect_timeout'] : 0.1;
                $this->_connect_attempts = 2;

                $this->_logger = isset( $args['logger'] ) ? $args['logger'] : new NullLogger();
        }

        // }}}
        // {{{ add()

        /**
         * Adds a key/value to the memcache server if one isn't already set with
         * that key
         *
         * @param string $key Key to set with data
         * @param mixed $val Value to store
         * @param int $exp (optional) Expiration time. This can be a number of seconds
         * to cache for (up to 30 days inclusive).  Any timespans of 30 days + 1 second or
         * longer must be the timestamp of the time at which the mapping should expire. It
         * is safe to use timestamps in all cases, regardless of expiration
         * eg: strtotime("+3 hour")
         *
         * @return bool
         */
        public function add( $key, $val, $exp = 0 ) {
                return $this->_set( 'add', $key, $val, $exp );
        }

        // }}}
        // {{{ decr()

        /**
         * Decrease a value stored on the memcache server
         *
         * @param string $key Key to decrease
         * @param int $amt (optional) amount to decrease
         *
         * @return mixed False on failure, value on success
         */
        public function decr( $key, $amt = 1 ) {
                return $this->_incrdecr( 'decr', $key, $amt );
        }

        // }}}
        // {{{ delete()

        /**
         * Deletes a key from the server, optionally after $time
         *
         * @param string $key Key to delete
         * @param int $time (optional) how long to wait before deleting
         *
         * @return bool True on success, false on failure
         */
        public function delete( $key, $time = 0 ) {
                if ( !$this->_active ) {
                        return false;
                }

                $sock = $this->get_sock( $key );
                if ( !is_resource( $sock ) ) {
                        return false;
                }

                $key = is_array( $key ) ? $key[1] : $key;

                if ( isset( $this->stats['delete'] ) ) {
                        $this->stats['delete']++;
                } else {
                        $this->stats['delete'] = 1;
                }
                $cmd = "delete $key $time\r\n";
                if ( !$this->_fwrite( $sock, $cmd ) ) {
                        return false;
                }
                $res = $this->_fgets( $sock );

                if ( $this->_debug ) {
                        $this->_debugprint( sprintf( "MemCache: delete %s (%s)", $key, $res ) );
                }

                if ( $res == "DELETED" || $res == "NOT_FOUND" ) {
                        return true;
                }

                return false;
        }

        /**
         * Changes the TTL on a key from the server to $time
         *
         * @param string $key Key
         * @param int $time TTL in seconds
         *
         * @return bool True on success, false on failure
         */
        public function touch( $key, $time = 0 ) {
                if ( !$this->_active ) {
                        return false;
                }

                $sock = $this->get_sock( $key );
                if ( !is_resource( $sock ) ) {
                        return false;
                }

                $key = is_array( $key ) ? $key[1] : $key;

                if ( isset( $this->stats['touch'] ) ) {
                        $this->stats['touch']++;
                } else {
                        $this->stats['touch'] = 1;
                }
                $cmd = "touch $key $time\r\n";
                if ( !$this->_fwrite( $sock, $cmd ) ) {
                        return false;
                }
                $res = $this->_fgets( $sock );

                if ( $this->_debug ) {
                        $this->_debugprint( sprintf( "MemCache: touch %s (%s)", $key, $res ) );
                }

                if ( $res == "TOUCHED" ) {
                        return true;
                }

                return false;
        }

        /**
         * @param string $key
         * @param int $timeout
         * @return bool
         */
        public function lock( $key, $timeout = 0 ) {
                /* stub */
                return true;
        }

        /**
         * @param string $key
         * @return bool
         */
        public function unlock( $key ) {
                /* stub */
                return true;
        }

        // }}}
        // {{{ disconnect_all()

        /**
         * Disconnects all connected sockets
         */
        public function disconnect_all() {
                foreach ( $this->_cache_sock as $sock ) {
                        fclose( $sock );
                }

                $this->_cache_sock = array();
        }

        // }}}
        // {{{ enable_compress()

        /**
         * Enable / Disable compression
         *
         * @param bool $enable True to enable, false to disable
         */
        public function enable_compress( $enable ) {
                $this->_compress_enable = $enable;
        }

        // }}}
        // {{{ forget_dead_hosts()

        /**
         * Forget about all of the dead hosts
         */
        public function forget_dead_hosts() {
                $this->_host_dead = array();
        }

        // }}}
        // {{{ get()

        /**
         * Retrieves the value associated with the key from the memcache server
         *
         * @param array|string $key key to retrieve
         * @param float $casToken [optional]
         *
         * @return mixed
         */
        public function get( $key, &$casToken = null ) {

                if ( $this->_debug ) {
                        $this->_debugprint( "get($key)" );
                }

                if ( !is_array( $key ) && strval( $key ) === '' ) {
                        $this->_debugprint( "Skipping key which equals to an empty string" );
                        return false;
                }

                if ( !$this->_active ) {
                        return false;
                }

                $sock = $this->get_sock( $key );

                if ( !is_resource( $sock ) ) {
                        return false;
                }

                $key = is_array( $key ) ? $key[1] : $key;
                if ( isset( $this->stats['get'] ) ) {
                        $this->stats['get']++;
                } else {
                        $this->stats['get'] = 1;
                }

                $cmd = "gets $key\r\n";
                if ( !$this->_fwrite( $sock, $cmd ) ) {
                        return false;
                }

                $val = array();
                $this->_load_items( $sock, $val, $casToken );

                if ( $this->_debug ) {
                        foreach ( $val as $k => $v ) {
                                $this->_debugprint( sprintf( "MemCache: sock %s got %s", serialize( $sock ), $k ) );
                        }
                }

                $value = false;
                if ( isset( $val[$key] ) ) {
                        $value = $val[$key];
                }
                return $value;
        }

        // }}}
        // {{{ get_multi()

        /**
         * Get multiple keys from the server(s)
         *
         * @param array $keys Keys to retrieve
         *
         * @return array
         */
        public function get_multi( $keys ) {
                if ( !$this->_active ) {
                        return array();
                }

                if ( isset( $this->stats['get_multi'] ) ) {
                        $this->stats['get_multi']++;
                } else {
                        $this->stats['get_multi'] = 1;
                }
                $sock_keys = array();
                $socks = array();
                foreach ( $keys as $key ) {
                        $sock = $this->get_sock( $key );
                        if ( !is_resource( $sock ) ) {
                                continue;
                        }
                        $key = is_array( $key ) ? $key[1] : $key;
                        if ( !isset( $sock_keys[$sock] ) ) {
                                $sock_keys[intval( $sock )] = array();
                                $socks[] = $sock;
                        }
                        $sock_keys[intval( $sock )][] = $key;
                }

                $gather = array();
                // Send out the requests
                foreach ( $socks as $sock ) {
                        $cmd = 'gets';
                        foreach ( $sock_keys[intval( $sock )] as $key ) {
                                $cmd .= ' ' . $key;
                        }
                        $cmd .= "\r\n";

                        if ( $this->_fwrite( $sock, $cmd ) ) {
                                $gather[] = $sock;
                        }
                }

                // Parse responses
                $val = array();
                foreach ( $gather as $sock ) {
                        $this->_load_items( $sock, $val, $casToken );
                }

                if ( $this->_debug ) {
                        foreach ( $val as $k => $v ) {
                                $this->_debugprint( sprintf( "MemCache: got %s", $k ) );
                        }
                }

                return $val;
        }

        // }}}
        // {{{ incr()

        /**
         * Increments $key (optionally) by $amt
         *
         * @param string $key Key to increment
         * @param int $amt (optional) amount to increment
         *
         * @return int|null Null if the key does not exist yet (this does NOT
         * create new mappings if the key does not exist). If the key does
         * exist, this returns the new value for that key.
         */
        public function incr( $key, $amt = 1 ) {
                return $this->_incrdecr( 'incr', $key, $amt );
        }

        // }}}
        // {{{ replace()

        /**
         * Overwrites an existing value for key; only works if key is already set
         *
         * @param string $key Key to set value as
         * @param mixed $value Value to store
         * @param int $exp (optional) Expiration time. This can be a number of seconds
         * to cache for (up to 30 days inclusive).  Any timespans of 30 days + 1 second or
         * longer must be the timestamp of the time at which the mapping should expire. It
         * is safe to use timestamps in all cases, regardless of exipration
         * eg: strtotime("+3 hour")
         *
         * @return bool
         */
        public function replace( $key, $value, $exp = 0 ) {
                return $this->_set( 'replace', $key, $value, $exp );
        }

        // }}}
        // {{{ run_command()

        /**
         * Passes through $cmd to the memcache server connected by $sock; returns
         * output as an array (null array if no output)
         *
         * @param Resource $sock Socket to send command on
         * @param string $cmd Command to run
         *
         * @return array Output array
         */
        public function run_command( $sock, $cmd ) {
                if ( !is_resource( $sock ) ) {
                        return array();
                }

                if ( !$this->_fwrite( $sock, $cmd ) ) {
                        return array();
                }

                $ret = array();
                while ( true ) {
                        $res = $this->_fgets( $sock );
                        $ret[] = $res;
                        if ( preg_match( '/^END/', $res ) ) {
                                break;
                        }
                        if ( strlen( $res ) == 0 ) {
                                break;
                        }
                }
                return $ret;
        }

        // }}}
        // {{{ set()

        /**
         * Unconditionally sets a key to a given value in the memcache.  Returns true
         * if set successfully.
         *
         * @param string $key Key to set value as
         * @param mixed $value Value to set
         * @param int $exp (optional) Expiration time. This can be a number of seconds
         * to cache for (up to 30 days inclusive).  Any timespans of 30 days + 1 second or
         * longer must be the timestamp of the time at which the mapping should expire. It
         * is safe to use timestamps in all cases, regardless of exipration
         * eg: strtotime("+3 hour")
         *
         * @return bool True on success
         */
        public function set( $key, $value, $exp = 0 ) {
                return $this->_set( 'set', $key, $value, $exp );
        }

        // }}}
        // {{{ cas()

        /**
         * Sets a key to a given value in the memcache if the current value still corresponds
         * to a known, given value.  Returns true if set successfully.
         *
         * @param float $casToken Current known value
         * @param string $key Key to set value as
         * @param mixed $value Value to set
         * @param int $exp (optional) Expiration time. This can be a number of seconds
         * to cache for (up to 30 days inclusive).  Any timespans of 30 days + 1 second or
         * longer must be the timestamp of the time at which the mapping should expire. It
         * is safe to use timestamps in all cases, regardless of exipration
         * eg: strtotime("+3 hour")
         *
         * @return bool True on success
         */
        public function cas( $casToken, $key, $value, $exp = 0 ) {
                return $this->_set( 'cas', $key, $value, $exp, $casToken );
        }

        // }}}
        // {{{ set_compress_threshold()

        /**
         * Set the compression threshold
         *
         * @param int $thresh Threshold to compress if larger than
         */
        public function set_compress_threshold( $thresh ) {
                $this->_compress_threshold = $thresh;
        }

        // }}}
        // {{{ set_debug()

        /**
         * Set the debug flag
         *
         * @see __construct()
         * @param bool $dbg True for debugging, false otherwise
         */
        public function set_debug( $dbg ) {
                $this->_debug = $dbg;
        }

        // }}}
        // {{{ set_servers()

        /**
         * Set the server list to distribute key gets and puts between
         *
         * @see __construct()
         * @param array $list Array of servers to connect to
         */
        public function set_servers( $list ) {
                $this->_servers = $list;
                $this->_active = count( $list );
                $this->_buckets = null;
                $this->_bucketcount = 0;

                $this->_single_sock = null;
                if ( $this->_active == 1 ) {
                        $this->_single_sock = $this->_servers[0];
                }
        }

        /**
         * Sets the timeout for new connections
         *
         * @param int $seconds Number of seconds
         * @param int $microseconds Number of microseconds
         */
        public function set_timeout( $seconds, $microseconds ) {
                $this->_timeout_seconds = $seconds;
                $this->_timeout_microseconds = $microseconds;
        }

        // }}}
        // }}}
        // {{{ private methods
        // {{{ _close_sock()

        /**
         * Close the specified socket
         *
         * @param string $sock Socket to close
         *
         * @access private
         */
        function _close_sock( $sock ) {
                $host = array_search( $sock, $this->_cache_sock );
                fclose( $this->_cache_sock[$host] );
                unset( $this->_cache_sock[$host] );
        }

        // }}}
        // {{{ _connect_sock()

        /**
         * Connects $sock to $host, timing out after $timeout
         *
         * @param int $sock Socket to connect
         * @param string $host Host:IP to connect to
         *
         * @return bool
         * @access private
         */
        function _connect_sock( &$sock, $host ) {
                list( $ip, $port ) = preg_split( '/:(?=\d)/', $host );
                $sock = false;
                $timeout = $this->_connect_timeout;
                $errno = $errstr = null;
                for ( $i = 0; !$sock && $i < $this->_connect_attempts; $i++ ) {
                        MediaWiki\suppressWarnings();
                        if ( $this->_persistent == 1 ) {
                                $sock = pfsockopen( $ip, $port, $errno, $errstr, $timeout );
                        } else {
                                $sock = fsockopen( $ip, $port, $errno, $errstr, $timeout );
                        }
                        MediaWiki\restoreWarnings();
                }
                if ( !$sock ) {
                        $this->_error_log( "Error connecting to $host: $errstr" );
                        $this->_dead_host( $host );
                        return false;
                }

                // Initialise timeout
                stream_set_timeout( $sock, $this->_timeout_seconds, $this->_timeout_microseconds );

                // If the connection was persistent, flush the read buffer in case there
                // was a previous incomplete request on this connection
                if ( $this->_persistent ) {
                        $this->_flush_read_buffer( $sock );
                }
                return true;
        }

        // }}}
        // {{{ _dead_sock()

        /**
         * Marks a host as dead until 30-40 seconds in the future
         *
         * @param string $sock Socket to mark as dead
         *
         * @access private
         */
        function _dead_sock( $sock ) {
                $host = array_search( $sock, $this->_cache_sock );
                $this->_dead_host( $host );
        }

        /**
         * @param string $host
         */
        function _dead_host( $host ) {
                $ip = explode( ':', $host )[0];
                $this->_host_dead[$ip] = time() + 30 + intval( rand( 0, 10 ) );
                $this->_host_dead[$host] = $this->_host_dead[$ip];
                unset( $this->_cache_sock[$host] );
        }

        // }}}
        // {{{ get_sock()

        /**
         * get_sock
         *
         * @param string $key Key to retrieve value for;
         *
         * @return Resource|bool Resource on success, false on failure
         * @access private
         */
        function get_sock( $key ) {
                if ( !$this->_active ) {
                        return false;
                }

                if ( $this->_single_sock !== null ) {
                        return $this->sock_to_host( $this->_single_sock );
                }

                $hv = is_array( $key ) ? intval( $key[0] ) : $this->_hashfunc( $key );
                if ( $this->_buckets === null ) {
                        $bu = array();
                        foreach ( $this->_servers as $v ) {
                                if ( is_array( $v ) ) {
                                        for ( $i = 0; $i < $v[1]; $i++ ) {
                                                $bu[] = $v[0];
                                        }
                                } else {
                                        $bu[] = $v;
                                }
                        }
                        $this->_buckets = $bu;
                        $this->_bucketcount = count( $bu );
                }

                $realkey = is_array( $key ) ? $key[1] : $key;
                for ( $tries = 0; $tries < 20; $tries++ ) {
                        $host = $this->_buckets[$hv % $this->_bucketcount];
                        $sock = $this->sock_to_host( $host );
                        if ( is_resource( $sock ) ) {
                                return $sock;
                        }
                        $hv = $this->_hashfunc( $hv . $realkey );
                }

                return false;
        }

        // }}}
        // {{{ _hashfunc()

        /**
         * Creates a hash integer based on the $key
         *
         * @param string $key Key to hash
         *
         * @return int Hash value
         * @access private
         */
        function _hashfunc( $key ) {
                # Hash function must be in [0,0x7ffffff]
                # We take the first 31 bits of the MD5 hash, which unlike the hash
                # function used in a previous version of this client, works
                return hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
        }

        // }}}
        // {{{ _incrdecr()

        /**
         * Perform increment/decriment on $key
         *
         * @param string $cmd Command to perform
         * @param string|array $key Key to perform it on
         * @param int $amt Amount to adjust
         *
         * @return int New value of $key
         * @access private
         */
        function _incrdecr( $cmd, $key, $amt = 1 ) {
                if ( !$this->_active ) {
                        return null;
                }

                $sock = $this->get_sock( $key );
                if ( !is_resource( $sock ) ) {
                        return null;
                }

                $key = is_array( $key ) ? $key[1] : $key;
                if ( isset( $this->stats[$cmd] ) ) {
                        $this->stats[$cmd]++;
                } else {
                        $this->stats[$cmd] = 1;
                }
                if ( !$this->_fwrite( $sock, "$cmd $key $amt\r\n" ) ) {
                        return null;
                }

                $line = $this->_fgets( $sock );
                $match = array();
                if ( !preg_match( '/^(\d+)/', $line, $match ) ) {
                        return null;
                }
                return $match[1];
        }

        // }}}
        // {{{ _load_items()

        /**
         * Load items into $ret from $sock
         *
         * @param Resource $sock Socket to read from
         * @param array $ret returned values
         * @param float $casToken [optional]
         * @return bool True for success, false for failure
         *
         * @access private
         */
        function _load_items( $sock, &$ret, &$casToken = null ) {
                $results = array();

                while ( 1 ) {
                        $decl = $this->_fgets( $sock );

                        if ( $decl === false ) {
                                /*
                                 * If nothing can be read, something is wrong because we know exactly when
                                 * to stop reading (right after "END") and we return right after that.
                                 */
                                return false;
                        } elseif ( preg_match( '/^VALUE (\S+) (\d+) (\d+) (\d+)$/', $decl, $match ) ) {
                                /*
                                 * Read all data returned. This can be either one or multiple values.
                                 * Save all that data (in an array) to be processed later: we'll first
                                 * want to continue reading until "END" before doing anything else,
                                 * to make sure that we don't leave our client in a state where it's
                                 * output is not yet fully read.
                                 */
                                $results[] = array(
                                        $match[1], // rkey
                                        $match[2], // flags
                                        $match[3], // len
                                        $match[4], // casToken
                                        $this->_fread( $sock, $match[3] + 2 ), // data
                                );
                        } elseif ( $decl == "END" ) {
                                if ( count( $results ) == 0 ) {
                                        return false;
                                }

                                /**
                                 * All data has been read, time to process the data and build
                                 * meaningful return values.
                                 */
                                foreach ( $results as $vars ) {
                                        list( $rkey, $flags, $len, $casToken, $data ) = $vars;

                                        if ( $data === false || substr( $data, -2 ) !== "\r\n" ) {
                                                $this->_handle_error( $sock,
                                                        'line ending missing from data block from $1' );
                                                return false;
                                        }
                                        $data = substr( $data, 0, -2 );
                                        $ret[$rkey] = $data;

                                        if ( $this->_have_zlib && $flags & self::COMPRESSED ) {
                                                $ret[$rkey] = gzuncompress( $ret[$rkey] );
                                        }

                                        /*
                                         * This unserialize is the exact reason that we only want to
                                         * process data after having read until "END" (instead of doing
                                         * this right away): "unserialize" can trigger outside code:
                                         * in the event that $ret[$rkey] is a serialized object,
                                         * unserializing it will trigger __wakeup() if present. If that
                                         * function attempted to read from memcached (while we did not
                                         * yet read "END"), these 2 calls would collide.
                                         */
                                        if ( $flags & self::SERIALIZED ) {
                                                $ret[$rkey] = unserialize( $ret[$rkey] );
                                        } elseif ( $flags & self::INTVAL ) {
                                                $ret[$rkey] = intval( $ret[$rkey] );
                                        }
                                }

                                return true;
                        } else {
                                $this->_handle_error( $sock, 'Error parsing response from $1' );
                                return false;
                        }
                }
        }

        // }}}
        // {{{ _set()

        /**
         * Performs the requested storage operation to the memcache server
         *
         * @param string $cmd Command to perform
         * @param string $key Key to act on
         * @param mixed $val What we need to store
         * @param int $exp (optional) Expiration time. This can be a number of seconds
         * to cache for (up to 30 days inclusive).  Any timespans of 30 days + 1 second or
         * longer must be the timestamp of the time at which the mapping should expire. It
         * is safe to use timestamps in all cases, regardless of exipration
         * eg: strtotime("+3 hour")
         * @param float $casToken [optional]
         *
         * @return bool
         * @access private
         */
        function _set( $cmd, $key, $val, $exp, $casToken = null ) {
                if ( !$this->_active ) {
                        return false;
                }

                $sock = $this->get_sock( $key );
                if ( !is_resource( $sock ) ) {
                        return false;
                }

                if ( isset( $this->stats[$cmd] ) ) {
                        $this->stats[$cmd]++;
                } else {
                        $this->stats[$cmd] = 1;
                }

                $flags = 0;

                if ( is_int( $val ) ) {
                        $flags |= self::INTVAL;
                } elseif ( !is_scalar( $val ) ) {
                        $val = serialize( $val );
                        $flags |= self::SERIALIZED;
                        if ( $this->_debug ) {
                                $this->_debugprint( sprintf( "client: serializing data as it is not scalar" ) );
                        }
                }

                $len = strlen( $val );

                if ( $this->_have_zlib && $this->_compress_enable
                        && $this->_compress_threshold && $len >= $this->_compress_threshold
                ) {
                        $c_val = gzcompress( $val, 9 );
                        $c_len = strlen( $c_val );

                        if ( $c_len < $len * ( 1 - self::COMPRESSION_SAVINGS ) ) {
                                if ( $this->_debug ) {
                                        $this->_debugprint( sprintf( "client: compressing data; was %d bytes is now %d bytes", $len, $c_len ) );
                                }
                                $val = $c_val;
                                $len = $c_len;
                                $flags |= self::COMPRESSED;
                        }
                }

                $command = "$cmd $key $flags $exp $len";
                if ( $casToken ) {
                        $command .= " $casToken";
                }

                if ( !$this->_fwrite( $sock, "$command\r\n$val\r\n" ) ) {
                        return false;
                }

                $line = $this->_fgets( $sock );

                if ( $this->_debug ) {
                        $this->_debugprint( sprintf( "%s %s (%s)", $cmd, $key, $line ) );
                }
                if ( $line == "STORED" ) {
                        return true;
                }
                return false;
        }

        // }}}
        // {{{ sock_to_host()

        /**
         * Returns the socket for the host
         *
         * @param string $host Host:IP to get socket for
         *
         * @return Resource|bool IO Stream or false
         * @access private
         */
        function sock_to_host( $host ) {
                if ( isset( $this->_cache_sock[$host] ) ) {
                        return $this->_cache_sock[$host];
                }

                $sock = null;
                $now = time();
                list( $ip, /* $port */) = explode( ':', $host );
                if ( isset( $this->_host_dead[$host] ) && $this->_host_dead[$host] > $now ||
                        isset( $this->_host_dead[$ip] ) && $this->_host_dead[$ip] > $now
                ) {
                        return null;
                }

                if ( !$this->_connect_sock( $sock, $host ) ) {
                        return null;
                }

                // Do not buffer writes
                stream_set_write_buffer( $sock, 0 );

                $this->_cache_sock[$host] = $sock;

                return $this->_cache_sock[$host];
        }

        /**
         * @param string $text
         */
        function _debugprint( $text ) {
                $this->_logger->debug( $text );
        }

        /**
         * @param string $text
         */
        function _error_log( $text ) {
                $this->_logger->error( "Memcached error: $text" );
        }

        /**
         * Write to a stream. If there is an error, mark the socket dead.
         *
         * @param Resource $sock The socket
         * @param string $buf The string to write
         * @return bool True on success, false on failure
         */
        function _fwrite( $sock, $buf ) {
                $bytesWritten = 0;
                $bufSize = strlen( $buf );
                while ( $bytesWritten < $bufSize ) {
                        $result = fwrite( $sock, $buf );
                        $data = stream_get_meta_data( $sock );
                        if ( $data['timed_out'] ) {
                                $this->_handle_error( $sock, 'timeout writing to $1' );
                                return false;
                        }
                        // Contrary to the documentation, fwrite() returns zero on error in PHP 5.3.
                        if ( $result === false || $result === 0 ) {
                                $this->_handle_error( $sock, 'error writing to $1' );
                                return false;
                        }
                        $bytesWritten += $result;
                }

                return true;
        }

        /**
         * Handle an I/O error. Mark the socket dead and log an error.
         *
         * @param Resource $sock
         * @param string $msg
         */
        function _handle_error( $sock, $msg ) {
                $peer = stream_socket_get_name( $sock, true /** remote **/ );
                if ( strval( $peer ) === '' ) {
                        $peer = array_search( $sock, $this->_cache_sock );
                        if ( $peer === false ) {
                                $peer = '[unknown host]';
                        }
                }
                $msg = str_replace( '$1', $peer, $msg );
                $this->_error_log( "$msg" );
                $this->_dead_sock( $sock );
        }

        /**
         * Read the specified number of bytes from a stream. If there is an error,
         * mark the socket dead.
         *
         * @param Resource $sock The socket
         * @param int $len The number of bytes to read
         * @return string|bool The string on success, false on failure.
         */
        function _fread( $sock, $len ) {
                $buf = '';
                while ( $len > 0 ) {
                        $result = fread( $sock, $len );
                        $data = stream_get_meta_data( $sock );
                        if ( $data['timed_out'] ) {
                                $this->_handle_error( $sock, 'timeout reading from $1' );
                                return false;
                        }
                        if ( $result === false ) {
                                $this->_handle_error( $sock, 'error reading buffer from $1' );
                                return false;
                        }
                        if ( $result === '' ) {
                                // This will happen if the remote end of the socket is shut down
                                $this->_handle_error( $sock, 'unexpected end of file reading from $1' );
                                return false;
                        }
                        $len -= strlen( $result );
                        $buf .= $result;
                }
                return $buf;
        }

        /**
         * Read a line from a stream. If there is an error, mark the socket dead.
         * The \r\n line ending is stripped from the response.
         *
         * @param Resource $sock The socket
         * @return string|bool The string on success, false on failure
         */
        function _fgets( $sock ) {
                $result = fgets( $sock );
                // fgets() may return a partial line if there is a select timeout after
                // a successful recv(), so we have to check for a timeout even if we
                // got a string response.
                $data = stream_get_meta_data( $sock );
                if ( $data['timed_out'] ) {
                        $this->_handle_error( $sock, 'timeout reading line from $1' );
                        return false;
                }
                if ( $result === false ) {
                        $this->_handle_error( $sock, 'error reading line from $1' );
                        return false;
                }
                if ( substr( $result, -2 ) === "\r\n" ) {
                        $result = substr( $result, 0, -2 );
                } elseif ( substr( $result, -1 ) === "\n" ) {
                        $result = substr( $result, 0, -1 );
                } else {
                        $this->_handle_error( $sock, 'line ending missing in response from $1' );
                        return false;
                }
                return $result;
        }

        /**
         * Flush the read buffer of a stream
         * @param Resource $f
         */
        function _flush_read_buffer( $f ) {
                if ( !is_resource( $f ) ) {
                        return;
                }
                $r = array( $f );
                $w = null;
                $e = null;
                $n = stream_select( $r, $w, $e, 0, 0 );
                while ( $n == 1 && !feof( $f ) ) {
                        fread( $f, 1024 );
                        $r = array( $f );
                        $w = null;
                        $e = null;
                        $n = stream_select( $r, $w, $e, 0, 0 );
                }
        }

        // }}}
        // }}}
        // }}}
}

// }}}