MemcachedBagOStuff.php

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<?php
abstract class MemcachedBagOStuff extends MediumSpecificBagOStuff {
    protected $routingPrefix;
 
    public function __construct( array $params ) {
        $params['segmentationSize'] = $params['segmentationSize'] ?? 917504; // < 1MiB
        parent::__construct( $params );
 
        $this->routingPrefix = $params['routingPrefix'] ?? '';
 
        // ...and does not use special disk-cache plugins
        $this->attrMap[self::ATTR_DURABILITY] = self::QOS_DURABILITY_SERVICE;
    }
 
    public function makeKeyInternal( $keyspace, $components ) {
        // Memcached keys have a maximum length of 255 characters. From that,
        // subtract the number of characters we need for the keyspace and for
        // the separator character needed for each argument. To handle some
        // custom prefixes used by thing like WANObjectCache, limit to 205.
        $charsLeft = 205 - strlen( $keyspace ) - count( $components );
 
        foreach ( $components as &$component ) {
            $component = strtr( $component, ' ', '_' );
 
            // Make sure %, #, and non-ASCII chars are escaped
            $component = preg_replace_callback(
                '/[^\x21-\x22\x24\x26-\x39\x3b-\x7e]+/',
                static function ( $m ) {
                    return rawurlencode( $m[0] );
                },
                $component
            );
 
            // 33 = 32 characters for the MD5 + 1 for the '#' prefix.
            if ( $charsLeft > 33 && strlen( $component ) > $charsLeft ) {
                $component = '#' . md5( $component );
            }
 
            $charsLeft -= strlen( $component );
        }
 
        if ( $charsLeft < 0 ) {
            return $keyspace . ':BagOStuff-long-key:##' . md5( implode( ':', $components ) );
        }
 
        return $keyspace . ':' . implode( ':', $components );
    }
 
    public function validateKeyEncoding( $key ) {
        if ( preg_match( '/[^\x21-\x7e]+/', $key ) ) {
            throw new Exception( "Key contains invalid characters: $key" );
        }
 
        return $key;
    }
 
    protected function validateKeyAndPrependRoute( $key ) {
        $this->validateKeyEncoding( $key );
 
        if ( $this->routingPrefix === '' ) {
            return $key;
        }
 
        if ( $key[0] === '/' ) {
            throw new RuntimeException( "Key '$key' already contains a route." );
        }
 
        return $this->routingPrefix . $key;
    }
 
    protected function stripRouteFromKey( $key ) {
        if ( $this->routingPrefix === '' ) {
            return $key;
        }
 
        $prefixLength = strlen( $this->routingPrefix );
        if ( substr( $key, 0, $prefixLength ) === $this->routingPrefix ) {
            return substr( $key, $prefixLength );
        }
 
        return $key;
    }
 
    protected function fixExpiry( $exptime ) {
        if ( $exptime < 0 ) {
            // The PECL driver does not seem to like negative relative values
            $expiresAt = $this->getCurrentTime() + $exptime;
        } elseif ( $this->isRelativeExpiration( $exptime ) ) {
            // TTLs higher than 30 days will be detected as absolute TTLs
            // (UNIX timestamps), and will result in the cache entry being
            // discarded immediately because the expiry is in the past.
            // Clamp expires >30d at 30d, unless they're >=1e9 in which
            // case they are likely to really be absolute (1e9 = 2011-09-09)
            $expiresAt = min( $exptime, self::TTL_MONTH );
        } else {
            $expiresAt = $exptime;
        }
 
        return (int)$expiresAt;
    }
}