}

		return $this->doDeleteMulti( $keys, $flags );
	}

	/**
	 * @param string[] $keys List of keys
	 * @param int $flags Bitfield of BagOStuff::WRITE_* constants
	 * @return bool Success
	 */
	protected function doDeleteMulti( array $keys, $flags = 0 ) {
		$res = true;
		foreach ( $keys as $key ) {
			$res = $this->doDelete( $key, $flags ) && $res;
		}
		return $res;
	}

	/**
	 * Change the expiration of multiple keys that exist
	 *
	 * @param string[] $keys List of keys
	 * @param int $exptime TTL or UNIX timestamp
	 * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
	 * @return bool Success
	 *
	 * @since 1.34
	 */
	public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
		return $this->doChangeTTLMulti( $keys, $exptime, $flags );
	}

	/**
	 * @param string[] $keys List of keys
	 * @param int $exptime TTL or UNIX timestamp
	 * @param int $flags Bitfield of BagOStuff::WRITE_* constants
	 * @return bool Success
	 */
	protected function doChangeTTLMulti( array $keys, $exptime, $flags = 0 ) {
		$res = true;
		foreach ( $keys as $key ) {
			$res = $this->doChangeTTL( $key, $exptime, $flags ) && $res;
		}

		return $res;
	}

	/**
	 * Get and reassemble the chunks of blob at the given key
	 *
	 * @param string $key
	 * @param mixed $mainValue
	 * @return string|null|bool The combined string, false if missing, null on error
	 */
	final protected function resolveSegments( $key, $mainValue ) {
		if ( SerializedValueContainer::isUnified( $mainValue ) ) {
			return $this->unserialize( $mainValue->{SerializedValueContainer::UNIFIED_DATA} );
		}

		if ( SerializedValueContainer::isSegmented( $mainValue ) ) {
			$orderedKeys = array_map(
				function ( $segmentHash ) use ( $key ) {
					return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
				},
				$mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
			);

			$segmentsByKey = $this->doGetMulti( $orderedKeys );

			$parts = [];
			foreach ( $orderedKeys as $segmentKey ) {
				if ( isset( $segmentsByKey[$segmentKey] ) ) {
					$parts[] = $segmentsByKey[$segmentKey];
				} else {
					// missing segment
					return false;
				}
			}

			return $this->unserialize( implode( '', $parts ) );
		}

		return $mainValue;
	}

	/**
	 * Check if a value should use a segmentation wrapper due to its size
	 *
	 * In order to avoid extra serialization and/or twice-serialized wrappers, just check if
	 * the value is a large string. Support cache wrappers (e.g. WANObjectCache) that use 2D
	 * arrays to wrap values. This does not recurse in order to avoid overhead from complex
	 * structures and the risk of infinite loops (due to references).
	 *
	 * @param mixed $value
	 * @param int $flags
	 * @return bool
	 */
	private function useSegmentationWrapper( $value, $flags ) {
		if (
			$this->segmentationSize === INF ||
			!$this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS )
		) {
			return false;
		}

		if ( is_string( $value ) ) {
			return ( strlen( $value ) >= $this->segmentationSize );
		}

		if ( is_array( $value ) ) {
			// Expect that the contained value will be one of the first array entries
			foreach ( array_slice( $value, 0, 4 ) as $v ) {
				if ( is_string( $v ) && strlen( $v ) >= $this->segmentationSize ) {
					return true;
				}
			}
		}

		// Avoid breaking functions for incrementing/decrementing integer key values
		return false;
	}

	/**
	 * Make the entry to store at a key (inline or segment list), storing any segments
	 *
	 * @param string $key
	 * @param mixed $value
	 * @param int $exptime
	 * @param int $flags
	 * @param mixed|null &$ok Whether the entry is usable (e.g. no missing segments) [returned]
	 * @return mixed The entry (inline value, wrapped inline value, or wrapped segment list)
	 * @since 1.34
	 */
	final protected function makeValueOrSegmentList( $key, $value, $exptime, $flags, &$ok ) {
		$entry = $value;
		$ok = true;

		if ( $this->useSegmentationWrapper( $value, $flags ) ) {
			$segmentSize = $this->segmentationSize;
			$maxTotalSize = $this->segmentedValueMaxSize;
			$serialized = $this->getSerialized( $value, $key );
			$size = strlen( $serialized );
			if ( $size > $maxTotalSize ) {
				$this->logger->warning(
					"Value for {key} exceeds $maxTotalSize bytes; cannot segment.",
					[ 'key' => $key ]
				);
			} else {
				// Split the serialized value into chunks and store them at different keys
				$chunksByKey = [];
				$segmentHashes = [];
				$count = intdiv( $size, $segmentSize ) + ( ( $size % $segmentSize ) ? 1 : 0 );
				for ( $i = 0; $i < $count; ++$i ) {
					$segment = substr( $serialized, $i * $segmentSize, $segmentSize );
					$hash = sha1( $segment );
					$chunkKey = $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $hash );
					$chunksByKey[$chunkKey] = $segment;
					$segmentHashes[] = $hash;
				}
				$flags &= ~self::WRITE_ALLOW_SEGMENTS;
				$ok = $this->setMulti( $chunksByKey, $exptime, $flags );
				$entry = SerializedValueContainer::newSegmented( $segmentHashes );
			}
		}

		return $entry;
	}

	/**
	 * @param int|float $exptime
	 * @return bool Whether the expiry is non-infinite, and, negative or not a UNIX timestamp
	 * @since 1.34
	 */
	final protected function isRelativeExpiration( $exptime ) {
		return ( $exptime !== self::TTL_INDEFINITE && $exptime < ( 10 * self::TTL_YEAR ) );
	}

	/**
	 * Convert an optionally relative timestamp to an absolute time
	 *
	 * The input value will be cast to an integer and interpreted as follows:
	 *   - zero: no expiry; return zero (e.g. TTL_INDEFINITE)
	 *   - negative: relative TTL; return UNIX timestamp offset by this value
	 *   - positive (< 10 years): relative TTL; return UNIX timestamp offset by this value
	 *   - positive (>= 10 years): absolute UNIX timestamp; return this value
	 *
	 * @param int $exptime
	 * @return int Expiration timestamp or TTL_INDEFINITE for indefinite
	 * @since 1.34
	 */
	final protected function getExpirationAsTimestamp( $exptime ) {
		if ( $exptime == self::TTL_INDEFINITE ) {
			return $exptime;
		}

		return $this->isRelativeExpiration( $exptime )
			? intval( $this->getCurrentTime() + $exptime )
			: $exptime;
	}

	/**
	 * Convert an optionally absolute expiry time to a relative time. If an
	 * absolute time is specified which is in the past, use a short expiry time.
	 *
	 * The input value will be cast to an integer and interpreted as follows:
	 *   - zero: no expiry; return zero (e.g. TTL_INDEFINITE)
	 *   - negative: relative TTL; return a short expiry time (1 second)
	 *   - positive (< 10 years): relative TTL; return this value
	 *   - positive (>= 10 years): absolute UNIX timestamp; return offset to current time
	 *
	 * @param int $exptime
	 * @return int Relative TTL or TTL_INDEFINITE for indefinite
	 * @since 1.34
	 */
	final protected function getExpirationAsTTL( $exptime ) {
		if ( $exptime == self::TTL_INDEFINITE ) {
			return $exptime;
		}

		return $this->isRelativeExpiration( $exptime )
			? $exptime
			: (int)max( $exptime - $this->getCurrentTime(), 1 );
	}

	/**
	 * Check if a value is an integer
	 *
	 * @param mixed $value
	 * @return bool
	 */
	final protected function isInteger( $value ) {
		if ( is_int( $value ) ) {
			return true;
		} elseif ( !is_string( $value ) ) {
			return false;
		}

		$integer = (int)$value;

		return ( $value === (string)$integer );
	}

	public function getQoS( $flag ) {
		return $this->attrMap[$flag] ?? self::QOS_UNKNOWN;
	}

	public function getSegmentationSize() {
		return $this->segmentationSize;
	}

	public function getSegmentedValueMaxSize() {
		return $this->segmentedValueMaxSize;
	}

	/**
	 * Get the serialized form a value, logging a warning if it involves custom classes
	 *
	 * @param mixed $value
	 * @param string $key
	 * @return string|int String/integer representation of value
	 * @since 1.35
	 */
	protected function getSerialized( $value, $key ) {
		$this->checkValueSerializability( $value, $key );

		return $this->serialize( $value );
	}

	/**
	 * Log if a new cache value does not appear suitable for serialization at a quick glance
	 *
	 * This aids migration of values to JSON-like structures and the debugging of exceptions
	 * due to serialization failure.
	 *
	 * This does not recurse more than one level into container structures.
	 *
	 * A proper cache key value is one of the following:
	 *  - null
	 *  - a scalar
	 *  - an array with scalar/null values
	 *  - an array tree with scalar/null "leaf" values
	 *  - an stdClass instance with scalar/null field values
	 *  - an stdClass instance tree with scalar/null "leaf" values
	 *  - an instance of a class that implements JsonSerializable
	 *
	 * @param mixed $value Result of the value generation callback for the key
	 * @param string $key Cache key
	 */
	private function checkValueSerializability( $value, $key ) {
		if ( is_array( $value ) ) {
			$this->checkIterableMapSerializability( $value, $key );
		} elseif ( is_object( $value ) ) {
			// Note that Closure instances count as objects
			if ( $value instanceof stdClass ) {
				$this->checkIterableMapSerializability( $value, $key );
			} elseif ( !( $value instanceof JsonSerializable ) ) {
				$this->logger->warning(
					"{class} value for '{cachekey}'; serialization is suspect.",
					[ 'cachekey' => $key, 'class' => get_class( $value ) ]
				);
			}
		}
	}

	/**
	 * @param array|stdClass $value Result of the value generation callback for the key
	 * @param string $key Cache key
	 */
	private function checkIterableMapSerializability( $value, $key ) {
		foreach ( $value as $index => $entry ) {
			if ( is_object( $entry ) ) {
				// Note that Closure instances count as objects
				if (
					!( $entry instanceof stdClass ) &&
					!( $entry instanceof JsonSerializable )
				) {
					$this->logger->warning(
						"{class} value for '{cachekey}' at '$index'; serialization is suspect.",
						[ 'cachekey' => $key, 'class' => get_class( $entry ) ]
					);

					return;
				}
			}
		}
	}

	/**
	 * @param mixed $value
	 * @return string|int|false String/integer representation
	 * @note Special handling is usually needed for integers so incr()/decr() work
	 */
	protected function serialize( $value ) {
		return is_int( $value ) ? $value : serialize( $value );
	}

	/**
	 * @param string|int|false $value
	 * @return mixed Original value or false on error
	 * @note Special handling is usually needed for integers so incr()/decr() work
	 */
	protected function unserialize( $value ) {
		return $this->isInteger( $value ) ? (int)$value : unserialize( $value );
	}

	/**
	 * @param string $text
	 */
	protected function debug( $text ) {
		$this->logger->debug( "{class} debug: $text", [ 'class' => static::class ] );
	}

	/**
	 * @param string $op Operation name as a MediumSpecificBagOStuff::METRIC_OP_* constant
	 * @param array<int,string>|array<string,int[]> $keyInfo Key list, if payload sizes are not
	 *  applicable, otherwise, map of (key => (send payload size, receive payload size)); send
	 *  and receive sizes are 0 where not applicable and receive sizes are "false" for keys
	 *  that were not found during read operations
	 */
	protected function updateOpStats( string $op, array $keyInfo ) {
		$deltasByMetric = [];

		foreach ( $keyInfo as $indexOrKey => $keyOrSizes ) {
			if ( is_array( $keyOrSizes ) ) {
				$key = $indexOrKey;
				[ $sPayloadSize, $rPayloadSize ] = $keyOrSizes;
			} else {
				$key = $keyOrSizes;
				$sPayloadSize = 0;
				$rPayloadSize = 0;
			}

			// Metric prefix for the cache wrapper and key collection name
			$prefix = $this->determineKeyPrefixForStats( $key );

			if ( $op === self::METRIC_OP_GET ) {
				// This operation was either a "hit" or "miss" for this key
				$name = "{$prefix}.{$op}_" . ( $rPayloadSize === false ? 'miss_rate' : 'hit_rate' );
			} else {
				// There is no concept of "hit" or "miss" for this operation
				$name = "{$prefix}.{$op}_call_rate";
			}
			$deltasByMetric[$name] = ( $deltasByMetric[$name] ?? 0 ) + 1;

			if ( $sPayloadSize > 0 ) {
				$name = "{$prefix}.{$op}_bytes_sent";
				$deltasByMetric[$name] = ( $deltasByMetric[$name] ?? 0 ) + $sPayloadSize;
			}

			if ( $rPayloadSize > 0 ) {
				$name = "{$prefix}.{$op}_bytes_read";
				$deltasByMetric[$name] = ( $deltasByMetric[$name] ?? 0 ) + $rPayloadSize;
			}
		}

		foreach ( $deltasByMetric as $name => $delta ) {
			$this->stats->updateCount( $name, $delta );
		}
	}
}