/**
 * Checks for too many topic levels to reduce the risk of Denial of Service
 *
 * @param value - The string to validate.
 * @returns `true` if the string contains more / signs than allowed`.
 */
export declare function invalidmaxTopicLevels(value: string, maxTopicLevels: number): boolean;
/**
 * Checks for invalid characters in an MQTT topic name.
 * It cannot contain wildcards (+, #)
 *
 * @param value - The topic name to validate.
 * @returns `true` if the topic is invalid, otherwise `false`.
 */
export declare function invalidTopic(value: string): boolean;
/**
 * Checks for MQTT wildcards in a string.
 *
 * @param value - The topic name to validate.
 * @returns `true` if the topic is invalid, otherwise `false`.
 */
export declare function hasWildcards(value: string): boolean;
/**
 * Checks for invalid characters and malformed wildcards in an MQTT topic filter.
 *
 * Wildcard rules according to the MQTT specification:
 * - '+' must occupy an entire level (e.g., 'a/+/b' is valid, 'a+/b' is invalid)
 * - '#' must only appear at the very end of the string (e.g., 'a/#' is valid, 'a/#/b' is invalid)
 *
 * @param value - The topic filter to validate.
 * @returns `true` if the topic filter is invalid, otherwise `false`.
 */
export declare function invalidTopicFilter(value: string): boolean;
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