mqtt_header.hpp

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#pragma once

#include "../acl_cpp_define.hpp"

namespace acl {

/**
 * all the mqtt types were defined below.
 */
typedef enum {
        MQTT_RESERVED_MIN       = 0,
        MQTT_CONNECT            = 1,
        MQTT_CONNACK            = 2,
        MQTT_PUBLISH            = 3,
        MQTT_PUBACK             = 4,
        MQTT_PUBREC             = 5,
        MQTT_PUBREL             = 6,
        MQTT_PUBCOMP            = 7,
        MQTT_SUBSCRIBE          = 8,
        MQTT_SUBACK             = 9,
        MQTT_UNSUBSCRIBE        = 10,
        MQTT_UNSUBACK           = 11,
        MQTT_PINGREQ            = 12,
        MQTT_PINGRESP           = 13,
        MQTT_DISCONNECT         = 14,
        MQTT_RESERVED_MAX       = 15,
} mqtt_type_t;

typedef enum {
        MQTT_NONE,
        MQTT_NEED,
        MQTT_MAYBE,
} mqtt_option_t;

/**
 * all the qos type of mqtt
 */
typedef enum {
        MQTT_QOS0       = 0x0,
        MQTT_QOS1       = 0x1,
        MQTT_QOS2       = 0x2,
} mqtt_qos_t;

struct mqtt_constrain {
        mqtt_type_t type;
        unsigned char flags:4;
        mqtt_option_t id;
        mqtt_option_t payload;
        const char* desc;
};

/**
 * get description of the specified mqtt type.
 * @param type {mqtt_type_t}
 * @return {const char*}
 */
const char* mqtt_type_desc(mqtt_type_t type);

/**
 * get description of the specified mqtt qos.
 * @param qos {mqtt_qos_t}
 * @return {const char*}
 */
const char* mqtt_qos_desc(mqtt_qos_t qos);

class string;

/**
 * mqtt message header class, used for building or parsing mqtt header data.
 */
class ACL_CPP_API mqtt_header {
public:
        /**
         * mqtt header constructor, usually for building mqtt message.
         * @param type {mqtt_type_t}
         */
        mqtt_header(mqtt_type_t type);

        /**
         * mqtt header constructor, usually for parsing mqtt message.
         * @param header {const mqtt_header&} will be copied internal.
         */
        mqtt_header(const mqtt_header& header);

        virtual ~mqtt_header(void);

public:
        /**
         * build mqtt header data after initializing the header object
         * by calling the setting methods below like set_xxx.
         * @param out {string&} store mqtt header data.
         * @return {bool} return true if build header successfully.
         */
        bool build_header(string& out);

        /**
         * parsing mqtt header data in streaming mode.
         * @param data {const char*} the mqtt header data, not NULL.
         * @param dlen {int} the length of data, must > 0
         * @return {int} return the length of the left data not consumed:
         *  > 0: the header has completed and the length of left data can
         *       be used as mqtt body or next mqtt message;
         *    0: the data input has been consumed, you can call finished() to
         *       check if the mqtt header has completed.
         *   -1: some error happened when parsing the input data.
         */
        int update(const char* data, int dlen);

        /**
         * check if the mqtt header has completed.
         * @return {bool}
         */
        bool finished(void) const {
                return finished_;
        }

        /**
         * reset the status of the mqtt header object for reusing the object.
         */
        void reset(void);

public:
        /**
         * set the mqtt message type in mqtt header
         * @param type {mqtt_type_t}
         * @return {mqtt_header&}
         */
        mqtt_header& set_type(mqtt_type_t type);

        /**
         * set the mqtt header flags.
         * @param flags {char}
         * @return {mqtt_header&}
         */
        mqtt_header& set_header_flags(char flags);

        /**
         * set the length of the mqtt message body.
         * @param len {unsigned}
         * @return {mqtt_header&}
         */
        mqtt_header& set_remaing_length(unsigned len);

        /**
         * set the qos of the mqtt message.
         * @param qos {mqtt_qos_t}
         * @return {mqtt_header&}
         */
        mqtt_header& set_qos(mqtt_qos_t qos);

        /**
         * set if the mqtt message be sent duplicated.
         * @param yes {bool}
         * @return {mqtt_header&}
         */
        mqtt_header& set_dup(bool yes);

        /**
         * set the remain flag in mqtt header.
         * @param yes {bool}
         * @return {mqtt_header&}
         */
        mqtt_header& set_remain(bool yes);

        /**
         * get the mqtt message type.
         * @return {mqtt_type_t}
         */
        mqtt_type_t get_type(void) const {
                return type_;
        }

        /**
         * get the mqtt header flags.
         * @return {unsigned char}
         */
        unsigned char get_header_flags(void) const {
                return hflags_;
        }

        /**
         * get the length of the mqtt message body.
         * @return {unsigned}
         */
        unsigned get_remaining_length(void) const {
                return dlen_;
        }

        /**
         * get the mqtt message's qos.
         * @return {mqtt_qos_t}
         */
        mqtt_qos_t get_qos(void) const;

        /**
         * check if the duplicated flag has been set in header.
         * @return {bool}
         */
        bool is_dup(void) const;

        /**
         * check if the remain flag has been set in header.
         * @return  {bool}
         */
        bool is_remain(void) const;

private:
        unsigned status_;
        bool finished_;

        mqtt_type_t type_;
        unsigned char hflags_:4;
        unsigned dlen_;

        char hbuf_[4];
        unsigned hlen_;

public:
        // parsing mqtt header in streaming mode, return the length of left
        // data that not consumed.

        int update_header_type(const char* data, int dlen);
        int update_header_len(const char* data, int dlen);
};

} // namespace acl