libhv/mqtt/mqtt_protocol.h

#ifndef HV_MQTT_PROTOCOL_H_
#define HV_MQTT_PROTOCOL_H_

#include "hexport.h"

#define DEFAULT_MQTT_PORT   1883

#define MQTT_PROTOCOL_V31   3 // Deprecated
#define MQTT_PROTOCOL_V311  4
#define MQTT_PROTOCOL_V5    5 // Not yet supproted

/*
 * MQTT connect
 * 2 + 4 protocol_name + 1 protocol_version + 1 conn_flags + 2 keepalive + 2 + [client_id] +
 * [2 + will_topic + 2 + will_payload] +
 * [2 + username] + [2 + password]
 */
#define MQTT_CONN_HEAD_LEN  12

/*
 * connect flags
 * 0        1               2       3-4         5           6           7
 * reserved clean_session has_will will_qos will_retain has_password has_username
 */
#define MQTT_CONN_CLEAN_SESSION 0x02
#define MQTT_CONN_HAS_WILL      0x04
#define MQTT_CONN_WILL_RETAIN   0x20
#define MQTT_CONN_HAS_PASSWORD  0x40
#define MQTT_CONN_HAS_USERNAME  0x80

typedef enum {
    MQTT_TYPE_CONNECT       = 1,
    MQTT_TYPE_CONNACK       = 2,
    MQTT_TYPE_PUBLISH       = 3,
    MQTT_TYPE_PUBACK        = 4,
    MQTT_TYPE_PUBREC        = 5,
    MQTT_TYPE_PUBREL        = 6,
    MQTT_TYPE_PUBCOMP       = 7,
    MQTT_TYPE_SUBSCRIBE     = 8,
    MQTT_TYPE_SUBACK        = 9,
    MQTT_TYPE_UNSUBSCRIBE   = 10,
    MQTT_TYPE_UNSUBACK      = 11,
    MQTT_TYPE_PINGREQ       = 12,
    MQTT_TYPE_PINGRESP      = 13,
    MQTT_TYPE_DISCONNECT    = 14,
} mqtt_type_e;

typedef enum {
    MQTT_CONNACK_ACCEPTED                       = 0,
    MQTT_CONNACK_REFUSED_PROTOCOL_VERSION       = 1,
    MQTT_CONNACK_REFUSED_IDENTIFIER_REJECTED    = 2,
    MQTT_CONNACK_REFUSED_SERVER_UNAVAILABLE     = 3,
    MQTT_CONNACK_REFUSED_BAD_USERNAME_PASSWORD  = 4,
    MQTT_CONNACK_REFUSED_NOT_AUTHORIZED         = 5,
} mqtt_connack_e;

typedef struct mqtt_head_s {
    unsigned char type:     4;
    unsigned char dup:      1;
    unsigned char qos:      2;
    unsigned char retain:   1;
    unsigned int  length;
} mqtt_head_t;

typedef struct mqtt_message_s {
    unsigned int    topic_len;
    const char*     topic;
    unsigned int    payload_len;
    const char*     payload;
    unsigned char   qos;
    unsigned char   retain;
} mqtt_message_t;

BEGIN_EXTERN_C

#define DEFAULT_MQTT_PACKAGE_MAX_LENGTH (1 << 28)   // 256M
HV_INLINE int mqtt_estimate_length(mqtt_head_t* head) {
    // 28 bits => 4*7 bits varint
    return 1 + 4 + head->length;
}

HV_EXPORT int mqtt_head_pack(mqtt_head_t* head, unsigned char buf[]);
HV_EXPORT int mqtt_head_unpack(mqtt_head_t* head, const unsigned char* buf, int len);

END_EXTERN_C

#endif // HV_MQTT_PROTOCOL_H_