/*
Copyright (c) 2010-2021 Roger Light <roger@atchoo.org>

All rights reserved. This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
and Eclipse Distribution License v1.0 which accompany this distribution.

The Eclipse Public License is available at
   https://www.eclipse.org/legal/epl-2.0/
and the Eclipse Distribution License is available at
  http://www.eclipse.org/org/documents/edl-v10.php.

SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause

Contributors:
   Roger Light - initial implementation and documentation.
*/

#ifndef MOSQUITTO_H
#define MOSQUITTO_H

/*
 * File: mosquitto.h
 *
 * This header contains functions and definitions for use with libmosquitto, the Mosquitto client library.
 *
 * The definitions are also used in Mosquitto broker plugins, and some functions are available to plugins.
 */
#ifdef __cplusplus
extern "C" {
#endif


#ifdef WIN32
#  ifdef mosquitto_EXPORTS
#    define libmosq_EXPORT __declspec(dllexport)
#  else
#    ifndef LIBMOSQUITTO_STATIC
#      ifdef libmosquitto_EXPORTS
#        define libmosq_EXPORT  __declspec(dllexport)
#      else
#        define libmosq_EXPORT  __declspec(dllimport)
#      endif
#    else
#      define libmosq_EXPORT
#    endif
#  endif
#else
#  define libmosq_EXPORT
#endif

#if defined(_MSC_VER) && _MSC_VER < 1900 && !defined(bool)
#	ifndef __cplusplus
#		define bool char
#		define true 1
#		define false 0
#	endif
#else
#	ifndef __cplusplus
#		include <stdbool.h>
#	endif
#endif

#include <stddef.h>
#include <stdint.h>

#include <mqtt_protocol.h>

#define LIBMOSQUITTO_MAJOR 2
#define LIBMOSQUITTO_MINOR 1
#define LIBMOSQUITTO_REVISION 0
/* LIBMOSQUITTO_VERSION_NUMBER looks like 1002001 for e.g. version 1.2.1. */
#define LIBMOSQUITTO_VERSION_NUMBER (LIBMOSQUITTO_MAJOR*1000000+LIBMOSQUITTO_MINOR*1000+LIBMOSQUITTO_REVISION)

/* Log types */
#define MOSQ_LOG_NONE			0
#define MOSQ_LOG_INFO			(1<<0)
#define MOSQ_LOG_NOTICE			(1<<1)
#define MOSQ_LOG_WARNING		(1<<2)
#define MOSQ_LOG_ERR			(1<<3)
#define MOSQ_LOG_DEBUG			(1<<4)
#define MOSQ_LOG_SUBSCRIBE		(1<<5)
#define MOSQ_LOG_UNSUBSCRIBE	(1<<6)
#define MOSQ_LOG_WEBSOCKETS		(1<<7)
#define MOSQ_LOG_INTERNAL		0x80000000U
#define MOSQ_LOG_ALL			0xFFFFFFFFU

/* Enum: mosq_err_t
 * Integer values returned from many libmosquitto functions. */
enum mosq_err_t {
	MOSQ_ERR_QUOTA_EXCEEDED = -6,
	MOSQ_ERR_AUTH_DELAYED = -5,
	MOSQ_ERR_AUTH_CONTINUE = -4,
	MOSQ_ERR_NO_SUBSCRIBERS = -3,
	MOSQ_ERR_SUB_EXISTS = -2,
	MOSQ_ERR_CONN_PENDING = -1,
	MOSQ_ERR_SUCCESS = 0,
	MOSQ_ERR_NOMEM = 1,
	MOSQ_ERR_PROTOCOL = 2,
	MOSQ_ERR_INVAL = 3,
	MOSQ_ERR_NO_CONN = 4,
	MOSQ_ERR_CONN_REFUSED = 5,
	MOSQ_ERR_NOT_FOUND = 6,
	MOSQ_ERR_CONN_LOST = 7,
	MOSQ_ERR_TLS = 8,
	MOSQ_ERR_PAYLOAD_SIZE = 9,
	MOSQ_ERR_NOT_SUPPORTED = 10,
	MOSQ_ERR_AUTH = 11,
	MOSQ_ERR_ACL_DENIED = 12,
	MOSQ_ERR_UNKNOWN = 13,
	MOSQ_ERR_ERRNO = 14,
	MOSQ_ERR_EAI = 15,
	MOSQ_ERR_PROXY = 16,
	MOSQ_ERR_PLUGIN_DEFER = 17,
	MOSQ_ERR_MALFORMED_UTF8 = 18,
	MOSQ_ERR_KEEPALIVE = 19,
	MOSQ_ERR_LOOKUP = 20,
	MOSQ_ERR_MALFORMED_PACKET = 21,
	MOSQ_ERR_DUPLICATE_PROPERTY = 22,
	MOSQ_ERR_TLS_HANDSHAKE = 23,
	MOSQ_ERR_QOS_NOT_SUPPORTED = 24,
	MOSQ_ERR_OVERSIZE_PACKET = 25,
	MOSQ_ERR_OCSP = 26,
	MOSQ_ERR_TIMEOUT = 27,
	/* 28, 29, 30 - was internal only, moved to MQTT v5 section. */
	MOSQ_ERR_ALREADY_EXISTS = 31,
	MOSQ_ERR_PLUGIN_IGNORE = 32,
	MOSQ_ERR_HTTP_BAD_ORIGIN = 33,

	/* MQTT v5 direct equivalents 128-255 */
	MOSQ_ERR_UNSPECIFIED = 128,
	MOSQ_ERR_IMPLEMENTATION_SPECIFIC = 131,
	MOSQ_ERR_CLIENT_IDENTIFIER_NOT_VALID = 133,
	MOSQ_ERR_BAD_USERNAME_OR_PASSWORD = 134,
	MOSQ_ERR_SERVER_UNAVAILABLE = 136,
	MOSQ_ERR_SERVER_BUSY = 137,
	MOSQ_ERR_BANNED = 138,
	MOSQ_ERR_BAD_AUTHENTICATION_METHOD = 140,
	MOSQ_ERR_SESSION_TAKEN_OVER = 142,
	MOSQ_ERR_RECEIVE_MAXIMUM_EXCEEDED = 147,
	MOSQ_ERR_TOPIC_ALIAS_INVALID = 148,
	MOSQ_ERR_ADMINISTRATIVE_ACTION = 152,
	MOSQ_ERR_RETAIN_NOT_SUPPORTED = 154,
	MOSQ_ERR_CONNECTION_RATE_EXCEEDED = 159,
};

/* Enum: mosq_opt_t
 *
 * Client options.
 *
 * See <mosquitto_int_option>, <mosquitto_string_option>, and <mosquitto_void_option>.
 */
enum mosq_opt_t {
	MOSQ_OPT_PROTOCOL_VERSION = 1,
	MOSQ_OPT_SSL_CTX = 2,
	MOSQ_OPT_SSL_CTX_WITH_DEFAULTS = 3,
	MOSQ_OPT_RECEIVE_MAXIMUM = 4,
	MOSQ_OPT_SEND_MAXIMUM = 5,
	MOSQ_OPT_TLS_KEYFORM = 6,
	MOSQ_OPT_TLS_ENGINE = 7,
	MOSQ_OPT_TLS_ENGINE_KPASS_SHA1 = 8,
	MOSQ_OPT_TLS_OCSP_REQUIRED = 9,
	MOSQ_OPT_TLS_ALPN = 10,
	MOSQ_OPT_TCP_NODELAY = 11,
	MOSQ_OPT_BIND_ADDRESS = 12,
	MOSQ_OPT_TLS_USE_OS_CERTS = 13,
	MOSQ_OPT_DISABLE_SOCKETPAIR = 14,
	MOSQ_OPT_TRANSPORT = 15,
	MOSQ_OPT_HTTP_PATH = 16,
	MOSQ_OPT_HTTP_HEADER_SIZE = 17,
};

enum mosq_transport_t {
	MOSQ_T_TCP = 1,
	MOSQ_T_WEBSOCKETS = 2,
};

/* MQTT specification restricts client ids to a maximum of 23 characters */
#define MOSQ_MQTT_ID_MAX_LENGTH 23

#define MQTT_PROTOCOL_V31 3
#define MQTT_PROTOCOL_V311 4
#define MQTT_PROTOCOL_V5 5

/* Struct: mosquitto_message
 *
 * Contains details of a PUBLISH message.
 *
 * int mid - the message/packet ID of the PUBLISH message, assuming this is a
 *           QoS 1 or 2 message. Will be set to 0 for QoS 0 messages.
 *
 * char *topic - the topic the message was delivered on.
 *
 * void *payload - the message payload. This will be payloadlen bytes long, and
 *                 may be NULL if a zero length payload was sent.
 *
 * int payloadlen - the length of the payload, in bytes.
 *
 * int qos - the quality of service of the message, 0, 1, or 2.
 *
 * bool retain - set to true for stale retained messages.
 */
struct mosquitto_message{
	int mid;
	char *topic;
	void *payload;
	int payloadlen;
	int qos;
	bool retain;
};

struct mosquitto;
typedef struct mqtt5__property mosquitto_property;

struct mosquitto_message_v5{
	void *payload;
	char *topic;
	mosquitto_property *properties;
	uint32_t payloadlen;
	uint8_t qos;
	bool retain;
	uint8_t padding[2];
};

/*
 * Topic: Threads
 *	libmosquitto provides thread safe operation, with the exception of
 *	<mosquitto_lib_init> which is not thread safe.
 *
 *	If the library has been compiled without thread support it is *not*
 *	guaranteed to be thread safe.
 *
 *	If your application uses threads you must use <mosquitto_threaded_set> to
 *	tell the library this is the case, otherwise it makes some optimisations
 *	for the single threaded case that may result in unexpected behaviour for
 *	the multi threaded case.
 */
/***************************************************
 * Important note
 *
 * The following functions that deal with network operations will return
 * MOSQ_ERR_SUCCESS on success, but this does not mean that the operation has
 * taken place. An attempt will be made to write the network data, but if the
 * socket is not available for writing at that time then the packet will not be
 * sent. To ensure the packet is sent, call mosquitto_loop() (which must also
 * be called to process incoming network data).
 * This is especially important when disconnecting a client that has a will. If
 * the broker does not receive the DISCONNECT command, it will assume that the
 * client has disconnected unexpectedly and send the will.
 *
 * mosquitto_connect()
 * mosquitto_disconnect()
 * mosquitto_subscribe()
 * mosquitto_unsubscribe()
 * mosquitto_publish()
 ***************************************************/


/* ======================================================================
 *
 * Section: Library version, init, and cleanup
 *
 * ====================================================================== */
/*
 * Function: mosquitto_lib_version
 *
 * Can be used to obtain version information for the mosquitto library.
 * This allows the application to compare the library version against the
 * version it was compiled against by using the LIBMOSQUITTO_MAJOR,
 * LIBMOSQUITTO_MINOR and LIBMOSQUITTO_REVISION defines.
 *
 * Parameters:
 *  major -    an integer pointer. If not NULL, the major version of the
 *             library will be returned in this variable.
 *  minor -    an integer pointer. If not NULL, the minor version of the
 *             library will be returned in this variable.
 *  revision - an integer pointer. If not NULL, the revision of the library will
 *             be returned in this variable.
 *
 * Returns:
 *	LIBMOSQUITTO_VERSION_NUMBER - which is a unique number based on the major,
 *		minor and revision values.
 * See Also:
 * 	<mosquitto_lib_cleanup>, <mosquitto_lib_init>
 */
libmosq_EXPORT int mosquitto_lib_version(int *major, int *minor, int *revision);

/*
 * Function: mosquitto_lib_init
 *
 * Must be called before any other mosquitto functions.
 *
 * This function is *not* thread safe.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_UNKNOWN - on Windows, if sockets couldn't be initialized.
 *
 * See Also:
 * 	<mosquitto_lib_cleanup>, <mosquitto_lib_version>
 */
libmosq_EXPORT int mosquitto_lib_init(void);

/*
 * Function: mosquitto_lib_cleanup
 *
 * Call to free resources associated with the library.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - always
 *
 * See Also:
 * 	<mosquitto_lib_init>, <mosquitto_lib_version>
 */
libmosq_EXPORT int mosquitto_lib_cleanup(void);


/* ======================================================================
 *
 * Section: Client creation, destruction, and reinitialisation
 *
 * ====================================================================== */
/*
 * Function: mosquitto_new
 *
 * Create a new mosquitto client instance.
 *
 * Parameters:
 * 	id -            String to use as the client id. If NULL, a random client id
 * 	                will be generated. If id is NULL, clean_session must be true.
 * 	clean_session - set to true to instruct the broker to clean all messages
 *                  and subscriptions on disconnect, false to instruct it to
 *                  keep them. See the man page mqtt(7) for more details.
 *                  Note that a client will never discard its own outgoing
 *                  messages on disconnect. Calling <mosquitto_connect> or
 *                  <mosquitto_reconnect> will cause the messages to be resent.
 *                  Use <mosquitto_reinitialise> to reset a client to its
 *                  original state.
 *                  Must be set to true if the id parameter is NULL.
 * 	obj -           A user pointer that will be passed as an argument to any
 *                  callbacks that are specified.
 *
 * Returns:
 * 	Pointer to a struct mosquitto on success.
 * 	NULL on failure. Interrogate errno to determine the cause for the failure:
 *      - ENOMEM on out of memory.
 *      - EINVAL on invalid input parameters.
 *
 * See Also:
 * 	<mosquitto_reinitialise>, <mosquitto_destroy>, <mosquitto_user_data_set>
 */
libmosq_EXPORT struct mosquitto *mosquitto_new(const char *id, bool clean_session, void *obj);

/*
 * Function: mosquitto_destroy
 *
 * Use to free memory associated with a mosquitto client instance.
 *
 * Parameters:
 * 	mosq - a struct mosquitto pointer to free.
 *
 * See Also:
 * 	<mosquitto_new>, <mosquitto_reinitialise>
 */
libmosq_EXPORT void mosquitto_destroy(struct mosquitto *mosq);

/*
 * Function: mosquitto_reinitialise
 *
 * This function allows an existing mosquitto client to be reused. Call on a
 * mosquitto instance to close any open network connections, free memory
 * and reinitialise the client with the new parameters. The end result is the
 * same as the output of <mosquitto_new>.
 *
 * Parameters:
 * 	mosq -          a valid mosquitto instance.
 * 	id -            string to use as the client id. If NULL, a random client id
 * 	                will be generated. If id is NULL, clean_session must be true.
 * 	clean_session - set to true to instruct the broker to clean all messages
 *                  and subscriptions on disconnect, false to instruct it to
 *                  keep them. See the man page mqtt(7) for more details.
 *                  Must be set to true if the id parameter is NULL.
 * 	obj -           A user pointer that will be passed as an argument to any
 *                  callbacks that are specified.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the client id is not valid UTF-8.
 *
 * See Also:
 * 	<mosquitto_new>, <mosquitto_destroy>
 */
libmosq_EXPORT int mosquitto_reinitialise(struct mosquitto *mosq, const char *id, bool clean_session, void *obj);


/* ======================================================================
 *
 * Section: Will
 *
 * ====================================================================== */
/*
 * Function: mosquitto_will_set
 *
 * Configure will information for a mosquitto instance. By default, clients do
 * not have a will.  This must be called before calling <mosquitto_connect>.
 *
 * It is valid to use this function for clients using all MQTT protocol versions.
 * If you need to set MQTT v5 Will properties, use <mosquitto_will_set_v5> instead.
 *
 * Parameters:
 * 	mosq -       a valid mosquitto instance.
 * 	topic -      the topic on which to publish the will.
 * 	payloadlen - the size of the payload (bytes). Valid values are between 0 and
 *               268,435,455.
 * 	payload -    pointer to the data to send. If payloadlen > 0 this must be a
 *               valid memory location.
 * 	qos -        integer value 0, 1 or 2 indicating the Quality of Service to be
 *               used for the will.
 * 	retain -     set to true to make the will a retained message.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS -      on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_PAYLOAD_SIZE -   if payloadlen is too large.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8.
 */
libmosq_EXPORT int mosquitto_will_set(struct mosquitto *mosq, const char *topic, int payloadlen, const void *payload, int qos, bool retain);

/*
 * Function: mosquitto_will_set_v5
 *
 * Configure will information for a mosquitto instance, with attached
 * properties. By default, clients do not have a will.  This must be called
 * before calling <mosquitto_connect>.
 *
 * If the mosquitto instance `mosq` is using MQTT v5, the `properties` argument
 * will be applied to the Will. For MQTT v3.1.1 and below, the `properties`
 * argument will be ignored.
 *
 * Set your client to use MQTT v5 immediately after it is created:
 *
 * mosquitto_int_option(mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
 *
 * Parameters:
 * 	mosq -       a valid mosquitto instance.
 * 	topic -      the topic on which to publish the will.
 * 	payloadlen - the size of the payload (bytes). Valid values are between 0 and
 *               268,435,455.
 * 	payload -    pointer to the data to send. If payloadlen > 0 this must be a
 *               valid memory location.
 * 	qos -        integer value 0, 1 or 2 indicating the Quality of Service to be
 *               used for the will.
 * 	retain -     set to true to make the will a retained message.
 * 	properties - list of MQTT 5 properties. Can be NULL. On success only, the
 * 	             property list becomes the property of libmosquitto once this
 * 	             function is called and will be freed by the library. The
 * 	             property list must be freed by the application on error.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS -      on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_PAYLOAD_SIZE -   if payloadlen is too large.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8.
 * 	MOSQ_ERR_NOT_SUPPORTED -  if properties is not NULL and the client is not
 * 	                          using MQTT v5
 * 	MOSQ_ERR_PROTOCOL -       if a property is invalid for use with wills.
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 */
libmosq_EXPORT int mosquitto_will_set_v5(struct mosquitto *mosq, const char *topic, int payloadlen, const void *payload, int qos, bool retain, mosquitto_property *properties);

/*
 * Function: mosquitto_will_clear
 *
 * Remove a previously configured will. This must be called before calling
 * <mosquitto_connect>.
 *
 * Parameters:
 * 	mosq - a valid mosquitto instance.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_will_clear(struct mosquitto *mosq);


/* ======================================================================
 *
 * Section: Username and password
 *
 * ====================================================================== */
/*
 * Function: mosquitto_username_pw_set
 *
 * Configure username and password for a mosquitto instance. By default, no
 * username or password will be sent. For v3.1 and v3.1.1 clients, if username
 * is NULL, the password argument is ignored.
 *
 * This is must be called before calling <mosquitto_connect>.
 *
 * Parameters:
 * 	mosq -     a valid mosquitto instance.
 * 	username - the username to send as a string, or NULL to disable
 *             authentication.
 * 	password - the password to send as a string. Set to NULL when username is
 * 	           valid in order to send just a username.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 */
libmosq_EXPORT int mosquitto_username_pw_set(struct mosquitto *mosq, const char *username, const char *password);


/* ======================================================================
 *
 * Section: Connecting, reconnecting, disconnecting
 *
 * ====================================================================== */
/*
 * Function: mosquitto_connect
 *
 * Connect to an MQTT broker.
 *
 * It is valid to use this function for clients using all MQTT protocol versions.
 * If you need to set MQTT v5 CONNECT properties, use <mosquitto_connect_bind_v5>
 * instead.
 *
 * Parameters:
 * 	mosq -      a valid mosquitto instance.
 * 	host -      the hostname or ip address of the broker to connect to.
 * 	port -      the network port to connect to. Usually 1883.
 * 	keepalive - the number of seconds after which the client should send a PING
 *              message to the broker if no other messages have been exchanged
 *              in that time.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid, which could be any of:
 * 	                   * mosq == NULL
 * 	                   * host == NULL
 * 	                   * port < 0
 * 	                   * keepalive < 5
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect_bind>, <mosquitto_connect_async>, <mosquitto_reconnect>, <mosquitto_disconnect>, <mosquitto_tls_set>
 */
libmosq_EXPORT int mosquitto_connect(struct mosquitto *mosq, const char *host, int port, int keepalive);

/*
 * Function: mosquitto_connect_bind
 *
 * Connect to an MQTT broker. This extends the functionality of
 * <mosquitto_connect> by adding the bind_address parameter. Use this function
 * if you need to restrict network communication over a particular interface.
 *
 * Parameters:
 * 	mosq -         a valid mosquitto instance.
 * 	host -         the hostname or ip address of the broker to connect to.
 * 	port -         the network port to connect to. Usually 1883.
 * 	keepalive -    the number of seconds after which the client should send a PING
 *                 message to the broker if no other messages have been exchanged
 *                 in that time.
 *  bind_address - the hostname or ip address of the local network interface to
 *                 bind to. If you do not want to bind to a specific interface,
 *                 set this to NULL.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect>, <mosquitto_connect_async>, <mosquitto_connect_bind_async>
 */
libmosq_EXPORT int mosquitto_connect_bind(struct mosquitto *mosq, const char *host, int port, int keepalive, const char *bind_address);

/*
 * Function: mosquitto_connect_bind_v5
 *
 * Connect to an MQTT broker. This extends the functionality of
 * <mosquitto_connect> by adding the bind_address parameter and MQTT v5
 * properties. Use this function if you need to restrict network communication
 * over a particular interface.
 *
 * Use e.g. <mosquitto_property_add_string> and similar to create a list of
 * properties, then attach them to this publish. Properties need freeing with
 * <mosquitto_property_free_all>.
 *
 * If the mosquitto instance `mosq` is using MQTT v5, the `properties` argument
 * will be applied to the CONNECT message. For MQTT v3.1.1 and below, the
 * `properties` argument will be ignored.
 *
 * Set your client to use MQTT v5 immediately after it is created:
 *
 * mosquitto_int_option(mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
 *
 * Parameters:
 * 	mosq -         a valid mosquitto instance.
 * 	host -         the hostname or ip address of the broker to connect to.
 * 	port -         the network port to connect to. Usually 1883.
 * 	keepalive -    the number of seconds after which the client should send a PING
 *                 message to the broker if no other messages have been exchanged
 *                 in that time.
 *  bind_address - the hostname or ip address of the local network interface to
 *                 bind to. If you do not want to bind to a specific interface,
 *                 set this to NULL.
 *  properties - the MQTT 5 properties for the connect (not for the Will).
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid, which could be any of:
 * 	                   * mosq == NULL
 * 	                   * host == NULL
 * 	                   * port < 0
 * 	                   * keepalive < 5
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 *	MOSQ_ERR_PROTOCOL - if any property is invalid for use with CONNECT.
 *
 * See Also:
 * 	<mosquitto_connect>, <mosquitto_connect_async>, <mosquitto_connect_bind_async>
 */
libmosq_EXPORT int mosquitto_connect_bind_v5(struct mosquitto *mosq, const char *host, int port, int keepalive, const char *bind_address, const mosquitto_property *properties);

/*
 * Function: mosquitto_connect_async
 *
 * Connect to an MQTT broker. This is a non-blocking call. If you use
 * <mosquitto_connect_async> your client must use the threaded interface
 * <mosquitto_loop_start>. If you need to use <mosquitto_loop>, you must use
 * <mosquitto_connect> to connect the client.
 *
 * May be called before or after <mosquitto_loop_start>.
 *
 * Parameters:
 * 	mosq -      a valid mosquitto instance.
 * 	host -      the hostname or ip address of the broker to connect to.
 * 	port -      the network port to connect to. Usually 1883.
 * 	keepalive - the number of seconds after which the client should send a PING
 *              message to the broker if no other messages have been exchanged
 *              in that time.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect_bind_async>, <mosquitto_connect>, <mosquitto_reconnect>, <mosquitto_disconnect>, <mosquitto_tls_set>
 */
libmosq_EXPORT int mosquitto_connect_async(struct mosquitto *mosq, const char *host, int port, int keepalive);

/*
 * Function: mosquitto_connect_bind_async
 *
 * Connect to an MQTT broker. This is a non-blocking call. If you use
 * <mosquitto_connect_bind_async> your client must use the threaded interface
 * <mosquitto_loop_start>. If you need to use <mosquitto_loop>, you must use
 * <mosquitto_connect> to connect the client.
 *
 * This extends the functionality of <mosquitto_connect_async> by adding the
 * bind_address parameter. Use this function if you need to restrict network
 * communication over a particular interface.
 *
 * May be called before or after <mosquitto_loop_start>.
 *
 * Parameters:
 * 	mosq -         a valid mosquitto instance.
 * 	host -         the hostname or ip address of the broker to connect to.
 * 	port -         the network port to connect to. Usually 1883.
 * 	keepalive -    the number of seconds after which the client should send a PING
 *                 message to the broker if no other messages have been exchanged
 *                 in that time.
 *  bind_address - the hostname or ip address of the local network interface to
 *                 bind to. If you do not want to bind to a specific interface,
 *                 set this to NULL.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid, which could be any of:
 * 	                   * mosq == NULL
 * 	                   * host == NULL
 * 	                   * port < 0
 * 	                   * keepalive < 5
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect_async>, <mosquitto_connect>, <mosquitto_connect_bind>
 */
libmosq_EXPORT int mosquitto_connect_bind_async(struct mosquitto *mosq, const char *host, int port, int keepalive, const char *bind_address);

/*
 * Function: mosquitto_connect_srv
 *
 * Connect to an MQTT broker.
 *
 * If you set `host` to `example.com`, then this call will attempt to retrieve
 * the DNS SRV record for `_secure-mqtt._tcp.example.com` or
 * `_mqtt._tcp.example.com` to discover which actual host to connect to.
 *
 * DNS SRV support is not usually compiled in to libmosquitto, use of this call
 * is not recommended.
 *
 * Parameters:
 * 	mosq -         a valid mosquitto instance.
 * 	host -         the hostname to search for an SRV record.
 * 	keepalive -    the number of seconds after which the client should send a PING
 *                 message to the broker if no other messages have been exchanged
 *                 in that time.
 *  bind_address - the hostname or ip address of the local network interface to
 *                 bind to. If you do not want to bind to a specific interface,
 *                 set this to NULL.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid, which could be any of:
 * 	                   * mosq == NULL
 * 	                   * host == NULL
 * 	                   * port < 0
 * 	                   * keepalive < 5
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect_async>, <mosquitto_connect>, <mosquitto_connect_bind>
 */
libmosq_EXPORT int mosquitto_connect_srv(struct mosquitto *mosq, const char *host, int keepalive, const char *bind_address);

/*
 * Function: mosquitto_reconnect
 *
 * Reconnect to a broker.
 *
 * This function provides an easy way of reconnecting to a broker after a
 * connection has been lost. It uses the values that were provided in the
 * <mosquitto_connect> call. It must not be called before
 * <mosquitto_connect>.
 *
 * Parameters:
 * 	mosq - a valid mosquitto instance.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect>, <mosquitto_disconnect>, <mosquitto_reconnect_async>
 */
libmosq_EXPORT int mosquitto_reconnect(struct mosquitto *mosq);

/*
 * Function: mosquitto_reconnect_async
 *
 * Reconnect to a broker. Non blocking version of <mosquitto_reconnect>.
 *
 * This function provides an easy way of reconnecting to a broker after a
 * connection has been lost. It uses the values that were provided in the
 * <mosquitto_connect> or <mosquitto_connect_async> calls. It must not be
 * called before <mosquitto_connect>.
 *
 * Parameters:
 * 	mosq - a valid mosquitto instance.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 * 	MOSQ_ERR_ERRNO -   if a system call returned an error. The variable errno
 *                     contains the error code, even on Windows.
 *                     Use strerror_r() where available or FormatMessage() on
 *                     Windows.
 *
 * See Also:
 * 	<mosquitto_connect>, <mosquitto_disconnect>
 */
libmosq_EXPORT int mosquitto_reconnect_async(struct mosquitto *mosq);

/*
 * Function: mosquitto_disconnect
 *
 * Disconnect from the broker.
 *
 * It is valid to use this function for clients using all MQTT protocol versions.
 * If you need to set MQTT v5 DISCONNECT properties, use
 * <mosquitto_disconnect_v5> instead.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NO_CONN -  if the client isn't connected to a broker.
 */
libmosq_EXPORT int mosquitto_disconnect(struct mosquitto *mosq);

/*
 * Function: mosquitto_disconnect_v5
 *
 * Disconnect from the broker, with attached MQTT properties.
 *
 * Use e.g. <mosquitto_property_add_string> and similar to create a list of
 * properties, then attach them to this publish. Properties need freeing with
 * <mosquitto_property_free_all>.
 *
 * If the mosquitto instance `mosq` is using MQTT v5, the `properties` argument
 * will be applied to the DISCONNECT message. For MQTT v3.1.1 and below, the
 * `properties` argument will be ignored.
 *
 * Set your client to use MQTT v5 immediately after it is created:
 *
 * mosquitto_int_option(mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	reason_code - the disconnect reason code.
 * 	properties - a valid mosquitto_property list, or NULL.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NO_CONN -  if the client isn't connected to a broker.
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 *	MOSQ_ERR_PROTOCOL - if any property is invalid for use with DISCONNECT.
 */
libmosq_EXPORT int mosquitto_disconnect_v5(struct mosquitto *mosq, int reason_code, const mosquitto_property *properties);


/* ======================================================================
 *
 * Section: Publishing, subscribing, unsubscribing
 *
 * ====================================================================== */
/*
 * Function: mosquitto_publish
 *
 * Publish a message on a given topic.
 *
 * It is valid to use this function for clients using all MQTT protocol versions.
 * If you need to set MQTT v5 PUBLISH properties, use <mosquitto_publish_v5>
 * instead.
 *
 * Parameters:
 * 	mosq -       a valid mosquitto instance.
 * 	mid -        pointer to an int. If not NULL, the function will set this
 *               to the message id of this particular message. This can be then
 *               used with the publish callback to determine when the message
 *               has been sent.
 *               Note that although the MQTT protocol doesn't use message ids
 *               for messages with QoS=0, libmosquitto assigns them message ids
 *               so they can be tracked with this parameter.
 *  topic -      null terminated string of the topic to publish to.
 * 	payloadlen - the size of the payload (bytes). Valid values are between 0 and
 *               268,435,455.
 * 	payload -    pointer to the data to send. If payloadlen > 0 this must be a
 *               valid memory location.
 * 	qos -        integer value 0, 1 or 2 indicating the Quality of Service to be
 *               used for the message.
 * 	retain -     set to true to make the message retained.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 *	MOSQ_ERR_PROTOCOL -       if there is a protocol error communicating with the
 *                            broker.
 * 	MOSQ_ERR_PAYLOAD_SIZE -   if payloadlen is too large.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *	MOSQ_ERR_QOS_NOT_SUPPORTED - if the QoS is greater than that supported by
 *	                             the broker.
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 *
 * See Also:
 *	<mosquitto_max_inflight_messages_set>
 */
libmosq_EXPORT int mosquitto_publish(struct mosquitto *mosq, int *mid, const char *topic, int payloadlen, const void *payload, int qos, bool retain);


/*
 * Function: mosquitto_publish_v5
 *
 * Publish a message on a given topic, with attached MQTT properties.
 *
 * Use e.g. <mosquitto_property_add_string> and similar to create a list of
 * properties, then attach them to this publish. Properties need freeing with
 * <mosquitto_property_free_all>.
 *
 * If the mosquitto instance `mosq` is using MQTT v5, the `properties` argument
 * will be applied to the PUBLISH message. For MQTT v3.1.1 and below, the
 * `properties` argument will be ignored.
 *
 * Set your client to use MQTT v5 immediately after it is created:
 *
 * mosquitto_int_option(mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
 *
 * Parameters:
 * 	mosq -       a valid mosquitto instance.
 * 	mid -        pointer to an int. If not NULL, the function will set this
 *               to the message id of this particular message. This can be then
 *               used with the publish callback to determine when the message
 *               has been sent.
 *               Note that although the MQTT protocol doesn't use message ids
 *               for messages with QoS=0, libmosquitto assigns them message ids
 *               so they can be tracked with this parameter.
 *  topic -      null terminated string of the topic to publish to.
 * 	payloadlen - the size of the payload (bytes). Valid values are between 0 and
 *               268,435,455.
 * 	payload -    pointer to the data to send. If payloadlen > 0 this must be a
 *               valid memory location.
 * 	qos -        integer value 0, 1 or 2 indicating the Quality of Service to be
 *               used for the message.
 * 	retain -     set to true to make the message retained.
 * 	properties - a valid mosquitto_property list, or NULL.
 *
 * Returns:
 * 	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 *	MOSQ_ERR_PROTOCOL -       if there is a protocol error communicating with the
 *                            broker.
 * 	MOSQ_ERR_PAYLOAD_SIZE -   if payloadlen is too large.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 *	MOSQ_ERR_PROTOCOL - if any property is invalid for use with PUBLISH.
 *	MOSQ_ERR_QOS_NOT_SUPPORTED - if the QoS is greater than that supported by
 *	                             the broker.
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_publish_v5(
		struct mosquitto *mosq,
		int *mid,
		const char *topic,
		int payloadlen,
		const void *payload,
		int qos,
		bool retain,
		const mosquitto_property *properties);


/*
 * Function: mosquitto_subscribe
 *
 * Subscribe to a topic.
 *
 * It is valid to use this function for clients using all MQTT protocol versions.
 * If you need to set MQTT v5 SUBSCRIBE properties, use <mosquitto_subscribe_v5>
 * instead.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	mid -  a pointer to an int. If not NULL, the function will set this to
 *	       the message id of this particular message. This can be then used
 *	       with the subscribe callback to determine when the message has been
 *	       sent.
 *	sub -  the subscription pattern - must not be NULL or an empty string.
 *	qos -  the requested Quality of Service for this subscription.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_subscribe(struct mosquitto *mosq, int *mid, const char *sub, int qos);

/*
 * Function: mosquitto_subscribe_v5
 *
 * Subscribe to a topic, with attached MQTT properties.
 *
 * Use e.g. <mosquitto_property_add_string> and similar to create a list of
 * properties, then attach them to this publish. Properties need freeing with
 * <mosquitto_property_free_all>.
 *
 * If the mosquitto instance `mosq` is using MQTT v5, the `properties` argument
 * will be applied to the PUBLISH message. For MQTT v3.1.1 and below, the
 * `properties` argument will be ignored.
 *
 * Set your client to use MQTT v5 immediately after it is created:
 *
 * mosquitto_int_option(mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	mid -  a pointer to an int. If not NULL, the function will set this to
 *	       the message id of this particular message. This can be then used
 *	       with the subscribe callback to determine when the message has been
 *	       sent.
 *	sub -  the subscription pattern - must not be NULL or an empty string.
 *	qos -  the requested Quality of Service for this subscription.
 *	options - options to apply to this subscription, OR'd together. Set to 0 to
 *	          use the default options, otherwise choose from list of <mqtt5_sub_options>
 * 	properties - a valid mosquitto_property list, or NULL.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 *	MOSQ_ERR_PROTOCOL - if any property is invalid for use with SUBSCRIBE.
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_subscribe_v5(struct mosquitto *mosq, int *mid, const char *sub, int qos, int options, const mosquitto_property *properties);

/*
 * Function: mosquitto_subscribe_multiple
 *
 * Subscribe to multiple topics.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	mid -  a pointer to an int. If not NULL, the function will set this to
 *	       the message id of this particular message. This can be then used
 *	       with the subscribe callback to determine when the message has been
 *	       sent.
 *  sub_count - the count of subscriptions to be made
 *	sub -  array of sub_count pointers, each pointing to a subscription string.
 *	       The "char *const *const" datatype ensures that neither the array of
 *	       pointers nor the strings that they point to are mutable. If you aren't
 *	       familiar with this, just think of it as a safer "char **",
 *	       equivalent to "const char *" for a simple string pointer.
 *	       Each string must not be NULL or an empty string.
 *	qos -  the requested Quality of Service for each subscription.
 *	options - options to apply to this subscription, OR'd together. This
 *	          argument is not used for MQTT v3 susbcriptions. Set to 0 to use
 *	          the default options, otherwise choose from list of <mqtt5_sub_options>
 * 	properties - a valid mosquitto_property list, or NULL. Only used with MQTT
 * 	             v5 clients.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if a topic is not valid UTF-8
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_subscribe_multiple(struct mosquitto *mosq, int *mid, int sub_count, char *const *const sub, int qos, int options, const mosquitto_property *properties);

/*
 * Function: mosquitto_unsubscribe
 *
 * Unsubscribe from a topic.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	mid -  a pointer to an int. If not NULL, the function will set this to
 *	       the message id of this particular message. This can be then used
 *	       with the unsubscribe callback to determine when the message has been
 *	       sent.
 *	sub -  the unsubscription pattern - must not by NULL or an empty string.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_unsubscribe(struct mosquitto *mosq, int *mid, const char *sub);

/*
 * Function: mosquitto_unsubscribe_v5
 *
 * Unsubscribe from a topic, with attached MQTT properties.
 *
 * It is valid to use this function for clients using all MQTT protocol versions.
 * If you need to set MQTT v5 UNSUBSCRIBE properties, use
 * <mosquitto_unsubscribe_v5> instead.
 *
 * Use e.g. <mosquitto_property_add_string> and similar to create a list of
 * properties, then attach them to this publish. Properties need freeing with
 * <mosquitto_property_free_all>.
 *
 * If the mosquitto instance `mosq` is using MQTT v5, the `properties` argument
 * will be applied to the PUBLISH message. For MQTT v3.1.1 and below, the
 * `properties` argument will be ignored.
 *
 * Set your client to use MQTT v5 immediately after it is created:
 *
 * mosquitto_int_option(mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	mid -  a pointer to an int. If not NULL, the function will set this to
 *	       the message id of this particular message. This can be then used
 *	       with the unsubscribe callback to determine when the message has been
 *	       sent.
 *	sub -  the unsubscription pattern - must not by NULL or an empty string.
 * 	properties - a valid mosquitto_property list, or NULL. Only used with MQTT
 * 	             v5 clients.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 *	MOSQ_ERR_PROTOCOL - if any property is invalid for use with UNSUBSCRIBE.
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_unsubscribe_v5(struct mosquitto *mosq, int *mid, const char *sub, const mosquitto_property *properties);

/*
 * Function: mosquitto_unsubscribe_multiple
 *
 * Unsubscribe from multiple topics.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *	mid -  a pointer to an int. If not NULL, the function will set this to
 *	       the message id of this particular message. This can be then used
 *	       with the subscribe callback to determine when the message has been
 *	       sent.
 *  sub_count - the count of unsubscriptions to be made
 *	sub -  array of sub_count pointers, each pointing to an unsubscription string.
 *	       The "char *const *const" datatype ensures that neither the array of
 *	       pointers nor the strings that they point to are mutable. If you aren't
 *	       familiar with this, just think of it as a safer "char **",
 *	       equivalent to "const char *" for a simple string pointer.
 *	       Each sub must not be NULL or an empty string.
 * 	properties - a valid mosquitto_property list, or NULL. Only used with MQTT
 * 	             v5 clients.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success.
 * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -        if the client isn't connected to a broker.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if a topic is not valid UTF-8
 *	MOSQ_ERR_OVERSIZE_PACKET - if the resulting packet would be larger than
 *	                           supported by the broker.
 */
libmosq_EXPORT int mosquitto_unsubscribe_multiple(struct mosquitto *mosq, int *mid, int sub_count, char *const *const sub, const mosquitto_property *properties);


/* ======================================================================
 *
 * Section: Struct mosquitto_message helper functions
 *
 * ====================================================================== */
/*
 * Function: mosquitto_message_copy
 *
 * Copy the contents of a mosquitto message to another message.
 * Useful for preserving a message received in the on_message() callback.
 *
 * Parameters:
 *	dst - a pointer to a valid mosquitto_message struct to copy to.
 *	src - a pointer to a valid mosquitto_message struct to copy from.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 *
 * See Also:
 * 	<mosquitto_message_free>
 */
libmosq_EXPORT int mosquitto_message_copy(struct mosquitto_message *dst, const struct mosquitto_message *src);

/*
 * Function: mosquitto_message_free
 *
 * Completely free a mosquitto_message struct.
 *
 * Parameters:
 *	message - pointer to a mosquitto_message pointer to free.
 *
 * See Also:
 * 	<mosquitto_message_copy>, <mosquitto_message_free_contents>
 */
libmosq_EXPORT void mosquitto_message_free(struct mosquitto_message **message);

/*
 * Function: mosquitto_message_free_contents
 *
 * Free a mosquitto_message struct contents, leaving the struct unaffected.
 *
 * Parameters:
 *	message - pointer to a mosquitto_message struct to free its contents.
 *
 * See Also:
 * 	<mosquitto_message_copy>, <mosquitto_message_free>
 */
libmosq_EXPORT void mosquitto_message_free_contents(struct mosquitto_message *message);


/* ======================================================================
 *
 * Section: Network loop (managed by libmosquitto)
 *
 * The internal network loop must be called at a regular interval. The two
 * recommended approaches are to use either <mosquitto_loop_forever> or
 * <mosquitto_loop_start>. <mosquitto_loop_forever> is a blocking call and is
 * suitable for the situation where you only want to handle incoming messages
 * in callbacks. <mosquitto_loop_start> is a non-blocking call, it creates a
 * separate thread to run the loop for you. Use this function when you have
 * other tasks you need to run at the same time as the MQTT client, e.g.
 * reading data from a sensor.
 *
 * ====================================================================== */

/*
 * Function: mosquitto_loop_forever
 *
 * This function call loop() for you in an infinite blocking loop. It is useful
 * for the case where you only want to run the MQTT client loop in your
 * program.
 *
 * It handles reconnecting in case server connection is lost. If you call
 * mosquitto_disconnect() in a callback it will return.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance.
 *	timeout -     Maximum number of milliseconds to wait for network activity
 *	              in the select() call before timing out. Set to 0 for instant
 *	              return.  Set negative to use the default of 1000ms.
 *	max_packets - this parameter is currently unused and should be set to 1 for
 *	              future compatibility.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -   on success.
 * 	MOSQ_ERR_INVAL -     if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -     if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -   if the client isn't connected to a broker.
 *  MOSQ_ERR_CONN_LOST - if the connection to the broker was lost.
 *	MOSQ_ERR_PROTOCOL -  if there is a protocol error communicating with the
 *                       broker.
 * 	MOSQ_ERR_ERRNO -     if a system call returned an error. The variable errno
 *                       contains the error code, even on Windows.
 *                       Use strerror_r() where available or FormatMessage() on
 *                       Windows.
 *
 * See Also:
 *	<mosquitto_loop>, <mosquitto_loop_start>
 */
libmosq_EXPORT int mosquitto_loop_forever(struct mosquitto *mosq, int timeout, int max_packets);

/*
 * Function: mosquitto_loop_start
 *
 * This is part of the threaded client interface. Call this once to start a new
 * thread to process network traffic. This provides an alternative to
 * repeatedly calling <mosquitto_loop> yourself.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -       on success.
 * 	MOSQ_ERR_INVAL -         if the input parameters were invalid.
 *	MOSQ_ERR_NOT_SUPPORTED - if thread support is not available.
 *
 * See Also:
 *	<mosquitto_connect_async>, <mosquitto_loop>, <mosquitto_loop_forever>, <mosquitto_loop_stop>
 */
libmosq_EXPORT int mosquitto_loop_start(struct mosquitto *mosq);

/*
 * Function: mosquitto_loop_stop
 *
 * This is part of the threaded client interface. Call this once to stop the
 * network thread previously created with <mosquitto_loop_start>. This call
 * will block until the network thread finishes. For the network thread to end,
 * you must have previously called <mosquitto_disconnect> or have set the force
 * parameter to true.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance.
 *	force - set to true to force thread cancellation. If false,
 *	        <mosquitto_disconnect> must have already been called.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -       on success.
 * 	MOSQ_ERR_INVAL -         if the input parameters were invalid.
 *	MOSQ_ERR_NOT_SUPPORTED - if thread support is not available.
 *
 * See Also:
 *	<mosquitto_loop>, <mosquitto_loop_start>
 */
libmosq_EXPORT int mosquitto_loop_stop(struct mosquitto *mosq, bool force);

/*
 * Function: mosquitto_loop
 *
 * The main network loop for the client. This must be called frequently
 * to keep communications between the client and broker working. This is
 * carried out by <mosquitto_loop_forever> and <mosquitto_loop_start>, which
 * are the recommended ways of handling the network loop. You may also use this
 * function if you wish. It must not be called inside a callback.
 *
 * If incoming data is present it will then be processed. Outgoing commands,
 * from e.g.  <mosquitto_publish>, are normally sent immediately that their
 * function is called, but this is not always possible. <mosquitto_loop> will
 * also attempt to send any remaining outgoing messages, which also includes
 * commands that are part of the flow for messages with QoS>0.
 *
 * This calls select() to monitor the client network socket. If you want to
 * integrate mosquitto client operation with your own select() call, use
 * <mosquitto_socket>, <mosquitto_loop_read>, <mosquitto_loop_write> and
 * <mosquitto_loop_misc>.
 *
 * Threads:
 *
 * Parameters:
 *	mosq -        a valid mosquitto instance.
 *	timeout -     Maximum number of milliseconds to wait for network activity
 *	              in the select() call before timing out. Set to 0 for instant
 *	              return.  Set negative to use the default of 1000ms.
 *	max_packets - this parameter is currently unused and should be set to 1 for
 *	              future compatibility.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -   on success.
 * 	MOSQ_ERR_INVAL -     if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -     if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -   if the client isn't connected to a broker.
 *  MOSQ_ERR_CONN_LOST - if the connection to the broker was lost.
 *	MOSQ_ERR_PROTOCOL -  if there is a protocol error communicating with the
 *                       broker.
 * 	MOSQ_ERR_ERRNO -     if a system call returned an error. The variable errno
 *                       contains the error code, even on Windows.
 *                       Use strerror_r() where available or FormatMessage() on
 *                       Windows.
 * See Also:
 *	<mosquitto_loop_forever>, <mosquitto_loop_start>, <mosquitto_loop_stop>
 */
libmosq_EXPORT int mosquitto_loop(struct mosquitto *mosq, int timeout, int max_packets);

/* ======================================================================
 *
 * Section: Network loop (for use in other event loops)
 *
 * ====================================================================== */
/*
 * Function: mosquitto_loop_read
 *
 * Carry out network read operations.
 * This should only be used if you are not using mosquitto_loop() and are
 * monitoring the client network socket for activity yourself.
 *
 * Parameters:
 *	mosq -        a valid mosquitto instance.
 *	max_packets - this parameter is currently unused and should be set to 1 for
 *	              future compatibility.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -   on success.
 * 	MOSQ_ERR_INVAL -     if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -     if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -   if the client isn't connected to a broker.
 *  MOSQ_ERR_CONN_LOST - if the connection to the broker was lost.
 *	MOSQ_ERR_PROTOCOL -  if there is a protocol error communicating with the
 *                       broker.
 * 	MOSQ_ERR_ERRNO -     if a system call returned an error. The variable errno
 *                       contains the error code, even on Windows.
 *                       Use strerror_r() where available or FormatMessage() on
 *                       Windows.
 *
 * See Also:
 *	<mosquitto_socket>, <mosquitto_loop_write>, <mosquitto_loop_misc>
 */
libmosq_EXPORT int mosquitto_loop_read(struct mosquitto *mosq, int max_packets);

/*
 * Function: mosquitto_loop_write
 *
 * Carry out network write operations.
 * This should only be used if you are not using mosquitto_loop() and are
 * monitoring the client network socket for activity yourself.
 *
 * Parameters:
 *	mosq -        a valid mosquitto instance.
 *	max_packets - this parameter is currently unused and should be set to 1 for
 *	              future compatibility.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -   on success.
 * 	MOSQ_ERR_INVAL -     if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -     if an out of memory condition occurred.
 * 	MOSQ_ERR_NO_CONN -   if the client isn't connected to a broker.
 *  MOSQ_ERR_CONN_LOST - if the connection to the broker was lost.
 *	MOSQ_ERR_PROTOCOL -  if there is a protocol error communicating with the
 *                       broker.
 * 	MOSQ_ERR_ERRNO -     if a system call returned an error. The variable errno
 *                       contains the error code, even on Windows.
 *                       Use strerror_r() where available or FormatMessage() on
 *                       Windows.
 *
 * See Also:
 *	<mosquitto_socket>, <mosquitto_loop_read>, <mosquitto_loop_misc>, <mosquitto_want_write>
 */
libmosq_EXPORT int mosquitto_loop_write(struct mosquitto *mosq, int max_packets);

/*
 * Function: mosquitto_loop_misc
 *
 * Carry out miscellaneous operations required as part of the network loop.
 * This should only be used if you are not using mosquitto_loop() and are
 * monitoring the client network socket for activity yourself.
 *
 * This function deals with handling PINGs and checking whether messages need
 * to be retried, so should be called fairly frequently, around once per second
 * is sufficient.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -   on success.
 * 	MOSQ_ERR_INVAL -     if the input parameters were invalid.
 * 	MOSQ_ERR_NO_CONN -   if the client isn't connected to a broker.
 *
 * See Also:
 *	<mosquitto_socket>, <mosquitto_loop_read>, <mosquitto_loop_write>
 */
libmosq_EXPORT int mosquitto_loop_misc(struct mosquitto *mosq);


/* ======================================================================
 *
 * Section: Network loop (helper functions)
 *
 * ====================================================================== */
/*
 * Function: mosquitto_socket
 *
 * Return the socket handle for a mosquitto instance. Useful if you want to
 * include a mosquitto client in your own select() calls.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *
 * Returns:
 *	The socket for the mosquitto client or -1 on failure.
 */
libmosq_EXPORT int mosquitto_socket(struct mosquitto *mosq);

/*
 * Function: mosquitto_want_write
 *
 * Returns true if there is data ready to be written on the socket.
 *
 * Parameters:
 *	mosq - a valid mosquitto instance.
 *
 * See Also:
 *	<mosquitto_socket>, <mosquitto_loop_read>, <mosquitto_loop_write>
 */
libmosq_EXPORT bool mosquitto_want_write(struct mosquitto *mosq);

/*
 * Function: mosquitto_threaded_set
 *
 * Used to tell the library that your application is using threads, but not
 * using <mosquitto_loop_start>. The library operates slightly differently when
 * not in threaded mode in order to simplify its operation. If you are managing
 * your own threads and do not use this function you will experience crashes
 * due to race conditions.
 *
 * When using <mosquitto_loop_start>, this is set automatically.
 *
 * Parameters:
 *  mosq -     a valid mosquitto instance.
 *  threaded - true if your application is using threads, false otherwise.
 */
libmosq_EXPORT int mosquitto_threaded_set(struct mosquitto *mosq, bool threaded);


/* ======================================================================
 *
 * Section: Client options
 *
 * ====================================================================== */
/*
 * Function: mosquitto_opts_set
 *
 * Used to set options for the client.
 *
 * This function is deprecated, the replacement <mosquitto_int_option>,
 * <mosquitto_string_option> and <mosquitto_void_option> functions should
 * be used instead.
 *
 * Parameters:
 *	mosq -   a valid mosquitto instance.
 *	option - the option to set.
 *	value -  the option specific value.
 *
 * Options:
 *	MOSQ_OPT_PROTOCOL_VERSION - Value must be an int, set to either
 *	          MQTT_PROTOCOL_V31 or MQTT_PROTOCOL_V311. Must be set
 *	          before the client connects.
 *	          Defaults to MQTT_PROTOCOL_V31.
 *
 *	MOSQ_OPT_SSL_CTX - Pass an openssl SSL_CTX to be used when creating
 *	          TLS connections rather than libmosquitto creating its own.
 *	          This must be called before connecting to have any effect.
 *	          If you use this option, the onus is on you to ensure that
 *	          you are using secure settings.
 *	          Setting to NULL means that libmosquitto will use its own SSL_CTX
 *	          if TLS is to be used.
 *	          This option is only available for openssl 1.1.0 and higher.
 *
 *	MOSQ_OPT_SSL_CTX_WITH_DEFAULTS - Value must be an int set to 1 or 0.
 *	          If set to 1, then the user specified SSL_CTX passed in using
 *	          MOSQ_OPT_SSL_CTX will have the default options applied to it.
 *	          This means that you only need to change the values that are
 *	          relevant to you. If you use this option then you must configure
 *	          the TLS options as normal, i.e. you should use
 *	          <mosquitto_tls_set> to configure the cafile/capath as a minimum.
 *	          This option is only available for openssl 1.1.0 and higher.
 */
libmosq_EXPORT int mosquitto_opts_set(struct mosquitto *mosq, enum mosq_opt_t option, void *value);

/*
 * Function: mosquitto_int_option
 *
 * Used to set integer options for the client.
 *
 * Parameters:
 *	mosq -   a valid mosquitto instance.
 *	option - the option to set.
 *	value -  the option specific value.
 *
 * Options:
 *	MOSQ_OPT_TCP_NODELAY - Set to 1 to disable Nagle's algorithm on client
 *	          sockets. This has the effect of reducing latency of individual
 *	          messages at the potential cost of increasing the number of
 *	          packets being sent.
 *	          Defaults to 0, which means Nagle remains enabled.
 *
 *	MOSQ_OPT_PROTOCOL_VERSION - Value must be set to either MQTT_PROTOCOL_V31,
 *	          MQTT_PROTOCOL_V311, or MQTT_PROTOCOL_V5. Must be set before the
 *	          client connects.  Defaults to MQTT_PROTOCOL_V311.
 *
 *	MOSQ_OPT_RECEIVE_MAXIMUM - Value can be set between 1 and 65535 inclusive,
 *	          and represents the maximum number of incoming QoS 1 and QoS 2
 *	          messages that this client wants to process at once. Defaults to
 *	          20. This option is not valid for MQTT v3.1 or v3.1.1 clients.
 *	          Note that if the MQTT_PROP_RECEIVE_MAXIMUM property is in the
 *	          proplist passed to mosquitto_connect_v5(), then that property
 *	          will override this option. Using this option is the recommended
 *	          method however.
 *
 *	MOSQ_OPT_SEND_MAXIMUM - Value can be set between 1 and 65535 inclusive,
 *	          and represents the maximum number of outgoing QoS 1 and QoS 2
 *	          messages that this client will attempt to have "in flight" at
 *	          once. Defaults to 20.
 *	          This option is not valid for MQTT v3.1 or v3.1.1 clients.
 *	          Note that if the broker being connected to sends a
 *	          MQTT_PROP_RECEIVE_MAXIMUM property that has a lower value than
 *	          this option, then the broker provided value will be used.
 *
 *	MOSQ_OPT_SSL_CTX_WITH_DEFAULTS - If value is set to a non zero value,
 *	          then the user specified SSL_CTX passed in using MOSQ_OPT_SSL_CTX
 *	          will have the default options applied to it. This means that
 *	          you only need to change the values that are relevant to you.
 *	          If you use this option then you must configure the TLS options
 *	          as normal, i.e.  you should use <mosquitto_tls_set> to
 *	          configure the cafile/capath as a minimum.
 *	          This option is only available for openssl 1.1.0 and higher.
 *
 *	MOSQ_OPT_TLS_OCSP_REQUIRED - Set whether OCSP checking on TLS
 *	          connections is required. Set to 1 to enable checking,
 *	          or 0 (the default) for no checking.
 *
 *	MOSQ_OPT_TLS_USE_OS_CERTS - Set to 1 to instruct the client to load and
 *	          trust OS provided CA certificates for use with TLS connections.
 *	          Set to 0 (the default) to only use manually specified CA certs.
 *
 *	MOSQ_OPT_DISABLE_SOCKETPAIR - By default, each client connected will create
 *            an internal pair of connected sockets to allow the network thread
 *            to be notified and woken up if another thread calls
 *            <mosquitto_publish> or other similar command. If you are
 *            operating with an external loop, this is not necessary and
 *            consumes an extra two sockets per client. Set this option to 1 to
 *            disable the use of the socket pair.
 *
 *	MOSQ_OPT_TRANSPORT - Have the client connect with either MQTT over TCP as
 *	          normal, or MQTT over WebSockets. Set the value to MOSQ_T_TCP or
 *	          MOSQ_T_WEBSOCKETS.
 *
 *	MOSQ_OPT_HTTP_HEADER_SIZE - Size the size of buffer that will be allocated
 *	          to store the incoming HTTP header when using Websocket transport.
 *	          Defaults to 4096. Setting to below 100 will result in a return
*	          value of MOSQ_ERR_INVAL. This should be set before starting the
*	          connection. If you try to set this when the initial http request
*	          is underway then it will return MOSQ_ERR_INVAL.
 */
libmosq_EXPORT int mosquitto_int_option(struct mosquitto *mosq, enum mosq_opt_t option, int value);


/*
 * Function: mosquitto_string_option
 *
 * Used to set const char* options for the client.
 *
 * Parameters:
 *	mosq -   a valid mosquitto instance.
 *	option - the option to set.
 *	value -  the option specific value.
 *
 * Options:
 *	MOSQ_OPT_TLS_ENGINE - Configure the client for TLS Engine support.
 *	          Pass a TLS Engine ID to be used when creating TLS
 *	          connections. Must be set before <mosquitto_connect>.
 *	          Must be a valid engine, and note that the string will not be used
 *	          until a connection attempt is made so this function will return
 *	          success even if an invalid engine string is passed.
 *
 *	MOSQ_OPT_TLS_KEYFORM - Configure the client to treat the keyfile
 *	          differently depending on its type.  Must be set
 *	          before <mosquitto_connect>.
 *	          Set as either "pem" or "engine", to determine from where the
 *	          private key for a TLS connection will be obtained. Defaults to
 *	          "pem", a normal private key file.
 *
 *	MOSQ_OPT_TLS_KPASS_SHA1 - Where the TLS Engine requires the use of
 *	          a password to be accessed, this option allows a hex encoded
 *	          SHA1 hash of the private key password to be passed to the
 *	          engine directly. Must be set before <mosquitto_connect>.
 *
 *	MOSQ_OPT_TLS_ALPN - If the broker being connected to has multiple
 *	          services available on a single TLS port, such as both MQTT
 *	          and WebSockets, use this option to configure the ALPN
 *	          option for the connection.
 *
 *	MOSQ_OPT_BIND_ADDRESS - Set the hostname or ip address of the local network
 *	          interface to bind to when connecting.
 */
libmosq_EXPORT int mosquitto_string_option(struct mosquitto *mosq, enum mosq_opt_t option, const char *value);


/*
 * Function: mosquitto_void_option
 *
 * Used to set void* options for the client.
 *
 * Parameters:
 *	mosq -   a valid mosquitto instance.
 *	option - the option to set.
 *	value -  the option specific value.
 *
 * Options:
 *	MOSQ_OPT_SSL_CTX - Pass an openssl SSL_CTX to be used when creating TLS
 *	          connections rather than libmosquitto creating its own.  This must
 *	          be called before connecting to have any effect. If you use this
 *	          option, the onus is on you to ensure that you are using secure
 *	          settings.
 *	          Setting to NULL means that libmosquitto will use its own SSL_CTX
 *	          if TLS is to be used.
 *	          This option is only available for openssl 1.1.0 and higher.
 */
libmosq_EXPORT int mosquitto_void_option(struct mosquitto *mosq, enum mosq_opt_t option, void *value);

/*
 * Function: mosquitto_reconnect_delay_set
 *
 * Control the behaviour of the client when it has unexpectedly disconnected in
 * <mosquitto_loop_forever> or after <mosquitto_loop_start>. The default
 * behaviour if this function is not used is to repeatedly attempt to reconnect
 * with a delay of 1 second until the connection succeeds.
 *
 * Use reconnect_delay parameter to change the delay between successive
 * reconnection attempts. You may also enable exponential backoff of the time
 * between reconnections by setting reconnect_exponential_backoff to true and
 * set an upper bound on the delay with reconnect_delay_max.
 *
 * Example 1:
 *	delay=2, delay_max=10, exponential_backoff=False
 *	Delays would be: 2, 4, 6, 8, 10, 10, ...
 *
 * Example 2:
 *	delay=3, delay_max=30, exponential_backoff=True
 *	Delays would be: 3, 6, 12, 24, 30, 30, ...
 *
 * Parameters:
 *  mosq -                          a valid mosquitto instance.
 *  reconnect_delay -               the number of seconds to wait between
 *                                  reconnects.
 *  reconnect_delay_max -           the maximum number of seconds to wait
 *                                  between reconnects.
 *  reconnect_exponential_backoff - use exponential backoff between
 *                                  reconnect attempts. Set to true to enable
 *                                  exponential backoff.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_reconnect_delay_set(struct mosquitto *mosq, unsigned int reconnect_delay, unsigned int reconnect_delay_max, bool reconnect_exponential_backoff);

/*
 * Function: mosquitto_max_inflight_messages_set
 *
 * This function is deprected. Use the <mosquitto_int_option> function with the
 * MOSQ_OPT_SEND_MAXIMUM option instead.
 *
 * Set the number of QoS 1 and 2 messages that can be "in flight" at one time.
 * An in flight message is part way through its delivery flow. Attempts to send
 * further messages with <mosquitto_publish> will result in the messages being
 * queued until the number of in flight messages reduces.
 *
 * A higher number here results in greater message throughput, but if set
 * higher than the maximum in flight messages on the broker may lead to
 * delays in the messages being acknowledged.
 *
 * Set to 0 for no maximum.
 *
 * Parameters:
 *  mosq -                  a valid mosquitto instance.
 *  max_inflight_messages - the maximum number of inflight messages. Defaults
 *                          to 20.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_max_inflight_messages_set(struct mosquitto *mosq, unsigned int max_inflight_messages);

/*
 * Function: mosquitto_message_retry_set
 *
 * This function now has no effect.
 */
libmosq_EXPORT void mosquitto_message_retry_set(struct mosquitto *mosq, unsigned int message_retry);

/*
 * Function: mosquitto_user_data_set
 *
 * When <mosquitto_new> is called, the pointer given as the "obj" parameter
 * will be passed to the callbacks as user data. The <mosquitto_user_data_set>
 * function allows this obj parameter to be updated at any time. This function
 * will not modify the memory pointed to by the current user data pointer. If
 * it is dynamically allocated memory you must free it yourself.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance.
 * 	obj -  A user pointer that will be passed as an argument to any callbacks
 * 	       that are specified.
 */
libmosq_EXPORT void mosquitto_user_data_set(struct mosquitto *mosq, void *obj);

/* Function: mosquitto_userdata
 *
 * Retrieve the "userdata" variable for a mosquitto client.
 *
 * Parameters:
 * 	mosq - a valid mosquitto instance.
 *
 * Returns:
 *	A pointer to the userdata member variable.
 */
libmosq_EXPORT void *mosquitto_userdata(struct mosquitto *mosq);


/* ======================================================================
 *
 * Section: TLS support
 *
 * ====================================================================== */
/*
 * Function: mosquitto_tls_set
 *
 * Configure the client for certificate based SSL/TLS support. Must be called
 * before <mosquitto_connect>.
 *
 * Cannot be used in conjunction with <mosquitto_tls_psk_set>.
 *
 * Define the Certificate Authority certificates to be trusted (ie. the server
 * certificate must be signed with one of these certificates) using cafile.
 *
 * If the server you are connecting to requires clients to provide a
 * certificate, define certfile and keyfile with your client certificate and
 * private key. If your private key is encrypted, provide a password callback
 * function or you will have to enter the password at the command line.
 *
 * Parameters:
 *  mosq -        a valid mosquitto instance.
 *  cafile -      path to a file containing the PEM encoded trusted CA
 *                certificate files. Either cafile or capath must not be NULL.
 *  capath -      path to a directory containing the PEM encoded trusted CA
 *                certificate files. See mosquitto.conf for more details on
 *                configuring this directory. Either cafile or capath must not
 *                be NULL.
 *  certfile -    path to a file containing the PEM encoded certificate file
 *                for this client. If NULL, keyfile must also be NULL and no
 *                client certificate will be used.
 *  keyfile -     path to a file containing the PEM encoded private key for
 *                this client. If NULL, certfile must also be NULL and no
 *                client certificate will be used.
 *  pw_callback - if keyfile is encrypted, set pw_callback to allow your client
 *                to pass the correct password for decryption. If set to NULL,
 *                the password must be entered on the command line.
 *                Your callback must write the password into "buf", which is
 *                "size" bytes long. The return value must be the length of the
 *                password. "userdata" will be set to the calling mosquitto
 *                instance. The mosquitto userdata member variable can be
 *                retrieved using <mosquitto_userdata>.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 *
 * See Also:
 *	<mosquitto_tls_opts_set>, <mosquitto_tls_psk_set>,
 *	<mosquitto_tls_insecure_set>, <mosquitto_userdata>
 */
libmosq_EXPORT int mosquitto_tls_set(struct mosquitto *mosq,
		const char *cafile, const char *capath,
		const char *certfile, const char *keyfile,
		int (*pw_callback)(char *buf, int size, int rwflag, void *userdata));

/*
 * Function: mosquitto_tls_insecure_set
 *
 * Configure verification of the server hostname in the server certificate. If
 * value is set to true, it is impossible to guarantee that the host you are
 * connecting to is not impersonating your server. This can be useful in
 * initial server testing, but makes it possible for a malicious third party to
 * impersonate your server through DNS spoofing, for example.
 * Do not use this function in a real system. Setting value to true makes the
 * connection encryption pointless.
 * Must be called before <mosquitto_connect>.
 *
 * Parameters:
 *  mosq -  a valid mosquitto instance.
 *  value - if set to false, the default, certificate hostname checking is
 *          performed. If set to true, no hostname checking is performed and
 *          the connection is insecure.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 *
 * See Also:
 *	<mosquitto_tls_set>
 */
libmosq_EXPORT int mosquitto_tls_insecure_set(struct mosquitto *mosq, bool value);

/*
 * Function: mosquitto_tls_opts_set
 *
 * Set advanced SSL/TLS options. Must be called before <mosquitto_connect>.
 *
 * Parameters:
 *  mosq -        a valid mosquitto instance.
 *	cert_reqs -   an integer defining the verification requirements the client
 *	              will impose on the server. This can be one of:
 *	              * SSL_VERIFY_NONE (0): the server will not be verified in any way.
 *	              * SSL_VERIFY_PEER (1): the server certificate will be verified
 *	                and the connection aborted if the verification fails.
 *	              The default and recommended value is SSL_VERIFY_PEER. Using
 *	              SSL_VERIFY_NONE provides no security.
 *	tls_version - the version of the SSL/TLS protocol to use as a string. If NULL,
 *	              the default value is used. The default value and the
 *	              available values depend on the version of openssl that the
 *	              library was compiled against. For openssl >= 1.0.1, the
 *	              available options are tlsv1.2, tlsv1.1 and tlsv1, with tlv1.2
 *	              as the default. For openssl < 1.0.1, only tlsv1 is available.
 *	ciphers -     a string describing the ciphers available for use. See the
 *	              "openssl ciphers" tool for more information. If NULL, the
 *	              default ciphers will be used.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 *
 * See Also:
 *	<mosquitto_tls_set>
 */
libmosq_EXPORT int mosquitto_tls_opts_set(struct mosquitto *mosq, int cert_reqs, const char *tls_version, const char *ciphers);

/*
 * Function: mosquitto_tls_psk_set
 *
 * Configure the client for pre-shared-key based TLS support. Must be called
 * before <mosquitto_connect>.
 *
 * Cannot be used in conjunction with <mosquitto_tls_set>.
 *
 * Parameters:
 *  mosq -     a valid mosquitto instance.
 *  psk -      the pre-shared-key in hex format with no leading "0x".
 *  identity - the identity of this client. May be used as the username
 *             depending on the server settings.
 *	ciphers -  a string describing the PSK ciphers available for use. See the
 *	           "openssl ciphers" tool for more information. If NULL, the
 *	           default ciphers will be used.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success.
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 * 	MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 *
 * See Also:
 *	<mosquitto_tls_set>
 */
libmosq_EXPORT int mosquitto_tls_psk_set(struct mosquitto *mosq, const char *psk, const char *identity, const char *ciphers);


/*
 * Function: mosquitto_ssl_get
 *
 * Retrieve a pointer to the SSL structure used for TLS connections in this
 * client. This can be used in e.g. the connect callback to carry out
 * additional verification steps.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance
 *
 * Returns:
 *  A valid pointer to an openssl SSL structure - if the client is using TLS.
 *  NULL - if the client is not using TLS, or TLS support is not compiled in.
 */
libmosq_EXPORT void *mosquitto_ssl_get(struct mosquitto *mosq);


/* ======================================================================
 *
 * Section: Callbacks
 *
 * ====================================================================== */
/*
 * Function: mosquitto_connect_callback_set
 *
 * Set the connect callback. This is called when the library receives a CONNACK
 * message in response to a connection.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_connect - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, int rc)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj - the user data provided in <mosquitto_new>
 *  rc -  the return code of the connection response. The values are defined by
 *        the MQTT protocol version in use.
 *        For MQTT v5.0, look at section 3.2.2.2 Connect Reason code: https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html
 *        For MQTT v3.1.1, look at section 3.2.2.3 Connect Return code: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html
 *
 * See Also:
 *  <mosquitto_pre_connect_callback_set>
 */
libmosq_EXPORT void mosquitto_connect_callback_set(struct mosquitto *mosq, void (*on_connect)(struct mosquitto *, void *, int));

/*
 * Function: mosquitto_connect_with_flags_callback_set
 *
 * Set the connect callback. This is called when the library receives a CONNACK
 * message in response to a connection.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_connect - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, int rc)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj - the user data provided in <mosquitto_new>
 *  rc -  the return code of the connection response. The values are defined by
 *        the MQTT protocol version in use.
 *        For MQTT v5.0, look at section 3.2.2.2 Connect Reason code: https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html
 *        For MQTT v3.1.1, look at section 3.2.2.3 Connect Return code: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html
 *  flags - the connect flags.
 *
 * See Also:
 *  <mosquitto_pre_connect_callback_set>
 */
libmosq_EXPORT void mosquitto_connect_with_flags_callback_set(struct mosquitto *mosq, void (*on_connect)(struct mosquitto *, void *, int, int));

/*
 * Function: mosquitto_connect_v5_callback_set
 *
 * Set the connect callback. This is called when the library receives a CONNACK
 * message in response to a connection.
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_connect - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, int rc)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj - the user data provided in <mosquitto_new>
 *  rc -  the return code of the connection response. The values are defined by
 *        the MQTT protocol version in use.
 *        For MQTT v5.0, look at section 3.2.2.2 Connect Reason code: https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html
 *        For MQTT v3.1.1, look at section 3.2.2.3 Connect Return code: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html
 *  flags - the connect flags.
 *  props - list of MQTT 5 properties, or NULL
 *
 * See Also:
 *  <mosquitto_pre_connect_callback_set>
 */
libmosq_EXPORT void mosquitto_connect_v5_callback_set(struct mosquitto *mosq, void (*on_connect)(struct mosquitto *, void *, int, int, const mosquitto_property *props));

/*
 * Function: mosquitto_pre_connect_callback_set
 *
 * Set the pre-connect callback. The pre-connect callback is called just before an attempt is made to connect to the broker. This may be useful if you are using <mosquitto_loop_start>, or
 * <mosquitto_loop_forever>, because when your client disconnects the library
 * will by default automatically reconnect. Using the pre-connect callback
 * allows you to set usernames, passwords, and TLS related parameters.
 *
 * Parameters:
 *  mosq -           a valid mosquitto instance.
 *  on_pre_connect - a callback function in the following form:
 *                   void callback(struct mosquitto *mosq, void *obj)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj - the user data provided in <mosquitto_new>
 */
libmosq_EXPORT void mosquitto_pre_connect_callback_set(struct mosquitto *mosq, void (*on_pre_connect)(struct mosquitto *, void *));

/*
 * Function: mosquitto_disconnect_callback_set
 *
 * Set the disconnect callback. This is called when the broker has received the
 * DISCONNECT command and has disconnected the client.
 *
 * Parameters:
 *  mosq -          a valid mosquitto instance.
 *  on_disconnect - a callback function in the following form:
 *                  void callback(struct mosquitto *mosq, void *obj)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj -  the user data provided in <mosquitto_new>
 *  rc -   integer value indicating the reason for the disconnect. A value of 0
 *         means the client has called <mosquitto_disconnect>. Any other value
 *         indicates that the disconnect is unexpected.
 */
libmosq_EXPORT void mosquitto_disconnect_callback_set(struct mosquitto *mosq, void (*on_disconnect)(struct mosquitto *, void *, int));

/*
 * Function: mosquitto_disconnect_v5_callback_set
 *
 * Set the disconnect callback. This is called when the broker has received the
 * DISCONNECT command and has disconnected the client.
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -          a valid mosquitto instance.
 *  on_disconnect - a callback function in the following form:
 *                  void callback(struct mosquitto *mosq, void *obj)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj -  the user data provided in <mosquitto_new>
 *  rc -   integer value indicating the reason for the disconnect. A value of 0
 *         means the client has called <mosquitto_disconnect>. Any other value
 *         indicates that the disconnect is unexpected.
 *  props - list of MQTT 5 properties, or NULL
 */
libmosq_EXPORT void mosquitto_disconnect_v5_callback_set(struct mosquitto *mosq, void (*on_disconnect)(struct mosquitto *, void *, int, const mosquitto_property *props));

/*
 * Function: mosquitto_publish_callback_set
 *
 * Set the publish callback. This is called when a message initiated with
 * <mosquitto_publish> has been sent to the broker. "Sent" means different
 * things depending on the QoS of the message:
 *
 * QoS 0: The PUBLISH was passed to the local operating system for delivery,
 *        there is no guarantee that it was delivered to the remote broker.
 * QoS 1: The PUBLISH was sent to the remote broker and the corresponding
 *        PUBACK was received by the library.
 * QoS 2: The PUBLISH was sent to the remote broker and the corresponding
 *        PUBCOMP was received by the library.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_publish - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, int mid)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj -  the user data provided in <mosquitto_new>
 *  mid -  the message id of the sent message.
 */
libmosq_EXPORT void mosquitto_publish_callback_set(struct mosquitto *mosq, void (*on_publish)(struct mosquitto *, void *, int));

/*
 * Function: mosquitto_publish_v5_callback_set
 *
 * Set the publish callback. This is called when a message initiated with
 * <mosquitto_publish> has been sent to the broker. This callback will be
 * called both if the message is sent successfully, or if the broker responded
 * with an error, which will be reflected in the reason_code parameter.
 * "Sent" means different things depending on the QoS of the message:
 *
 * QoS 0: The PUBLISH was passed to the local operating system for delivery,
 *        there is no guarantee that it was delivered to the remote broker.
 * QoS 1: The PUBLISH was sent to the remote broker and the corresponding
 *        PUBACK was received by the library.
 * QoS 2: The PUBLISH was sent to the remote broker and the corresponding
 *        PUBCOMP was received by the library.
 *
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_publish - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, int mid)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj -  the user data provided in <mosquitto_new>
 *  mid -  the message id of the sent message.
 *  reason_code - the MQTT 5 reason code
 *  props - list of MQTT 5 properties, or NULL
 */
libmosq_EXPORT void mosquitto_publish_v5_callback_set(struct mosquitto *mosq, void (*on_publish)(struct mosquitto *, void *, int, int, const mosquitto_property *props));

/*
 * Function: mosquitto_message_callback_set
 *
 * Set the message callback. This is called when a message is received from the
 * broker and the required QoS flow has completed.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_message - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
 *
 * Callback Parameters:
 *  mosq -    the mosquitto instance making the callback.
 *  obj -     the user data provided in <mosquitto_new>
 *  message - the message data. This variable and associated memory will be
 *            freed by the library after the callback completes. The client
 *            should make copies of any of the data it requires.
 *
 * See Also:
 * 	<mosquitto_message_copy>
 */
libmosq_EXPORT void mosquitto_message_callback_set(struct mosquitto *mosq, void (*on_message)(struct mosquitto *, void *, const struct mosquitto_message *));

/*
 * Function: mosquitto_message_v5_callback_set
 *
 * Set the message callback. This is called when a message is received from the
 * broker and the required QoS flow has completed.
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  on_message - a callback function in the following form:
 *               void callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
 *
 * Callback Parameters:
 *  mosq -    the mosquitto instance making the callback.
 *  obj -     the user data provided in <mosquitto_new>
 *  message - the message data. This variable and associated memory will be
 *            freed by the library after the callback completes. The client
 *            should make copies of any of the data it requires.
 *  props - list of MQTT 5 properties, or NULL
 *
 * See Also:
 * 	<mosquitto_message_copy>
 */
libmosq_EXPORT void mosquitto_message_v5_callback_set(struct mosquitto *mosq, void (*on_message)(struct mosquitto *, void *, const struct mosquitto_message *, const mosquitto_property *props));

/*
 * Function: mosquitto_subscribe_callback_set
 *
 * Set the subscribe callback. This is called when the library receives a
 * SUBACK message in response to a SUBSCRIBE.
 *
 * Parameters:
 *  mosq -         a valid mosquitto instance.
 *  on_subscribe - a callback function in the following form:
 *                 void callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
 *
 * Callback Parameters:
 *  mosq -        the mosquitto instance making the callback.
 *  obj -         the user data provided in <mosquitto_new>
 *  mid -         the message id of the subscribe message.
 *  qos_count -   the number of granted subscriptions (size of granted_qos).
 *  granted_qos - an array of integers indicating the granted QoS for each of
 *                the subscriptions.
 */
libmosq_EXPORT void mosquitto_subscribe_callback_set(struct mosquitto *mosq, void (*on_subscribe)(struct mosquitto *, void *, int, int, const int *));

/*
 * Function: mosquitto_subscribe_v5_callback_set
 *
 * Set the subscribe callback. This is called when the library receives a
 * SUBACK message in response to a SUBSCRIBE.
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -         a valid mosquitto instance.
 *  on_subscribe - a callback function in the following form:
 *                 void callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
 *
 * Callback Parameters:
 *  mosq -        the mosquitto instance making the callback.
 *  obj -         the user data provided in <mosquitto_new>
 *  mid -         the message id of the subscribe message.
 *  qos_count -   the number of granted subscriptions (size of granted_qos).
 *  granted_qos - an array of integers indicating the granted QoS for each of
 *                the subscriptions.
 *  props - list of MQTT 5 properties, or NULL
 */
libmosq_EXPORT void mosquitto_subscribe_v5_callback_set(struct mosquitto *mosq, void (*on_subscribe)(struct mosquitto *, void *, int, int, const int *, const mosquitto_property *props));

/*
 * Function: mosquitto_unsubscribe_callback_set
 *
 * Set the unsubscribe callback. This is called when the library receives a
 * UNSUBACK message in response to an UNSUBSCRIBE.
 *
 * Parameters:
 *  mosq -           a valid mosquitto instance.
 *  on_unsubscribe - a callback function in the following form:
 *                   void callback(struct mosquitto *mosq, void *obj, int mid)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj -  the user data provided in <mosquitto_new>
 *  mid -  the message id of the unsubscribe message.
 */
libmosq_EXPORT void mosquitto_unsubscribe_callback_set(struct mosquitto *mosq, void (*on_unsubscribe)(struct mosquitto *, void *, int));

/*
 * Function: mosquitto_unsubscribe_v5_callback_set
 *
 * Set the unsubscribe callback. This is called when the library receives a
 * UNSUBACK message in response to an UNSUBSCRIBE.
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -           a valid mosquitto instance.
 *  on_unsubscribe - a callback function in the following form:
 *                   void callback(struct mosquitto *mosq, void *obj, int mid, const mosquitto_property *props)
 *
 * Callback Parameters:
 *  mosq - the mosquitto instance making the callback.
 *  obj -  the user data provided in <mosquitto_new>
 *  mid -  the message id of the unsubscribe message.
 *  props - list of MQTT 5 properties, or NULL
 */
libmosq_EXPORT void mosquitto_unsubscribe_v5_callback_set(struct mosquitto *mosq, void (*on_unsubscribe)(struct mosquitto *, void *, int, const mosquitto_property *props));

/*
 * Function: mosquitto_unsubscribe2_v5_callback_set
 *
 * Set the unsubscribe callback. This is called when the library receives a
 * UNSUBACK message in response to an UNSUBSCRIBE.
 *
 * It is valid to set this callback for all MQTT protocol versions. If it is
 * used with MQTT clients that use MQTT v3.1.1 or earlier, then the `props`
 * argument will always be NULL.
 *
 * Parameters:
 *  mosq -           a valid mosquitto instance.
 *  on_unsubscribe - a callback function in the following form:
 *                   void callback(struct mosquitto *mosq, void *obj, int mid,
 *                   int reason_code_count, const int *reason_codes, const mosquitto_property *props)
 *
 * Callback Parameters:
 *  mosq -              the mosquitto instance making the callback.
 *  obj -               the user data provided in <mosquitto_new>
 *  mid -               the message id of the unsubscribe message.
 *  reason_code_count - the count of reason code responses
 *  reason_codes -      an array of integers indicating the reason codes for each of
 *                      the unsubscription requests.
 *  mid -               the message id of the unsubscribe message.
 *  props -             list of MQTT 5 properties, or NULL
 */
libmosq_EXPORT void mosquitto_unsubscribe2_v5_callback_set(struct mosquitto *mosq, void (*on_unsubscribe)(struct mosquitto *, void *, int, int, const int *, const mosquitto_property *props));

/*
 * Function: mosquitto_log_callback_set
 *
 * Set the logging callback. This should be used if you want event logging
 * information from the client library.
 *
 *  mosq -   a valid mosquitto instance.
 *  on_log - a callback function in the following form:
 *           void callback(struct mosquitto *mosq, void *obj, int level, const char *str)
 *
 * Callback Parameters:
 *  mosq -  the mosquitto instance making the callback.
 *  obj -   the user data provided in <mosquitto_new>
 *  level - the log message level from the values:
 *	        MOSQ_LOG_INFO
 *	        MOSQ_LOG_NOTICE
 *	        MOSQ_LOG_WARNING
 *	        MOSQ_LOG_ERR
 *	        MOSQ_LOG_DEBUG
 *	str -   the message string.
 */
libmosq_EXPORT void mosquitto_log_callback_set(struct mosquitto *mosq, void (*on_log)(struct mosquitto *, void *, int, const char *));


/* =============================================================================
 *
 * Section: SOCKS5 proxy functions
 *
 * =============================================================================
 */

/*
 * Function: mosquitto_socks5_set
 *
 * Configure the client to use a SOCKS5 proxy when connecting. Must be called
 * before connecting. "None" and "username/password" authentication is
 * supported.
 *
 * Parameters:
 *   mosq - a valid mosquitto instance.
 *   host - the SOCKS5 proxy host to connect to.
 *   port - the SOCKS5 proxy port to use.
 *   username - if not NULL, use this username when authenticating with the proxy.
 *   password - if not NULL and username is not NULL, use this password when
 *              authenticating with the proxy.
 */
libmosq_EXPORT int mosquitto_socks5_set(struct mosquitto *mosq, const char *host, int port, const char *username, const char *password);


/* =============================================================================
 *
 * Section: Utility functions
 *
 * =============================================================================
 */

/*
 * Function: mosquitto_strerror
 *
 * Call to obtain a const string description of a mosquitto error number.
 *
 * Parameters:
 *	mosq_errno - a mosquitto error number.
 *
 * Returns:
 *	A constant string describing the error.
 */
libmosq_EXPORT const char *mosquitto_strerror(int mosq_errno);

/*
 * Function: mosquitto_connack_string
 *
 * Call to obtain a const string description of an MQTT connection result.
 *
 * Parameters:
 *	connack_code - an MQTT connection result.
 *
 * Returns:
 *	A constant string describing the result.
 */
libmosq_EXPORT const char *mosquitto_connack_string(int connack_code);

/*
 * Function: mosquitto_reason_string
 *
 * Call to obtain a const string description of an MQTT reason code.
 *
 * Parameters:
 *	reason_code - an MQTT reason code.
 *
 * Returns:
 *	A constant string describing the reason.
 */
libmosq_EXPORT const char *mosquitto_reason_string(int reason_code);

/* Function: mosquitto_string_to_command
 *
 * Take a string input representing an MQTT command and convert it to the
 * libmosquitto integer representation.
 *
 * Parameters:
 *   str - the string to parse.
 *   cmd - pointer to an int, for the result.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - on an invalid input.
 *
 * Example:
 * (start code)
 *  mosquitto_string_to_command("CONNECT", &cmd);
 *  // cmd == CMD_CONNECT
 * (end)
 */
libmosq_EXPORT int mosquitto_string_to_command(const char *str, int *cmd);

/*
 * Function: mosquitto_sub_topic_tokenise
 *
 * Tokenise a topic or subscription string into an array of strings
 * representing the topic hierarchy.
 *
 * For example:
 *
 *    subtopic: "a/deep/topic/hierarchy"
 *
 *    Would result in:
 *
 *       topics[0] = "a"
 *       topics[1] = "deep"
 *       topics[2] = "topic"
 *       topics[3] = "hierarchy"
 *
 *    and:
 *
 *    subtopic: "/a/deep/topic/hierarchy/"
 *
 *    Would result in:
 *
 *       topics[0] = NULL
 *       topics[1] = "a"
 *       topics[2] = "deep"
 *       topics[3] = "topic"
 *       topics[4] = "hierarchy"
 *
 * Parameters:
 *	subtopic - the subscription/topic to tokenise
 *	topics -   a pointer to store the array of strings
 *	count -    an int pointer to store the number of items in the topics array.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS -        on success
 * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
 * 	MOSQ_ERR_MALFORMED_UTF8 - if the topic is not valid UTF-8
 *
 * Example:
 *
 * > char **topics;
 * > int topic_count;
 * > int i;
 * >
 * > mosquitto_sub_topic_tokenise("$SYS/broker/uptime", &topics, &topic_count);
 * >
 * > for(i=0; i<token_count; i++){
 * >     printf("%d: %s\n", i, topics[i]);
 * > }
 *
 * See Also:
 *	<mosquitto_sub_topic_tokens_free>
 */
libmosq_EXPORT int mosquitto_sub_topic_tokenise(const char *subtopic, char ***topics, int *count);

/*
 * Function: mosquitto_sub_topic_tokens_free
 *
 * Free memory that was allocated in <mosquitto_sub_topic_tokenise>.
 *
 * Parameters:
 *	topics - pointer to string array.
 *	count - count of items in string array.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 *
 * See Also:
 *	<mosquitto_sub_topic_tokenise>
 */
libmosq_EXPORT int mosquitto_sub_topic_tokens_free(char ***topics, int count);

/*
 * Function: mosquitto_topic_matches_sub
 *
 * Check whether a topic matches a subscription.
 *
 * For example:
 *
 * foo/bar would match the subscription foo/# or +/bar
 * non/matching would not match the subscription non/+/+
 *
 * Parameters:
 *	sub - subscription string to check topic against.
 *	topic - topic to check.
 *	result - bool pointer to hold result. Will be set to true if the topic
 *	         matches the subscription.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_topic_matches_sub(const char *sub, const char *topic, bool *result);

/*
 * Function: mosquitto_topic_matches_sub2
 *
 * Identical to <mosquitto_topic_matches_sub>. The sublen and topiclen
 * parameters are *IGNORED*.
 */
libmosq_EXPORT int mosquitto_topic_matches_sub2(const char *sub, size_t sublen, const char *topic, size_t topiclen, bool *result);


/*
 * Function: mosquitto_topic_matches_sub_with_pattern
 *
 * Check whether a topic matches a subscription, with client id/username
 * pattern substitution.
 *
 * Any instances of a subscriptions hierarchy that are exactly %c or %u will be
 * replaced with the client id or username respectively.
 *
 * For example:
 *
 * mosquitto_topic_matches_sub_with_pattern("sensors/%c/temperature", "sensors/kitchen/temperature", "kitchen", NULL, &result)
 * -> this will match
 *
 * mosquitto_topic_matches_sub_with_pattern("sensors/%c/temperature", "sensors/bathroom/temperature", "kitchen", NULL, &result)
 * -> this will not match
 *
 * mosquitto_topic_matches_sub_with_pattern("sensors/%count/temperature", "sensors/kitchen/temperature", "kitchen", NULL, &result)
 * -> this will not match - the `%count` is not treated as a pattern
 *
 * mosquitto_topic_matches_sub_with_pattern("%c/%c/%u/%u", "kitchen/kitchen/bathroom/bathroom", "kitchen", "bathroom", &result)
 * -> this will match
 *
 * Parameters:
 *	sub - subscription string to check topic against.
 *	topic - topic to check.
 *	clientid - client id to substitute in patterns. If NULL, then any %c patterns will not match.
 *	username - username to substitute in patterns. If NULL, then any %u patterns will not match.
 *	result - bool pointer to hold result. Will be set to true if the topic
 *	         matches the subscription.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_topic_matches_sub_with_pattern(const char *sub, const char *topic, const char *clientid, const char *username, bool *result);


/*
 * Function: mosquitto_sub_matches_acl
 *
 * Check whether a subscription matches an ACL topic filter
 *
 * For example:
 *
 * The subscription $SYS/broker/# would match against the ACL $SYS/#
 * The subscription $SYS/broker/# would not match against the ACL $SYS/broker/uptime
 *
 * Parameters:
 *	acl - topic filter string to check sub against.
 *	sub - subscription topic to check.
 *	result - bool pointer to hold result. Will be set to true if the subscription
 *	         matches the acl.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 * 	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_sub_matches_acl(const char *acl, const char *sub, bool *result);


/*
 * Function: mosquitto_sub_matches_acl_with_pattern
 *
 * Check whether a subscription (a topic filter with wildcards) matches an ACL
 * (a topic filter with wildcards) , with client id/username pattern
 * substitution.
 *
 * Any instances of an ACL hierarchy that are exactly %c or %u will be
 * replaced with the client id or username respectively.
 *
 * For example:
 *
 * mosquitto_sub_matches_acl_with_pattern("sensors/%c/+", "sensors/kitchen/temperature", "kitchen", NULL, &result)
 * -> this will match
 *
 * mosquitto_sub_matches_acl_with_pattern("sensors/%c/+", "sensors/bathroom/temperature", "kitchen", NULL, &result)
 * -> this will not match
 *
 * mosquitto_sub_matches_acl_with_pattern("sensors/%count/+", "sensors/kitchen/temperature", "kitchen", NULL, &result)
 * -> this will not match - the `%count` is not treated as a pattern
 *
 * mosquitto_sub_matches_acl_with_pattern("%c/%c/%u/+", "kitchen/kitchen/bathroom/bathroom", "kitchen", "bathroom", &result)
 * -> this will match
 *
 * Parameters:
 *	acl - ACL topic filter string to check sub against.
 *	sub - subscription to check.
 *	clientid - client id to substitute in patterns. If NULL, then any %c patterns will not match.
 *	username - username to substitute in patterns. If NULL, then any %u patterns will not match.
 *	result - bool pointer to hold result. Will be set to true if the subscription
 *	         matches the ACL.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL -   if the input parameters were invalid.
 */
libmosq_EXPORT int mosquitto_sub_matches_acl_with_pattern(const char *acl, const char *sub, const char *clientid, const char *username, bool *result);


/*
 * Function: mosquitto_pub_topic_check
 *
 * Check whether a topic to be used for publishing is valid.
 *
 * This searches for + or # in a topic and checks its length.
 *
 * This check is already carried out in <mosquitto_publish> and
 * <mosquitto_will_set>, there is no need to call it directly before them. It
 * may be useful if you wish to check the validity of a topic in advance of
 * making a connection for example.
 *
 * Parameters:
 *   topic - the topic to check
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS -        for a valid topic
 *   MOSQ_ERR_INVAL -          if the topic contains a + or a #, or if it is too long.
 *   MOSQ_ERR_MALFORMED_UTF8 - if topic is not valid UTF-8
 *
 * See Also:
 *   <mosquitto_sub_topic_check>
 */
libmosq_EXPORT int mosquitto_pub_topic_check(const char *topic);

/*
 * Function: mosquitto_pub_topic_check2
 *
 * Check whether a topic to be used for publishing is valid.
 *
 * This searches for + or # in a topic and checks its length.
 *
 * This check is already carried out in <mosquitto_publish> and
 * <mosquitto_will_set>, there is no need to call it directly before them. It
 * may be useful if you wish to check the validity of a topic in advance of
 * making a connection for example.
 *
 * Parameters:
 *   topic - the topic to check
 *   topiclen - length of the topic in bytes
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS -        for a valid topic
 *   MOSQ_ERR_INVAL -          if the topic contains a + or a #, or if it is too long.
 *   MOSQ_ERR_MALFORMED_UTF8 - if topic is not valid UTF-8
 *
 * See Also:
 *   <mosquitto_sub_topic_check>
 */
libmosq_EXPORT int mosquitto_pub_topic_check2(const char *topic, size_t topiclen);

/*
 * Function: mosquitto_sub_topic_check
 *
 * Check whether a topic to be used for subscribing is valid.
 *
 * This searches for + or # in a topic and checks that they aren't in invalid
 * positions, such as with foo/#/bar, foo/+bar or foo/bar#, and checks its
 * length.
 *
 * This check is already carried out in <mosquitto_subscribe> and
 * <mosquitto_unsubscribe>, there is no need to call it directly before them.
 * It may be useful if you wish to check the validity of a topic in advance of
 * making a connection for example.
 *
 * Parameters:
 *   topic - the topic to check
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS -        for a valid topic
 *   MOSQ_ERR_INVAL -          if the topic contains a + or a # that is in an
 *                             invalid position, or if it is too long.
 *   MOSQ_ERR_MALFORMED_UTF8 - if topic is not valid UTF-8
 *
 * See Also:
 *   <mosquitto_sub_topic_check>
 */
libmosq_EXPORT int mosquitto_sub_topic_check(const char *topic);

/*
 * Function: mosquitto_sub_topic_check2
 *
 * Check whether a topic to be used for subscribing is valid.
 *
 * This searches for + or # in a topic and checks that they aren't in invalid
 * positions, such as with foo/#/bar, foo/+bar or foo/bar#, and checks its
 * length.
 *
 * This check is already carried out in <mosquitto_subscribe> and
 * <mosquitto_unsubscribe>, there is no need to call it directly before them.
 * It may be useful if you wish to check the validity of a topic in advance of
 * making a connection for example.
 *
 * Parameters:
 *   topic - the topic to check
 *   topiclen - the length in bytes of the topic
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS -        for a valid topic
 *   MOSQ_ERR_INVAL -          if the topic contains a + or a # that is in an
 *                             invalid position, or if it is too long.
 *   MOSQ_ERR_MALFORMED_UTF8 - if topic is not valid UTF-8
 *
 * See Also:
 *   <mosquitto_sub_topic_check>
 */
libmosq_EXPORT int mosquitto_sub_topic_check2(const char *topic, size_t topiclen);


/*
 * Function: mosquitto_validate_utf8
 *
 * Helper function to validate whether a UTF-8 string is valid, according to
 * the UTF-8 spec and the MQTT additions.
 *
 * Parameters:
 *   str - a string to check
 *   len - the length of the string in bytes
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS -        on success
 *   MOSQ_ERR_INVAL -          if str is NULL or len<0 or len>65536
 *   MOSQ_ERR_MALFORMED_UTF8 - if str is not valid UTF-8
 */
libmosq_EXPORT int mosquitto_validate_utf8(const char *str, int len);


/* =============================================================================
 *
 * Section: One line client helper functions
 *
 * =============================================================================
 */

struct libmosquitto_will {
	char *topic;
	void *payload;
	int payloadlen;
	int qos;
	bool retain;
};

struct libmosquitto_auth {
	char *username;
	char *password;
};

struct libmosquitto_tls {
	char *cafile;
	char *capath;
	char *certfile;
	char *keyfile;
	char *ciphers;
	char *tls_version;
	int (*pw_callback)(char *buf, int size, int rwflag, void *userdata);
	int cert_reqs;
};

/*
 * Function: mosquitto_subscribe_simple
 *
 * Helper function to make subscribing to a topic and retrieving some messages
 * very straightforward.
 *
 * This connects to a broker, subscribes to a topic, waits for msg_count
 * messages to be received, then returns after disconnecting cleanly.
 *
 * Parameters:
 *   messages - pointer to a "struct mosquitto_message *". The received
 *              messages will be returned here. On error, this will be set to
 *              NULL.
 *   msg_count - the number of messages to retrieve.
 *   want_retained - if set to true, stale retained messages will be treated as
 *                   normal messages with regards to msg_count. If set to
 *                   false, they will be ignored.
 *   topic - the subscription topic to use (wildcards are allowed).
 *   qos - the qos to use for the subscription.
 *   host - the broker to connect to.
 *   port - the network port the broker is listening on.
 *   clientid - the client id to use, or NULL if a random client id should be
 *               generated.
 *   keepalive - the MQTT keepalive value.
 *   clean_session - the MQTT clean session flag.
 *   username - the username string, or NULL for no username authentication.
 *   password - the password string, or NULL for an empty password.
 *   will - a libmosquitto_will struct containing will information, or NULL for
 *          no will.
 *   tls - a libmosquitto_tls struct containing TLS related parameters, or NULL
 *         for no use of TLS.
 *
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS - on success
 *   Greater than 0 - on error.
 */
libmosq_EXPORT int mosquitto_subscribe_simple(
		struct mosquitto_message **messages,
		int msg_count,
		bool want_retained,
		const char *topic,
		int qos,
		const char *host,
		int port,
		const char *clientid,
		int keepalive,
		bool clean_session,
		const char *username,
		const char *password,
		const struct libmosquitto_will *will,
		const struct libmosquitto_tls *tls);


/*
 * Function: mosquitto_subscribe_callback
 *
 * Helper function to make subscribing to a topic and processing some messages
 * very straightforward.
 *
 * This connects to a broker, subscribes to a topic, then passes received
 * messages to a user provided callback. If the callback returns a 1, it then
 * disconnects cleanly and returns.
 *
 * Parameters:
 *   callback - a callback function in the following form:
 *              int callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
 *              Note that this is the same as the normal on_message callback,
 *              except that it returns an int.
 *   userdata - user provided pointer that will be passed to the callback.
 *   topic - the subscription topic to use (wildcards are allowed).
 *   qos - the qos to use for the subscription.
 *   host - the broker to connect to.
 *   port - the network port the broker is listening on.
 *   clientid - the client id to use, or NULL if a random client id should be
 *               generated.
 *   keepalive - the MQTT keepalive value.
 *   clean_session - the MQTT clean session flag.
 *   username - the username string, or NULL for no username authentication.
 *   password - the password string, or NULL for an empty password.
 *   will - a libmosquitto_will struct containing will information, or NULL for
 *          no will.
 *   tls - a libmosquitto_tls struct containing TLS related parameters, or NULL
 *         for no use of TLS.
 *
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS - on success
 *   Greater than 0 - on error.
 */
libmosq_EXPORT int mosquitto_subscribe_callback(
		int (*callback)(struct mosquitto *, void *, const struct mosquitto_message *),
		void *userdata,
		const char *topic,
		int qos,
		const char *host,
		int port,
		const char *clientid,
		int keepalive,
		bool clean_session,
		const char *username,
		const char *password,
		const struct libmosquitto_will *will,
		const struct libmosquitto_tls *tls);


/* =============================================================================
 *
 * Section: Properties
 *
 * =============================================================================
 */


/*
 * Function: mosquitto_property_add_byte
 *
 * Add a new byte property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - integer value for the new property
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_byte(&proplist, MQTT_PROP_PAYLOAD_FORMAT_IDENTIFIER, 1);
 */
libmosq_EXPORT int mosquitto_property_add_byte(mosquitto_property **proplist, int identifier, uint8_t value);

/*
 * Function: mosquitto_property_add_int16
 *
 * Add a new int16 property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_RECEIVE_MAXIMUM)
 *	value - integer value for the new property
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_int16(&proplist, MQTT_PROP_RECEIVE_MAXIMUM, 1000);
 */
libmosq_EXPORT int mosquitto_property_add_int16(mosquitto_property **proplist, int identifier, uint16_t value);

/*
 * Function: mosquitto_property_add_int32
 *
 * Add a new int32 property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_MESSAGE_EXPIRY_INTERVAL)
 *	value - integer value for the new property
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_int32(&proplist, MQTT_PROP_MESSAGE_EXPIRY_INTERVAL, 86400);
 */
libmosq_EXPORT int mosquitto_property_add_int32(mosquitto_property **proplist, int identifier, uint32_t value);

/*
 * Function: mosquitto_property_add_varint
 *
 * Add a new varint property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_SUBSCRIPTION_IDENTIFIER)
 *	value - integer value for the new property
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_varint(&proplist, MQTT_PROP_SUBSCRIPTION_IDENTIFIER, 1);
 */
libmosq_EXPORT int mosquitto_property_add_varint(mosquitto_property **proplist, int identifier, uint32_t value);

/*
 * Function: mosquitto_property_add_binary
 *
 * Add a new binary property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to the property data
 *	len - length of property data in bytes
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_binary(&proplist, MQTT_PROP_AUTHENTICATION_DATA, auth_data, auth_data_len);
 */
libmosq_EXPORT int mosquitto_property_add_binary(mosquitto_property **proplist, int identifier, const void *value, uint16_t len);

/*
 * Function: mosquitto_property_add_string
 *
 * Add a new string property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_CONTENT_TYPE)
 *	value - string value for the new property, must be UTF-8 and zero terminated
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, if value is NULL, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *	MOSQ_ERR_MALFORMED_UTF8 - value is not valid UTF-8.
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_string(&proplist, MQTT_PROP_CONTENT_TYPE, "application/json");
 */
libmosq_EXPORT int mosquitto_property_add_string(mosquitto_property **proplist, int identifier, const char *value);

/*
 * Function: mosquitto_property_add_string_pair
 *
 * Add a new string pair property to a property list.
 *
 * If *proplist == NULL, a new list will be created, otherwise the new property
 * will be appended to the list.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_USER_PROPERTY)
 *	name - string name for the new property, must be UTF-8 and zero terminated
 *	value - string value for the new property, must be UTF-8 and zero terminated
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if identifier is invalid, if name or value is NULL, or if proplist is NULL
 *	MOSQ_ERR_NOMEM - on out of memory
 *	MOSQ_ERR_MALFORMED_UTF8 - if name or value are not valid UTF-8.
 *
 * Example:
 * > mosquitto_property *proplist = NULL;
 * > mosquitto_property_add_string_pair(&proplist, MQTT_PROP_USER_PROPERTY, "client", "mosquitto_pub");
 */
libmosq_EXPORT int mosquitto_property_add_string_pair(mosquitto_property **proplist, int identifier, const char *name, const char *value);


/*
 * Function: mosquitto_property_remove
 *
 * Remove a property from a property list. The property will not be freed.
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *	property - pointer to the property to remove
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if proplist is NULL or property is NULL
 *	MOSQ_ERR_NOT_FOUND - if the property was not found
 */
libmosq_EXPORT int mosquitto_property_remove(mosquitto_property **proplist, const mosquitto_property *property);


/*
 * Function: mosquitto_property_identifier
 *
 * Return the property identifier for a single property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  A valid property identifier on success
 *  0 - on error
 */
libmosq_EXPORT int mosquitto_property_identifier(const mosquitto_property *property);


/*
 * Function: mosquitto_property_next
 *
 * Return the next property in a property list. Use to iterate over a property
 * list, e.g.:
 *
 * (start code)
 * for(prop = proplist; prop != NULL; prop = mosquitto_property_next(prop)){
 * 	if(mosquitto_property_identifier(prop) == MQTT_PROP_CONTENT_TYPE){
 * 		...
 * 	}
 * }
 * (end)
 *
 * Parameters:
 *	proplist - pointer to mosquitto_property pointer, the list of properties
 *
 * Returns:
 *	Pointer to the next item in the list
 *	NULL, if proplist is NULL, or if there are no more items in the list.
 */
libmosq_EXPORT mosquitto_property *mosquitto_property_next(const mosquitto_property *proplist);


/*
 * Function: mosquitto_property_read_byte
 *
 * Attempt to read a byte property matching an identifier, from a property list
 * or single property. This function can search for multiple entries of the
 * same identifier by using the returned value and skip_first. Note however
 * that it is forbidden for most properties to be duplicated.
 *
 * If the property is not found, *value will not be modified, so it is safe to
 * pass a variable with a default value to be potentially overwritten:
 *
 * (start code)
 * uint16_t keepalive = 60; // default value
 * // Get value from property list, or keep default if not found.
 * mosquitto_property_read_int16(proplist, MQTT_PROP_SERVER_KEEP_ALIVE, &keepalive, false);
 * (end)
 *
 * Parameters:
 *	proplist - mosquitto_property pointer, the list of properties or single property
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to store the value, or NULL if the value is not required.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL.
 *
 * Example:
 * (start code)
 *	// proplist is obtained from a callback
 *	mosquitto_property *prop;
 *	prop = mosquitto_property_read_byte(proplist, identifier, &value, false);
 *	while(prop){
 *		printf("value: %s\n", value);
 *		prop = mosquitto_property_read_byte(prop, identifier, &value);
 *	}
 * (end)
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_byte(
		const mosquitto_property *proplist,
		int identifier,
		uint8_t *value,
		bool skip_first);

/*
 * Function: mosquitto_property_read_int16
 *
 * Read an int16 property value from a property.
 *
 * Parameters:
 *	property - property to read
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to store the value, or NULL if the value is not required.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL.
 *
 * Example:
 *	See <mosquitto_property_read_byte>
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_int16(
		const mosquitto_property *proplist,
		int identifier,
		uint16_t *value,
		bool skip_first);

/*
 * Function: mosquitto_property_read_int32
 *
 * Read an int32 property value from a property.
 *
 * Parameters:
 *	property - pointer to mosquitto_property pointer, the list of properties
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to store the value, or NULL if the value is not required.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL.
 *
 * Example:
 *	See <mosquitto_property_read_byte>
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_int32(
		const mosquitto_property *proplist,
		int identifier,
		uint32_t *value,
		bool skip_first);

/*
 * Function: mosquitto_property_read_varint
 *
 * Read a varint property value from a property.
 *
 * Parameters:
 *	property - property to read
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to store the value, or NULL if the value is not required.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL.
 *
 * Example:
 *	See <mosquitto_property_read_byte>
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_varint(
		const mosquitto_property *proplist,
		int identifier,
		uint32_t *value,
		bool skip_first);

/*
 * Function: mosquitto_property_read_binary
 *
 * Read a binary property value from a property.
 *
 * On success, value must be free()'d by the application.
 *
 * Parameters:
 *	property - property to read
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to store the value, or NULL if the value is not required.
 *	        Will be set to NULL if the value has zero length.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL, or if an out of memory condition occurred.
 *
 * Example:
 *	See <mosquitto_property_read_byte>
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_binary(
		const mosquitto_property *proplist,
		int identifier,
		void **value,
		uint16_t *len,
		bool skip_first);

/*
 * Function: mosquitto_property_read_string
 *
 * Read a string property value from a property.
 *
 * On success, value must be free()'d by the application.
 *
 * Parameters:
 *	property - property to read
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	value - pointer to char*, for the property data to be stored in, or NULL if
 *	        the value is not required.
 *	        Will be set to NULL if the value has zero length.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL, or if an out of memory condition occurred.
 *
 * Example:
 *	See <mosquitto_property_read_byte>
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_string(
		const mosquitto_property *proplist,
		int identifier,
		char **value,
		bool skip_first);

/*
 * Function: mosquitto_property_read_string_pair
 *
 * Read a string pair property value pair from a property.
 *
 * On success, name and value must be free()'d by the application.
 *
 * Parameters:
 *	property - property to read
 *	identifier - property identifier (e.g. MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
 *	name - pointer to char* for the name property data to be stored in, or NULL
 *	       if the name is not required.
 *	       Will be set to NULL if the name has zero length.
 *	value - pointer to char*, for the property data to be stored in, or NULL if
 *	        the value is not required.
 *	        Will be set to NULL if the value has zero length.
 *	skip_first - boolean that indicates whether the first item in the list
 *	             should be ignored or not. Should usually be set to false.
 *
 * Returns:
 *	A valid property pointer if the property is found
 *	NULL, if the property is not found, or proplist is NULL, or if an out of memory condition occurred.
 *
 * Example:
 *	See <mosquitto_property_read_byte>
 */
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_string_pair(
		const mosquitto_property *proplist,
		int identifier,
		char **name,
		char **value,
		bool skip_first);

/*
 * Function: mosquitto_property_type
 *
 * Return the property type for a single property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  A valid property type on success
 *  0 - on error
 */
libmosq_EXPORT int mosquitto_property_type(const mosquitto_property *property);


/*
 * Function: mosquitto_property_byte_value
 *
 * Return the property value for a byte type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Byte value on success
 *  0 - on error (property is NULL, or not a byte)
 */
libmosq_EXPORT uint8_t mosquitto_property_byte_value(const mosquitto_property *property);


/*
 * Function: mosquitto_property_int16_value
 *
 * Return the property value for an int16 type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Int16 value on success
 *  0 - on error (property is NULL, or not a int16)
 */
libmosq_EXPORT uint16_t mosquitto_property_int16_value(const mosquitto_property *property);


/*
 * Function: mosquitto_property_int32_value
 *
 * Return the property value for an int32 type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Int32 value on success
 *  0 - on error (property is NULL, or not a int32)
 */
libmosq_EXPORT uint32_t mosquitto_property_int32_value(const mosquitto_property *property);


/*
 * Function: mosquitto_property_varint_value
 *
 * Return the property value for a varint type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Varint value on success
 *  0 - on error (property is NULL, or not a varint)
 */
libmosq_EXPORT uint32_t mosquitto_property_varint_value(const mosquitto_property *property);


/*
 * Function: mosquitto_property_binary_value
 *
 * Return the property value for a binary type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Binary value on success
 *  NULL - on error (property is NULL, or not a binary)
 */
libmosq_EXPORT const void *mosquitto_property_binary_value(const mosquitto_property *property);


/*
 * Function: mosquitto_property_byte_value_length
 *
 * Return the property value for a byte type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Binary value length on success
 *  0 - on error (property is NULL, or not a binary)
 */
libmosq_EXPORT uint16_t mosquitto_property_binary_value_length(const mosquitto_property *property);


/*
 * Function: mosquitto_property_string_value
 *
 * Return the property value for a string or string pair type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  String value on success
 *  NULL - on error (property is NULL, or not a string or string pair)
 */
libmosq_EXPORT const char *mosquitto_property_string_value(const mosquitto_property *property);


/*
 * Function: mosquitto_property_string_value_length
 *
 * Return the length of the property value for a string or string pair type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Value length on success
 *  0 - on error (property is NULL, or not a string or string pair)
 */
libmosq_EXPORT uint16_t mosquitto_property_string_value_length(const mosquitto_property *property);


/*
 * Function: mosquitto_property_string_value
 *
 * Return the property name for a string pair type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  String name on success
 *  NULL - on error (property is NULL, or not a string pair)
 */
libmosq_EXPORT const char *mosquitto_property_string_name(const mosquitto_property *property);


/*
 * Function: mosquitto_property_string_name_length
 *
 * Return the property name length for a string pair type property.
 *
 * Parameters:
 *	property - pointer to a valid mosquitto_property pointer.
 *
 * Returns:
 *  Name length on success
 *  0 - on error (property is NULL, or not a string pair)
 */
libmosq_EXPORT uint16_t mosquitto_property_string_name_length(const mosquitto_property *property);


/*
 * Function: mosquitto_property_free_all
 *
 * Free all properties from a list of properties. Frees the list and sets *properties to NULL.
 *
 * Parameters:
 *   properties - list of properties to free
 *
 * Example:
 * > mosquitto_properties *properties = NULL;
 * > // Add properties
 * > mosquitto_property_free_all(&properties);
 */
libmosq_EXPORT void mosquitto_property_free_all(mosquitto_property **properties);

/*
 * Function: mosquitto_property_copy_all
 *
 * Parameters:
 *    dest - pointer for new property list
 *    src - property list
 *
 * Returns:
 *    MOSQ_ERR_SUCCESS - on successful copy
 *    MOSQ_ERR_INVAL - if dest is NULL
 *    MOSQ_ERR_NOMEM - on out of memory (dest will be set to NULL)
 */
libmosq_EXPORT int mosquitto_property_copy_all(mosquitto_property **dest, const mosquitto_property *src);

/*
 * Function: mosquitto_property_check_command
 *
 * Check whether a property identifier is valid for the given command.
 *
 * Parameters:
 *   command - MQTT command (e.g. CMD_CONNECT)
 *   identifier - MQTT property (e.g. MQTT_PROP_USER_PROPERTY)
 *
 * Returns:
 *   MOSQ_ERR_SUCCESS - if the identifier is valid for command
 *   MOSQ_ERR_PROTOCOL - if the identifier is not valid for use with command.
 */
libmosq_EXPORT int mosquitto_property_check_command(int command, int identifier);


/*
 * Function: mosquitto_property_check_all
 *
 * Check whether a list of properties are valid for a particular command,
 * whether there are duplicates, and whether the values are valid where
 * possible.
 *
 * Note that this function is used internally in the library whenever
 * properties are passed to it, so in basic use this is not needed, but should
 * be helpful to check property lists *before* the point of using them.
 *
 * Parameters:
 *	command - MQTT command (e.g. CMD_CONNECT)
 *	properties - list of MQTT properties to check.
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - if all properties are valid
 *	MOSQ_ERR_DUPLICATE_PROPERTY - if a property is duplicated where it is forbidden.
 *	MOSQ_ERR_PROTOCOL - if any property is invalid
 */
libmosq_EXPORT int mosquitto_property_check_all(int command, const mosquitto_property *properties);

/*
 * Function: mosquitto_property_identifier_to_string
 *
 * Return the property name as a string for a property identifier.
 * The property name is as defined in the MQTT specification, with - as a
 * separator, for example: payload-format-indicator.
 *
 * Parameters:
 *	identifier - valid MQTT property identifier integer
 *
 * Returns:
 *  A const string to the property name on success
 *  NULL on failure
 */
libmosq_EXPORT const char *mosquitto_property_identifier_to_string(int identifier);


/* Function: mosquitto_string_to_property_info
 *
 * Parse a property name string and convert to a property identifier and data type.
 * The property name is as defined in the MQTT specification, with - as a
 * separator, for example: payload-format-indicator.
 *
 * Parameters:
 *	propname - the string to parse
 *	identifier - pointer to an int to receive the property identifier
 *	type - pointer to an int to receive the property type
 *
 * Returns:
 *	MOSQ_ERR_SUCCESS - on success
 *	MOSQ_ERR_INVAL - if the string does not match a property
 *
 * Example:
 * (start code)
 *	mosquitto_string_to_property_info("response-topic", &id, &type);
 *	// id == MQTT_PROP_RESPONSE_TOPIC
 *	// type == MQTT_PROP_TYPE_STRING
 * (end)
 */
libmosq_EXPORT int mosquitto_string_to_property_info(const char *propname, int *identifier, int *type);


#ifdef __cplusplus
}
#endif

#endif
