An example of updating a list of IP addresses with Azure IoT Edge Module Twin

main.c

#include <stdio.h>
#include <stdlib.h>

#include "iothub_module_client_ll.h"
#include "iothub_client_options.h"
#include "iothub_message.h"
#include "azure_c_shared_utility/threadapi.h"
#include "azure_c_shared_utility/crt_abstractions.h"
#include "azure_c_shared_utility/platform.h"
#include "azure_c_shared_utility/shared_util_options.h"
#include "iothubtransportmqtt.h"
#include "iothub.h"
#include "time.h"
#include "parson.h"

typedef struct IP_ADDRESS_NODE
{
    const char * address;
    struct IP_ADDRESS_NODE * next;
} ip_address_node;

ip_address_node * add_address(const char * address,ip_address_node * previous)
{
    ip_address_node * new_node = (ip_address_node *)malloc(sizeof(ip_address_node));
    new_node->address = address;
    new_node->next = NULL;
    if (previous == NULL)
    {
        return new_node;
    }
    previous->next = new_node;
    return previous;
}

void delete_address(ip_address_node * current)
{
    if (current == NULL)
    {
        return;
    }
    delete_address(current->next);
    //free(current->address);
    free(current);
}

ip_address_node * root_node = NULL;

ip_address_node * add_address_to_root(const char * address)
{
    if (root_node = NULL)
    {
        root_node = add_address(address,root_node);
    }
    ip_address_node * current = root_node;
    while(current->next != NULL)
    {
        current = current->next;
    }
    add_address(address,current);
}

static void moduleTwinCallback(DEVICE_TWIN_UPDATE_STATE update_state, const unsigned char* payLoad, size_t size, void* userContextCallback)
{
    printf("\r\nTwin callback called with (state=%s, size=%zu):\r\n%s\r\n",
        ENUM_TO_STRING(DEVICE_TWIN_UPDATE_STATE, update_state), size, payLoad);
    JSON_Value *root_value = json_parse_string(payLoad);
    JSON_Object *root_object = json_value_get_object(root_value);
    JSON_Array * ipaddresses = json_object_dotget_array(root_object, "desired.CameraAddresses");
    if (ipaddresses != NULL) {
        delete_address(root_node);
        for (int i = 0; i < json_array_get_count(ipaddresses); i++) {
            add_address_to_root(json_array_get_string(ipaddresses,i));
        }
        return;
    }
    ipaddresses = json_object_get_array(root_object, "CameraAddresses");
    if (ipaddresses != NULL) {
        delete_address(root_node);
        for (int i = 0; i < json_array_get_count(ipaddresses); i++) {
            add_address_to_root(json_array_get_string(ipaddresses,i));
        }
        return;
    }
}