Example MongoDB Embedded Application

iot_guestbook.c

#include <mongoc_embedded/mongoc_embedded.h>

int main (int argc, char *argv[])
{
  mongo_embedded_v1_status *status;
  mongo_embedded_v1_lib *lib;
  mongo_embedded_v1_instance *instance;
  mongoc_client_t *client;
  mongoc_collection_t *collection;
  mongoc_cursor_t *cursor;
  bson_t *insert, *query, *opts, *doc;
  bson_error_t error;
  char *str, *name, *message;
   
  /*
   * If they've specified their name as the first arg, let's use it in the doc
   */
  if (argc > 1){
    if (strcmp (argv[1], "--help") == 0 || argc > 3) {
      printf ("Usage: iot_guestbook [name] [message]\n");
      return EXIT_FAILURE;
    }

    name = argv[1];
  } else {
    name = "anonymous";
  }
   
  /*
   * If they've specified a message as the second arg, let's use it in the doc
   */
  if (argc > 2){
    message = argv[2];
  } else {
    message = "Hello IoT World";
  }
  
  /*
   * Create a new local storage instance
   */
  status = mongo_embedded_v1_status_create();
  mongoc_init ();
  mongo_embedded_v1_init_params params;
  params.yaml_config = "dbpath=/tmp";
  params.log_flags = 0;
  params.log_callback = NULL;
  params.log_user_data = NULL;
  mongoc_log_set_handler (NULL, NULL);

  lib = mongo_embedded_v1_lib_init (&params, status);
  if (!lib) {
    fprintf (stderr, "Could not get a handle to the Embedded library: %s!\n", mongo_embedded_v1_status_get_explanation (status));
    return EXIT_FAILURE;
  }

  instance = mongo_embedded_v1_instance_create (lib, params.yaml_config, status);
  if (!instance) {
    fprintf (stderr, "Could not intialize local storage instance: %s!\n", mongo_embedded_v1_status_get_explanation (status));
    return EXIT_FAILURE;
  }

  /*
   * Create a mongoc client that can be used with the standard C driver calls
   */
  client = mongoc_embedded_v1_client_create (instance);
  if (!client) {
    fprintf (stderr, "Could not create mongodb client!\n");
    return EXIT_FAILURE;
  }

  /*
   * Get a handle on the "sensor_data" collection in the "iot_test" database
   */
  collection = mongoc_client_get_collection (client, "iot_test", "sensor_data");

  /*
   * We will insert a new document in the collection and then print out
   * all existing documents in the collection
   */
  insert = bson_new ();
  BSON_APPEND_UTF8 (insert, "message", message);
  BSON_APPEND_UTF8 (insert, "from", name);
  // need to multiply the unix timestamp as MongoDB Dates are milliseconds since unix epoch
  int64_t curtime = time (NULL);
  bson_append_date_time (insert, "date", -1, curtime*1000);

  if (!mongoc_collection_insert_one (collection, insert, NULL, NULL, &error)) {
    fprintf (stderr, "Could not insert document: %s\n", error.message);
    return EXIT_FAILURE;
  }

  /*
   * This is where we'll specify our query predicates and other modifiers
   */
  query = bson_new ();
  opts = BCON_NEW ("projection", "{",
                     "_id", BCON_BOOL (false),
                     "from", BCON_BOOL (true),
                     "message", BCON_BOOL (true),
                     "date", BCON_BOOL (true),
                   "}",
                   "sort", "{", "date", BCON_INT32 (1), "}"
                  );

  cursor = mongoc_collection_find_with_opts (collection, query, opts, NULL);

  if (!cursor || mongoc_cursor_error (cursor, &error)) {
    fprintf (stderr, "An error occurred: %s\n", error.message);
    return EXIT_FAILURE;
  }

  while (mongoc_cursor_next (cursor, &doc)) {
    str = bson_as_json (doc, NULL);
    printf ("%s\n", str);
    bson_free (str);
  }

  /*
   * Release our handles and clean everything up
   */
  bson_destroy (insert);
  bson_destroy (query);
  bson_destroy (opts);
  bson_destroy (doc);
  mongoc_cursor_destroy (cursor);
  mongoc_collection_destroy (collection);
  mongoc_client_destroy (client);
  mongoc_cleanup ();

  mongo_embedded_v1_instance_destroy (instance, status);
  mongo_embedded_v1_lib_fini (lib, status);
  mongo_embedded_v1_status_destroy (status);

  return EXIT_SUCCESS;
}