Provided by: libmongoc-doc_1.15.0-1_all bug

NAME

       mongoc_gridfs_t - mongoc_gridfs_t

       WARNING:
          This  GridFS implementation does not conform to the MongoDB GridFS specification. For a
          spec compliant implementation, use mongoc_gridfs_bucket_t.

SYNOPSIS

          #include <mongoc/mongoc.h>

          typedef struct _mongoc_gridfs_t mongoc_gridfs_t;

DESCRIPTION

       mongoc_gridfs_t provides a MongoDB gridfs implementation. The system as a whole is made up
       of gridfs objects, which contain gridfs_files and gridfs_file_lists.  Essentially, a basic
       file system API.

       There are extensive caveats about the kind of  use  cases  gridfs  is  practical  for.  In
       particular, any writing after initial file creation is likely to both break any concurrent
       readers and be quite expensive. That said, this implementation does  allow  for  arbitrary
       writes to existing gridfs object, just use them with caution.

       mongoc_gridfs also integrates tightly with the mongoc_stream_t abstraction, which provides
       some convenient wrapping for file creation and reading/writing.  It can be  used  without,
       but its worth looking to see if your problem can fit that model.

       WARNING:
          mongoc_gridfs_t does not support read preferences. In a replica set, GridFS queries are
          always routed to the primary.

THREAD SAFETY

       mongoc_gridfs_t is NOT thread-safe and should only be used  in  the  same  thread  as  the
       owning mongoc_client_t.

LIFECYCLE

       It  is  an  error  to  free  a  mongoc_gridfs_t  before  freeing  all related instances of
       mongoc_gridfs_file_t and mongoc_gridfs_file_list_t.

EXAMPLE

       example-gridfs.c

          #include <assert.h>
          #include <mongoc/mongoc.h>
          #include <stdio.h>
          #include <stdlib.h>
          #include <fcntl.h>

          int
          main (int argc, char *argv[])
          {
             mongoc_gridfs_t *gridfs;
             mongoc_gridfs_file_t *file;
             mongoc_gridfs_file_list_t *list;
             mongoc_gridfs_file_opt_t opt = {0};
             mongoc_client_t *client;
             const char *uri_string = "mongodb://127.0.0.1:27017/?appname=gridfs-example";
             mongoc_uri_t *uri;
             mongoc_stream_t *stream;
             bson_t filter;
             bson_t opts;
             bson_t child;
             bson_error_t error;
             ssize_t r;
             char buf[4096];
             mongoc_iovec_t iov;
             const char *filename;
             const char *command;
             bson_value_t id;

             if (argc < 2) {
                fprintf (stderr, "usage - %s command ...\n", argv[0]);
                return EXIT_FAILURE;
             }

             mongoc_init ();

             iov.iov_base = (void *) buf;
             iov.iov_len = sizeof buf;

             /* connect to localhost client */
             uri = mongoc_uri_new_with_error (uri_string, &error);
             if (!uri) {
                fprintf (stderr,
                         "failed to parse URI: %s\n"
                         "error message:       %s\n",
                         uri_string,
                         error.message);
                return EXIT_FAILURE;
             }

             client = mongoc_client_new_from_uri (uri);
             assert (client);
             mongoc_client_set_error_api (client, 2);

             /* grab a gridfs handle in test prefixed by fs */
             gridfs = mongoc_client_get_gridfs (client, "test", "fs", &error);
             assert (gridfs);

             command = argv[1];
             filename = argv[2];

             if (strcmp (command, "read") == 0) {
                if (argc != 3) {
                   fprintf (stderr, "usage - %s read filename\n", argv[0]);
                   return EXIT_FAILURE;
                }
                file = mongoc_gridfs_find_one_by_filename (gridfs, filename, &error);
                assert (file);

                stream = mongoc_stream_gridfs_new (file);
                assert (stream);

                for (;;) {
                   r = mongoc_stream_readv (stream, &iov, 1, -1, 0);

                   assert (r >= 0);

                   if (r == 0) {
                      break;
                   }

                   if (fwrite (iov.iov_base, 1, r, stdout) != r) {
                      MONGOC_ERROR ("Failed to write to stdout. Exiting.\n");
                      exit (1);
                   }
                }

                mongoc_stream_destroy (stream);
                mongoc_gridfs_file_destroy (file);
             } else if (strcmp (command, "list") == 0) {
                bson_init (&filter);

                bson_init (&opts);
                bson_append_document_begin (&opts, "sort", -1, &child);
                BSON_APPEND_INT32 (&child, "filename", 1);
                bson_append_document_end (&opts, &child);

                list = mongoc_gridfs_find_with_opts (gridfs, &filter, &opts);

                bson_destroy (&filter);
                bson_destroy (&opts);

                while ((file = mongoc_gridfs_file_list_next (list))) {
                   const char *name = mongoc_gridfs_file_get_filename (file);
                   printf ("%s\n", name ? name : "?");

                   mongoc_gridfs_file_destroy (file);
                }

                mongoc_gridfs_file_list_destroy (list);
             } else if (strcmp (command, "write") == 0) {
                if (argc != 4) {
                   fprintf (stderr, "usage - %s write filename input_file\n", argv[0]);
                   return EXIT_FAILURE;
                }

                stream = mongoc_stream_file_new_for_path (argv[3], O_RDONLY, 0);
                assert (stream);

                opt.filename = filename;

                /* the driver generates a file_id for you */
                file = mongoc_gridfs_create_file_from_stream (gridfs, stream, &opt);
                assert (file);

                id.value_type = BSON_TYPE_INT32;
                id.value.v_int32 = 1;

                /* optional: the following method specifies a file_id of any
                   BSON type */
                if (!mongoc_gridfs_file_set_id (file, &id, &error)) {
                   fprintf (stderr, "%s\n", error.message);
                   return EXIT_FAILURE;
                }

                if (!mongoc_gridfs_file_save (file)) {
                   mongoc_gridfs_file_error (file, &error);
                   fprintf (stderr, "Could not save: %s\n", error.message);
                   return EXIT_FAILURE;
                }

                mongoc_gridfs_file_destroy (file);
             } else {
                fprintf (stderr, "Unknown command");
                return EXIT_FAILURE;
             }

             mongoc_gridfs_destroy (gridfs);
             mongoc_uri_destroy (uri);
             mongoc_client_destroy (client);

             mongoc_cleanup ();

             return EXIT_SUCCESS;
          }

SEE ALSO

       · The MongoDB GridFS specification.

       · The spec-compliant mongoc_gridfs_bucket_t.

AUTHOR

       MongoDB, Inc

COPYRIGHT

       2017-present, MongoDB, Inc