NAME

       mongoc_gridfs_t  - 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.

SYNOPSIS

       #include <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.

       NOTE
              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

       #include <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;
          mongoc_stream_t *stream;
          bson_t query;
          bson_t child;
          bson_error_t error;
          ssize_t r;
          char buf[4096];
          mongoc_iovec_t iov;
          const char * filename;
          const char * command;

          if (argc < 2) {
             fprintf(stderr, "usage ‐ %s command ...\n", argv[0]);
             return 1;
          }

          mongoc_init();

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

          /* connect to localhost client */
          client = mongoc_client_new ("mongodb://127.0.0.1:27017");
          assert(client);

          /* 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 1;
             }
             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 (&query);
             bson_append_document_begin (&query, "$orderby", ‐1, &child);
             bson_append_int32 (&child, "filename", ‐1, 1);
             bson_append_document_end (&query, &child);
             bson_append_document_begin (&query, "$query", ‐1, &child);
             bson_append_document_end (&query, &child);

             list = mongoc_gridfs_find (gridfs, &query);

             bson_destroy (&query);

             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 1;
             }

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

             opt.filename = filename;

             file = mongoc_gridfs_create_file_from_stream (gridfs, stream, &opt);
             assert(file);

             mongoc_gridfs_file_save(file);
             mongoc_gridfs_file_destroy(file);
          } else {
             fprintf(stderr, "Unknown command");
             return 1;
          }

          mongoc_gridfs_destroy (gridfs);
          mongoc_client_destroy (client);

          mongoc_cleanup ();

          return 0;
       }

COLOPHON

       This    page   is   part   of   MongoDB   C   Driver.    Please   report   any   bugs   at
       https://jira.mongodb.org/browse/CDRIVER.