1MONGOC_GRIDFS_T(3) MongoDB C Driver MONGOC_GRIDFS_T(3)
2
6 mongoc_gridfs_t - mongoc_gridfs_t
7
9 #include <mongoc/mongoc.h>
10 typedef struct _mongoc_gridfs_t mongoc_gridfs_t;
12
14 mongoc_gridfs_t provides a MongoDB gridfs implementation. The system as
15 a whole is made up of gridfs objects, which contain gridfs_files and
16 gridfs_file_lists. Essentially, a basic file system API.
17 There are extensive caveats about the kind of use cases gridfs is prac‐
19 tical for. In particular, any writing after initial file creation is
20 likely to both break any concurrent readers and be quite expensive.
21 That said, this implementation does allow for arbitrary writes to
22 existing gridfs object, just use them with caution.
23 mongoc_gridfs also integrates tightly with the mongoc_stream_t abstrac‐
25 tion, which provides some convenient wrapping for file creation and
26 reading/writing. It can be used without, but its worth looking to see
27 if your problem can fit that model.
28 WARNING:
30 mongoc_gridfs_t does not support read preferences. In a replica set,
31 GridFS queries are always routed to the primary.
32
34 mongoc_gridfs_t is NOT thread-safe and should only be used in the same
35 thread as the owning mongoc_client_t.
36
38 It is an error to free a mongoc_gridfs_t before freeing all related
39 instances of mongoc_gridfs_file_t and mongoc_gridfs_file_list_t.
40
42 example-gridfs.c.INDENT 0.0
43 #include <assert.h>
45 #include <mongoc/mongoc.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <fcntl.h>
49 int
51 main (int argc, char *argv[])
52 {
53 mongoc_gridfs_t *gridfs;
54 mongoc_gridfs_file_t *file;
55 mongoc_gridfs_file_list_t *list;
56 mongoc_gridfs_file_opt_t opt = {0};
57 mongoc_client_t *client;
58 const char *uri_string = "mongodb://127.0.0.1:27017/?appname=gridfs-example";
59 mongoc_uri_t *uri;
60 mongoc_stream_t *stream;
61 bson_t filter;
62 bson_t opts;
63 bson_t child;
64 bson_error_t error;
65 ssize_t r;
66 char buf[4096];
67 mongoc_iovec_t iov;
68 const char *filename;
69 const char *command;
70 bson_value_t id;
71 if (argc < 2) {
73 fprintf (stderr, "usage - %s command ...\n", argv[0]);
74 return EXIT_FAILURE;
75 }
76 mongoc_init ();
78 iov.iov_base = (void *) buf;
80 iov.iov_len = sizeof buf;
81 /* connect to localhost client */
83 uri = mongoc_uri_new_with_error (uri_string, &error);
84 if (!uri) {
85 fprintf (stderr,
86 "failed to parse URI: %s\n"
87 "error message: %s\n",
88 uri_string,
89 error.message);
90 return EXIT_FAILURE;
91 }
92 client = mongoc_client_new_from_uri (uri);
94 assert (client);
95 mongoc_client_set_error_api (client, 2);
96 /* grab a gridfs handle in test prefixed by fs */
98 gridfs = mongoc_client_get_gridfs (client, "test", "fs", &error);
99 assert (gridfs);
100 command = argv[1];
102 filename = argv[2];
103 if (strcmp (command, "read") == 0) {
105 if (argc != 3) {
106 fprintf (stderr, "usage - %s read filename\n", argv[0]);
107 return EXIT_FAILURE;
108 }
109 file = mongoc_gridfs_find_one_by_filename (gridfs, filename, &error);
110 assert (file);
111 stream = mongoc_stream_gridfs_new (file);
113 assert (stream);
114 for (;;) {
116 r = mongoc_stream_readv (stream, &iov, 1, -1, 0);
117 assert (r >= 0);
119 if (r == 0) {
121 break;
122 }
123 if (fwrite (iov.iov_base, 1, r, stdout) != r) {
125 MONGOC_ERROR ("Failed to write to stdout. Exiting.\n");
126 exit (1);
127 }
128 }
129 mongoc_stream_destroy (stream);
131 mongoc_gridfs_file_destroy (file);
132 } else if (strcmp (command, "list") == 0) {
133 bson_init (&filter);
134 bson_init (&opts);
136 bson_append_document_begin (&opts, "sort", -1, &child);
137 BSON_APPEND_INT32 (&child, "filename", 1);
138 bson_append_document_end (&opts, &child);
139 list = mongoc_gridfs_find_with_opts (gridfs, &filter, &opts);
141 bson_destroy (&filter);
143 bson_destroy (&opts);
144 while ((file = mongoc_gridfs_file_list_next (list))) {
146 const char *name = mongoc_gridfs_file_get_filename (file);
147 printf ("%s\n", name ? name : "?");
148 mongoc_gridfs_file_destroy (file);
150 }
151 mongoc_gridfs_file_list_destroy (list);
153 } else if (strcmp (command, "write") == 0) {
154 if (argc != 4) {
155 fprintf (stderr, "usage - %s write filename input_file\n", argv[0]);
156 return EXIT_FAILURE;
157 }
158 stream = mongoc_stream_file_new_for_path (argv[3], O_RDONLY, 0);
160 assert (stream);
161 opt.filename = filename;
163 /* the driver generates a file_id for you */
165 file = mongoc_gridfs_create_file_from_stream (gridfs, stream, &opt);
166 assert (file);
167 id.value_type = BSON_TYPE_INT32;
169 id.value.v_int32 = 1;
170 /* optional: the following method specifies a file_id of any
172 BSON type */
173 if (!mongoc_gridfs_file_set_id (file, &id, &error)) {
174 fprintf (stderr, "%s\n", error.message);
175 return EXIT_FAILURE;
176 }
177 if (!mongoc_gridfs_file_save (file)) {
179 mongoc_gridfs_file_error (file, &error);
180 fprintf (stderr, "Could not save: %s\n", error.message);
181 return EXIT_FAILURE;
182 }
183 mongoc_gridfs_file_destroy (file);
185 } else {
186 fprintf (stderr, "Unknown command");
187 return EXIT_FAILURE;
188 }
189 mongoc_gridfs_destroy (gridfs);
191 mongoc_uri_destroy (uri);
192 mongoc_client_destroy (client);
193 mongoc_cleanup ();
195 return EXIT_SUCCESS;
197 }
198
201 MongoDB, Inc
202
204 2017-present, MongoDB, Inc
2051.13.1 Jan 24, 2019 MONGOC_GRIDFS_T(3)