1MONGOC_GRIDFS_T(3) libmongoc MONGOC_GRIDFS_T(3)
2
6 mongoc_gridfs_t - mongoc_gridfs_t
7 WARNING:
9 This GridFS implementation does not conform to the MongoDB GridFS
10 specification. For a spec compliant implementation, use
11 mongoc_gridfs_bucket_t.
12
14 #include <mongoc/mongoc.h>
15 typedef struct _mongoc_gridfs_t mongoc_gridfs_t;
17
19 mongoc_gridfs_t provides a MongoDB gridfs implementation. The system as
20 a whole is made up of gridfs objects, which contain gridfs_files and
21 gridfs_file_lists. Essentially, a basic file system API.
22 There are extensive caveats about the kind of use cases gridfs is prac‐
24 tical for. In particular, any writing after initial file creation is
25 likely to both break any concurrent readers and be quite expensive.
26 That said, this implementation does allow for arbitrary writes to ex‐
27 isting gridfs object, just use them with caution.
28 mongoc_gridfs also integrates tightly with the mongoc_stream_t abstrac‐
30 tion, which provides some convenient wrapping for file creation and
31 reading/writing. It can be used without, but its worth looking to see
32 if your problem can fit that model.
33 WARNING:
35 mongoc_gridfs_t does not support read preferences. In a replica set,
36 GridFS queries are always routed to the primary.
37
39 mongoc_gridfs_t is NOT thread-safe and should only be used in the same
40 thread as the owning mongoc_client_t.
41
43 It is an error to free a mongoc_gridfs_t before freeing all related in‐
44 stances of mongoc_gridfs_file_t and mongoc_gridfs_file_list_t.
45
47 example-gridfs.c
48 #include <assert.h>
50 #include <mongoc/mongoc.h>
51 #include <stdio.h>
52 #include <stdlib.h>
53 #include <fcntl.h>
54 int
56 main (int argc, char *argv[])
57 {
58 mongoc_gridfs_t *gridfs;
59 mongoc_gridfs_file_t *file;
60 mongoc_gridfs_file_list_t *list;
61 mongoc_gridfs_file_opt_t opt = {0};
62 mongoc_client_t *client;
63 const char *uri_string = "mongodb://127.0.0.1:27017/?appname=gridfs-example";
64 mongoc_uri_t *uri;
65 mongoc_stream_t *stream;
66 bson_t filter;
67 bson_t opts;
68 bson_t child;
69 bson_error_t error;
70 ssize_t r;
71 char buf[4096];
72 mongoc_iovec_t iov;
73 const char *filename;
74 const char *command;
75 bson_value_t id;
76 if (argc < 2) {
78 fprintf (stderr, "usage - %s command ...\n", argv[0]);
79 return EXIT_FAILURE;
80 }
81 mongoc_init ();
83 iov.iov_base = (void *) buf;
85 iov.iov_len = sizeof buf;
86 /* connect to localhost client */
88 uri = mongoc_uri_new_with_error (uri_string, &error);
89 if (!uri) {
90 fprintf (stderr,
91 "failed to parse URI: %s\n"
92 "error message: %s\n",
93 uri_string,
94 error.message);
95 return EXIT_FAILURE;
96 }
97 client = mongoc_client_new_from_uri (uri);
99 assert (client);
100 mongoc_client_set_error_api (client, 2);
101 /* grab a gridfs handle in test prefixed by fs */
103 gridfs = mongoc_client_get_gridfs (client, "test", "fs", &error);
104 assert (gridfs);
105 command = argv[1];
107 filename = argv[2];
108 if (strcmp (command, "read") == 0) {
110 if (argc != 3) {
111 fprintf (stderr, "usage - %s read filename\n", argv[0]);
112 return EXIT_FAILURE;
113 }
114 file = mongoc_gridfs_find_one_by_filename (gridfs, filename, &error);
115 assert (file);
116 stream = mongoc_stream_gridfs_new (file);
118 assert (stream);
119 for (;;) {
121 r = mongoc_stream_readv (stream, &iov, 1, -1, 0);
122 assert (r >= 0);
124 if (r == 0) {
126 break;
127 }
128 if (fwrite (iov.iov_base, 1, r, stdout) != r) {
130 MONGOC_ERROR ("Failed to write to stdout. Exiting.\n");
131 exit (1);
132 }
133 }
134 mongoc_stream_destroy (stream);
136 mongoc_gridfs_file_destroy (file);
137 } else if (strcmp (command, "list") == 0) {
138 bson_init (&filter);
139 bson_init (&opts);
141 bson_append_document_begin (&opts, "sort", -1, &child);
142 BSON_APPEND_INT32 (&child, "filename", 1);
143 bson_append_document_end (&opts, &child);
144 list = mongoc_gridfs_find_with_opts (gridfs, &filter, &opts);
146 bson_destroy (&filter);
148 bson_destroy (&opts);
149 while ((file = mongoc_gridfs_file_list_next (list))) {
151 const char *name = mongoc_gridfs_file_get_filename (file);
152 printf ("%s\n", name ? name : "?");
153 mongoc_gridfs_file_destroy (file);
155 }
156 mongoc_gridfs_file_list_destroy (list);
158 } else if (strcmp (command, "write") == 0) {
159 if (argc != 4) {
160 fprintf (stderr, "usage - %s write filename input_file\n", argv[0]);
161 return EXIT_FAILURE;
162 }
163 stream = mongoc_stream_file_new_for_path (argv[3], O_RDONLY, 0);
165 assert (stream);
166 opt.filename = filename;
168 /* the driver generates a file_id for you */
170 file = mongoc_gridfs_create_file_from_stream (gridfs, stream, &opt);
171 assert (file);
172 id.value_type = BSON_TYPE_INT32;
174 id.value.v_int32 = 1;
175 /* optional: the following method specifies a file_id of any
177 BSON type */
178 if (!mongoc_gridfs_file_set_id (file, &id, &error)) {
179 fprintf (stderr, "%s\n", error.message);
180 return EXIT_FAILURE;
181 }
182 if (!mongoc_gridfs_file_save (file)) {
184 mongoc_gridfs_file_error (file, &error);
185 fprintf (stderr, "Could not save: %s\n", error.message);
186 return EXIT_FAILURE;
187 }
188 mongoc_gridfs_file_destroy (file);
190 } else {
191 fprintf (stderr, "Unknown command");
192 return EXIT_FAILURE;
193 }
194 mongoc_gridfs_destroy (gridfs);
196 mongoc_uri_destroy (uri);
197 mongoc_client_destroy (client);
198 mongoc_cleanup ();
200 return EXIT_SUCCESS;
202 }
203 SEE ALSO:
206 The MongoDB GridFS specification.
207 The spec-compliant mongoc_gridfs_bucket_t.
209
212 MongoDB, Inc
213
215 2017-present, MongoDB, Inc
2161.23.1 Oct 20, 2022 MONGOC_GRIDFS_T(3)