BSON_STREAMING_BSON(3)

bson_reader_t provides a streaming reader which can be initialized with a filedescriptor or memory region. bson_writer_t provides a streaming writer which can be initialized with a memory region. (Streaming BSON to a file descriptor is not yet supported.)

READING FROM A BSON STREAM

bson_reader_t provides a convenient API to read sequential BSON documents from a file-descriptor or memory buffer. The bson_reader_read() function will read forward in the underlying stream and return a bson_t that can be inspected and iterated upon.

            #include <stdio.h>
            #include <bson/bson.h>

            int
            main (int argc, char *argv[])
            {
               bson_reader_t *reader;
               const bson_t *doc;
               bson_error_t error;
               bool eof;

               reader = bson_reader_new_from_file ("mycollection.bson", &error);

               if (!reader) {
                  fprintf (stderr, "Failed to open file.\n");
                  return 1;
               }

               while ((doc = bson_reader_read (reader, &eof))) {
                  char *str = bson_as_canonical_extended_json (doc, NULL);
                  printf ("%s\n", str);
                  bson_free (str);
               }

               if (!eof) {
                  fprintf (stderr,
                           "corrupted bson document found at %u\n",
                           (unsigned) bson_reader_tell (reader));
               }

               bson_reader_destroy (reader);

               return 0;
            }

See bson_reader_new_from_fd(), bson_reader_new_from_file(), and bson_reader_new_from_data() for more information.

WRITING A SEQUENCE OF BSON DOCUMENTS

bson_writer_t provides a convenient API to write a sequence of BSON documents to a memory buffer that can grow with realloc(). The bson_writer_begin() and bson_writer_end() functions will manage the underlying buffer while building the sequence of documents.

This could also be useful if you want to write to a network packet while serializing the documents from a higher level language, (but do so just after the packets header).

            #include <stdio.h>
            #include <bson/bson.h>
            #include <assert.h>

            int
            main (int argc, char *argv[])
            {
               bson_writer_t *writer;
               bson_t *doc;
               uint8_t *buf = NULL;
               size_t buflen = 0;
               bool r;
               int i;

               writer = bson_writer_new (&buf, &buflen, 0, bson_realloc_ctx, NULL);

               for (i = 0; i < 10000; i++) {
                  r = bson_writer_begin (writer, &doc);
                  assert (r);

                  r = BSON_APPEND_INT32 (doc, "i", i);
                  assert (r);

                  bson_writer_end (writer);
               }

               bson_free (buf);

               return 0;
            }

See bson_writer_new() for more information.

AUTHOR
MongoDB, Inc

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