Scroll to navigation

BSON_STREAMING_BSON(3) libbson 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

COPYRIGHT

2017-present, MongoDB, Inc

May 7, 2024 1.27.1