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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