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.TH "BSON_STREAMING_BSON" "3" "Apr 02, 2024" "1.26.2" "libbson"
.sp
\fI\%bson_reader_t\fP provides a streaming reader which can be initialized with a filedescriptor or memory region. \fI\%bson_writer_t\fP provides a streaming writer which can be initialized with a memory region. (Streaming BSON to a file descriptor is not yet supported.)
.SH READING FROM A BSON STREAM
.sp
\fI\%bson_reader_t\fP provides a convenient API to read sequential BSON documents from a file\-descriptor or memory buffer. The \fI\%bson_reader_read()\fP function will read forward in the underlying stream and return a \fI\%bson_t\fP that can be inspected and iterated upon.
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.INDENT 3.5
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.EX
#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 (\(dqmycollection.bson\(dq, &error);

   if (!reader) {
      fprintf (stderr, \(dqFailed to open file.\en\(dq);
      return 1;
   }

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

   if (!eof) {
      fprintf (stderr,
               \(dqcorrupted bson document found at %u\en\(dq,
               (unsigned) bson_reader_tell (reader));
   }

   bson_reader_destroy (reader);

   return 0;
}
.EE
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.sp
See \fI\%bson_reader_new_from_fd()\fP, \fI\%bson_reader_new_from_file()\fP, and \fI\%bson_reader_new_from_data()\fP for more information.
.SH WRITING A SEQUENCE OF BSON DOCUMENTS
.sp
\fI\%bson_writer_t\fP provides a convenient API to write a sequence of BSON documents to a memory buffer that can grow with \fBrealloc()\fP\&. The \fI\%bson_writer_begin()\fP and \fI\%bson_writer_end()\fP functions will manage the underlying buffer while building the sequence of documents.
.sp
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).
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.INDENT 3.5
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.EX
#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, \(dqi\(dq, i);
      assert (r);

      bson_writer_end (writer);
   }

   bson_free (buf);

   return 0;
}
.EE
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.sp
See \fI\%bson_writer_new()\fP for more information.
.SH AUTHOR
MongoDB, Inc
.SH COPYRIGHT
2017-present, MongoDB, Inc
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