focal (3) bson_oid.3.gz

NAME

       bson_oid - ObjectIDs

       Libbson  provides  a  simple  way  to  generate  ObjectIDs.  It  can  be  used  in  a  single-threaded or
       multi-threaded manner depending on your requirements.

       The bson_oid_t structure represents an ObjectID in MongoDB. It is a 96-bit identifier.

COMPOSITION

       • 4 bytes : The UNIX timestamp in big-endian format.

       • 5 bytes : A random number.

       • 3 bytes : A 24-bit monotonic counter incrementing from rand() in big-endian.

SORTING OBJECTIDS

       The typical way to sort in C is using qsort(). Therefore, Libbson provides a qsort() compatible  callback
       function named bson_oid_compare(). It returns less than 1, greater than 1, or 0 depending on the equality
       of two bson_oid_t structures.

COMPARING OBJECT IDS

       If you simply want to compare two bson_oid_t structures for equality, use bson_oid_equal().

GENERATING

       To generate a bson_oid_t, you may use the following.

          bson_oid_t oid;

          bson_oid_init (&oid, NULL);

PARSING OBJECTID STRINGS

       You can also parse a string containing a bson_oid_t. The input string MUST be 24 characters  or  more  in
       length.

          bson_oid_t oid;

          bson_oid_init_from_string (&oid, "123456789012345678901234");

          bson_oid_t oid;

          bson_oid_init_from_string_unsafe (&oid, "123456789012345678901234");

HASHING OBJECTIDS

       If  you  need  to  store  items  in  a  hashtable, you may want to use the bson_oid_t as the key. Libbson
       provides a hash function for just this purpose. It is based on DJB hash.

          unsigned hash;

          hash = bson_oid_hash (oid);

FETCHING OBJECTID CREATION TIME

       You can easily fetch the time that a bson_oid_t was generated using bson_oid_get_time_t().

          time_t t;

          t = bson_oid_get_time_t (oid);
          printf ("The OID was generated at %u\n", (unsigned) t);

AUTHOR

       MongoDB, Inc

COPYRIGHT

       2017-present, MongoDB, Inc