BSON_OID(3)

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