bson_oid3

Composition

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);