COMPOSITION
- \[bu]
- 4 bytes : The UNIX timestamp in big-endian format.
- \[bu]
- 3 bytes : The first 3 bytes of MD5(hostname) \&.
- \[bu]
- 2 bytes : The pid_t of the current process. Alternatively the task-id if configured.
- \[bu]
-
3 bytes : A 24-bit monotonic counter incrementing from
rand(3)
in big-endian.
SORTING OBJECTIDS
The typical way to sort in C is using qsort(3) \&. Therefore, Libbson provides a qsort(3) compatible callback function named bson_oid_compare(3) \&. 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(3) \&.
GENERATING
To generate a bson_oid_t , you may use the following.
PARSING OBJECTID STRINGS
You can also parse a string contianing a bson_oid_t \&. The input string MUST be 24 characters or more in length.
If you need to parse may bson_oid_t in a tight loop and can guarantee the data is safe, you might consider using the inline variant. It will be inlined into your code and reduce the need for a foreign function call.
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.
FETCHING OBJECTID CREATION TIME
You can easily fetch the time that a bson_oid_t was generated using bson_oid_get_time_t(3) \&.