NAME

       ObjectIDs - None

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)
       \&.

COLOPHON

       This     page     is     part     of    libbson.     Please    report    any    bugs    at
       https://jira.mongodb.org/browse/CDRIVER.