msdn link

The SAMPR_PSID_ARRAY structure holds an array of SID values.

 typedef struct _SAMPR_PSID_ARRAY {
   [range(0,1024)] unsigned long Count;
   [size_is(Count)] PSAMPR_SID_INFORMATION Sids;
 } SAMPR_PSID_ARRAY,
  *PSAMPR_PSID_ARRAY;

Count: The number of elements in the Sids field. If zero, Sids MUST be ignored. If nonzero, Sids MUST point to at least Count * sizeof(SAMPR_SID_INFORMATION) bytes of memory.

Sids: An array of pointers to SID values. For more information, see section 2.2.7.6.