How to check constraints before call of simple_heap_insert()?

Hi all.
I'm writting some trigger i C, and I use simple_heap_insert() function
to insert HeapTuple to a table. But unfortunatelly that function does
not check constraints before inserting values to the table. Does anyone
know there is some function that checks constraints while inserting
HeapTuple structure?
Thanks in advice

Best regards.
Vanyel