PL_BLOB_NOCOPY flag set and the blob type implements the
release()
callback. It causes the release()
callback to be called, after which the data and size are set to 0 if the release()
returns TRUE. After this sequence, the release()
for this blob is never called again. The related atom_t
handle remains valid until it is no longer referenced and reclaimed by
the atom garbage collector. If the blob data is accessed using e.g., PL_get_blob()
it returns NULL for the data and 0 for the size.227This
means that any predicates or callbacks that use the blob must check the
result of PL_blob_data().
If the release()
function is not called, or if it returns FALSE, FALSE
is returned.
PL_free_blob()
may be called multiple times on the same
atom_t, provided the handle is still valid. Subsequent
calls after a successful call have no effect and return FALSE.