Add Sqlite3.column_is_null function

lib/sqlite3.ml

@@ -343,6 +343,9 @@ external data_count : stmt -> (int[@untagged])
 external column_count : stmt -> (int[@untagged])
   = "caml_sqlite3_column_count_bc" "caml_sqlite3_column_count"
 
+external column_is_null : stmt -> (int[@untagged]) -> bool
+  = "caml_sqlite3_column_is_null_bc" "caml_sqlite3_column_is_null"
+
 external column_blob : stmt -> (int[@untagged]) -> string
   = "caml_sqlite3_column_blob_bc" "caml_sqlite3_column_blob"
 

lib/sqlite3.mli

@@ -495,6 +495,15 @@ val column_count : stmt -> int
 
     @raise SqliteError if the statement is invalid. *)
 
+val column_is_null : stmt -> int -> bool
+(** [column_is_null stmt n]
+    @return
+      [true] if the data in column [n] of the result of the last step of
+      statement [stmt] is NULL, [false] otherwise.
+
+    @raise RangeError if [n] is out of range.
+    @raise SqliteError if the statement is invalid. *)
+
 val column : stmt -> int -> Data.t
 (** [column stmt n]
     @return

lib/sqlite3_stubs.c

@@ -1137,6 +1137,18 @@ CAMLprim value caml_sqlite3_column_count_bc(value v_stmt) {
   return Val_int(caml_sqlite3_column_count(v_stmt));
 }
 
+/* column_is_null */
+
+CAMLprim value caml_sqlite3_column_is_null(value v_stmt, intnat pos) {
+  sqlite3_stmt *stmt = safe_get_stmtw("column_is_null", v_stmt)->stmt;
+  range_check(pos, sqlite3_column_count(stmt));
+  return Val_bool(sqlite3_column_type(stmt, pos) == SQLITE_NULL);
+}
+
+CAMLprim value caml_sqlite3_column_is_null_bc(value v_stmt, value v_pos) {
+  return caml_sqlite3_column_is_null(v_stmt, Int_val(v_pos));
+}
+
 /* column_blob */
 
 CAMLprim value caml_sqlite3_column_blob(value v_stmt, intnat pos) {

test/test_values.ml

@@ -65,7 +65,8 @@ let%test "test_values" =
     assert (column_int32 select_stmt 1 = 0l);
     assert (column_int64 select_stmt 2 = 0L);
     assert (column_double select_stmt 3 = 0.0);
-    assert (column_bool select_stmt 4 = false));
+    assert (column_bool select_stmt 4 = false);
+    assert (column_is_null select_stmt 4));
 
   (* Clean up *)
   ignore (finalize insert_stmt);