The SHA-256 implementation behind the interface

751    if (TransformD64_8way) {
752        while (blocks >= 8) {
753            TransformD64_8way(out, in);
754            out += 256;
755            in += 512;
756            blocks -= 8;
757        }
758    }
759    if (TransformD64_4way) {
760        while (blocks >= 4) {
761            TransformD64_4way(out, in);
762            out += 128;
763            in += 256;
764            blocks -= 4;
765        }
766    }
767    if (TransformD64_2way) {
768        while (blocks >= 2) {
769            TransformD64_2way(out, in);
770            out += 64;
771            in += 128;
772            blocks -= 2;
773        }
774    }
775    while (blocks) {
776        TransformD64(out, in);
777        out += 32;
778        in += 64;
779        --blocks;
780    }
781}
782