htobe64
header->size = htobe64(*size);
val = htobe64(opts.feature_flags);
CASE_TEST(htobe64); EXPECT_EQ(1, htobe64(is_le ? 0x0123456789000000 : 0x8967452301), 0x8967452301); break;
#define put64(ST, REG, X) (ST.REG = htobe64(X))
#define putp64(ST, REG, X) ((ST)->REG = htobe64(X))