C++ do_div 宏

#define do_div(n, base) ({ \
    uint32_t __base = (base); \
    uint32_t __rem; \
    __rem = ((uint64_t)(n)) % __base; \
    (n) = ((uint64_t)(n)) / __base; \
    __rem; \
})

用法：

u64 ns = 1234567890;
u32 remainder_ns;
remainder_ns = do_div(ns, 1000000);
// 执行后：ns 被修改为商 (1234)，remainder_ns 为余数 (567890)