struct timeval 和 struct timespec
http://blog.youkuaiyun.com/perfectpdl/article/details/6182777
gettimeofday() -- 获取当前时间(保存在结构体timeval中)
http://hi.baidu.com/zengzhaonong/item/9a3fff2f92b82bd50e37f950
snprintf与strncpy效率对比
http://blog.youkuaiyun.com/one132/article/details/5683880
字符串copy效率大比拼~
http://blog.youkuaiyun.com/wavemoon/article/details/4952904