sprintf源码。独立一个文件就可用。在嵌入式等系统中可能用到。网上找了很多，多数都不能用或功能不全。这个是本人下了一翻功夫完善过的代码。-sprintf source. Separate a file can be used. In the embedded and other systems may be used. The Internet is a lot, most are not usable or insufficiency. This is the effort I made