用PB9写的base64的编码、解码源代码，可以对字符串进行编码，也可以对文件进行编码解码，文件可以是图片文件，也可以是其它任何文件-PB9 written with base64 encoding, decoding source code, can be encoded string, you can also file for the codec, the file can be image files, it can be any other file