Base64相关的正则

1.匹配头部的文件类型信息
val const BASE64_TYPE = "\w+\/\w+";

2.匹配base64 ,无论带不带信息头都行
const val BASE64 ="^(data:\S+/\S+;base64,)?(([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)){1}\$"

3.匹配base64,不能包含头信息
const val BASE64_NO_HEAD = "^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)\$"

4.匹配base64必须带头信息的base64

const val BASE64_HAED_CONTENT = "^(data:\S+/\S+;base64,)(([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)){1}\$"

5.头信息匹配

const val BASE64_HEAD = "data:\S+/\S+;base64,"
const val BASE64_HEAD1 = "\w+:\w+\/\w+;base64,"