Flavors of Base64 encoding
source link: https://quuxplusone.github.io/blog/2020/11/17/base64/
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The Oracle documentation for java.util.Base64
refers to three different kinds of Base64,
but only by reference to RFCs. Here it is in one place.
RFC 4648 Table 1: Normal base64
Both RFC 2045 “Multipurpose Internet Mail Extensions” (November 1996) and RFC 4648 Table 1 “The Base16, Base32, and Base64 Data Encodings” (October 2006) define this same alphabet:
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ padded with =
This is the alphabet used by Java’s Base64.getEncoder(), and also by Base64.getMimeEncoder().
The only difference is that getMimeEncoder also inserts \r\n every 76 characters, and
ignores non-base64 characters (including any \r and \n) during decoding.
In Java, new String(Base64.getEncoder().encode("Hello??".getBytes())) should give you "SGVsbG8/Pw==".
In Kotlin, it’s String(Base64.getEncoder().encode("Hello??".toByteArray())).
RFC 4648 Table 2: URL-safe base64
RFC 4648 Table 2 “The Base16, Base32, and Base64 Data Encodings” (October 2006) defines this “URL- and filename-safe” alphabet:
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_ padded with =
This is the alphabet used by Java’s Base64.getUrlEncoder().
In Java, new String(Base64.getUrlEncoder().encode("Hello??".getBytes())) should give you "SGVsbG8_Pw==".
In Kotlin, it’s String(Base64.getUrlEncoder().encode("Hello??".toByteArray())).
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