Charsets for hex/base64

[Jonas Konrad]

Hi,

Conceptually, a 'charset' (in java) is a pair of transformations from 
bytes to utf-16 code units and vice versa. Could it be useful to have 
charset implementations that convert from bytes to the hex (or base64) 
representations of those? The idea is as follows:

"0a0b0c".getBytes(HexCharset.getInstance()) = new byte[] { 0x0a, 0x0b, 
0x0c }
new String(new byte[] { 0x0a, 0x0b, 0x0c }, HexCharset.getInstance()) = 
"0a0b0c"

The motivation behind this idea is that there are lots of APIs that 
provide efficient transformations between chars and bytes using 
charsets, but converting to/from hex for debugging is usually more 
involved. One example of this is netty ByteBuf.toString ( 
https://netty.io/4.0/api/io/netty/buffer/ByteBuf.html#toString-int-int-java.nio.charset.Charset- 
) - it would be really convenient to be able to just plug in a hex 
charset to get nice debug output.

Of course this is only one example and there are other ways to get hex 
output from ByteBuf in netty in particular, but I still think that a hex 
charset would be an interesting tool to reuse code. I understand this is 
a somewhat dubious use of a Charset, but I'd like to hear other thoughts 
on it.

I built such a charset a while back for fun, here is the source code: 
https://gist.github.com/yawkat/6e80f21f5d418a85c3283e55b80fb607

- Jonas