Charsets for hex/base64

[Alan Bateman]

On 02/05/2018 09:35, Jonas Konrad wrote:
> 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.
>
Have you looked at the Hex API proposed in JDK-8170769? It needs to be 
dusted off but the last iteration discussed here got to the point where 
it provides conversion of binary data to/from hex string representation. 
It also supported both bulk and stream operations.

-Alan