Charsets for hex/base64 (original) (raw)

Jonas Konrad me at yawk.at
Wed May 2 09:55:45 UTC 2018

I did not know about the old HexDumpEncoder. It extends an internal class CharacterEncoder which seems to be pretty similar purpose-wise to what I am suggesting with CharsetEncoder. There is also the good old DatatypeConverter.printHexBinary, though it can't stream.

But this is not really what I mean. The interesting part about doing this as a charset is the unified API aspect of it, the fact that you can reuse existing code utilizing Charset for hex operations.

On 05/02/2018 11:44 AM, Alan Bateman wrote:

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

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