RFR 8251989: Hex encoder and decoder utility

[Raffaello Giulietti]

Hi Roger,

I'm only a contributor, not an official reviewer. Despite this, I would 
like to make some notes about the encoder part.


(1) Comparing with other APIs that accept a range of a byte[], my 
understanding is that encode(byte[], int, int) should throw IOOE when 
index < 0 or too big, even if length == 0. Since other parts of the code 
already invokes Objects.checkFromIndexSize() in other methods, it would 
be more consistent to add this check to this one as well.

(2) The code on L.334 throws an exception when encodeOptDelim() is 
invoked with an empty byte[]. This can happen precisely because the 
checks mentioned in (1) are not strict enough. E.g., given an 
appropriate encoder, encode(new byte[0], 0, 1) will invoke 
encodeOptDelim() and throw on L.334

(3) I guess "NYI" on L.343 stands for "not yet implemented", but 
shouldn't this more likely be an AssertionError? What else needs to be 
implemented here?

(4) The private toHex(int, boolean) can be declared static.

(5) To maintain consistency with the other ranges, on L.599 "0123456789" 
could be replaced by "0-9".

(6) As already noted by Tagir, there's a duplication of checks in L.290-291


Greetings
Raffaello



> Please review a java.util.Hex API to encode and decode hexadecimal 
> strings to and from byte arrays.
> 
> Within the JDK and JDK tests there are multiple implementations to 
> encode and decode
> hexadecimal strings to byte arrays. Hex encoders and decoders support
> upper or lower case hexadecimal characters, delimiters, prefix, and suffix.
> The API is modeled after the java.util.Base64 API providing static 
> factories,
> immutable threadsafe instances with methods to encode to and decode from
> string and StringBuilder.