Is the pattern for "hex encoded 256 bit unsigned integer" correct?

[fvictorio]

The pattern for hex encoded 256 bit unsigned integer doesn't look correct to me:

^0x([1-9a-f]+[0-9a-f]{0,31})|0$

I think there are two problems here. The first one is that the + there means that one million 1s would be a valid value, which is obviously incorrect.

And if the + is removed, there's still a problem, because then the string has a length of at most 32 hex characters, but for a 32-byte value the max length should be 64 hex characters.

I think the right pattern should be:

^0x([1-9a-f][0-9a-f]{0,63})|0$

I don't know why the test for this works fine though. I haven't checked how these tests are executed, and if they validate the patterns somehow.