Reading compound dataset with string contents errors

[pfitzseb]

This line errors when trying to read a compound dataset with string contents. Specifically, unpad is defined to take a String and a Cint as inputs, while read(io, UInt8, dsize) is an Array of UInt8s and H5T_STR_NULLPAD is a Int64 on my machine, while Cint is an alias for Int32.

Wrapping the read in a String constructor and relaxing unpads second argument's type restriction should work imho, but with my sample dataset I'm then getting a UnicodeError: invalid character index. I'm not sure if that's specific to my dataset's layout though (the Vector{UInt8} read spits out doesn't seem to be related to the string I'm expecting there at all, which might be a deeper issue).

I'd be happy to investigate this more, but I think I'll need some guidance from someone more familiar with the codebase...

cc @grahamrow, because you implemented read_row in #365

[musm]

@grahamrow could you please take a look at this? thanks

[pfitzseb]

Small file that reproduces this issue:
compound_dataset.zip

[musm]

Hmm, so is it not correctly identifying the membertype?
It fails for this 'string'
UInt8[0x60, 0xa2, 0x01, 0x00, 0xe8, 0x03, 0x00, 0x00]
what are you expected there?

[kleinhenz]

This should be closed by #592.