Incorrect Reading of 8-bit Signed Char Attributes

[a-shahba]

I was trying to read an array-valued attribute from an HDF file using PDL::IO::HDF5 package and noticed that the return value is incorrect. The attribute datatype is 8-bit signed char (H5T_STD_I8LE) and I expected the package to return [-127, 127], but instead it returned [129, 127]. Examining the source code, I found out why this is happening.

The code maps H5T_STD_I8LE to $PDL::Types::PDL_B here. However, $PDL::Types::PDL_B represents an unsigned char datatype. Therefore, the bits representing -127 in the buffer are interpreted as 129 by PDL.

To correct this behavior, I suggest that H5T_STD_I8LE and H5T_STD_I8BE are mapped to $PDL::Types::PDL_SB which represents signed char datatype.

[mohawk2]

I agree! Feel like making a pull request implementing that? You'll need to add a test case similar to what triggered this.

[a-shahba]

Thanks, @mohawk2. Sure, I will work on it and submit a PR.

[mohawk2]

This is fixed and released as 0.76.

[a-shahba]

Thanks. You are very fast. I was going to work on it this weekend.