Every 2-byte float was decoded as IEEE half, so bfloat16 (HDF5 2.0's
H5T_FLOAT_BFLOAT16*, or any custom 8-bit-exponent type) read wrong:
1.5 as 1.9375, +inf as NaN. 1-byte FP8 floats were refused.
Read the exponent/mantissa location and size and the bias from the
datatype message: IEEE half/single/double keep their existing paths
(half still through clawhdf5_format::float16), any other IEEE-style
layout up to 64 bits whose values fit f64 (bfloat16, FP8 E4M3/E5M2, ...)
is decoded generically, and the bulk-copy and zero-copy fast paths now
require the IEEE layout rather than just the size. Datatypes with fields
that describe no float still fall back to IEEE by size; layouts that
cannot be represented in f64 (x87 80-bit, binary128) remain an error.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
