feat: check HDF5 2.x small floats against libhdf5 2.2.0

Fixture written by libhdf5 2.2.0 (built from tag 2.2.0) through ctypes: every bit pattern of FP4 E2M1, FP6 E2M3/E3M2, FP8 E4M3/E5M2 and a bfloat16 LE/BE set, as datasets and attributes, with what H5Dread/H5Aread return into double and float and the conversion exceptions libhdf5 raises. clawhdf5 already decoded every value as libhdf5 does, including an all-ones exponent as inf/NaN in the OCP formats that have none (documented as a deliberate match in known-issues). - data_read: NaNs of non-native float layouts get libhdf5's bits (sign kept, every mantissa bit set) in f64 and f32. - h5rs dump/ls name these types as h5dump/h5ls 2.x do (H5T_FLOAT_F4E2M1, "FP4 E2M1 4-bit float", float4-e2m1 ...), checked against h5dump 2.2.0's output of the fixture. - Python bindings read them as h5py 3.16 does (float32 for bfloat16, float16 for the 1-byte formats, file byte order, same bytes as h5py); writing them in 'r+' is refused. Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
2026-09-28 21:25:03 -05:00
parent 31efac1ae1
commit bce07e9cb9
16 changed files with 1207 additions and 13 deletions
@@ -48,7 +48,12 @@ fn not_implemented(what: impl std::fmt::Display) -> PyErr {
 pub(crate) fn category(dt: &Datatype) -> PyResult<&'static str> {
    match dt {
        Datatype::FixedPoint { .. } => Ok("int"),
-        Datatype::FloatingPoint { .. } => Ok("float"),
+        Datatype::FloatingPoint { .. } if crate::convert::is_ieee_float(dt) => Ok("float"),
+        // Read as a wider IEEE float; writing would need the reverse
+        // conversion (rounding into bfloat16, FP8, ...).
+        Datatype::FloatingPoint { .. } => Err(not_implemented(
+            "writing non-IEEE floats (bfloat16, FP8, FP6, FP4, ...)",
+        )),
        Datatype::Enumeration {
            base_type, members, ..
        } => {