# clawhdf5-derive

`#[derive(H5Type)]`: maps a Rust struct with named fields to an HDF5
compound datatype. The derive generates three inherent methods:

- `hdf5_datatype() -> clawhdf5_format::datatype::Datatype` — the
  `Datatype::Compound` (members in field order, packed, little-endian);
- `to_bytes(&self) -> Vec<u8>` — one element in that layout;
- `from_bytes(&[u8]) -> Self` — the reverse (panics if the slice is shorter
  than the compound).

Supported field types: `f32`, `f64`, `i8`–`i64`, `u8`–`u64`, `bool`
(stored as `u8`) and fixed-size arrays `[T; N]` of those numeric types.
Tuple structs, enums and nested structs are refused at compile time.

The generated code names `clawhdf5_format`, so the crate using the derive
must depend on [`clawhdf5-format`](../clawhdf5-format/README.md) too. Not
on crates.io yet:

```toml
[dependencies]
clawhdf5-derive = { git = "https://git.redclaw.dev/quantumclaw/clawhdf5" }
clawhdf5-format = { git = "https://git.redclaw.dev/quantumclaw/clawhdf5" }
```

## Example

```rust
use clawhdf5_derive::H5Type;
use clawhdf5_format::datatype::Datatype;

#[derive(H5Type, Debug, PartialEq)]
struct Point {
    id: u32,
    pos: [f64; 3],
    valid: bool,
}

let p = Point { id: 7, pos: [1.0, 2.0, 3.0], valid: true };
let bytes = p.to_bytes();
assert_eq!(bytes.len(), 4 + 24 + 1);
assert_eq!(Point::from_bytes(&bytes), p);
assert!(matches!(Point::hdf5_datatype(), Datatype::Compound { size: 29, .. }));
```

Tests: `crates/clawhdf5-format/tests/derive_tests.rs`.

## License

MIT