Merge pull request #210 from mulimoen/feature/complex

Implement H5Type for complex

Author: aldanor

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Add a `ByteReader` which implements `std::io::{Read, Seek}` for 1D `u8`
   datasets. Usage via `Dataset::as_byte_reader()`.
 - Add `chunk_visit` to visit all chunks in a dataset.
+- Implement `H5Type` for `num_complex::Complex`.
 
 ### Changed
 

hdf5-types/Cargo.toml

@@ -15,12 +15,14 @@ edition.workspace = true
 
 [features]
 h5-alloc = []
+complex = ["num-complex"]
 
 [dependencies]
 ascii = "1.1"
 cfg-if = { workspace = true }
 hdf5-sys = { workspace = true }
 libc = { workspace = true }
+num-complex = { version = "0.4", optional = true, default-features = false }
 
 [dev-dependencies]
 quickcheck = { version = "1.0", default-features = false }

hdf5-types/src/complex.rs

@@ -0,0 +1,52 @@
+use super::{CompoundField, CompoundType, H5Type, TypeDescriptor};
+
+use std::mem::size_of;
+
+use num_complex::Complex;
+
+unsafe impl<T: H5Type> H5Type for Complex<T> {
+    fn type_descriptor() -> TypeDescriptor {
+        // Complex<T> should be FFI-equivalent to [T; 2]
+        // https://docs.rs/num-complex/0.4.3/num_complex/struct.Complex.html#representation-and-foreign-function-interface-compatibility
+        TypeDescriptor::Compound(CompoundType {
+            fields: vec![
+                // Compatible with h5py definition of complex
+                CompoundField::typed::<T>("r", 0, 0),
+                CompoundField::typed::<T>("i", size_of::<T>(), 1),
+            ],
+            size: size_of::<T>() * 2,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use num_complex::{Complex32, Complex64};
+    use std::mem::size_of_val;
+
+    #[test]
+    fn complex() {
+        assert_eq!(Complex32::type_descriptor().size(), 8);
+        assert_eq!(Complex32::type_descriptor().size(), size_of::<Complex32>());
+        assert_eq!(Complex64::type_descriptor().size(), 16);
+        assert_eq!(Complex64::type_descriptor().size(), size_of::<Complex64>());
+    }
+
+    #[test]
+    fn alignment() {
+        use std::ptr::addr_of;
+
+        let a = Complex { re: 0.0, im: 1.0 };
+
+        assert_eq!(size_of_val(&a), size_of_val(&a.re) + size_of_val(&a.im));
+        assert_eq!(size_of_val(&a.re), size_of_val(&a.im));
+
+        let base: *const u8 = addr_of!(a).cast::<u8>();
+        let ptr_r = addr_of!(a.re).cast::<u8>();
+        let ptr_i = addr_of!(a.im).cast::<u8>();
+
+        assert_eq!(unsafe { ptr_r.offset_from(base) }, 0);
+        assert_eq!(unsafe { ptr_i.offset_from(base) }, size_of_val(&a.re) as isize);
+    }
+}

hdf5-types/src/lib.rs

@@ -22,6 +22,9 @@ pub mod dyn_value;
 mod h5type;
 mod string;
 
+#[cfg(feature = "complex")]
+mod complex;
+
 pub use self::array::VarLenArray;
 pub use self::dyn_value::{DynValue, OwnedDynValue};
 pub use self::h5type::{