Implement Send+Sync for VarLenAscii/Unicode/Array

Author: watsaig

hdf5-types/src/array.rs

@@ -142,6 +142,13 @@ impl<T: Copy + fmt::Debug> fmt::Debug for VarLenArray<T> {
     }
 }
 
+// Safety: `VarLenArray` allocates and frees memory for its data, which is copied
+// from its original location; it never holds a reference to the data used to create it.
+// Therefore if `T` is Send, so is `VarLenArray<T>`
+unsafe impl<T: Copy + Send> Send for VarLenArray<T> {}
+// Safety: No interior mutability or potential for data races if `T` is `Sync`.
+unsafe impl<T: Copy + Sync> Sync for VarLenArray<T> {}
+
 #[cfg(test)]
 pub mod tests {
     use super::VarLenArray;

hdf5-types/src/string.rs

@@ -282,6 +282,12 @@ impl AsAsciiStr for VarLenAscii {
     }
 }
 
+// Safety: `VarLenAscii` allocates and frees memory for its data, which is copied
+// from its original location; it never holds a reference to the data used to create it.
+unsafe impl Send for VarLenAscii {}
+// Safety: No interior mutability or potential for data races.
+unsafe impl Sync for VarLenAscii {}
+
 // ================================================================================
 
 #[repr(C)]
@@ -371,6 +377,12 @@ impl FromStr for VarLenUnicode {
     }
 }
 
+// Safety: `VarLenUnicode` allocates and frees memory for its data, which is copied
+// from its original location; it never holds a reference to the data used to create it.
+unsafe impl Send for VarLenUnicode {}
+// Safety: No interior mutability or potential for data races.
+unsafe impl Sync for VarLenUnicode {}
+
 // ================================================================================
 
 #[repr(C)]