From cb2a88b162638e8627e09e4ea11e278b4b9d175c Mon Sep 17 00:00:00 2001
From: Craig Watson <craig@watsons.ch>
Date: Wed, 7 Feb 2024 10:20:42 -0700
Subject: [PATCH 1/2] Implement Send+Sync for VarLenAscii/Unicode/Array

---
 hdf5-types/src/array.rs  |  7 +++++++
 hdf5-types/src/string.rs | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/hdf5-types/src/array.rs b/hdf5-types/src/array.rs
index f5b8956c5..f21feff4f 100644
--- a/hdf5-types/src/array.rs
+++ b/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;
diff --git a/hdf5-types/src/string.rs b/hdf5-types/src/string.rs
index 5f587f500..17e65d464 100644
--- a/hdf5-types/src/string.rs
+++ b/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)]

From 1455a777ea39f2a880b024788f596b5d596ae43a Mon Sep 17 00:00:00 2001
From: Craig Watson <686868+watsaig@users.noreply.github.com>
Date: Tue, 13 Feb 2024 14:34:29 -0700
Subject: [PATCH 2/2] Apply suggestions from review

Co-authored-by: Magnus Ulimoen <mulimoen@users.noreply.github.com>
Signed-off-by: Craig Watson <686868+watsaig@users.noreply.github.com>
---
 hdf5-types/src/array.rs  |  6 ++----
 hdf5-types/src/string.rs | 10 ++++------
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/hdf5-types/src/array.rs b/hdf5-types/src/array.rs
index f21feff4f..cf0909246 100644
--- a/hdf5-types/src/array.rs
+++ b/hdf5-types/src/array.rs
@@ -142,11 +142,9 @@ 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>`
+// Safety: Memory backed by `VarLenArray` can be accessed and freed from any thread
 unsafe impl<T: Copy + Send> Send for VarLenArray<T> {}
-// Safety: No interior mutability or potential for data races if `T` is `Sync`.
+// Safety: `VarLenArray` has no interior mutability
 unsafe impl<T: Copy + Sync> Sync for VarLenArray<T> {}
 
 #[cfg(test)]
diff --git a/hdf5-types/src/string.rs b/hdf5-types/src/string.rs
index 17e65d464..612f462c7 100644
--- a/hdf5-types/src/string.rs
+++ b/hdf5-types/src/string.rs
@@ -282,10 +282,9 @@ 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.
+// Safety: Memory backed by `VarLenAscii` can be accessed and freed from any thread
 unsafe impl Send for VarLenAscii {}
-// Safety: No interior mutability or potential for data races.
+// Safety: `VarLenAscii` has no interior mutability
 unsafe impl Sync for VarLenAscii {}
 
 // ================================================================================
@@ -377,10 +376,9 @@ 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.
+// Safety: Memory backed by `VarLenUnicode` can be accessed and freed from any thread
 unsafe impl Send for VarLenUnicode {}
-// Safety: No interior mutability or potential for data races.
+// Safety: `VarLenUnicode` has no interior mutability
 unsafe impl Sync for VarLenUnicode {}
 
 // ================================================================================