Add Global deallocation variant (#3516)

arrow-buffer/src/alloc/mod.rs

@@ -135,20 +135,26 @@ pub(crate) enum Deallocation {
     /// An allocation of the given capacity that needs to be deallocated using arrows's cache aligned allocator.
     /// See [allocate_aligned] and [free_aligned].
     Arrow(usize),
-    /// An allocation from an external source like the FFI interface or a Rust Vec.
-    /// Deallocation will happen
+    /// An allocation using the system's default global allocator and the provided layout
+    #[allow(unused)]
+    Global(Layout),
+    /// An allocation from an external source like the FFI interface
+    /// Deallocation should happen when `Allocation` is dropped
     Custom(Arc<dyn Allocation>),
 }
 
 impl Debug for Deallocation {
     fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
         match self {
             Deallocation::Arrow(capacity) => {
-                write!(f, "Deallocation::Arrow {{ capacity: {} }}", capacity)
+                write!(f, "Deallocation::Arrow {{ capacity: {capacity} }}")
             }
             Deallocation::Custom(_) => {
                 write!(f, "Deallocation::Custom {{ capacity: unknown }}")
             }
+            Deallocation::Global(layout) => {
+                write!(f, "Deallocation::Global {{ alignment: {layout:?} }}")
+            }
         }
     }
 }

arrow-buffer/src/bytes.rs

@@ -94,6 +94,7 @@ impl Bytes {
     pub fn capacity(&self) -> usize {
         match self.deallocation {
             Deallocation::Arrow(capacity) => capacity,
+            Deallocation::Global(l) => l.size(),
             // we cannot determine this in general,
             // and thus we state that this is externally-owned memory
             Deallocation::Custom(_) => 0,
@@ -118,6 +119,9 @@ impl Drop for Bytes {
             Deallocation::Arrow(capacity) => {
                 unsafe { alloc::free_aligned(self.ptr, *capacity) };
             }
+            Deallocation::Global(layout) => {
+                unsafe { std::alloc::dealloc(self.ptr.as_ptr(), *layout) };
+            }
             // The automatic drop implementation will free the memory once the reference count reaches zero
             Deallocation::Custom(_allocation) => (),
         }