Fix: Fix buffer ownership for mmap

Author: pbower

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "minarrow"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2024"
 authors = ['Peter G. Bower']
 build = "build.rs"

Cargo.toml

@@ -170,6 +170,17 @@ impl Bitmask {
         !self.all_set()
     }
 
+    /// Creates an owned copy of the bitmask.
+    /// Always creates a fresh owned copy, even if already owned.
+    #[inline]
+    pub fn to_owned_copy(&self) -> Self {
+        let owned_bits = self.bits.to_owned_copy();
+        Bitmask {
+            bits: owned_bits,
+            len: self.len,
+        }
+    }
+
     /// Returns bit *idx*.  
     /// - If `idx ≥ self.len` but still inside the physical buffer, returns `false`.  
     /// Panics only when `idx` exceeds the physical capacity.
@@ -720,6 +731,7 @@ impl Display for Bitmask {
     }
 }
 
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/structs/bitmask.rs

@@ -358,6 +358,19 @@ impl<T> Buffer<T> {
     pub fn is_shared(&self) -> bool {
         matches!(self.storage, Storage::Shared { .. })
     }
+
+    /// Creates an owned copy of the buffer data.
+    /// If the buffer is already owned, this clones the data.
+    /// If the buffer is shared, this copies the data into a new owned Vec64.
+    #[inline]
+    pub fn to_owned_copy(&self) -> Self
+    where
+        T: Clone,
+    {
+        // Always create a fresh owned copy
+        let vec: Vec64<T> = self.as_ref().iter().cloned().collect();
+        Buffer::from_vec64(vec)
+    }
 }
 
 impl<T: Clone> Buffer<T> {
@@ -593,6 +606,7 @@ impl<T: Display> Display for Buffer<T> {
     }
 }
 
+
 // SAFETY: Shared buffers are read-only and `Arc` ensures memory is valid.
 // `Owned` is already `Send + Sync` via `Vec64<T>`.
 unsafe impl<T: Sync> Sync for Buffer<T> {}