[GitHub] [arrow] Dandandan commented on a change in pull request #9076: [Rust] Fixed performance issue in mutableBuffer.

[GitBox <gi...@apache.org>]

Dandandan commented on a change in pull request #9076:
URL: https://github.com/apache/arrow/pull/9076#discussion_r550881085



##########
File path: rust/arrow/src/buffer.rs
##########
@@ -44,18 +44,35 @@ use crate::util::bit_util::ceil;
 #[cfg(any(feature = "simd", feature = "avx512"))]
 use std::borrow::BorrowMut;
 
-/// Buffer is a contiguous memory region of fixed size and is aligned at a 64-byte
-/// boundary. Buffer is immutable.
+/// Buffer represents a contiguous memory region that can be shared with other buffers and across
+/// thread boundaries.
 #[derive(Clone, PartialEq, Debug)]
 pub struct Buffer {
-    /// Reference-counted pointer to the internal byte buffer.
+    /// the internal byte buffer.
     data: Arc<Bytes>,
 
     /// The offset into the buffer.
     offset: usize,
 }
 
 impl Buffer {
+    /// Initializes a [Buffer] from a slice of items.
+    pub fn from_slice_ref<U: ArrowNativeType, T: AsRef<[U]>>(items: &T) -> Self {
+        // allocate aligned memory buffer
+        let slice = items.as_ref();
+        let len = slice.len() * std::mem::size_of::<U>();
+        let capacity = bit_util::round_upto_multiple_of_64(len);
+        let buffer = memory::allocate_aligned(capacity);
+        unsafe {

Review comment:
       Maybe document a justification for the unsafe here? :) 




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