[arrow-rs] branch master updated: MutableBuffer::typed_data - shared ref access to the typed slice (#2652)

[tustvold]

This is an automated email from the ASF dual-hosted git repository.

tustvold pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/arrow-rs.git


The following commit(s) were added to refs/heads/master by this push:
     new 43d847442 MutableBuffer::typed_data - shared ref access to the typed 
slice (#2652)
43d847442 is described below

commit 43d8474429227a267141ea49d9e2ee5df1bd9239
Author: Michael Edwards <medwa...@walledcity.ca>
AuthorDate: Mon Sep 5 17:46:56 2022 +0200

    MutableBuffer::typed_data - shared ref access to the typed slice (#2652)
---
 arrow/src/buffer/immutable.rs |  2 +-
 arrow/src/buffer/mutable.rs   | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/arrow/src/buffer/immutable.rs b/arrow/src/buffer/immutable.rs
index 28042a381..6d4d624ef 100644
--- a/arrow/src/buffer/immutable.rs
+++ b/arrow/src/buffer/immutable.rs
@@ -181,7 +181,7 @@ impl Buffer {
         unsafe { self.data.ptr().as_ptr().add(self.offset) }
     }
 
-    /// View buffer as typed slice.
+    /// View buffer as a slice of a specific type.
     ///
     /// # Panics
     ///
diff --git a/arrow/src/buffer/mutable.rs b/arrow/src/buffer/mutable.rs
index 96c837922..d1e633993 100644
--- a/arrow/src/buffer/mutable.rs
+++ b/arrow/src/buffer/mutable.rs
@@ -288,7 +288,7 @@ impl MutableBuffer {
         Buffer::from_bytes(bytes)
     }
 
-    /// View this buffer as a slice of a specific type.
+    /// View this buffer as a mutable slice of a specific type.
     ///
     /// # Panics
     ///
@@ -304,6 +304,21 @@ impl MutableBuffer {
         offsets
     }
 
+    /// View buffer as a immutable slice of a specific type.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if the underlying buffer is not aligned
+    /// correctly for type `T`.
+    pub fn typed_data<T: ArrowNativeType>(&self) -> &[T] {
+        // SAFETY
+        // ArrowNativeType is trivially transmutable, is sealed to prevent 
potentially incorrect
+        // implementation outside this crate, and this method checks alignment
+        let (prefix, offsets, suffix) = unsafe { 
self.as_slice().align_to::<T>() };
+        assert!(prefix.is_empty() && suffix.is_empty());
+        offsets
+    }
+
     /// Extends this buffer from a slice of items that can be represented in 
bytes, increasing its capacity if needed.
     /// # Example
     /// ```