tustvold commented on code in PR #3115:
URL: https://github.com/apache/arrow-rs/pull/3115#discussion_r1023450806
##########
arrow-array/src/array/primitive_array.rs:
##########
@@ -397,6 +397,61 @@ impl<T: ArrowPrimitiveType> PrimitiveArray<T> {
unsafe { build_primitive_array(len, buffer, null_count, null_buffer) }
}
+ /// Applies an unary and infallible function to a mutable primitive array.
+ /// Mutable primitive array means that the buffer is not shared with other
arrays.
+ /// As a result, this mutates the buffer directly without allocating new
buffer.
+ ///
+ /// # Implementation
+ ///
+ /// This will apply the function for all values, including those on null
slots.
+ /// This implies that the operation must be infallible for any value of
the corresponding type
+ /// or this function may panic.
+ /// # Example
+ /// ```rust
+ /// # use arrow_array::{Int32Array, types::Int32Type};
+ /// # fn main() {
+ /// let array = Int32Array::from(vec![Some(5), Some(7), None]);
+ /// let c = array.unary_mut(|x| x * 2 + 1).unwrap();
+ /// assert_eq!(c, Int32Array::from(vec![Some(11), Some(15), None]));
+ /// # }
+ /// ```
+ pub fn unary_mut<F>(self, op: F) -> Result<PrimitiveArray<T>,
PrimitiveArray<T>>
+ where
+ F: Fn(T::Native) -> T::Native,
+ {
+ let data = self.data();
+ let len = self.len();
+ let null_count = self.null_count();
+ let null_buffer = data.null_buffer().map(|b|
b.bit_slice(data.offset(), len));
+
+ let buffer = self.data.buffers()[0].clone();
Review Comment:
I think we need call `slice_with_length` to apply the offset, something like
```
let element_len = std::mem::size_of::<T::Native>();
let buffer = self.data.buffers()[0].slice_with_length(data.offset() *
element_len, len * element_len)
```
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