Jefffrey commented on code in PR #10438:
URL: https://github.com/apache/arrow-rs/pull/10438#discussion_r3809189439
##########
arrow-buffer/src/buffer/boolean.rs:
##########
@@ -610,6 +610,53 @@ impl BooleanBuffer {
}
}
+ /// Try to convert self into a [`BooleanBufferBuilder`] without copying.
+ ///
+ /// Reuses the underlying [`Buffer`] allocation if
+ /// 1. it is not shared (no other references to it exist) and
+ /// 2. the bit offset is zero
+ ///
+ /// Returns `Err(self)` if the allocation cannot be reused.
+ ///
+ /// # Example
+ /// ```
+ /// # use arrow_buffer::BooleanBuffer;
+ /// let buffer = BooleanBuffer::from(vec![true, false, true]);
+ /// // The buffer is not shared, so the builder reuses its allocation
+ /// let mut builder = buffer.try_into_builder().expect("buffer was not
shared");
+ /// builder.append(false);
+ /// assert_eq!(builder.finish(), BooleanBuffer::from(vec![true, false,
true, false]));
+ ///
+ /// // Conversion fails if the buffer is shared
+ /// let buffer = BooleanBuffer::from(vec![true, false, true]);
+ /// let shared = buffer.clone();
+ /// let buffer = buffer.try_into_builder().expect_err("buffer was shared");
+ /// # assert_eq!(buffer, shared);
+ /// ```
+ pub fn try_into_builder(self) -> Result<BooleanBufferBuilder, Self> {
Review Comment:
do we still want this new method?
##########
arrow-array/src/array/boolean_array.rs:
##########
@@ -607,10 +607,35 @@ impl BooleanArray {
return self;
};
- let mut builder = BooleanBufferBuilder::new(len);
- builder.append_buffer(&self.values.slice(0, end));
- builder.append_n(len - end, false);
- BooleanArray::new(builder.finish(), self.nulls)
+ let bit_offset = self.values.offset();
+ let inner_buf = self.values.into_inner();
+
+ match inner_buf.into_mutable() {
Review Comment:
only concern now is if our existing unit tests cover both these paths
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