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new 7f37a7f Mutablebuffer::shrink_to_fit (#318)
7f37a7f is described below
commit 7f37a7f2a119dd83c497766265707a64d9b82307
Author: Ritchie Vink <[email protected]>
AuthorDate: Wed May 19 15:37:57 2021 +0200
Mutablebuffer::shrink_to_fit (#318)
* Mutablebuffer::shrink_to_fit
* add shrink_to_fit explicit test
---
arrow/src/buffer/mutable.rs | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/arrow/src/buffer/mutable.rs b/arrow/src/buffer/mutable.rs
index d7fd5b9..35b123d 100644
--- a/arrow/src/buffer/mutable.rs
+++ b/arrow/src/buffer/mutable.rs
@@ -176,6 +176,37 @@ impl MutableBuffer {
self.len = new_len;
}
+ /// Shrinks the capacity of the buffer as much as possible.
+ /// The new capacity will aligned to the nearest 64 bit alignment.
+ ///
+ /// # Example
+ /// ```
+ /// # use arrow::buffer::{Buffer, MutableBuffer};
+ /// // 2 cache lines
+ /// let mut buffer = MutableBuffer::new(128);
+ /// assert_eq!(buffer.capacity(), 128);
+ /// buffer.push(1);
+ /// buffer.push(2);
+ ///
+ /// buffer.shrink_to_fit();
+ /// assert!(buffer.capacity() >= 64 && buffer.capacity() < 128);
+ /// ```
+ pub fn shrink_to_fit(&mut self) {
+ let new_capacity = bit_util::round_upto_multiple_of_64(self.len);
+ if new_capacity < self.capacity {
+ // JUSTIFICATION
+ // Benefit
+ // necessity
+ // Soundness
+ // `self.data` is valid for `self.capacity`.
+ let ptr =
+ unsafe { alloc::reallocate(self.data, self.capacity,
new_capacity) };
+
+ self.data = ptr;
+ self.capacity = new_capacity;
+ }
+ }
+
/// Returns whether this buffer is empty or not.
#[inline]
pub const fn is_empty(&self) -> bool {
@@ -746,4 +777,15 @@ mod tests {
buf2.reserve(65);
assert!(buf != buf2);
}
+
+ #[test]
+ fn test_mutable_shrink_to_fit() {
+ let mut buffer = MutableBuffer::new(128);
+ assert_eq!(buffer.capacity(), 128);
+ buffer.push(1);
+ buffer.push(2);
+
+ buffer.shrink_to_fit();
+ assert!(buffer.capacity() >= 64 && buffer.capacity() < 128);
+ }
}
