emilk commented on code in PR #6790:
URL: https://github.com/apache/arrow-rs/pull/6790#discussion_r1859090032
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arrow-buffer/src/buffer/immutable.rs:
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@@ -576,30 +591,30 @@ mod tests {
#[test]
fn test_shrink_to_fit() {
- let original = Buffer::from(&[1, 2, 3, 4, 5, 6, 7]);
- assert_eq!(original.len(), 7);
+ let original = Buffer::from(&[0, 1, 2, 3, 4, 5, 6, 7]);
+ assert_eq!(original.as_slice(), &[0, 1, 2, 3, 4, 5, 6, 7]);
assert_eq!(original.capacity(), 64);
- let slice = original.slice(3);
+ let slice = original.slice_with_length(2, 3);
drop(original); // Make sure the buffer isn't shared (or shrink_to_fit
won't work)
- assert_eq!(slice.len(), 4);
+ assert_eq!(slice.as_slice(), &[2, 3, 4]);
assert_eq!(slice.capacity(), 64);
let mut shrunk = slice;
shrunk.shrink_to_fit();
- assert_eq!(shrunk.len(), 4);
- assert_eq!(shrunk.capacity(), 4);
+ assert_eq!(shrunk.as_slice(), &[2, 3, 4]);
+ assert_eq!(shrunk.capacity(), 5); // shrink_to_fit is allowed to keep
the elements before the offset
// Test that we can handle empty slices:
- let empty_slice = shrunk.slice(4);
+ let empty_slice = shrunk.slice_with_length(1, 0);
drop(shrunk); // Make sure the buffer isn't shared (or shrink_to_fit
won't work)
- assert_eq!(empty_slice.len(), 0);
- assert_eq!(empty_slice.capacity(), 4);
+ assert_eq!(empty_slice.as_slice(), &[]);
+ assert_eq!(empty_slice.capacity(), 5);
let mut shrunk_empty = empty_slice;
shrunk_empty.shrink_to_fit();
- assert_eq!(shrunk_empty.len(), 0);
- assert_eq!(shrunk_empty.capacity(), 1); // `Buffer` and `Bytes`
doesn't support 0-capacity, so we shrink to 1
+ assert_eq!(shrunk_empty.as_slice(), &[]);
+ assert_eq!(shrunk_empty.capacity(), 1); // NOTE: `Buffer` and `Bytes`
doesn't support 0-capacity
Review Comment:
For `MutableBuffer` there is special handling for the size=0 case, with a
[`dangling_ptr`](https://github.com/rerun-io/arrow-rs/blob/3b7cdebbe306b1e58f9ecfb4ce3b7a1b635a5d07/arrow-buffer/src/buffer/mutable.rs#L471-L472)
helper. We could copy all that logic to `Bytes`, but I rather not add all that
complexity in this PR.
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