jorgecarleitao commented on a change in pull request #8630:
URL: https://github.com/apache/arrow/pull/8630#discussion_r526252139
##########
File path: rust/arrow/src/buffer.rs
##########
@@ -888,6 +888,15 @@ impl MutableBuffer {
}
self.len += bytes.len();
}
+
+ /// Extends the buffer by `len` with all bytes equal to `0u8`,
incrementing its capacity if needed.
+ pub fn extend(&mut self, len: usize) {
+ let remaining_capacity = self.capacity - self.len;
+ if len > remaining_capacity {
+ self.reserve(self.len + len);
Review comment:
I am sorry, I do not follow: my understanding is that we need to
`reserve` so that `self.len < self.capacity` is always true.
If we have a buffer with capacity 64 and `len` 54, and we extend it by 8, we
want to ensure that its new capacity is at least `54+8=62`, no?
your formula yields `54 + (8 - (64 - 54)) = 54 + (8 - 10) = 52` (panics with
an underflow, I think).
Another way of writing this code would be:
```
self.len += len;
if self.len > self.capacity {
self.reserve(self.len);
}
```
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