Add ArrayVec::leak #235
Add ArrayVec::leak #235
Conversation
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Why do you want to leak the values? |
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My use case is a reusable buffer. The bytes are pushed into the buffer, and when the content is finalized it can be handed out as a &[u8]. The borrow checker makes sure that the buffer isn't re-used as long as a reference to the contents are live, and the old content will never be seen after the &[u8] ref is dropped. "leak()" isn't the best of names for the operation, as the memory isn't actually leaked, but it aligns with std :: Vec. The values will not be dropped however, so in that sense "leak()" is correct. |
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Names along the lines of take are also interesting then, but they don't convey the leaking (when it applies). You mentioned that Vec has Vec::leak, and that should be in the first PR description - that's usually a good enough argument for any new arrayvec method. Then it's easy for us to just adapt the same idea. |
| pub fn leak(&mut self) -> &mut [T] { | ||
| unsafe { | ||
| let s = slice::from_raw_parts_mut(self.as_mut_ptr(), self.len()); | ||
| self.set_len(0); |
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I would be more comfortable to swap the order of these two lines actually!
A. We create a borrow of the whole vec as a &mut [T]
B. We modify self (set_len)
This is better in the order of B, then A, so that it's clear we don't invalidate the borrow. Miri apparently didn't react on this though?
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no github actions run, don't immediately see why |
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I have swapped the order of creating the slice and setting the length to 0 now, as per your suggestion. An alternative name to leak might be "forget", but I would expect a return value from that method. "into_slice_and_forget" is a bit of a mouth-full. The old saying about cache invalidation and naming things still applies.. |
You can enable action runs for first-time contributors in the settings. |
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ok, changed to a more permissive setting |
Hello,
This pull request adds leak() to ArrayVec, which can be useful if you want to hand out a reference to the contained data, and at the same time want to be sure that the vec is empty when the reference is dropped. Especially useful for !Drop types.