Bytes: Add try_into_mut. #687
Conversation
Add try_into_mut that allows getting a BytesMut from an unique Bytes.
| /// ``` | ||
| pub fn try_into_mut(self) -> std::result::Result<BytesMut, Bytes> { | ||
| if self.is_unique() { | ||
| Ok(BytesMut::from_vec(self.into())) |
There was a problem hiding this comment.
Although this does avoid allocating a new vector, it can still result in a copy of the data when it's not stored at the beginning of the allocation. For example, this happens here:
Lines 996 to 997 in 4eb62b9
and here:
Lines 1127 to 1128 in 4eb62b9
Actually avoiding the copy will be a more involved change.
There was a problem hiding this comment.
This is probably unavoidable right? Or are the slices of bytes aware of their parents?
There was a problem hiding this comment.
The BytesMut type is also able to reference only part of the allocation. So, it's not unavoidable. (But it will be rather involved.)
There was a problem hiding this comment.
Ha I read the code and I understand, so essentially if the user did a slice, dropped the other references and then calls try_into_mut then it will shift left the data so it can fit into a Vec. But we don't really need this shift since the BytesMut could take the same pointer with the offset and length.
There was a problem hiding this comment.
Re-reading this, ptr::copy offers no guarantee that it won't copy even if ptr == buf (at least I could not find it). So we should treat it as if it was always copying (or add an if clause).
| /// let bytes = Bytes::from(b"hello".to_vec()); | ||
| /// assert_eq!(bytes.try_into_mut(), Ok(BytesMut::from(&b"hello"[..]))); | ||
| /// ``` | ||
| pub fn try_into_mut(self) -> std::result::Result<BytesMut, Bytes> { |
There was a problem hiding this comment.
This use of std fails in builds without the standard library.
| pub fn try_into_mut(self) -> std::result::Result<BytesMut, Bytes> { | |
| pub fn try_into_mut(self) -> Result<BytesMut, Bytes> { |
|
@Darksonn we can close this |
Add try_into_mut that allows getting a BytesMut from an unique Bytes.
Implements #611