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Use ManuallyDrop instead of mem::forget #675

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merged 3 commits into from
Mar 14, 2024
Merged

Use ManuallyDrop instead of mem::forget #675

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92bf9d4
use ManuallyDrop in BytesMut#freeze
braddunbar Mar 2, 2024
cad19a6
use ManuallyDrop in BytesMut#from_vec
braddunbar Mar 2, 2024
7bf4afd
use ManuallyDrop in Vec::from(bytes_mut)
braddunbar Mar 2, 2024
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26 changes: 12 additions & 14 deletions src/bytes_mut.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -244,23 +244,22 @@ impl BytesMut {
/// ```
#[inline]
pub fn freeze(self) -> Bytes {
if self.kind() == KIND_VEC {
let bytes = ManuallyDrop::new(self);
if bytes.kind() == KIND_VEC {
// Just re-use `Bytes` internal Vec vtable
unsafe {
let off = self.get_vec_pos();
let vec = rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off);
mem::forget(self);
let off = bytes.get_vec_pos();
let vec = rebuild_vec(bytes.ptr.as_ptr(), bytes.len, bytes.cap, off);
let mut b: Bytes = vec.into();
b.advance(off);
b
}
} else {
debug_assert_eq!(self.kind(), KIND_ARC);
debug_assert_eq!(bytes.kind(), KIND_ARC);

let ptr = self.ptr.as_ptr();
let len = self.len;
let data = AtomicPtr::new(self.data.cast());
mem::forget(self);
let ptr = bytes.ptr.as_ptr();
let len = bytes.len;
let data = AtomicPtr::new(bytes.data.cast());
unsafe { Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE) }
}
}
Expand Down Expand Up @@ -829,11 +828,11 @@ impl BytesMut {
// internal change could make a simple pattern (`BytesMut::from(vec)`)
// suddenly a lot more expensive.
#[inline]
pub(crate) fn from_vec(mut vec: Vec<u8>) -> BytesMut {
pub(crate) fn from_vec(vec: Vec<u8>) -> BytesMut {
let mut vec = ManuallyDrop::new(vec);
let ptr = vptr(vec.as_mut_ptr());
let len = vec.len();
let cap = vec.capacity();
mem::forget(vec);

let original_capacity_repr = original_capacity_to_repr(cap);
let data = (original_capacity_repr << ORIGINAL_CAPACITY_OFFSET) | KIND_VEC;
Expand Down Expand Up @@ -1618,6 +1617,7 @@ impl PartialEq<Bytes> for BytesMut {
impl From<BytesMut> for Vec<u8> {
fn from(bytes: BytesMut) -> Self {
let kind = bytes.kind();
let bytes = ManuallyDrop::new(bytes);

let mut vec = if kind == KIND_VEC {
unsafe {
Expand All @@ -1634,7 +1634,7 @@ impl From<BytesMut> for Vec<u8> {

vec
} else {
return bytes.deref().to_vec();
return ManuallyDrop::into_inner(bytes).deref().to_vec();
}
};

Expand All @@ -1645,8 +1645,6 @@ impl From<BytesMut> for Vec<u8> {
vec.set_len(len);
}

mem::forget(bytes);

vec
}
}
Expand Down