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vec: Use Vec::extend specializations in extend_from_slice and more

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The new Vec::extend covers the duties of .extend_from_slice() and some
previous specializations.
This commit is contained in:
Ulrik Sverdrup 2016-10-21 13:51:31 +02:00
parent a3cab90fda
commit 622f24f6d9
1 changed files with 2 additions and 38 deletions
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40
src/libcollections/vec.rs
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@ -1212,26 +1212,7 @@ impl<T: Clone> Vec<T> {
/// ```
#[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
pub fn extend_from_slice(&mut self, other: &[T]) {
self.reserve(other.len());
// Unsafe code so this can be optimised to a memcpy (or something
// similarly fast) when T is Copy. LLVM is easily confused, so any
// extra operations during the loop can prevent this optimisation.
unsafe {
let len = self.len();
let ptr = self.get_unchecked_mut(len) as *mut T;
// Use SetLenOnDrop to work around bug where compiler
// may not realize the store through `ptr` trough self.set_len()
// don't alias.
let mut local_len = SetLenOnDrop::new(&mut self.len);
for i in 0..other.len() {
ptr::write(ptr.offset(i as isize), other.get_unchecked(i).clone());
local_len.increment_len(1);
}
// len set by scope guard
}
self.extend(other.iter().cloned())
}
}
@ -1640,24 +1621,7 @@ impl<T> Vec<T> {
#[stable(feature = "extend_ref", since = "1.2.0")]
impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
<I as SpecExtendVec<T>>::extend_vec(iter, self);
}
}
// helper trait for specialization of Vec's Extend impl
trait SpecExtendVec<T> {
fn extend_vec(self, vec: &mut Vec<T>);
}
impl <'a, T: 'a + Copy, I: IntoIterator<Item=&'a T>> SpecExtendVec<T> for I {
default fn extend_vec(self, vec: &mut Vec<T>) {
vec.extend(self.into_iter().cloned());
}
}
impl<'a, T: Copy> SpecExtendVec<T> for &'a [T] {
fn extend_vec(self, vec: &mut Vec<T>) {
vec.extend_from_slice(self);
self.extend(iter.into_iter().map(|&x| x))
}
}