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use crate::alloc::Allocator;
use core::iter::TrustedLen;
use core::ptr::{self};
use core::slice::{self};
use super::{IntoIter, SetLenOnDrop, Vec};
pub(super) trait SpecExtend<T, I> {
fn spec_extend(&mut self, iter: I);
}
impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
where
I: Iterator<Item = T>,
{
default fn spec_extend(&mut self, iter: I) {
self.extend_desugared(iter)
}
}
impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
where
I: TrustedLen<Item = T>,
{
default fn spec_extend(&mut self, iterator: I) {
let (low, high) = iterator.size_hint();
if let Some(additional) = high {
debug_assert_eq!(
low,
additional,
"TrustedLen iterator's size hint is not exact: {:?}",
(low, high)
);
self.reserve(additional);
unsafe {
let mut ptr = self.as_mut_ptr().add(self.len());
let mut local_len = SetLenOnDrop::new(&mut self.len);
iterator.for_each(move |element| {
ptr::write(ptr, element);
ptr = ptr.offset(1);
local_len.increment_len(1);
});
}
} else {
panic!("capacity overflow");
}
}
}
impl<T, A: Allocator> SpecExtend<T, IntoIter<T>> for Vec<T, A> {
fn spec_extend(&mut self, mut iterator: IntoIter<T>) {
unsafe {
self.append_elements(iterator.as_slice() as _);
}
iterator.ptr = iterator.end;
}
}
impl<'a, T: 'a, I, A: Allocator + 'a> SpecExtend<&'a T, I> for Vec<T, A>
where
I: Iterator<Item = &'a T>,
T: Clone,
{
default fn spec_extend(&mut self, iterator: I) {
self.spec_extend(iterator.cloned())
}
}
impl<'a, T: 'a, A: Allocator + 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T, A>
where
T: Copy,
{
fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
let slice = iterator.as_slice();
unsafe { self.append_elements(slice) };
}
}