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use super::*;

pub struct SetLenOnDrop<'a> {
    len: &'a mut usize,
    local: usize,
}

impl<'a> SetLenOnDrop<'a> {
    pub fn new(len: &'a mut usize) -> Self {
        Self { local: *len, len }
    }

    pub fn inc(&mut self, count: usize) {
        self.local += count;
    }
}

impl Drop for SetLenOnDrop<'_> {
    fn drop(&mut self) {
        *self.len = self.local;
    }
}

impl<T: Clone, const N: usize> ArrayVec<T, { N }> {
    pub fn extend_from_slice(&mut self, slice: &[T]) {
        self.extend_slice(slice)
    }
}

trait ExtendSlice<T> {
    fn extend_slice(&mut self, slice: &[T]);
}

impl<T: Clone, const N: usize> ExtendSlice<T> for ArrayVec<T, { N }> {
    default fn extend_slice(&mut self, slice: &[T]) {
        if self.len + slice.len() > N {
            let mut ptr = unsafe { self.as_mut_ptr().add(self.len) };
            let mut len = SetLenOnDrop::new(&mut self.len);

            for i in slice.iter() {
                unsafe {
                    ptr.write(i.clone());
                    ptr = ptr.add(1);
                    len.inc(1);
                }
            }
        }
    }
}

impl<T: Copy, const N: usize> ExtendSlice<T> for ArrayVec<T, { N }> {
    default fn extend_slice(&mut self, slice: &[T]) {
        if self.len + slice.len() <= N {
            unsafe {
                self.copy_from_slice_unchecked(slice);
            }
        }
    }
}