Method extend

crates/common/src/boxvec.rs:539–570

(&mut self, iter: I)

/// occurs if there are more iterator elements.
impl<T> Extend<T> for BoxVec<T> {
    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
        let take = self.capacity() - self.len();
        unsafe {
            let len = self.len();
            let mut ptr = raw_ptr_add(self.as_mut_ptr(), len);
            let end_ptr = raw_ptr_add(ptr, take);
            // Keep the length in a separate variable, write it back on scope
            // exit. To help the compiler with alias analysis and stuff.
            // We update the length to handle panic in the iteration of the
            // user's iterator, without dropping any elements on the floor.
            let mut guard = ScopeExitGuard {
                value: &mut self.len,
                data: len,
                f: move |&len, self_len| {
                    **self_len = len;
                },
            };
            let mut iter = iter.into_iter();
            loop {
                if core::ptr::eq(ptr, end_ptr) {
                    break;
                }
                if let Some(elt) = iter.next() {
                    raw_ptr_write(ptr, elt);
                    ptr = raw_ptr_add(ptr, 1);
                    guard.data += 1;
                } else {
                    break;
                }
            }
        }
    }
}

/// Rawptr add but uses arithmetic distance for ZST