Function reverse_impl

datafusion/functions/src/unicode/reverse.rs:122–155

(
    string_array: &StringArrType,
    mut array_builder: B,
)

}

fn reverse_impl<'a, StringArrType, B>(
    string_array: &StringArrType,
    mut array_builder: B,
) -> Result<ArrayRef>
where
    StringArrType: StringArrayType<'a>,
    B: BulkNullStringArrayBuilder,
{
    let item_len = string_array.len();
    // Null-preserving: reuse the input null buffer as the output null buffer.
    let nulls = string_array.nulls().cloned();
    let mut string_buf = String::new();
    let mut byte_buf = Vec::<u8>::new();

    if let Some(ref n) = nulls {
        for i in 0..item_len {
            if n.is_null(i) {
                array_builder.append_placeholder();
            } else {
                // SAFETY: `n.is_null(i)` was false in the branch above.
                let s = unsafe { string_array.value_unchecked(i) };
                append_reversed(s, &mut array_builder, &mut byte_buf, &mut string_buf);
            }
        }
    } else {
        for i in 0..item_len {
            // SAFETY: no null buffer means every index is valid.
            let s = unsafe { string_array.value_unchecked(i) };
            append_reversed(s, &mut array_builder, &mut byte_buf, &mut string_buf);
        }
    }

    array_builder.finish(nulls)
}

#[inline]
fn append_reversed<B: BulkNullStringArrayBuilder>(