reduce heap allocation with mem::take

main.rs

// ref: https://ferrous-systems.com/blog/rustls-borrow-checker-p1/
#[derive(Debug)]
struct Reader<'a> {
    buffer: &'a mut [u8]
}
impl<'a> Reader<'a> {
    pub fn new(buffer: &'a mut [u8]) -> Self {
        Self {
            buffer,
        }
    }
    fn take<'s>(&'s mut self, length: usize) -> Option<&'a mut [u8]> {
        if self.buffer.len() < length {
            return None;
        }
        
        let buffer = std::mem::take(&mut self.buffer);
        
        let (taken, rest) = buffer.split_at_mut(length);
        
        self.buffer = rest;
        
        Some(taken)
    }
}
fn main() {
    let mut buffer = [0, 1, 2, 3, 4];
    let mut reader = Reader::new(&mut buffer);
    let first = reader.take(2);
    
    dbg!(&first);
    let second = reader.take(1);
    dbg!(second);
    drop(first);
    
    dbg!(reader);
}