Ownership and Borrowing

Prefer borrowing over ownership:

// Good - borrows
pub fn process(data: &[u8]) -> Vec<u8> { ... }

// Avoid - takes ownership unnecessarily
pub fn process(data: Vec<u8>) -> Vec<u8> { ... }

Use Cow for flexible string handling:

use std::borrow::Cow;

pub fn normalize(s: &str) -> Cow<'_, str> {
    if s.contains(' ') {
        Cow::Owned(s.replace(' ', "_"))
    } else {
        Cow::Borrowed(s)
    }
}