How to get a '&str' from a NUL-terminated byte slice if the NUL terminator isn't at the end of the slice?

Question

While CStr is typically used for FFI, I am reading from a &[u8] which is NUL-terminated and is ensured to be valid UTF-8 so no checks are neede

Answer 1

This example finds the first NUL byte using a simple for loop, then uses Rust's standard library to return the slice as a &str (referencing the original data - zero copy).

There may well be a better way to find the first NUL byte using closures:

pub unsafe fn str_from_u8_nul_utf8_unchecked(utf8_src: &[u8]) -> &str {
    // does Rust have a built-in 'memchr' equivalent? 
    let mut nul_range_end = 1_usize;
    for b in utf8_src {
        if *b == 0 {
            break;
        }
        nul_range_end += 1;
    }
    return ::std::str::from_utf8_unchecked(&utf8_src[0..nul_range_end]);
}

---

While utf8_src.iter().position(|&c| c == b'\0').unwrap_or(utf8_src.len()); returns the first NUL byte (or the total length), Rust 1.15 does not optimize it into something like memchr, so a for loop might not be such a bad option for now.