use std::io::Read;

// Since I cannot implement additional methods, for the sake of this example
// I will use MyCString as it represents a CString.
#[derive(Debug)]
struct MyCString
{
    inner: Box<[u8]>,
}


impl MyCString
{
    /// Option 1: Add a new method to CString
    fn from_reader(mut reader: impl Read) -> Result<MyCString, std::io::Error>
    {
        let mut buffer = Vec::new();
        let mut character: u8 = 0;

        loop {

            let slice = std::slice::from_mut(&mut character);
            reader.read_exact(slice)?;

            // Check if a null character has been found, if so return the Vec as CString.
            if character == 0 {
                return Ok(unsafe { MyCString::from_vec_unchecked(buffer) });
            }

            // Push a new character.
            buffer.push(character);
        }
    }

    /// This method is already implemented by CString.
    pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> MyCString {
        v.reserve_exact(1);
        v.push(0);
        MyCString { inner: v.into_boxed_slice() }
    }
}

fn main() {

    let test = "Hello this is my world!\0";
    let string = MyCString::from_reader(test.as_bytes());
    println!("{:?}", string.unwrap());

    let test2 = "Hello this \0is my world!\0";
    let string2 = MyCString::from_reader(test2.as_bytes());
    println!("{:?}", string2.unwrap());

    let test3 = "Hello this is my world!";
    let result = MyCString::from_reader(test3.as_bytes());
    println!("{:?}", result);
}