memcpy in rust

Cargo.toml

[package]
name = "memcpy"
version = "0.1.0"
authors = ["Keishi Kawada <megumish@exploitouri.st>"]
edition = "2018"

[dependencies]
failure = "0.1.3"

main.rs

fn memcpy(input: &[u8], output: &mut [u8], size: usize) -> Result<(), failure::Error> {
    if output.len() > size {
        return Err(failure::err_msg("Too Big"));
    }
    let mut i = 0;
    for x in input[0..size].iter() {
        output[i] = *x;
        i += 1;
    }
    Ok(())
}

fn main() -> Result<(), failure::Error>{
    let u = [1; 10];
    let mut v = [0; 10];
    memcpy(&u, &mut v, 10)?;
    println!("{:?}", v);
    Ok(())
}