Final ruby reverse string

a-rubyist-rusting-part-2-9.rs

#![feature(libc)]
#![feature(cstr_to_str)]
#![feature(cstr_memory)]
extern crate libc;
use std::ffi::{CStr, CString};
#[no_mangle]
pub extern fn ruby_reverse(s: *const libc::c_char) -> *const libc::c_char {
  let rust_cstr = unsafe { CStr::from_ptr(s) };     // &std::ffi::c_str::CStr
  let str = rust_cstr.to_str().unwrap();            // &str
  let string: String = str.chars().rev().collect(); // collections::string::String
  let cstring = CString::new(string).unwrap();      // std::ffi::c_str::CString
  cstring.into_ptr()                                // *const i8
}