I am trying to pass a string in Ruby to a rust executable, manipulate it and pass the manipulated string back.
So far I can pass the string in and return it but I am at a loss as to how to convert it into a rust string, manipulate it and then pass it back to ruby. Here is what I have so far:
// lib.rs
use std::ffi::CStr;
#[no_mangle]
pub extern fn return_string(test_str: &CStr) -> &CStr {
// working funciton
test_str
}
#[no_mangle]
pub extern fn manipulate_and_return_string(mystr: &CStr) -> &CStr {
// mystr type == &std::ffi::c_str::CStr
// println!("{:?}", mystr); => std::ffi::c_str::CStr` cannot be formatted using `:?`
let cstr = mystr.to_bytes_with_nul();
// println!("{:?}", mystr); => []
// cstr type == &[u8]
let ptr = cstr.as_ptr();
// ptr type == *const u8
// println!("{:?}", mystr); => 0x7fd898edb520
let str_slice: &str = std::str::from_utf8(cstr).unwrap();
// str type == &str
// println!("{:?}", mystr); => ""
let str_buf: String = str_slice.to_owned();
// str_bug == collections::string::String
// println!("{:?}", mystr); => ""
}
# rust.rb
require 'ffi'
module Rust
extend FFI::Library
ffi_lib './bin/libembed.dylib'
attach_function :return_string, [:string], :string
attach_function :manipulate_and_return_string, [:string], :string
end
Thanks to some guidance from Steve Klabnik, shepmaster and DK I figured out how to write a external string concat function in Rust and use it in Ruby.