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.
// lib.rs
#![feature(libc)]
#![feature(cstr_to_str)]
#![feature(cstr_memory)]
extern crate libc;
use std::ffi::{CStr,CString};
#[no_mangle]
pub extern fn concat(s1: *const libc::c_char, s2: *const libc::c_char) -> *const libc::c_char {
let s1_cstr = unsafe { CStr::from_ptr(s1) }; // &std::ffi::c_str::CStr
let s2_cstr = unsafe { CStr::from_ptr(s2) }; // &std::ffi::c_str::CStr
let s1_and_str = s1_cstr.to_str().unwrap(); // &str
let s2_and_str = s2_cstr.to_str().unwrap(); // &str
let mut s1_string = s1_and_str.to_string(); // collections::string::String
s1_string.push_str(s2_and_str);
// s1_string + s2_and_str); // same thing
let concated_string = CString::new(s1_string).unwrap(); // std::ffi::c_str::CString
concated_string.into_ptr() // const i8
}
# rust.rb
require 'ffi'
module Rust
extend FFI::Library
ffi_lib './bin/libembed.dylib'
attach_function :concat, [:string, :string], :string
end
#calling the function in Ruby
Rust.concat('This is a ', 'cohesive sentence') # => 'This is a cohesive sentence'
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With