build_and_execute.sh

rustc --crate-type=staticlib jexl_evaluator.rs
g++ main.cpp -L. -ljexl_evaluator -o main
./main

jexl_evaluator.rs

// jexl_evaluator.rs

use std::ffi::{CString, CStr};
use std::os::raw::c_char;

#[no_mangle]
pub extern "C" fn evaluate_jexl(exp: *const c_char, ctx: *const c_char) -> *mut c_char {
    // Convert C string to Rust strings
    let c_exp = unsafe { CStr::from_ptr(exp) };
    let c_ctx = unsafe { CStr::from_ptr(ctx) };

    let exp = c_exp.to_str().unwrap();
    let ctx = c_ctx.to_str().unwrap();

    // Concatenate them
    let result = format!("Expression: {}, Context: {}", exp, ctx);

    // Convert the result to a C string and return it
    CString::new(result).unwrap().into_raw()
}

main.cpp

// main.cpp
#include <iostream>

extern "C" {
   char* evaluate_jexl(const char* exp, const char* ctx);
}

int main() {
    char* result = evaluate_jexl("x|uppercase", "{\"x\": \"holaaa\"}");
    printf("Result: %s\n", result);
    return 0;
}