Rust example

test.rs

extern crate libc;

use std::ffi::CStr;

#[no_mangle]
pub extern fn testing(argc: i64, argv: *const *const libc::c_char) {
    let l = unsafe { array_len(argv) };
    println!("argc {}", argc);
    println!("len {}", l);
    let v = unsafe { array_to_vec(argv, l) };
    println!("The array {:?}", v);
}

unsafe fn array_len(mut ptr: *const *const libc::c_char) -> usize {
    let mut len = 0;

    if !ptr.is_null() {
        while !(*ptr).is_null() {
            len += 1;
            ptr = ptr.offset(1);
        }
    }
    len
}

unsafe fn array_to_vec(mut argv: *const *const libc::c_char, l: usize) -> Vec<String> {
    if l == 0 || argv.is_null() {
        return Vec::new();
    }

    let mut myvec: Vec<String> = Vec::with_capacity(l);
    while !(*argv).is_null() {
        myvec.push(pointer_to_string(*argv));
        argv = argv.offset(1);
    }
    myvec
}

unsafe fn pointer_to_string(s: *const libc::c_char) -> String {
    CStr::from_ptr(s).to_string_lossy().into_owned()
}