Rust Unsafe Code — Unsafe Blocks, Raw Pointers, and FFI with C Code

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

// Raw pointers
fn raw_pointer_example() {
    let x = 42;
    let raw_ptr: *const i32 = &x as *const i32;

    unsafe {
        println!("Raw pointer value: {}", *raw_ptr);
    }

    let mut y = 10;
    let raw_mut: *mut i32 = &mut y as *mut i32;
    unsafe {
        *raw_mut = 20;
    }
    println!("Modified: {}", y);
}

// FFI with C
extern "C" {
    fn strlen(s: *const c_char) -> usize;
    fn puts(s: *const c_char) -> i32;
}

fn ffi_example() {
    let rust_string = "Hello from Rust!";
    let c_string = CString::new(rust_string).unwrap();

    unsafe {
        let len = strlen(c_string.as_ptr());
        println!("C string length: {}", len);
        puts(c_string.as_ptr());
    }
}

// Unsafe function
unsafe fn dangerous() {
    println!("This is unsafe!");
}

fn main() {
    unsafe {
        dangerous();
    }

    raw_pointer_example();
    // ffi_example(); // Needs linking with libc
}