Rust и FFI: вызов C-библиотек

1// Объявление внешней функции
2extern "C" {
3    fn strlen(s: *const std::ffi::c_char) -> usize;
4}
5
6fn main() {
7    let c_str = std::ffi::CString::new("hello").unwrap();
8
9    unsafe {
10        let len = strlen(c_str.as_ptr());
11        println!("Length: {}", len);
12    }
13}

1use std::ffi::{CStr, CString};
2use std::os::raw::c_char;
3
4// Внешняя функция
5extern "C" {
6    fn strlen(s: *const c_char) -> usize;
7}
8
9// Безопасная обёртка
10fn safe_strlen(s: &str) -> usize {
11    let c_str = CString::new(s).expect("CString::new failed");
12
13    unsafe { strlen(c_str.as_ptr()) }
14}
15
16fn main() {
17    let len = safe_strlen("hello");
18    println!("Length: {}", len);
19}

1cargo install bindgen-cli

1bindgen input.h -o bindings.rs

1fn main() {
2    println!("cargo:rerun-if-changed=wrapper.h");
3
4    let bindings = bindgen::Builder::default()
5        .header("wrapper.h")
6        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
7        .generate()
8        .expect("Unable to generate bindings");
9
10    let out_path = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
11    bindings
12        .write_to_file(out_path.join("bindings.rs"))
13        .unwrap();
14}

1use std::ffi::CString;
2use std::os::raw::c_char;
3
4fn main() {
5    let c_str = CString::new("Hello, world!").unwrap();
6
7    unsafe {
8        libc::printf(c_str.as_ptr() as *const c_char);
9    }
10}

1use rusqlite::{Connection, Result};
2
3fn main() -> Result<()> {
4    let conn = Connection::open("my_database.db")?;
5
6    conn.execute(
7        "CREATE TABLE IF NOT EXISTS users (
8            id INTEGER PRIMARY KEY,
9            name TEXT NOT NULL
10        )",
11        (),
12    )?;
13
14    conn.execute(
15        "INSERT INTO users (name) VALUES (?1)",
16        ["Alice"],
17    )?;
18
19    let mut stmt = conn.prepare("SELECT id, name FROM users")?;
20    let users = stmt.query_map([], |row| {
21        Ok((row.get(0)?, row.get(1)?))
22    })?;
23
24    for user in users {
25        println!("User: {:?}", user?);
26    }
27
28    Ok(())
29}

1// 1. Вызов FFI функций
2unsafe { strlen(ptr) }
3
4// 2. Разыменование raw pointer
5let x = 5;
6let r = &x as *const i32;
7unsafe { println!("{}", *r); }
8
9// 3. Доступ к mutable static
10static mut COUNTER: u32 = 0;
11
12unsafe {
13    COUNTER += 1;
14    println!("{}", COUNTER);
15}
16
17// 4. Реализация unsafe trait
18unsafe trait Foo {
19    fn foo(&self);
20}
21
22// 5. Доступ к полям union
23union MyUnion {
24    i: i32,
25    f: f32,
26}

1// unsafe не отключает проверкуborrow checker
2// unsafe позволяет:
3// - Разыменовывать raw pointers
4// - Вызывать unsafe функции
5// - Доступ к mutable static
6// - Реализовывать unsafe traits
7
8// Каждый unsafe блок должен иметь комментарий
9unsafe {
10    // SAFETY: pointer is valid and aligned
11    *ptr = 5;
12}

1// build.rs
2fn main() {
3    let dst = cmake::build_new("my_c_lib");
4
5    println!("cargo:rustc-link-search=native={}/lib", dst.display());
6    println!("cargo:rustc-link-lib=static=my_c_lib");
7    println!("cargo:rustc-link-lib=dylib=stdc++");
8}

1use openssl::ssl::{SslMethod, SslConnector};
2use std::net::TcpStream;
3
4fn main() {
5    let connector = SslConnector::new(SslMethod::tls()).unwrap();
6
7    let stream = TcpStream::connect("example.com:443").unwrap();
8    let mut stream = connector.connect("example.com", stream).unwrap();
9
10    use std::io::Write;
11    stream.write_all(b"GET / HTTP/1.1
12Host: example.com
13
14").unwrap();
15
16    use std::io::Read;
17    let mut response = String::new();
18    stream.read_to_string(&mut response).unwrap();
19    println!("{}", response);
20}

1#[cfg(test)]
2mod tests {
3    use super::*;
4
5    #[test]
6    fn test_safe_strlen() {
7        assert_eq!(safe_strlen(""), 0);
8        assert_eq!(safe_strlen("hello"), 5);
9        assert_eq!(safe_strlen("rust"), 4);
10    }
11}

1// Всегда проверяйте указатели
2unsafe {
3    if ptr.is_null() {
4        return Err(Error::NullPointer);
5    }
6    // Используйте ptr::read/write вместо *ptr
7    let value = ptr::read(ptr);
8}