opaque-pointer 0.8.6

Generic functions to work with opaque pointers when use FFI to expose Rust structs
Documentation 
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use opaque_pointer;

#[derive(Debug)]
struct TestIt {
    value: u8,
}

impl TestIt {
    pub fn new(value: u8) -> Self {
        Self { value }
    }
    pub fn add(&mut self, value: u8) {
        self.value += value;
    }
    pub fn get(&self) -> u8 {
        self.value
    }
}

#[test]
fn own_back() {
    let pointer = opaque_pointer::raw(TestIt::new(2));
    let test_it = unsafe { opaque_pointer::own_back(pointer).unwrap() };
    assert_eq!(test_it.get(), 2);
}

#[cfg(all(feature = "std", feature = "lender"))]
#[test]
fn own_back_invalid_pointer() {
    let pointer = Box::into_raw(Box::new(TestIt::new(2)));
    let invalid_pointer_error = unsafe { opaque_pointer::own_back(pointer).unwrap_err() };
    assert_eq!(
        invalid_pointer_error,
        opaque_pointer::error::PointerError::Invalid
    );
}

#[test]
fn immutable_reference() {
    let pointer = opaque_pointer::raw(TestIt::new(2));
    let object = unsafe { opaque_pointer::object(pointer).unwrap() };
    assert_eq!(object.get(), 2);
    unsafe { opaque_pointer::own_back(pointer).unwrap() };
}

#[test]
fn mutable_reference() {
    let pointer = opaque_pointer::raw(TestIt::new(2));
    let object = unsafe { opaque_pointer::mut_object(pointer).unwrap() };
    object.add(3);
    assert_eq!(object.get(), 5);
    unsafe { opaque_pointer::own_back(pointer).unwrap() };
}