Function insert_shared

src/borrow/shared.rs:121–172

(py: Python<'py>)

#[cold]
fn insert_shared<'py>(py: Python<'py>) -> PyResult<NonNull<Shared>> {
    let module = get_array_module(py)?;

    let capsule = match module.getattr("_RUST_NUMPY_BORROW_CHECKING_API") {
        Ok(capsule) => capsule.cast_into::<PyCapsule>()?,
        Err(_err) => {
            let flags: *mut BorrowFlags = Box::into_raw(Box::default());

            let shared = Shared {
                version: 1,
                flags: flags as *mut c_void,
                acquire: acquire_shared,
                acquire_mut: acquire_mut_shared,
                release: release_shared,
                release_mut: release_mut_shared,
            };

            let capsule = PyCapsule::new_with_value_and_destructor(
                py,
                shared,
                c"_RUST_NUMPY_BORROW_CHECKING_API",
                |shared, _ctx| {
                    // SAFETY: `shared.flags` was initialized using `Box::into_raw`.
                    let _ = unsafe { Box::from_raw(shared.flags as *mut BorrowFlags) };
                },
            )?;
            module.setattr("_RUST_NUMPY_BORROW_CHECKING_API", &capsule)?;
            capsule
        }
    };

    // SAFETY: All versions of the shared borrow checking API start with a version field.
    let version = unsafe {
        *capsule
            .pointer_checked(Some(c_str!("_RUST_NUMPY_BORROW_CHECKING_API")))?
            .cast::<u64>()
            .as_ptr() // FIXME(icxolu): use read on MSRV 1.80
    };
    if version < 1 {
        return Err(PyTypeError::new_err(format!(
            "Version {version} of borrow checking API is not supported by this version of rust-numpy"
        )));
    }

    let ptr = capsule.pointer_checked(Some(c_str!("_RUST_NUMPY_BORROW_CHECKING_API")))?;

    // Intentionally leak a reference to the capsule
    // so we can safely cache a pointer into its interior.
    forget(capsule);

    Ok(ptr.cast())
}

// These entry points will be used to access the shared borrow checking API from this extension: