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use core::{ffi::c_void, ptr::NonNull};
use objc2::{
msg_send,
rc::Retained,
runtime::{AnyObject, ProtocolObject},
};
use objc2_foundation::NSError;
use objc2_metal::{MTLDevice, MTLLibrary};
#[link(name = "System")] // libdispatch lives inside libSystem
extern "C" {
fn dispatch_data_create(
buffer: NonNull<c_void>,
size: usize,
queue: Option<NonNull<c_void>>, // dispatch_queue_t _Nullable
destructor: *mut c_void, // dispatch_block_t _Nullable
) -> *mut AnyObject; // dispatch_data_t
fn dispatch_release(object: *mut AnyObject); // dispatch_data_t
}
const DISPATCH_DATA_DESTRUCTOR_DEFAULT: *mut c_void = core::ptr::null_mut();
/// See <https://github.com/madsmtm/objc2/issues/819>.
///
/// newLibraryWithData requires DispatchData, part of the Dispatch library.
/// Not only is this a big additional dependency for a glorified `Vec<u8>`
/// in this case, but the code in the dispatch2 rust crate is a WIP and
/// Mozilla has decided not to vendor it yet.
///
/// This function allows us to deal with DispatchData without dealing
/// with these problems.
pub(crate) fn new_library_from_metallib_bytes(
device: &ProtocolObject<dyn MTLDevice>,
data: &[u8],
) -> Result<Retained<ProtocolObject<dyn MTLLibrary>>, Retained<NSError>> {
let buffer = NonNull::new(data.as_ptr().cast_mut()).unwrap().cast();
let data =
unsafe { dispatch_data_create(buffer, data.len(), None, DISPATCH_DATA_DESTRUCTOR_DEFAULT) };
assert!(!data.is_null());
let res: Result<Retained<ProtocolObject<dyn MTLLibrary>>, Retained<NSError>> =
unsafe { msg_send![device, newLibraryWithData: data, error: _] };
unsafe { dispatch_release(data) };
res
}