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use std::convert::Infallible; use std::error::Error; use std::marker::PhantomData; use super::null_ptr_error; use super::{FromForeign, InputType, ReturnType, ToForeign}; /// The `Box` marshaler is the catch-all just-throw-it-on-the-heap opaque pointer solution. /// /// It supports the following modes of operation: /// /// ### To the foreign interface: /// /// - `T` → `*const/mut T` /// - `Box<T>` → `*const/*mut T` /// /// ### From the foreign interface: /// /// - `*const/mut T` → `Box<T>` (owned) /// - `*const T` → `&T` (ref) /// - `*mut T` → `&mut T` (mut ref) /// /// ## Freeing `T` /// /// Your foreign code should ensure that they call `BoxMarshaler::<*mut/const T, Box<T>>::from_foreign`, /// which will allow you to consume the boxed `T` and allow it to drop as per Rust's usual rules. /// /// ## Example /// /// ```rust /// use cffi::{BoxMarshaler, FromForeign, ToForeign}; /// /// struct Something { /// data: Vec<u8> /// } /// /// fn demo() { /// let something = Something { data: vec![1, 3, 55] }; /// /// // BoxMarshaler::to_foreign is Infallible /// let ptr: *const Something = BoxMarshaler::to_foreign(something).unwrap(); /// /// /* send `ptr` over ffi, process it in some way, etc */ /// /// // This isn't infallible though, checks for null pointers. /// let boxed: Box<Something> = match BoxMarshaler::from_foreign(ptr) { /// Ok(v) => v, /// Err(e) => panic!("!") /// }; /// /// // Let the boxed item drop and it is freed. :) /// } /// ``` pub struct BoxMarshaler<T: ?Sized>(PhantomData<T>); impl<T> InputType for BoxMarshaler<T> { type Foreign = *const T; type ForeignTraitObject = (); } impl<T> ReturnType for BoxMarshaler<T> { type Foreign = *const T; type ForeignTraitObject = (); fn foreign_default() -> Self::Foreign { std::ptr::null() } } impl<T> ToForeign<Box<T>, *const T> for BoxMarshaler<T> { type Error = Infallible; #[inline(always)] fn to_foreign(local: Box<T>) -> Result<*const T, Self::Error> { log::debug!( "<BoxMarshaler<{ty}> as ToForeign<{ty}, {o}>>::to_foreign", ty = std::any::type_name::<T>(), o = "*const T" ); Ok(Box::into_raw(local) as *const _ as *const _) } } impl<T: ?Sized> ToForeign<Result<Box<T>, Box<dyn Error>>, *const T> for BoxMarshaler<T> { type Error = Box<dyn Error>; #[inline(always)] fn to_foreign(local: Result<Box<T>, Box<dyn Error>>) -> Result<*const T, Self::Error> { local.and_then(|x| Ok(Box::into_raw(x) as *const _ as *const _)) } } // impl<T> ToForeign<Box<T>, *mut T> for BoxMarshaler<T> { // type Error = Infallible; // #[inline(always)] // fn to_foreign(local: Box<T>) -> Result<*mut T, Self::Error> { // Ok(Box::into_raw(local as *mut _ as *mut _) // } // } impl<T> FromForeign<*const T, Box<T>> for BoxMarshaler<T> { type Error = Box<dyn Error>; #[inline(always)] unsafe fn from_foreign(foreign: *const T) -> Result<Box<T>, Self::Error> { log::debug!( "<BoxMarshaler<{ty}> as FromForeign<*const T, T>>::from_foreign({:?})", foreign, ty = std::any::type_name::<T>() ); if foreign.is_null() { return Err(null_ptr_error()); } Ok(Box::from_raw(foreign as *mut _)) } } // impl<T: ?Sized> FromForeign<*mut T, Box<T>> for BoxMarshaler<T> { // type Error = Box<dyn Error>; // #[inline(always)] // unsafe fn from_foreign(foreign: *mut T) -> Result<Box<T>, Self::Error> { // log::debug!("<BoxMarshaler<{ty}> as FromForeign<*mut {ty}, &'a {ty}>>::from_foreign({:?})", // foreign, // ty = std::any::type_name::<T>() // ); // if foreign.is_null() { // return Err(null_ptr_error()); // } // Ok(unsafe { Box::from_raw(foreign) }) // } // } // // impl<'a, T: Clone> ToForeign<&'a T, *const T> for BoxMarshaler<T> { // type Error = Infallible; // #[inline(always)] // fn to_foreign(local: &'a T) -> Result<*const T, Self::Error> { // Ok(Box::into_raw(Box::new(local.clone()))) // } // } // impl<'a, T: Clone> ToForeign<&'a T, *mut T> for BoxMarshaler<T> { // type Error = Infallible; // #[inline(always)] // fn to_foreign(local: &'a T) -> Result<*mut T, Self::Error> { // Ok(Box::into_raw(Box::new(local.clone()))) // } // } // impl<T: ?Sized> ToForeign<Box<T>, *mut T> for BoxMarshaler<T> { // type Error = Infallible; // #[inline(always)] // fn to_foreign(local: Box<T>) -> Result<*mut T, Self::Error> { // Ok(Box::into_raw(local)) // } // } // impl<'a, T: ?Sized> FromForeign<*mut T, &'a mut T> for BoxMarshaler<T> { // type Error = Box<dyn Error>; // #[inline(always)] // unsafe fn from_foreign(foreign: *mut T) -> Result<&'a mut T, Self::Error> { // if foreign.is_null() { // return Err(null_ptr_error()); // } // Ok(unsafe { &mut *foreign }) // } // }