diff options
Diffstat (limited to '')
| -rw-r--r-- | third_party/rust/uniffi_core/src/ffi/callbackinterface.rs | 125 |
1 files changed, 13 insertions, 112 deletions
diff --git a/third_party/rust/uniffi_core/src/ffi/callbackinterface.rs b/third_party/rust/uniffi_core/src/ffi/callbackinterface.rs index 7be66880bb..e7a4faab64 100644 --- a/third_party/rust/uniffi_core/src/ffi/callbackinterface.rs +++ b/third_party/rust/uniffi_core/src/ffi/callbackinterface.rs @@ -91,121 +91,20 @@ //! //! Uniffi generates a protocol or interface in client code in the foreign language must implement. //! -//! For each callback interface, a `CallbackInternals` (on the Foreign Language side) and `ForeignCallbackInternals` -//! (on Rust side) manages the process through a `ForeignCallback`. There is one `ForeignCallback` per callback interface. +//! For each callback interface, UniFFI defines a VTable. +//! This is a `repr(C)` struct where each field is a `repr(C)` callback function pointer. +//! There is one field for each method, plus an extra field for the `uniffi_free` method. +//! The foreign code registers one VTable per callback interface with Rust. //! -//! Passing a callback interface implementation from foreign language (e.g. `AndroidKeychain`) into Rust causes the -//! `KeychainCallbackInternals` to store the instance in a handlemap. -//! -//! The object handle is passed over to Rust, and used to instantiate a struct `KeychainProxy` which implements -//! the trait. This proxy implementation is generate by Uniffi. The `KeychainProxy` object is then passed to -//! client code as `Box<dyn Keychain>`. -//! -//! Methods on `KeychainProxy` objects (e.g. `self.keychain.get("username".into())`) encode the arguments into a `RustBuffer`. -//! Using the `ForeignCallback`, it calls the `CallbackInternals` object on the foreign language side using the -//! object handle, and the method selector. -//! -//! The `CallbackInternals` object unpacks the arguments from the passed buffer, gets the object out from the handlemap, -//! and calls the actual implementation of the method. -//! -//! If there's a return value, it is packed up in to another `RustBuffer` and used as the return value for -//! `ForeignCallback`. The caller of `ForeignCallback`, the `KeychainProxy` unpacks the returned buffer into the correct -//! type and then returns to client code. +//! VTable methods have a similar signature to Rust scaffolding functions. +//! The one difference is that values are returned via an out pointer to work around a Python bug (https://bugs.python.org/issue5710). //! +//! The foreign object that implements the interface is represented by an opaque handle. +//! UniFFI generates a struct that implements the trait by calling VTable methods, passing the handle as the first parameter. +//! When the struct is dropped, the `uniffi_free` method is called. -use crate::{ForeignCallback, ForeignCallbackCell, Lift, LiftReturn, RustBuffer}; use std::fmt; -/// The method index used by the Drop trait to communicate to the foreign language side that Rust has finished with it, -/// and it can be deleted from the handle map. -pub const IDX_CALLBACK_FREE: u32 = 0; - -/// Result of a foreign callback invocation -#[repr(i32)] -#[derive(Debug, PartialEq, Eq)] -pub enum CallbackResult { - /// Successful call. - /// The return value is serialized to `buf_ptr`. - Success = 0, - /// Expected error. - /// This is returned when a foreign method throws an exception that corresponds to the Rust Err half of a Result. - /// The error value is serialized to `buf_ptr`. - Error = 1, - /// Unexpected error. - /// An error message string is serialized to `buf_ptr`. - UnexpectedError = 2, -} - -impl TryFrom<i32> for CallbackResult { - // On errors we return the unconverted value - type Error = i32; - - fn try_from(value: i32) -> Result<Self, i32> { - match value { - 0 => Ok(Self::Success), - 1 => Ok(Self::Error), - 2 => Ok(Self::UnexpectedError), - n => Err(n), - } - } -} - -/// Struct to hold a foreign callback. -pub struct ForeignCallbackInternals { - callback_cell: ForeignCallbackCell, -} - -impl ForeignCallbackInternals { - pub const fn new() -> Self { - ForeignCallbackInternals { - callback_cell: ForeignCallbackCell::new(), - } - } - - pub fn set_callback(&self, callback: ForeignCallback) { - self.callback_cell.set(callback); - } - - /// Invoke a callback interface method on the foreign side and return the result - pub fn invoke_callback<R, UniFfiTag>(&self, handle: u64, method: u32, args: RustBuffer) -> R - where - R: LiftReturn<UniFfiTag>, - { - let mut ret_rbuf = RustBuffer::new(); - let callback = self.callback_cell.get(); - let raw_result = unsafe { - callback( - handle, - method, - args.data_pointer(), - args.len() as i32, - &mut ret_rbuf, - ) - }; - let result = CallbackResult::try_from(raw_result) - .unwrap_or_else(|code| panic!("Callback failed with unexpected return code: {code}")); - match result { - CallbackResult::Success => R::lift_callback_return(ret_rbuf), - CallbackResult::Error => R::lift_callback_error(ret_rbuf), - CallbackResult::UnexpectedError => { - let reason = if !ret_rbuf.is_empty() { - match <String as Lift<UniFfiTag>>::try_lift(ret_rbuf) { - Ok(s) => s, - Err(e) => { - log::error!("{{ trait_name }} Error reading ret_buf: {e}"); - String::from("[Error reading reason]") - } - } - } else { - RustBuffer::destroy(ret_rbuf); - String::from("[Unknown Reason]") - }; - R::handle_callback_unexpected_error(UnexpectedUniFFICallbackError { reason }) - } - } - } -} - /// Used when internal/unexpected error happened when calling a foreign callback, for example when /// a unknown exception is raised /// @@ -216,8 +115,10 @@ pub struct UnexpectedUniFFICallbackError { } impl UnexpectedUniFFICallbackError { - pub fn from_reason(reason: String) -> Self { - Self { reason } + pub fn new(reason: impl fmt::Display) -> Self { + Self { + reason: reason.to_string(), + } } } |