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Merge pull request #383 from signalapp/jrose/simplify-ffi_bridge_handle

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bridge: Simplify the ffi_bridge_handle macro using a marker trait
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Jordan Rose 2021-10-19 10:05:49 -07:00 committed by GitHub
commit d3bd5b5564
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1 changed files with 76 additions and 61 deletions
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137
rust/bridge/shared/src/ffi/convert.rs
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@ -347,71 +347,86 @@ impl crate::support::Env for Env {
}
}
/// A marker for Rust objects exposed as opaque pointers.
pub trait BridgeHandle {}
impl<T: BridgeHandle + 'static> SimpleArgTypeInfo for &T {
type ArgType = *const T;
#[allow(clippy::not_unsafe_ptr_arg_deref)]
fn convert_from(foreign: *const T) -> SignalFfiResult<Self> {
unsafe { native_handle_cast(foreign) }
}
}
impl<T: BridgeHandle + 'static> SimpleArgTypeInfo for Option<&T> {
type ArgType = *const T;
fn convert_from(foreign: *const T) -> SignalFfiResult<Self> {
if foreign.is_null() {
Ok(None)
} else {
<&T>::convert_from(foreign).map(Some)
}
}
}
impl<T: BridgeHandle + 'static> SimpleArgTypeInfo for &mut T {
type ArgType = *mut T;
#[allow(clippy::not_unsafe_ptr_arg_deref)]
fn convert_from(foreign: *mut T) -> SignalFfiResult<Self> {
unsafe { native_handle_cast_mut(foreign) }
}
}
impl<T: BridgeHandle> SizedArgTypeInfo for &[&T] {
type ArgType = *const *const T;
fn convert_from(input: Self::ArgType, input_len: usize) -> SignalFfiResult<Self> {
if input.is_null() {
if input_len != 0 {
return Err(SignalFfiError::NullPointer);
}
// We can't just fall through because slice::from_raw_parts still expects a non-null pointer. Reference a dummy buffer instead.
return Ok(&[]);
}
let slice_of_pointers = unsafe { std::slice::from_raw_parts(input, input_len) };
if slice_of_pointers.contains(&std::ptr::null()) {
return Err(SignalFfiError::NullPointer);
}
let base_ptr_for_slice_of_refs = input as *const &T;
unsafe {
Ok(std::slice::from_raw_parts(
base_ptr_for_slice_of_refs,
input_len,
))
}
}
}
impl<T: BridgeHandle> ResultTypeInfo for T {
type ResultType = *mut T;
fn convert_into(self) -> SignalFfiResult<Self::ResultType> {
Ok(Box::into_raw(Box::new(self)))
}
}
impl<T: BridgeHandle> ResultTypeInfo for Option<T> {
type ResultType = *mut T;
fn convert_into(self) -> SignalFfiResult<Self::ResultType> {
match self {
Some(obj) => obj.convert_into(),
None => Ok(std::ptr::null_mut()),
}
}
}
/// Implementation of [`bridge_handle`](crate::support::bridge_handle) for FFI.
macro_rules! ffi_bridge_handle {
( $typ:ty as false $(, $($_:tt)*)? ) => {};
( $typ:ty as $ffi_name:ident, clone = false ) => {
impl ffi::SimpleArgTypeInfo for &$typ {
type ArgType = *const $typ;
#[allow(clippy::not_unsafe_ptr_arg_deref)]
fn convert_from(foreign: *const $typ) -> ffi::SignalFfiResult<Self> {
unsafe { ffi::native_handle_cast(foreign) }
}
}
impl ffi::SimpleArgTypeInfo for Option<&$typ> {
type ArgType = *const $typ;
fn convert_from(foreign: *const $typ) -> ffi::SignalFfiResult<Self> {
if foreign.is_null() {
Ok(None)
} else {
<&$typ>::convert_from(foreign).map(Some)
}
}
}
impl ffi::SimpleArgTypeInfo for &mut $typ {
type ArgType = *mut $typ;
#[allow(clippy::not_unsafe_ptr_arg_deref)]
fn convert_from(foreign: *mut $typ) -> ffi::SignalFfiResult<Self> {
unsafe { ffi::native_handle_cast_mut(foreign) }
}
}
impl ffi::SizedArgTypeInfo for &[& $typ] {
type ArgType = *const *const $typ;
fn convert_from(input: Self::ArgType, input_len: usize) -> ffi::SignalFfiResult<Self> {
if input.is_null() {
if input_len != 0 {
return Err(ffi::SignalFfiError::NullPointer);
}
// We can't just fall through because slice::from_raw_parts still expects a non-null pointer. Reference a dummy buffer instead.
return Ok(&[]);
}
let slice_of_pointers = unsafe { std::slice::from_raw_parts(input, input_len) };
if slice_of_pointers.contains(&std::ptr::null()) {
return Err(ffi::SignalFfiError::NullPointer);
}
let base_ptr_for_slice_of_refs = input as *const & $typ;
unsafe { Ok(std::slice::from_raw_parts(base_ptr_for_slice_of_refs, input_len)) }
}
}
impl ffi::ResultTypeInfo for $typ {
type ResultType = *mut $typ;
fn convert_into(self) -> ffi::SignalFfiResult<Self::ResultType> {
Ok(Box::into_raw(Box::new(self)))
}
}
impl ffi::ResultTypeInfo for Option<$typ> {
type ResultType = *mut $typ;
fn convert_into(self) -> ffi::SignalFfiResult<Self::ResultType> {
match self {
Some(obj) => obj.convert_into(),
None => Ok(std::ptr::null_mut()),
}
}
}
impl ffi::BridgeHandle for $typ {}
ffi_bridge_destroy!($typ as $ffi_name);
};
( $typ:ty as $ffi_name:ident ) => {