pezkuwichain
b6d35f6faf
Updated 4763 files with dual copyright: - Parity Technologies (UK) Ltd. - Dijital Kurdistan Tech Institute
109 lines
3.5 KiB
Rust
109 lines
3.5 KiB
Rust
// This file is part of Bizinikiwi.
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// Copyright (C) Parity Technologies (UK) Ltd. and Dijital Kurdistan Tech Institute
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// SPDX-License-Identifier: Apache-2.0
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//! Traits required by the runtime interface from the wasm side.
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use crate::RIType;
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use core::cell::Cell;
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/// A type used as a return value in a host function. Can be created from an FFI value.
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///
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/// Implementations are safe to assume that the `arg` given to `from_ffi_value`
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/// is only generated by the corresponding [`host::IntoFFIValue`](crate::host::IntoFFIValue)
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/// implementation.
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pub trait FromFFIValue: Sized + RIType {
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/// Create `Self::Inner` from the given FFI value.
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fn from_ffi_value(arg: Self::FFIType) -> Self::Inner;
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}
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/// A type used as a parameter in a host function. Can be turned into an FFI value.
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pub trait IntoFFIValue: RIType {
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/// Destructor for the value passed into `into_ffi_value`.
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type Destructor;
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/// Convert `Self::Inner` into an FFI type, with an optional destructor.
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fn into_ffi_value(value: &mut Self::Inner) -> (Self::FFIType, Self::Destructor);
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}
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/// The state of an exchangeable function.
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#[derive(Clone, Copy)]
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enum ExchangeableFunctionState {
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/// Original function is present
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Original,
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/// The function has been replaced.
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Replaced,
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}
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/// A function which implementation can be exchanged.
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///
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/// Internally this works by swapping function pointers.
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pub struct ExchangeableFunction<T>(Cell<(T, ExchangeableFunctionState)>);
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impl<T> ExchangeableFunction<T> {
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/// Create a new instance of `ExchangeableFunction`.
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pub const fn new(impl_: T) -> Self {
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Self(Cell::new((impl_, ExchangeableFunctionState::Original)))
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}
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}
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impl<T: Copy> ExchangeableFunction<T> {
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/// Replace the implementation with `new_impl`.
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///
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/// # Panics
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///
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/// Panics when trying to replace an already replaced implementation.
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///
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/// # Returns
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///
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/// Returns the original implementation wrapped in [`RestoreImplementation`].
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pub fn replace_implementation(&'static self, new_impl: T) -> RestoreImplementation<T> {
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if let ExchangeableFunctionState::Replaced = self.0.get().1 {
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panic!("Trying to replace an already replaced implementation!")
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}
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let old = self.0.replace((new_impl, ExchangeableFunctionState::Replaced));
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RestoreImplementation(self, Some(old.0))
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}
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/// Restore the original implementation.
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fn restore_orig_implementation(&self, orig: T) {
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self.0.set((orig, ExchangeableFunctionState::Original));
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}
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/// Returns the internal function pointer.
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pub fn get(&self) -> T {
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self.0.get().0
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}
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}
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// Wasm does not support threads, so this is safe; qed.
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unsafe impl<T> Sync for ExchangeableFunction<T> {}
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/// Restores a function implementation on drop.
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///
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/// Stores a static reference to the function object and the original implementation.
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pub struct RestoreImplementation<T: 'static + Copy>(&'static ExchangeableFunction<T>, Option<T>);
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impl<T: Copy> Drop for RestoreImplementation<T> {
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fn drop(&mut self) {
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self.0
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.restore_orig_implementation(self.1.take().expect("Value is only taken on drop; qed"));
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}
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}
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