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// Copyright 2019-2020 Parity Technologies (UK) Ltd. // This file is part of Substrate. // Substrate is free software: you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // Substrate is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with Substrate. If not, see <http://www.gnu.org/licenses/>. //! Traits required by the runtime interface from the host side. use crate::RIType; use sp_wasm_interface::{FunctionContext, Result}; /// Something that can be converted into a ffi value. pub trait IntoFFIValue: RIType { /// Convert `self` into a ffi value. fn into_ffi_value(self, context: &mut dyn FunctionContext) -> Result<Self::FFIType>; } /// Something that can be converted into a preallocated ffi value. /// /// Every type parameter that should be given as `&mut` into a runtime interface function, needs /// to implement this trait. After executing the host implementation of the runtime interface /// function, the value is copied into the preallocated wasm memory. /// /// This should only be used for types which have a fixed size, like slices. Other types like a vec /// do not work with this interface, as we can not call into wasm to reallocate memory. So, this /// trait should be implemented carefully. pub trait IntoPreallocatedFFIValue: RIType { /// As `Self` can be an unsized type, it needs to be represented by a sized type at the host. /// This `SelfInstance` is the sized type. type SelfInstance; /// Convert `self_instance` into the given preallocated ffi value. fn into_preallocated_ffi_value( self_instance: Self::SelfInstance, context: &mut dyn FunctionContext, allocated: Self::FFIType, ) -> Result<()>; } /// Something that can be created from a ffi value. /// Implementations are safe to assume that the `arg` given to `from_ffi_value` /// is only generated by the corresponding [`wasm::IntoFFIValue`](crate::wasm::IntoFFIValue) /// implementation. pub trait FromFFIValue: RIType { /// As `Self` can be an unsized type, it needs to be represented by a sized type at the host. /// This `SelfInstance` is the sized type. type SelfInstance; /// Create `SelfInstance` from the given fn from_ffi_value( context: &mut dyn FunctionContext, arg: Self::FFIType, ) -> Result<Self::SelfInstance>; }