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// Copyright 2018-2022 Parity Technologies (UK) Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Definitions and utilities for calling chain extension methods.
//!
//! Users should not use these types and definitions directly but rather use the provided
//! `#[ink::chain_extension]` procedural macro defined in the `ink_lang` crate.
use crate::{
backend::EnvBackend,
engine::{
EnvInstance,
OnInstance,
},
};
use core::marker::PhantomData;
/// Implemented by error codes in order to construct them from status codes.
///
/// A status code is returned by calling an ink! chain extension method.
/// It is the `u32` return value.
///
/// The purpose of an `ErrorCode` type that implements this trait is to provide
/// more context information about the status of an ink! chain extension method call.
pub trait FromStatusCode: Sized {
/// Returns `Ok` if the status code for the called chain extension method is valid.
///
/// Returning `Ok` will query the output buffer of the call if the chain extension
/// method definition has a return value.
///
/// # Note
///
/// The convention is to use `0` as the only `raw` value that yields `Ok` whereas
/// every other value represents one error code. By convention this mapping should
/// never panic and therefore every `raw` value must map to either `Ok` or to a proper
/// `ErrorCode` variant.
fn from_status_code(status_code: u32) -> Result<(), Self>;
}
/// A concrete instance of a chain extension method.
///
/// This is a utility type used to drive the execution of a chain extension method call.
/// It has several specializations of its `call` method for different ways to manage
/// error handling when calling a predefined chain extension method.
///
/// - `I` represents the input type of the chain extension method.
/// All tuple types that may act as input parameters for the chain extension method are valid.
/// Examples include `()`, `i32`, `(u8, [u8; 5], i32)`, etc.
/// - `O` represents the return (or output) type of the chain extension method.
/// Only `Result<T, E>` or `NoResult<O>` generic types are allowed for `O`.
/// The `Result<T, E>` type says that the chain extension method returns a `Result` type
/// whereas the `NoResult<O>` type says that the chain extension method returns a non-`Result` value
/// of type `O`.
/// - `ErrorCode` represents how the chain extension method handles the chain extension's error code.
/// Only `HandleErrorCode<E>` and `IgnoreErrorCode` types are allowed that each say to either properly
/// handle or ignore the chain extension's error code respectively.
///
/// The type states for type parameter `O` and `ErrorCode` represent 4 different states:
///
/// 1. The chain extension method makes use of the chain extension's error code: `HandleErrorCode(E)`
/// - **A:** The chain extension method returns a `Result<T, E>` type.
/// - **B:** The chain extension method returns a type `T` that is not a `Result` type: `NoResult<T>`
/// 2. The chain extension ignores the chain extension's error code: `IgnoreErrorCode`
/// - **A:** The chain extension method returns a `Result<T, E>` type.
/// - **B:** The chain extension method returns a type `T` that is not a `Result` type: `NoResult<T>`
#[derive(Debug)]
pub struct ChainExtensionMethod<I, O, ErrorCode> {
func_id: u32,
#[allow(clippy::type_complexity)]
state: PhantomData<fn() -> (I, O, ErrorCode)>,
}
impl ChainExtensionMethod<(), (), ()> {
/// Creates a new chain extension method instance.
#[inline]
pub fn build(func_id: u32) -> Self {
Self {
func_id,
state: Default::default(),
}
}
}
impl<O, ErrorCode> ChainExtensionMethod<(), O, ErrorCode> {
/// Sets the input types of the chain extension method call to `I`.
///
/// # Note
///
/// `I` represents the input type of the chain extension method.
/// All tuple types that may act as input parameters for the chain extension method are valid.
/// Examples include `()`, `i32`, `(u8, [u8; 5], i32)`, etc.
#[inline]
pub fn input<I>(self) -> ChainExtensionMethod<I, O, ErrorCode>
where
I: scale::Encode,
{
ChainExtensionMethod {
func_id: self.func_id,
state: Default::default(),
}
}
}
impl<I, ErrorCode> ChainExtensionMethod<I, (), ErrorCode> {
/// Sets the output type of the chain extension method call to `Result<T, E>`.
///
/// # Note
///
/// This indicates that the chain extension method return value might represent a failure.
#[inline]
pub fn output_result<T, E>(self) -> ChainExtensionMethod<I, Result<T, E>, ErrorCode>
where
Result<T, E>: scale::Decode,
E: From<scale::Error>,
{
ChainExtensionMethod {
func_id: self.func_id,
state: Default::default(),
}
}
/// Sets the output type of the chain extension method call to `O`.
///
/// # Note
///
/// The set returned type `O` must not be of type `Result<T, E>`.
/// When using the `#[ink::chain_extension]` procedural macro to define
/// this chain extension method the above constraint is enforced at
/// compile time.
#[inline]
pub fn output<O>(self) -> ChainExtensionMethod<I, state::NoResult<O>, ErrorCode>
where
O: scale::Decode,
{
ChainExtensionMethod {
func_id: self.func_id,
state: Default::default(),
}
}
}
impl<I, O> ChainExtensionMethod<I, O, ()> {
/// Makes the chain extension method call assume that the returned status code is always success.
///
/// # Note
///
/// This will avoid handling of failure status codes returned by the chain extension method call.
/// Use this only if you are sure that the chain extension method call will never return an error
/// code that represents failure.
///
/// The output of the chain extension method call is always decoded and returned in this case.
#[inline]
pub fn ignore_error_code(self) -> ChainExtensionMethod<I, O, state::IgnoreErrorCode> {
ChainExtensionMethod {
func_id: self.func_id,
state: Default::default(),
}
}
/// Makes the chain extension method call handle the returned status code.
///
/// # Note
///
/// This will handle the returned status code and only loads and decodes the value
/// returned as the output of the chain extension method call in case of success.
#[inline]
pub fn handle_error_code<ErrorCode>(
self,
) -> ChainExtensionMethod<I, O, state::HandleErrorCode<ErrorCode>>
where
ErrorCode: FromStatusCode,
{
ChainExtensionMethod {
func_id: self.func_id,
state: Default::default(),
}
}
}
/// Type states of the chain extension method instance.
pub mod state {
use core::marker::PhantomData;
/// Type state meaning that the chain extension method ignores the chain extension's error code.
#[derive(Debug)]
pub enum IgnoreErrorCode {}
/// Type state meaning that the chain extension method uses the chain extension's error code.
#[derive(Debug)]
pub struct HandleErrorCode<T> {
error_code: PhantomData<fn() -> T>,
}
/// Type state meaning that the chain extension method deliberately does not return a `Result` type.
///
/// Additionally this is enforced by the `#[ink::chain_extension]` procedural macro when used.
#[derive(Debug)]
pub struct NoResult<T> {
no_result: PhantomData<fn() -> T>,
}
}
impl<I, T, E, ErrorCode>
ChainExtensionMethod<I, Result<T, E>, state::HandleErrorCode<ErrorCode>>
where
I: scale::Encode,
T: scale::Decode,
E: scale::Decode + From<ErrorCode> + From<scale::Error>,
ErrorCode: FromStatusCode,
{
/// Calls the chain extension method for case 1.A described [here].
///
/// [here]: [`ChainExtensionMethod`]
///
/// # Errors
///
/// - If the called chain extension method returns a non-successful error code.
/// - If the `Result` return value of the called chain extension represents an error.
/// - If the `Result` return value cannot be SCALE decoded properly.
/// - If custom constraints specified by the called chain extension method are violated.
/// - These constraints are determined and defined by the author of the chain extension method.
///
/// # Example
///
/// Declares a chain extension method with the unique ID of 5 that requires a `bool` and an `i32`
/// as input parameters and returns a `Result<i32, MyError>` upon completion.
/// It will handle the shared error code from the chain extension.
/// The call is finally invoked with arguments `true` and `42` for the `bool` and `i32` input
/// parameter respectively.
///
/// ```should_panic
/// # // Panics because the off-chain environment has not
/// # // registered a chain extension method for the ID.
/// # use ink_env::chain_extension::{ChainExtensionMethod, FromStatusCode};
/// let result = ChainExtensionMethod::build(5)
/// .input::<(bool, i32)>()
/// .output_result::<i32, MyError>()
/// .handle_error_code::<MyErrorCode>()
/// .call(&(true, 42));
/// # #[derive(scale::Encode, scale::Decode)]
/// # pub struct MyError {}
/// # impl From<scale::Error> for MyError {
/// # fn from(_error: scale::Error) -> Self { Self {} }
/// # }
/// # impl From<MyErrorCode> for MyError {
/// # fn from(_error: MyErrorCode) -> Self { Self {} }
/// # }
/// # pub struct MyErrorCode {}
/// # impl FromStatusCode for MyErrorCode {
/// # fn from_status_code(status_code: u32) -> Result<(), Self> { Ok(()) }
/// # }
/// ```
#[inline]
pub fn call(self, input: &I) -> Result<T, E> {
<EnvInstance as OnInstance>::on_instance(|instance| {
EnvBackend::call_chain_extension::<I, T, E, ErrorCode, _, _>(
instance,
self.func_id,
input,
ErrorCode::from_status_code,
|mut output| scale::Decode::decode(&mut output).map_err(Into::into),
)
})
}
}
impl<I, T, E> ChainExtensionMethod<I, Result<T, E>, state::IgnoreErrorCode>
where
I: scale::Encode,
T: scale::Decode,
E: scale::Decode + From<scale::Error>,
{
/// Calls the chain extension method for case 2.A described [here].
///
/// [here]: [`ChainExtensionMethod`]
///
/// # Errors
///
/// - If the `Result` return value of the called chain extension represents an error.
/// - If the `Result` return value cannot be SCALE decoded properly.
/// - If custom constraints specified by the called chain extension method are violated.
/// - These constraints are determined and defined by the author of the chain extension method.
///
/// # Example
///
/// Declares a chain extension method with the unique ID of 5 that requires a `bool` and an `i32`
/// as input parameters and returns a `Result<i32, MyError>` upon completion.
/// It will ignore the shared error code from the chain extension and assumes that the call succeeds.
/// The call is finally invoked with arguments `true` and `42` for the `bool` and `i32` input
/// parameter respectively.
///
/// ```should_panic
/// # // Panics because the off-chain environment has not
/// # // registered a chain extension method for the ID.
/// # use ink_env::chain_extension::{ChainExtensionMethod};
/// let result = ChainExtensionMethod::build(5)
/// .input::<(bool, i32)>()
/// .output_result::<i32, MyError>()
/// .ignore_error_code()
/// .call(&(true, 42));
/// # #[derive(scale::Encode, scale::Decode)]
/// # pub struct MyError {}
/// # impl From<scale::Error> for MyError {
/// # fn from(_error: scale::Error) -> Self { Self {} }
/// # }
/// ```
#[inline]
pub fn call(self, input: &I) -> Result<T, E> {
<EnvInstance as OnInstance>::on_instance(|instance| {
EnvBackend::call_chain_extension::<I, T, E, E, _, _>(
instance,
self.func_id,
input,
|_status_code| Ok(()),
|mut output| scale::Decode::decode(&mut output).map_err(Into::into),
)
})
}
}
impl<I, O, ErrorCode>
ChainExtensionMethod<I, state::NoResult<O>, state::HandleErrorCode<ErrorCode>>
where
I: scale::Encode,
O: scale::Decode,
ErrorCode: FromStatusCode,
{
/// Calls the chain extension method for case 1.B described [here].
///
/// [here]: [`ChainExtensionMethod`]
///
/// # Errors
///
/// - If the called chain extension method returns a non-successful error code.
/// - If custom constraints specified by the called chain extension method are violated.
/// - These constraints are determined and defined by the author of the chain extension method.
///
/// # Panics
///
/// - If the return value cannot be SCALE decoded properly.
///
/// # Example
///
/// Declares a chain extension method with the unique ID of 5 that requires a `bool` and an `i32`
/// as input parameters and returns a `Result<i32, MyErrorCode>` upon completion.
/// It will handle the shared error code from the chain extension.
/// The call is finally invoked with arguments `true` and `42` for the `bool` and `i32` input
/// parameter respectively.
///
/// ```should_panic
/// # // Panics because the off-chain environment has not
/// # // registered a chain extension method for the ID.
/// # use ink_env::chain_extension::{ChainExtensionMethod, FromStatusCode};
/// let result = ChainExtensionMethod::build(5)
/// .input::<(bool, i32)>()
/// .output::<i32>()
/// .handle_error_code::<MyErrorCode>()
/// .call(&(true, 42));
/// # pub struct MyErrorCode {}
/// # impl FromStatusCode for MyErrorCode {
/// # fn from_status_code(status_code: u32) -> Result<(), Self> { Ok(()) }
/// # }
/// ```
#[inline]
pub fn call(self, input: &I) -> Result<O, ErrorCode> {
<EnvInstance as OnInstance>::on_instance(|instance| {
EnvBackend::call_chain_extension::<I, O, ErrorCode, ErrorCode, _, _>(
instance,
self.func_id,
input,
ErrorCode::from_status_code,
|mut output| {
let decoded = <O as scale::Decode>::decode(&mut output)
.expect("encountered error while decoding chain extension method call return value");
Ok(decoded)
},
)
})
}
}
impl<I, O> ChainExtensionMethod<I, state::NoResult<O>, state::IgnoreErrorCode>
where
I: scale::Encode,
O: scale::Decode,
{
/// Calls the chain extension method for case 2.B described [here].
///
/// [here]: [`ChainExtensionMethod`]
///
/// # Panics
///
/// - If the return value cannot be SCALE decoded properly.
///
/// # Example
///
/// Declares a chain extension method with the unique ID of 5 that requires a `bool` and an `i32`
/// as input parameters and returns a `Result<i32, MyErrorCode>` upon completion.
/// It will ignore the shared error code from the chain extension and assumes that the call succeeds.
/// The call is finally invoked with arguments `true` and `42` for the `bool` and `i32` input
/// parameter respectively.
///
/// ```should_panic
/// # // Panics because the off-chain environment has not
/// # // registered a chain extension method for the ID.
/// # use ink_env::chain_extension::ChainExtensionMethod;
/// let result = ChainExtensionMethod::build(5)
/// .input::<(bool, i32)>()
/// .output::<i32>()
/// .ignore_error_code()
/// .call(&(true, 42));
/// ```
#[inline]
pub fn call(self, input: &I) -> O {
<EnvInstance as OnInstance>::on_instance(|instance| {
EnvBackend::call_chain_extension::<I, O, (), (), _, _>(
instance,
self.func_id,
input,
|_status_code| Ok(()),
|mut output| {
let decoded = <O as scale::Decode>::decode(&mut output)
.expect("encountered error while decoding chain extension method call return value");
Ok(decoded)
},
).expect("assume the chain extension method never fails")
})
}
}