ink_engine/
chain_extension.rs

1// Copyright (C) Use Ink (UK) Ltd.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use super::Error;
16use derive_more::From;
17use std::collections::{
18    hash_map::Entry,
19    HashMap,
20};
21
22/// Chain extension registry.
23///
24/// Allows to register chain extension methods and call them.
25pub struct ChainExtensionHandler {
26    /// The currently registered runtime call handler.
27    registered: HashMap<ExtensionId, Box<dyn ChainExtension>>,
28    /// The output buffer used and reused for chain extension method call results.
29    output: Vec<u8>,
30}
31
32/// The unique ID of the registered chain extension.
33#[derive(
34    Debug, From, scale::Encode, scale::Decode, PartialEq, Eq, PartialOrd, Ord, Hash,
35)]
36pub struct ExtensionId(u16);
37
38/// Types implementing this trait can be used as chain extensions.
39///
40/// This trait is only useful for testing contract via the off-chain environment.
41pub trait ChainExtension {
42    /// The static ID of the chain extension.
43    ///
44    /// # Note
45    ///
46    /// This is expected to return a constant value.
47    fn ext_id(&self) -> u16;
48
49    /// Calls the chain extension with the given input.
50    ///
51    /// Returns an error code and may fill the `output` buffer with a SCALE encoded
52    /// result.
53    #[allow(clippy::ptr_arg)]
54    fn call(&mut self, func_id: u16, input: &[u8], output: &mut Vec<u8>) -> u32;
55}
56
57impl Default for ChainExtensionHandler {
58    fn default() -> Self {
59        ChainExtensionHandler::new()
60    }
61}
62
63impl ChainExtensionHandler {
64    /// Creates a new chain extension handler.
65    ///
66    /// Initialized with an empty set of chain extensions.
67    pub fn new() -> Self {
68        Self {
69            registered: HashMap::new(),
70            output: Vec::new(),
71        }
72    }
73
74    /// Resets the chain extension handler to uninitialized state.
75    pub fn reset(&mut self) {
76        self.registered.clear();
77        self.output.clear();
78    }
79
80    /// Register a new chain extension.
81    pub fn register(&mut self, extension: Box<dyn ChainExtension>) {
82        let ext_id = extension.ext_id();
83        self.registered.insert(ExtensionId::from(ext_id), extension);
84    }
85
86    /// Evaluates the chain extension with the given parameters.
87    ///
88    /// Upon success returns the values returned by the evaluated chain extension.
89    pub fn eval(&mut self, id: u32, input: &[u8]) -> Result<(u32, &[u8]), Error> {
90        self.output.clear();
91
92        let func_id = (id & 0x0000FFFF) as u16;
93        let ext_id = (id >> 16) as u16;
94
95        let extension_id = ExtensionId::from(ext_id);
96        match self.registered.entry(extension_id) {
97            Entry::Occupied(occupied) => {
98                let status_code =
99                    occupied.into_mut().call(func_id, input, &mut self.output);
100                Ok((status_code, &mut self.output))
101            }
102            Entry::Vacant(_vacant) => Err(Error::UnregisteredChainExtension),
103        }
104    }
105}
ink_engine/chain_extension.rs

ink_engine/
chain_extension.rs
