sp_runtime_interface/
util.rs

1// This file is part of Substrate.
2
3// Copyright (C) Parity Technologies (UK) Ltd.
4// SPDX-License-Identifier: Apache-2.0
5
6// Licensed under the Apache License, Version 2.0 (the "License");
7// you may not use this file except in compliance with the License.
8// You may obtain a copy of the License at
9//
10// 	http://www.apache.org/licenses/LICENSE-2.0
11//
12// Unless required by applicable law or agreed to in writing, software
13// distributed under the License is distributed on an "AS IS" BASIS,
14// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15// See the License for the specific language governing permissions and
16// limitations under the License.
17
18//! Various utilities that help interfacing with wasm runtime code.
19
20/// Pack a pointer and length into an `u64`.
21pub fn pack_ptr_and_len(ptr: u32, len: u32) -> u64 {
22	// The static assertions from above are changed into a runtime check.
23	#[cfg(all(not(feature = "std"), feature = "disable_target_static_assertions"))]
24	assert_eq!(4, core::mem::size_of::<usize>());
25
26	(u64::from(len) << 32) | u64::from(ptr)
27}
28
29/// Unpacks an `u64` into the pointer and length.
30///
31/// Runtime API functions return a 64-bit value which encodes a pointer in the least-significant
32/// 32-bits and a length in the most-significant 32 bits. This interprets the returned value as a
33/// pointer, length tuple.
34pub fn unpack_ptr_and_len(val: u64) -> (u32, u32) {
35	// The static assertions from above are changed into a runtime check.
36	#[cfg(all(not(feature = "std"), feature = "disable_target_static_assertions"))]
37	assert_eq!(4, core::mem::size_of::<usize>());
38
39	let ptr = (val & (!0u32 as u64)) as u32;
40	let len = (val >> 32) as u32;
41
42	(ptr, len)
43}
44
45#[cfg(test)]
46mod tests {
47	use super::{pack_ptr_and_len, unpack_ptr_and_len};
48
49	#[test]
50	fn ptr_len_packing_unpacking() {
51		const PTR: u32 = 0x1337;
52		const LEN: u32 = 0x7f000000;
53
54		let packed = pack_ptr_and_len(PTR, LEN);
55		let (ptr, len) = unpack_ptr_and_len(packed);
56
57		assert_eq!(PTR, ptr);
58		assert_eq!(LEN, len);
59	}
60}
sp_runtime_interface/util.rs

sp_runtime_interface/
util.rs
