weight.rs 4.42 KB
Newer Older
Gavin Wood's avatar
Gavin Wood committed
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
// Copyright 2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot 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.

// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.

use crate::Assets;
Shawn Tabrizi's avatar
Shawn Tabrizi committed
18
19
use frame_support::weights::Weight;
use sp_std::result::Result;
Gavin Wood's avatar
Gavin Wood committed
20
use xcm::latest::{Error, MultiAsset, MultiLocation, Xcm};
Gavin Wood's avatar
Gavin Wood committed
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43

/// Determine the weight of an XCM message.
pub trait WeightBounds<Call> {
	/// Return the minimum amount of weight that an attempted execution of this message would definitely
	/// consume.
	///
	/// This is useful to gauge how many fees should be paid up front to begin execution of the message.
	/// It is not useful for determining whether execution should begin lest it result in surpassing weight
	/// limits - in that case `deep` is the function to use.
	fn shallow(message: &mut Xcm<Call>) -> Result<Weight, ()>;

	/// Return the deep amount of weight, over `shallow` that complete, successful and worst-case execution of
	/// `message` would incur.
	///
	/// This is perhaps overly pessimistic for determining how many fees should be paid for up-front since
	/// fee payment (or any other way of offsetting the execution costs such as an voucher-style NFT) may
	/// happen in stages throughout execution of the XCM.
	///
	/// A reminder: if it is possible that `message` may have alternative means of successful completion
	/// (perhaps a conditional path), then the *worst case* weight must be reported.
	///
	/// This is guaranteed equal to the eventual sum of all `shallow` XCM messages that get executed through
	/// any internal effects. Inner XCM messages may be executed by:
Denis_P's avatar
Denis_P committed
44
	/// - `Order::BuyExecution`
Gavin Wood's avatar
Gavin Wood committed
45
	fn deep(message: &mut Xcm<Call>) -> Result<Weight, ()>;
46
47
48
49
50
51
52
53
54
55
56
57

	/// Return the total weight for executing `message`.
	fn weight(message: &mut Xcm<Call>) -> Result<Weight, ()> {
		Self::shallow(message)?.checked_add(Self::deep(message)?).ok_or(())
	}
}

/// A means of getting approximate weight consumption for a given destination message executor and a
/// message.
pub trait UniversalWeigher {
	/// Get the upper limit of weight required for `dest` to execute `message`.
	fn weigh(dest: MultiLocation, message: Xcm<()>) -> Result<Weight, ()>;
Gavin Wood's avatar
Gavin Wood committed
58
59
60
}

/// Charge for weight in order to execute XCM.
61
62
63
64
65
///
/// A `WeightTrader` may also be put into a tuple, in which case the default behavior of
/// `buy_weight` and `refund_weight` would be to attempt to call each tuple element's own
/// implementation of these two functions, in the order of which they appear in the tuple,
/// returning early when a successful result is returned.
66
pub trait WeightTrader: Sized {
Gavin Wood's avatar
Gavin Wood committed
67
68
69
70
71
72
	/// Create a new trader instance.
	fn new() -> Self;

	/// Purchase execution weight credit in return for up to a given `fee`. If less of the fee is required
	/// then the surplus is returned. If the `fee` cannot be used to pay for the `weight`, then an error is
	/// returned.
73
	fn buy_weight(&mut self, weight: Weight, payment: Assets) -> Result<Assets, Error>;
Gavin Wood's avatar
Gavin Wood committed
74
75
76
77
78

	/// Attempt a refund of `weight` into some asset. The caller does not guarantee that the weight was
	/// purchased using `buy_weight`.
	///
	/// Default implementation refunds nothing.
Gavin Wood's avatar
Gavin Wood committed
79
80
	fn refund_weight(&mut self, _weight: Weight) -> Option<MultiAsset> {
		None
Shawn Tabrizi's avatar
Shawn Tabrizi committed
81
	}
Gavin Wood's avatar
Gavin Wood committed
82
}
83

84
85
#[impl_trait_for_tuples::impl_for_tuples(30)]
impl WeightTrader for Tuple {
Shawn Tabrizi's avatar
Shawn Tabrizi committed
86
	fn new() -> Self {
87
		for_tuples!( ( #( Tuple::new() ),* ) )
Shawn Tabrizi's avatar
Shawn Tabrizi committed
88
	}
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109

	fn buy_weight(&mut self, weight: Weight, payment: Assets) -> Result<Assets, Error> {
		let mut last_error = None;
		for_tuples!( #(
			match Tuple.buy_weight(weight, payment.clone()) {
				Ok(assets) => return Ok(assets),
				Err(e) => { last_error = Some(e) }
			}
		)* );
		let last_error = last_error.unwrap_or(Error::TooExpensive);
		log::trace!(target: "xcm::buy_weight", "last_error: {:?}", last_error);
		Err(last_error)
	}

	fn refund_weight(&mut self, weight: Weight) -> Option<MultiAsset> {
		for_tuples!( #(
			if let Some(asset) = Tuple.refund_weight(weight) {
				return Some(asset);
			}
		)* );
		None
110
111
	}
}