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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
// 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 <>.
//! # Primitives for transaction weighting.
//! All dispatchable functions defined in `decl_module!` must provide two trait implementations:
//! - [`WeightData`]: To determine the weight of the dispatch.
//! - [`ClassifyDispatch`]: To determine the class of the dispatch. See the enum definition for
//! more information on dispatch classes.
//! Every dispatchable function is responsible for providing this data via an optional `#[weight =
//! $x]` attribute. In this snipped, `$x` can be any user provided struct that implements the
//! two aforementioned traits.
//! Substrate then bundles then output information of the two traits into [`DispatchInfo`] struct
//! and provides it by implementing the [`GetDispatchInfo`] for all `Call` variants, and opaque
//! extrinsic types.
//! If no `#[weight]` is defined, the macro automatically injects the `Default` implementation of
//! the [`SimpleDispatchInfo`].
//! Note that the decl_module macro _cannot_ enforce this and will simply fail if an invalid struct
//! (something that does not implement `Weighable`) is passed in.
#[cfg(feature = "std")]
use serde::{Serialize, Deserialize};
use codec::{Encode, Decode};
use sp_arithmetic::traits::Bounded;
use sp_runtime::{
generic::{CheckedExtrinsic, UncheckedExtrinsic},
/// Re-export priority as type
pub use sp_runtime::transaction_validity::TransactionPriority;
/// Numeric range of a transaction weight.
pub type Weight = u32;
/// Means of weighing some particular kind of data (`T`).
pub trait WeighData<T> {
/// Weigh the data `T` given by `target`. When implementing this for a dispatchable, `T` will be
/// a tuple of all arguments given to the function (except origin).
fn weigh_data(&self, target: T) -> Weight;
/// Means of classifying a dispatchable function.
pub trait ClassifyDispatch<T> {
/// Classify the dispatch function based on input data `target` of type `T`. When implementing
/// this for a dispatchable, `T` will be a tuple of all arguments given to the function (except
/// origin).
fn classify_dispatch(&self, target: T) -> DispatchClass;
/// Indicates if dispatch function should pay fees or not.
/// If set to false, the block resource limits are applied, yet no fee is deducted.
pub trait PaysFee<T> {
fn pays_fee(&self, _target: T) -> bool {
/// A generalized group of dispatch types. This is only distinguishing normal, user-triggered transactions
/// (`Normal`) and anything beyond which serves a higher purpose to the system (`Operational`).
#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "std", serde(rename_all = "camelCase"))]
#[derive(PartialEq, Eq, Clone, Copy, Encode, Decode, RuntimeDebug)]
pub enum DispatchClass {
/// A normal dispatch.
/// An operational dispatch.
impl Default for DispatchClass {
fn default() -> Self {
impl From<SimpleDispatchInfo> for DispatchClass {
fn from(tx: SimpleDispatchInfo) -> Self {
match tx {
SimpleDispatchInfo::FixedOperational(_) => DispatchClass::Operational,
SimpleDispatchInfo::MaxOperational => DispatchClass::Operational,
SimpleDispatchInfo::FixedNormal(_) => DispatchClass::Normal,
SimpleDispatchInfo::MaxNormal => DispatchClass::Normal,
SimpleDispatchInfo::InsecureFreeNormal => DispatchClass::Normal,
/// A bundle of static information collected from the `#[weight = $x]` attributes.
#[derive(Clone, Copy, Eq, PartialEq, Default, RuntimeDebug, Encode, Decode)]
pub struct DispatchInfo {
/// Weight of this transaction.
pub weight: Weight,
/// Class of this transaction.
pub class: DispatchClass,
/// Does this transaction pay fees.
pub pays_fee: bool,
/// A `Dispatchable` function (aka transaction) that can carry some static information along with
/// it, using the `#[weight]` attribute.
pub trait GetDispatchInfo {
/// Return a `DispatchInfo`, containing relevant information of this dispatch.
/// This is done independently of its encoded size.
fn get_dispatch_info(&self) -> DispatchInfo;
/// Default type used with the `#[weight = x]` attribute in a substrate chain.
/// A user may pass in any other type that implements the correct traits. If not, the `Default`
/// implementation of [`SimpleDispatchInfo`] is used.
/// For each generalized group (`Normal` and `Operation`):
/// - A `Fixed` variant means weight fee is charged normally and the weight is the number
/// specified in the inner value of the variant.
/// - A `Free` variant is equal to `::Fixed(0)`. Note that this does not guarantee inclusion.
/// - A `Max` variant is equal to `::Fixed(Weight::max_value())`.
/// As for the generalized groups themselves:
/// - `Normal` variants will be assigned a priority proportional to their weight. They can only
/// consume a portion (defined in the system module) of the maximum block resource limits.
/// - `Operational` variants will be assigned the maximum priority. They can potentially consume
/// the entire block resource limit.
#[derive(Clone, Copy)]
pub enum SimpleDispatchInfo {
/// A normal dispatch with fixed weight.
/// A normal dispatch with the maximum weight.
/// A normal dispatch with no weight. Base and bytes fees still need to be paid.
/// An operational dispatch with fixed weight.
/// An operational dispatch with the maximum weight.
impl<T> WeighData<T> for SimpleDispatchInfo {
fn weigh_data(&self, _: T) -> Weight {
match self {
SimpleDispatchInfo::FixedNormal(w) => *w,
SimpleDispatchInfo::MaxNormal => Bounded::max_value(),
SimpleDispatchInfo::InsecureFreeNormal => Bounded::min_value(),
SimpleDispatchInfo::FixedOperational(w) => *w,
SimpleDispatchInfo::MaxOperational => Bounded::max_value(),
impl<T> ClassifyDispatch<T> for SimpleDispatchInfo {
fn classify_dispatch(&self, _: T) -> DispatchClass {
impl<T> PaysFee<T> for SimpleDispatchInfo {
fn pays_fee(&self, _: T) -> bool {
match self {
SimpleDispatchInfo::FixedNormal(_) => true,
SimpleDispatchInfo::MaxNormal => true,
SimpleDispatchInfo::InsecureFreeNormal => true,
SimpleDispatchInfo::FixedOperational(_) => true,
SimpleDispatchInfo::MaxOperational => true,
impl Default for SimpleDispatchInfo {
fn default() -> Self {
// Default weight of all transactions.
impl SimpleDispatchInfo {
/// An _additive zero_ variant of SimpleDispatchInfo.
pub fn zero() -> Self {
/// A struct to represent a weight which is a function of the input arguments. The given items have
/// the following types:
/// - `WD`: a raw `Weight` value or a closure that returns a `Weight` with the same
/// argument list as the dispatched, wrapped in a tuple.
/// - `CD`: a raw `DispatchClass` value or a closure that returns a `DispatchClass`
/// with the same argument list as the dispatched, wrapped in a tuple.
/// - `PF`: a `bool` for whether this dispatch pays fee or not or a closure that
/// returns a bool with the same argument list as the dispatched, wrapped in a tuple.
pub struct FunctionOf<WD, CD, PF>(pub WD, pub CD, pub PF);
// `WeighData` as a raw value
impl<Args, CD, PF> WeighData<Args> for FunctionOf<Weight, CD, PF> {
fn weigh_data(&self, _: Args) -> Weight {
// `WeighData` as a closure
impl<Args, WD, CD, PF> WeighData<Args> for FunctionOf<WD, CD, PF> where
WD : Fn(Args) -> Weight
fn weigh_data(&self, args: Args) -> Weight {
// `ClassifyDispatch` as a raw value
impl<Args, WD, PF> ClassifyDispatch<Args> for FunctionOf<WD, DispatchClass, PF> {
fn classify_dispatch(&self, _: Args) -> DispatchClass {
// `ClassifyDispatch` as a raw value
impl<Args, WD, CD, PF> ClassifyDispatch<Args> for FunctionOf<WD, CD, PF> where
CD : Fn(Args) -> DispatchClass
fn classify_dispatch(&self, args: Args) -> DispatchClass {
// `PaysFee` as a raw value
impl<Args, WD, CD> PaysFee<Args> for FunctionOf<WD, CD, bool> {
fn pays_fee(&self, _: Args) -> bool {
// `PaysFee` as a closure
impl<Args, WD, CD, PF> PaysFee<Args> for FunctionOf<WD, CD, PF> where
PF : Fn(Args) -> bool
fn pays_fee(&self, args: Args) -> bool {
/// Implementation for unchecked extrinsic.
impl<Address, Call, Signature, Extra> GetDispatchInfo
for UncheckedExtrinsic<Address, Call, Signature, Extra>
Call: GetDispatchInfo,
Extra: SignedExtension,
fn get_dispatch_info(&self) -> DispatchInfo {
/// Implementation for checked extrinsic.
impl<AccountId, Call, Extra> GetDispatchInfo
for CheckedExtrinsic<AccountId, Call, Extra>
Call: GetDispatchInfo,
fn get_dispatch_info(&self) -> DispatchInfo {
/// Implementation for test extrinsic.
#[cfg(feature = "std")]
impl<Call: Encode, Extra: Encode> GetDispatchInfo for sp_runtime::testing::TestXt<Call, Extra> {
fn get_dispatch_info(&self) -> DispatchInfo {
// for testing: weight == size.
DispatchInfo {
weight: self.encode().len() as _,
pays_fee: true,
mod tests {
use crate::decl_module;
use super::*;
pub trait Trait {
type Origin;
type Balance;
type BlockNumber;
pub struct TraitImpl {}
impl Trait for TraitImpl {
type Origin = u32;
type BlockNumber = u32;
type Balance = u32;
decl_module! {
pub struct Module<T: Trait> for enum Call where origin: T::Origin {
// no arguments, fixed weight
#[weight = SimpleDispatchInfo::FixedNormal(1000)]
fn f0(_origin) { unimplemented!(); }
// weight = a x 10 + b
#[weight = FunctionOf(|args: (&u32, &u32)| args.0 * 10 + args.1, DispatchClass::Normal, true)]
fn f11(_origin, _a: u32, _eb: u32) { unimplemented!(); }
#[weight = FunctionOf(|_: (&u32, &u32)| 0, DispatchClass::Operational, true)]
fn f12(_origin, _a: u32, _eb: u32) { unimplemented!(); }
fn weights_are_correct() {
assert_eq!(Call::<TraitImpl>::f11(10, 20).get_dispatch_info().weight, 120);
assert_eq!(Call::<TraitImpl>::f11(10, 20).get_dispatch_info().class, DispatchClass::Normal);
assert_eq!(Call::<TraitImpl>::f0().get_dispatch_info().weight, 1000);
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