Runtime agnostic Events (#20)

* Introduce OpaqueEvent * Look up event by module and variant * Index events by module * Get events by module * Dynamically decode events * Decode System events and EventRecord topics * Use type sizes to decode raw events * Remove unused imports * rustfmt * Unify error types, fix some compiler errors * Make dynamic event decoding work - fix compilation errors - skip modules with no events when indexing - preallocate vec for raw event data * Remove printlns, replace where required with log * Remove unused import * Check missing type sizes * Ignore unknown event arg type sizes * Decode concrete System events, assumes every Runtime has the module * Reorganise usings * pub use some types * Code docs * Export Error * Error Display impls * Format code
2026-06-18 03:41:02 +00:00 · 2019-09-26 17:48:25 +01:00
parent f9ae14bdb9
commit ee6db12917
8 changed files with 595 additions and 99 deletions
@@ -0,0 +1,236 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of substrate-subxt.
+//
+// subxt 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.
+//
+// subxt 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 substrate-subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::{
+    metadata::{
+        EventArg,
+        Metadata,
+        MetadataError,
+    },
+    srml::balances::Balances,
+    System,
+    SystemEvent,
+};
+use log;
+use parity_scale_codec::{
+    Codec,
+    Compact,
+    Decode,
+    Encode,
+    Error as CodecError,
+    Input,
+    Output,
+};
+use srml_system::Phase;
+use std::{
+    collections::{
+        HashMap,
+        HashSet,
+    },
+    convert::TryFrom,
+    marker::{
+        PhantomData,
+        Send,
+    },
+};
+
+/// Top level Event that can be produced by a substrate runtime
+#[derive(Debug)]
+pub enum RuntimeEvent {
+    System(SystemEvent),
+    Raw(RawEvent),
+}
+
+/// Raw bytes for an Event
+#[derive(Debug)]
+pub struct RawEvent {
+    /// The name of the module from whence the Event originated
+    pub module: String,
+    /// The name of the Event
+    pub variant: String,
+    /// The raw Event data
+    pub data: Vec<u8>,
+}
+
+#[derive(Debug, derive_more::From, derive_more::Display)]
+pub enum EventsError {
+    CodecError(CodecError),
+    Metadata(MetadataError),
+    #[display(fmt = "Type Sizes Missing: {:?}", _0)]
+    TypeSizesMissing(Vec<String>),
+    TypeSizeUnavailable(String),
+}
+
+pub struct EventsDecoder<T> {
+    metadata: Metadata, // todo: [AJ] borrow?
+    type_sizes: HashMap<String, usize>,
+    marker: PhantomData<fn() -> T>,
+}
+
+impl<T: System + Balances + 'static> TryFrom<Metadata> for EventsDecoder<T> {
+    type Error = EventsError;
+
+    fn try_from(metadata: Metadata) -> Result<Self, Self::Error> {
+        let mut decoder = Self {
+            metadata,
+            type_sizes: HashMap::new(),
+            marker: PhantomData,
+        };
+        // register default event arg type sizes for dynamic decoding of events
+        decoder.register_type_size::<bool>("bool")?;
+        decoder.register_type_size::<u32>("ReferendumIndex")?;
+        decoder.register_type_size::<[u8; 16]>("Kind")?;
+        decoder.register_type_size::<[u8; 32]>("AuthorityId")?;
+        decoder.register_type_size::<u8>("u8")?;
+        decoder.register_type_size::<u32>("u32")?;
+        decoder.register_type_size::<u32>("AccountIndex")?;
+        decoder.register_type_size::<u32>("SessionIndex")?;
+        decoder.register_type_size::<u32>("PropIndex")?;
+        decoder.register_type_size::<u32>("ProposalIndex")?;
+        decoder.register_type_size::<u32>("AuthorityIndex")?;
+        decoder.register_type_size::<u64>("AuthorityWeight")?;
+        decoder.register_type_size::<u32>("MemberCount")?;
+        decoder.register_type_size::<T::AccountId>("AccountId")?;
+        decoder.register_type_size::<T::BlockNumber>("BlockNumber")?;
+        decoder.register_type_size::<T::Hash>("Hash")?;
+        decoder.register_type_size::<<T as Balances>::Balance>("Balance")?;
+        // VoteThreshold enum index
+        decoder.register_type_size::<u8>("VoteThreshold")?;
+
+        // Ignore these unregistered types, which are not fixed size primitives
+        decoder.check_missing_type_sizes(vec![
+            "DispatchError",
+            "OpaqueTimeSlot",
+            "rstd::marker::PhantomData<(AccountId, Event)>",
+        ])?;
+        Ok(decoder)
+    }
+}
+
+impl<T: System + Balances + 'static> EventsDecoder<T> {
+    pub fn register_type_size<U>(&mut self, name: &str) -> Result<usize, EventsError>
+    where
+        U: Default + Codec + Send + 'static,
+    {
+        let size = U::default().encode().len();
+        if size > 0 {
+            self.type_sizes.insert(name.to_string(), size);
+            Ok(size)
+        } else {
+            Err(EventsError::TypeSizeUnavailable(name.to_owned()))
+        }
+    }
+
+    fn check_missing_type_sizes<I: IntoIterator<Item = &'static str>>(
+        &self,
+        ignore: I,
+    ) -> Result<(), Vec<String>> {
+        let mut missing = HashSet::new();
+        let mut ignore_set = HashSet::new();
+        ignore_set.extend(ignore);
+        for module in self.metadata.modules() {
+            for event in module.events() {
+                for arg in event.arguments() {
+                    for primitive in arg.primitives() {
+                        if !self.type_sizes.contains_key(&primitive)
+                            && !ignore_set.contains(primitive.as_str())
+                        {
+                            missing.insert(primitive);
+                        }
+                    }
+                }
+            }
+        }
+        if missing.is_empty() {
+            Ok(())
+        } else {
+            Err(missing.into_iter().collect())
+        }
+    }
+
+    fn decode_raw_bytes<I: Input, W: Output>(
+        &self,
+        args: &[EventArg],
+        input: &mut I,
+        output: &mut W,
+    ) -> Result<(), EventsError> {
+        for arg in args {
+            match arg {
+                EventArg::Vec(arg) => {
+                    let len = <Compact<u32>>::decode(input)?;
+                    len.encode_to(output);
+                    for _ in 0..len.0 {
+                        self.decode_raw_bytes(&[*arg.clone()], input, output)?
+                    }
+                }
+                EventArg::Tuple(args) => self.decode_raw_bytes(args, input, output)?,
+                EventArg::Primitive(name) => {
+                    if let Some(size) = self.type_sizes.get(name) {
+                        let mut buf = vec![0; *size];
+                        input.read(&mut buf)?;
+                        buf.encode_to(output);
+                    } else {
+                        return Err(EventsError::TypeSizeUnavailable(name.to_owned()))
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+
+    pub fn decode_events(
+        &self,
+        input: &mut &[u8],
+    ) -> Result<Vec<(Phase, RuntimeEvent)>, EventsError> {
+        let compact_len = <Compact<u32>>::decode(input)?;
+        let len = compact_len.0 as usize;
+
+        let mut r = Vec::new();
+        for _ in 0..len {
+            // decode EventRecord
+            let phase = Phase::decode(input)?;
+            let module_variant = input.read_byte()? as u8;
+
+            let module_name = self.metadata.module_name(module_variant)?;
+            let event = if module_name == "System" {
+                let system_event = SystemEvent::decode(input)?;
+                RuntimeEvent::System(system_event)
+            } else {
+                let event_variant = input.read_byte()? as u8;
+                let module = self.metadata.module(&module_name)?;
+                let event_metadata = module.event(event_variant)?;
+                log::debug!("decoding event '{}::{}'", module_name, event_metadata.name);
+
+                let mut event_data = Vec::<u8>::new();
+                self.decode_raw_bytes(
+                    &event_metadata.arguments(),
+                    input,
+                    &mut event_data,
+                )?;
+                RuntimeEvent::Raw(RawEvent {
+                    module: module_name.clone(),
+                    variant: event_metadata.name.clone(),
+                    data: event_data,
+                })
+            };
+
+            // topics come after the event data in EventRecord
+            let _topics = Vec::<T::Hash>::decode(input)?;
+            r.push((phase, event));
+        }
+        Ok(r)
+    }
+}