191 lines
5.8 KiB
Rust
191 lines
5.8 KiB
Rust
// Copyright 2015-2017 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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//! Request chain builder utility.
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//! Push requests with `push`. Back-references and data required to verify responses must be
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//! supplied as well.
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use std::collections::HashMap;
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use request::{
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IncompleteRequest, CompleteRequest, Request,
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OutputKind, Output, NoSuchOutput, Response, ResponseError,
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};
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/// Build chained requests. Push them onto the series with `push`,
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/// and produce a `Requests` object with `build`. Outputs are checked for consistency.
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#[derive(Debug, Default, Clone, PartialEq, Eq)]
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pub struct RequestBuilder {
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output_kinds: HashMap<(usize, usize), OutputKind>,
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requests: Vec<Request>,
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}
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impl RequestBuilder {
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/// Attempt to push a request onto the request chain. Fails if the request
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/// references a non-existent output of a prior request.
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pub fn push(&mut self, request: Request) -> Result<(), NoSuchOutput> {
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request.check_outputs(|req, idx, kind| {
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match self.output_kinds.get(&(req, idx)) {
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Some(k) if k == &kind => Ok(()),
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_ => Err(NoSuchOutput),
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}
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})?;
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let req_idx = self.requests.len();
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request.note_outputs(|idx, kind| { self.output_kinds.insert((req_idx, idx), kind); });
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self.requests.push(request);
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Ok(())
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}
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/// Get a reference to the output kinds map.
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pub fn output_kinds(&self) -> &HashMap<(usize, usize), OutputKind> {
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&self.output_kinds
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}
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/// Convert this into a "requests" object.
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pub fn build(self) -> Requests {
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Requests {
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outputs: HashMap::new(),
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requests: self.requests,
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answered: 0,
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}
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}
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}
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/// Requests pending responses.
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct Requests {
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outputs: HashMap<(usize, usize), Output>,
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requests: Vec<Request>,
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answered: usize,
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}
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impl Requests {
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/// For each request, produce responses for each.
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/// The responses vector produced goes up to the point where the responder
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/// first returns `None`, an invalid response, or until all requests have been responded to.
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pub fn respond_to_all<F>(mut self, responder: F) -> Vec<Response>
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where F: Fn(CompleteRequest) -> Option<Response>
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{
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let mut responses = Vec::new();
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while let Some(response) = self.next_complete().and_then(&responder) {
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match self.supply_response(&response) {
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Ok(()) => responses.push(response),
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Err(e) => {
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debug!(target: "pip", "produced bad response to request: {:?}", e);
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return responses;
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}
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}
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}
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responses
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}
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/// Get access to the underlying slice of requests.
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// TODO: unimplemented -> Vec<Request>, // do we _have to_ allocate?
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pub fn requests(&self) -> &[Request] { &self.requests }
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/// Get the number of answered requests.
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pub fn num_answered(&self) -> usize { self.answered }
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/// Get the next request as a filled request. Returns `None` when all requests answered.
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pub fn next_complete(&self) -> Option<CompleteRequest> {
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if self.answered == self.requests.len() {
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None
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} else {
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Some(self.requests[self.answered].clone()
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.complete()
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.expect("All outputs checked as invariant of `Requests` object; qed"))
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}
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}
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/// Supply a response for the next request.
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/// Fails on: wrong request kind, all requests answered already.
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pub fn supply_response(&mut self, response: &Response) -> Result<(), ResponseError> {
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let idx = self.answered;
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// check validity.
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if idx == self.requests.len() { return Err(ResponseError::Unexpected) }
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if self.requests[idx].kind() != response.kind() { return Err(ResponseError::WrongKind) }
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let outputs = &mut self.outputs;
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response.fill_outputs(|out_idx, output| {
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// we don't need to check output kinds here because all back-references
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// are validated in the builder.
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// TODO: optimization for only storing outputs we "care about"?
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outputs.insert((idx, out_idx), output);
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});
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self.answered += 1;
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// fill as much of the next request as we can.
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if let Some(ref mut req) = self.requests.get_mut(self.answered) {
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req.fill(|req_idx, out_idx| outputs.get(&(req_idx, out_idx)).cloned().ok_or(NoSuchOutput))
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}
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Ok(())
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}
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}
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#[cfg(test)]
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mod tests {
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use request::*;
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use super::RequestBuilder;
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use util::H256;
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#[test]
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fn all_scalar() {
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let mut builder = RequestBuilder::default();
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builder.push(Request::HeaderProof(IncompleteHeaderProofRequest {
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num: 100.into(),
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})).unwrap();
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builder.push(Request::Receipts(IncompleteReceiptsRequest {
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hash: H256::default().into(),
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})).unwrap();
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}
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#[test]
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#[should_panic]
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fn missing_backref() {
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let mut builder = RequestBuilder::default();
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builder.push(Request::HeaderProof(IncompleteHeaderProofRequest {
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num: Field::BackReference(100, 3),
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})).unwrap();
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}
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#[test]
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#[should_panic]
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fn wrong_kind() {
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let mut builder = RequestBuilder::default();
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assert!(builder.push(Request::HeaderProof(IncompleteHeaderProofRequest {
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num: 100.into(),
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})).is_ok());
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builder.push(Request::HeaderProof(IncompleteHeaderProofRequest {
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num: Field::BackReference(0, 0),
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})).unwrap();
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}
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#[test]
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fn good_backreference() {
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let mut builder = RequestBuilder::default();
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builder.push(Request::HeaderProof(IncompleteHeaderProofRequest {
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num: 100.into(), // header proof puts hash at output 0.
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})).unwrap();
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builder.push(Request::Receipts(IncompleteReceiptsRequest {
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hash: Field::BackReference(0, 0),
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})).unwrap();
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}
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}
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