openethereum/parity/light_helpers/epoch_fetch.rs

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// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.
// Parity Ethereum 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.
// Parity Ethereum 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 Parity Ethereum. If not, see <http://www.gnu.org/licenses/>.
use std::sync::{Arc, Weak};
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use ethcore::{
engines::{EthEngine, StateDependentProof},
machine::EthereumMachine,
};
use sync::{LightNetworkDispatcher, LightSync};
use types::{encoded, header::Header, receipt::Receipt};
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use futures::{future, future::Either, Future};
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use light::{
client::fetch::ChainDataFetcher,
on_demand::{request, OnDemand, OnDemandRequester},
};
use ethereum_types::H256;
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use parking_lot::RwLock;
const ALL_VALID_BACKREFS: &str = "no back-references, therefore all back-references valid; qed";
type BoxFuture<T, E> = Box<Future<Item = T, Error = E>>;
/// Allows on-demand fetch of data useful for the light client.
pub struct EpochFetch {
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/// A handle to the sync service.
pub sync: Arc<RwLock<Weak<LightSync>>>,
/// The on-demand request service.
pub on_demand: Arc<OnDemand>,
}
impl EpochFetch {
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fn request<T>(&self, req: T) -> BoxFuture<T::Out, &'static str>
where
T: Send + request::RequestAdapter + 'static,
T::Out: Send + 'static,
{
Box::new(match self.sync.read().upgrade() {
Some(sync) => {
let on_demand = &self.on_demand;
let maybe_future = sync.with_context(move |ctx| {
on_demand.request(ctx, req).expect(ALL_VALID_BACKREFS)
});
match maybe_future {
Some(x) => Either::A(x.map_err(|_| "Request canceled")),
None => Either::B(future::err("Unable to access network.")),
}
}
None => Either::B(future::err("Unable to access network")),
})
}
}
impl ChainDataFetcher for EpochFetch {
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type Error = &'static str;
type Body = BoxFuture<encoded::Block, &'static str>;
type Receipts = BoxFuture<Vec<Receipt>, &'static str>;
type Transition = BoxFuture<Vec<u8>, &'static str>;
fn block_body(&self, header: &Header) -> Self::Body {
self.request(request::Body(header.encoded().into()))
}
/// Fetch block receipts.
fn block_receipts(&self, header: &Header) -> Self::Receipts {
self.request(request::BlockReceipts(header.encoded().into()))
}
/// Fetch epoch transition proof at given header.
fn epoch_transition(
&self,
hash: H256,
engine: Arc<EthEngine>,
checker: Arc<StateDependentProof<EthereumMachine>>,
) -> Self::Transition {
self.request(request::Signal {
hash: hash,
engine: engine,
proof_check: checker,
})
}
}