openethereum/parity/light_helpers/epoch_fetch.rs
2017-08-24 15:17:48 +02:00

90 lines
2.7 KiB
Rust

// Copyright 2015-2017 Parity Technologies (UK) Ltd.
// This file is part of Parity.
// Parity 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 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. If not, see <http://www.gnu.org/licenses/>.
use std::sync::{Arc, Weak};
use ethcore::encoded;
use ethcore::engines::{Engine, StateDependentProof};
use ethcore::header::Header;
use ethcore::receipt::Receipt;
use ethsync::LightSync;
use futures::{future, Future, BoxFuture};
use light::client::fetch::ChainDataFetcher;
use light::on_demand::{request, OnDemand};
use util::{RwLock, H256};
const ALL_VALID_BACKREFS: &str = "no back-references, therefore all back-references valid; qed";
/// Allows on-demand fetch of data useful for the light client.
pub struct EpochFetch {
/// A handle to the sync service.
pub sync: Arc<RwLock<Weak<LightSync>>>,
/// The on-demand request service.
pub on_demand: Arc<OnDemand>,
}
impl EpochFetch {
fn request<T>(&self, req: T) -> BoxFuture<T::Out, &'static str>
where T: Send + request::RequestAdapter + 'static, T::Out: Send + 'static
{
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) => x.map_err(|_| "Request canceled").boxed(),
None => future::err("Unable to access network.").boxed(),
}
}
None => future::err("Unable to access network").boxed(),
}
}
}
impl ChainDataFetcher for EpochFetch {
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<Engine>, checker: Arc<StateDependentProof>)
-> Self::Transition
{
self.request(request::Signal {
hash: hash,
engine: engine,
proof_check: checker,
})
}
}