openethereum/hash-fetch/src/client.rs

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2016-12-11 19:15:58 +01:00
// Copyright 2015, 2016 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/>.
//! Hash-addressed content resolver & fetcher.
use std::{io, fs};
use std::sync::Arc;
use std::path::PathBuf;
use util::{Mutex, H256, sha3};
use fetch::{Fetch, FetchError, Client as FetchClient};
use urlhint::{ContractClient, URLHintContract, URLHint, URLHintResult};
/// API for fetching by hash.
pub trait HashFetch: Send + Sync + 'static {
/// Fetch hash-addressed content.
/// Parameters:
/// 1. `hash` - content hash
/// 2. `on_done` - callback function invoked when the content is ready (or there was error during fetch)
///
/// This function may fail immediately when fetch cannot be initialized or content cannot be resolved.
fn fetch(&self, hash: H256, on_done: Box<Fn(Result<PathBuf, Error>) + Send>) -> Result<(), Error>;
}
/// Hash-fetching error.
#[derive(Debug)]
pub enum Error {
/// Hash could not be resolved to a valid content address.
NoResolution,
/// Downloaded content hash does not match.
HashMismatch {
/// Expected hash
expected: H256,
/// Computed hash
got: H256,
},
/// IO Error while validating hash.
IO(io::Error),
/// Error during fetch.
Fetch(FetchError),
}
impl From<FetchError> for Error {
fn from(error: FetchError) -> Self {
Error::Fetch(error)
}
}
impl From<io::Error> for Error {
fn from(error: io::Error) -> Self {
Error::IO(error)
}
}
/// Default Hash-fetching client using on-chain contract to resolve hashes to URLs.
pub struct Client {
contract: URLHintContract,
fetch: Mutex<FetchClient>,
}
impl Client {
/// Creates new instance of the `Client` given on-chain contract client.
pub fn new(contract: Arc<ContractClient>) -> Self {
Client {
contract: URLHintContract::new(contract),
fetch: Mutex::new(FetchClient::default()),
}
}
}
impl HashFetch for Client {
fn fetch(&self, hash: H256, on_done: Box<Fn(Result<PathBuf, Error>) + Send>) -> Result<(), Error> {
debug!(target: "fetch", "Fetching: {:?}", hash);
let url = try!(
self.contract.resolve(hash.to_vec()).map(|content| match content {
URLHintResult::Dapp(dapp) => {
dapp.url()
},
URLHintResult::Content(content) => {
content.url
},
}).ok_or_else(|| Error::NoResolution)
);
debug!(target: "fetch", "Resolved {:?} to {:?}. Fetching...", hash, url);
self.fetch.lock().request_async(&url, Default::default(), Box::new(move |result| {
fn validate_hash(hash: H256, result: Result<PathBuf, FetchError>) -> Result<PathBuf, Error> {
let path = try!(result);
let mut file_reader = io::BufReader::new(try!(fs::File::open(&path)));
let content_hash = try!(sha3(&mut file_reader));
if content_hash != hash {
Err(Error::HashMismatch{ got: content_hash, expected: hash })
} else {
Ok(path)
}
}
debug!(target: "fetch", "Content fetched, validating hash ({:?})", hash);
on_done(validate_hash(hash, result))
})).map_err(Into::into)
}
}