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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
* Copyright (c) 2013-2014 Regents of the University of California.
*
* This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
*
* ndn-cxx library is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later version.
*
* ndn-cxx library 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 Lesser General Public License for more details.
*
* You should have received copies of the GNU General Public License and GNU Lesser
* General Public License along with ndn-cxx, e.g., in COPYING.md file. If not, see
* <http://www.gnu.org/licenses/>.
*
* See AUTHORS.md for complete list of ndn-cxx authors and contributors.
*/
#ifndef NDN_UTIL_SEGMENT_FETCHER_HPP
#define NDN_UTIL_SEGMENT_FETCHER_HPP
#include "../common.hpp"
#include "../face.hpp"
namespace ndn {
class OBufferStream;
namespace util {
/**
* @brief Functor to skip validation of individual packets by SegmentFetcher
*/
class DontVerifySegment
{
public:
bool
operator()(const Data& data) const
{
return true;
}
};
/**
* @brief Utility class to fetch latest version of the segmented data
*
* SegmentFetcher assumes that the data is named /<prefix>/<version>/<segment>,
* where:
* - <prefix> is the specified prefix,
* - <version> is an unknown version that needs to be discovered, and
* - <segment> is a segment number (number of segments is unknown and is controlled
* by `FinalBlockId` field in at least the last Data packet
*
* The following logic is implemented in SegmentFetcher:
*
* 1. Express first interest to discover version:
*
* >> Interest: /<prefix>?ChildSelector=1&MustBeFresh=yes
*
* 2. Infer the latest version of Data: <version> = Data.getName().get(-2)
*
* 3. If segment number in the retrieved packet == 0, go to step 5.
*
* 4. Send Interest for segment 0:
*
* >> Interest: /<prefix>/<version>/<segment=0>
*
* 5. Keep sending Interests for the next segment while the retrieved Data does not have
* FinalBlockId or FinalBlockId != Data.getName().get(-1).
*
* >> Interest: /<prefix>/<version>/<segment=(N+1))>
*
* 6. Fire onCompletion callback with memory block that combines content part from all
* segmented objects.
*
* If an error occurs during the fetching process, an error callback is fired
* with a proper error code. The following errors are possible:
*
* - `INTEREST_TIMEOUT`: if any of the Interests times out
* - `DATA_HAS_NO_SEGMENT`: if any of the retrieved Data packets don't have segment
* as a last component of the name (not counting implicit digest)
* - `SEGMENT_VERIFICATION_FAIL`: if any retrieved segment fails user-provided validation
*
* In order to validate individual segments, an VerifySegment callback needs to be specified.
* If the callback returns false, fetching process is aborted with SEGMENT_VERIFICATION_FAIL.
* If data validation is not required, provided DontVerifySegment() functor can be used.
*
* Examples:
*
* void
* onComplete(const ConstBufferPtr& data)
* {
* ...
* }
*
* void
* onError(uint32_t errorCode, const std::string& errorMsg)
* {
* ...
* }
*
* ...
* SegmentFetcher::fetch(face, Interest("/data/prefix", time::seconds(1000)),
* DontVerifySegment(),
* bind(&onComplete, this, _1),
* bind(&onError, this, _1, _2));
*
*/
class SegmentFetcher : noncopyable
{
public:
typedef function<void (const ConstBufferPtr& data)> CompleteCallback;
typedef function<bool (const Data& data)> VerifySegment;
typedef function<void (uint32_t code, const std::string& msg)> ErrorCallback;
/**
* @brief Error codes that can be passed to ErrorCallback
*/
enum ErrorCode {
INTEREST_TIMEOUT = 1,
DATA_HAS_NO_SEGMENT = 2,
SEGMENT_VERIFICATION_FAIL = 3
};
/**
* @brief Initiate segment fetching
*
* @param face Reference to the Face that should be used to fetch data
* @param baseInterest An Interest for the initial segment of requested data.
* This interest may include custom InterestLifetime and selectors that
* will propagate to all subsequent Interests. The only exception is that
* the initial Interest will be forced to include "ChildSelector=1" and
* "MustBeFresh=true" selectors, which will be turned off in subsequent
* Interests.
* @param verifySegment Functor to be called when Data segment is received. If
* functor return false, fetching will be aborted with
* SEGMENT_VERIFICATION_FAIL error
* @param completeCallback Callback to be fired when all segments are fetched
* @param errorCallback Callback to be fired when an error occurs (@see Errors)
*/
static
void
fetch(Face& face,
const Interest& baseInterest,
const VerifySegment& verifySegment,
const CompleteCallback& completeCallback,
const ErrorCallback& errorCallback);
private:
SegmentFetcher(Face& face,
const VerifySegment& verifySegment,
const CompleteCallback& completeCallback,
const ErrorCallback& errorCallback);
void
fetchFirstSegment(const Interest& baseInterest, const shared_ptr<SegmentFetcher>& self);
void
fetchNextSegment(const Interest& origInterest, const Name& dataName, uint64_t segmentNo,
const shared_ptr<SegmentFetcher>& self);
void
onSegmentReceived(const Interest& origInterest,
const Data& data, bool isSegmentZeroExpected,
const shared_ptr<SegmentFetcher>& self);
private:
Face& m_face;
VerifySegment m_verifySegment;
CompleteCallback m_completeCallback;
ErrorCallback m_errorCallback;
shared_ptr<OBufferStream> m_buffer;
};
} // util
} // ndn
#endif // NDN_UTIL_SEGMENT_FETCHER_HPP