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/* -*- C++ -*-; c-basic-offset: 4; indent-tabs-mode: nil */
/*!
* @file VectorClock.h
* @brief Interface definition file for VectorClock
*/
/* Copyright (c) 2009 Webroot Software, Inc.
*
* Licensed under the Apache License, VectorClock 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
#ifndef VECTORCLOCK_H
#define VECTORCLOCK_H
#include <stdint.h>
#include <voldemort/Version.h>
#include <list>
#include <utility>
#include <ostream>
namespace Voldemort {
/**
* A vector of the number of writes mastered by each node. The vector is stored
* sparsly, since, in general, writes will be mastered by only one node. This
* means implicitly all the versions are at zero, but we only actually store
* those greater than zero.
*
*/
class VectorClock: public Version
{
public:
/**
* Construct an empty VectorClock
*/
VectorClock();
/**
* Construct an empty VectorClock using the provided timestamp
*
* @param timestamp the timestamp to initialize to
*/
VectorClock(uint64_t timestamp);
/**
* Construct a VectorClock using the provided versions and timestamp
*
* @param versions the versions to include in the clock
* @param timestamp the timestamp to initialize to
*/
VectorClock(std::list<std::pair<short, uint64_t> >* versions, uint64_t timestamp);
virtual ~VectorClock();
/**
* Get the list of version entries
*/
const std::list<std::pair<short, uint64_t> >* getEntries() const;
/**
* Compare two VectorClocks, the outcomes will be one of the
* following: -- Clock 1 is BEFORE clock 2 if there exists an i
* such that c1(i) <= c(2) and there does not exist a j such that
* c1(j) > c2(j). -- Clock 1 is CONCURRENT to clock 2 if there
* exists an i, j such that c1(i) < c2(i) and c1(j) > c2(j) --
* Clock 1 is AFTER clock 2 otherwise
*
* @param v1 The first VectorClock
* @param v2 The second VectorClock
* @return one of the Occurred values
*/
static Occurred compare(const VectorClock* v1, const VectorClock* v2);
/**
* Get the timestamp
*/
uint64_t getTimestamp();
// Version interface
virtual VectorClock* copy() const;
virtual Occurred compare(const Version* v) const;
virtual void toStream(std::ostream& output) const;
private:
// Disable copy constructor
VectorClock(const VectorClock& v) { }
/**
* The time of the last update on the server on which the update
* was performed
*/
uint64_t timestamp;
/**
* The versions contained in this clock
*/
std::list<std::pair<short, uint64_t> >* versions;
};
} /* namespace Voldemort */
#endif // VECTORCLOCK_H
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