コード例 #1
0
        /// <summary>
        /// Is this Reflexive, AntiSymetic, and Transitive? 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 CONCURRANT 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
        /// </summary>
        /// <param name="v1">The first VectorClock</param>
        /// <param name="v2">The second VectorClock</param>
        /// <returns>Whether the change occured before, after or concurrently</returns>
        public static Occured Compare(VectorClock v1, VectorClock v2)
        {
            if (v1 == null || v2 == null)
                throw new ArgumentException("Can't compare null vector clocks!");

            // We do two checks: v1 <= v2 and v2 <= v1 if both are true then
            bool v1Bigger = false;
            bool v2Bigger = false;
            int p1 = 0;
            int p2 = 0;

            while (p1 < v1.versions.Count && p2 < v2.versions.Count)
            {
                ClockEntry ver1 = v1.versions[p1];
                ClockEntry ver2 = v2.versions[p2];

                if (ver1.NodeId == ver2.NodeId)
                {
                    if (ver1.Version > ver2.Version)
                        v1Bigger = true;
                    else if (ver2.Version > ver1.Version)
                        v2Bigger = true;
                    p1++;
                    p2++;
                }
                else if (ver1.NodeId > ver2.NodeId)
                {
                    // since ver1 is bigger that means it is missing a version that ver2 has
                    v2Bigger = true;
                    p2++;
                }
                else
                {
                    // this means ver2 is bigger which means it is missing a version ver1 has
                    v1Bigger = true;
                    p1++;
                }
            }

            // Check for left overs
            if (p1 < v1.versions.Count)
                v1Bigger = true;
            else if (p2 < v2.versions.Count)
                v2Bigger = true;

            // This is the case where they are equal, return BEFORE arbitrarily
            if (!v1Bigger && !v2Bigger)
                return Occured.Before;
            // This is the case where v1 is a successor clock to v2
            else if (v1Bigger && !v2Bigger)
                return Occured.After;
            // This is the case where v2 is a successor clock to v1
            else if (!v1Bigger && v2Bigger)
                return Occured.Before;
            // This is the case where both clocks are parallel to one another
            else
                return Occured.Concurrently;
        }
コード例 #2
0
        public VectorClock Merge(VectorClock clock)
        {
            VectorClock newClock = new VectorClock();
            int i = 0;
            int j = 0;
            while (i < this.versions.Count && j < clock.versions.Count)
            {
                ClockEntry v1 = this.versions[i];
                ClockEntry v2 = clock.versions[j];
                if (v1.NodeId == v2.NodeId)
                {
                    newClock.versions.Add(new ClockEntry(v1.NodeId,
                                                         (short)Math.Max(v1.Version,
                                                                          v2.Version)));
                    i++;
                    j++;
                }
                else if (v1.NodeId < v2.NodeId)
                {
                    newClock.versions.Add(v1.Clone());
                    i++;
                }
                else
                {
                    newClock.versions.Add(v2.Clone());
                    j++;
                }
            }

            // Okay now there may be leftovers on one or the other list remaining
            for (int k = i; k < this.versions.Count; k++)
                newClock.versions.Add(this.versions[k].Clone());
            for (int k = j; k < clock.versions.Count; k++)
                newClock.versions.Add(clock.versions[k].Clone());

            return newClock;
        }