/// <summary> /// Find the difference in 2 arrays of integers. /// </summary> /// <param name="arrayA">A-version of the numbers (usually the old one)</param> /// <param name="arrayB">B-version of the numbers (usually the new one)</param> /// <returns>Returns a array of Items that describe the differences.</returns> public Difference[] DiffInt(int[] arrayA, int[] arrayB) { // The A-Version of the data (original data) to be compared. var dataA = new DiffData(arrayA); // The B-Version of the data (modified data) to be compared. var dataB = new DiffData(arrayB); var max = dataA.Length + dataB.Length + 1; // vector for the (0,0) to (x,y) search var downVector = new int[(2 * max) + 2]; // vector for the (u,v) to (N,M) search var upVector = new int[(2 * max) + 2]; this.LongestCommonSubsequence(dataA, 0, dataA.Length, dataB, 0, dataB.Length, downVector, upVector); return(this.CreateDiffs(dataA, dataB)); }
/// <summary> /// Find the difference in 2 arrays of integers. /// </summary> /// <param name="arrayA">A-version of the numbers (usually the old one)</param> /// <param name="arrayB">B-version of the numbers (usually the new one)</param> /// <returns>Returns a array of Items that describe the differences.</returns> public Difference[] DiffInt(int[] arrayA, int[] arrayB) { // The A-Version of the data (original data) to be compared. var dataA = new DiffData(arrayA); // The B-Version of the data (modified data) to be compared. var dataB = new DiffData(arrayB); var max = dataA.Length + dataB.Length + 1; // vector for the (0,0) to (x,y) search var downVector = new int[(2 * max) + 2]; // vector for the (u,v) to (N,M) search var upVector = new int[(2 * max) + 2]; this.LongestCommonSubsequence(dataA, 0, dataA.Length, dataB, 0, dataB.Length, downVector, upVector); return this.CreateDiffs(dataA, dataB); }
/// <summary> /// Find the difference in 2 text documents, comparing by textlines. /// The algorithm itself is comparing 2 arrays of numbers so when comparing 2 text documents /// each line is converted into a (hash) number. This hash-value is computed by storing all /// textlines into a common hashtable so i can find duplicates in there, and generating a /// new number each time a new textline is inserted. /// </summary> /// <param name="textA">A-version of the text (usually the old one)</param> /// <param name="textB">B-version of the text (usually the new one)</param> /// <param name="trimSpace">When set to true, all leading and trailing whitespace characters are stripped out before the comparation is done.</param> /// <param name="ignoreSpace">When set to true, all whitespace characters are converted to a single space character before the comparation is done.</param> /// <param name="ignoreCase">When set to true, all characters are converted to their lowercase equivivalence before the comparation is done.</param> /// <returns>Returns a array of Items that describe the differences.</returns> public Difference[] DiffText( string textA, string textB, bool trimSpace, bool ignoreSpace, bool ignoreCase) { // prepare the input-text and convert to comparable numbers. var h = new Hashtable(textA.Length + textB.Length); // The A-Version of the data (original data) to be compared. var dataA = new DiffData(this.DiffCodes(textA, h, trimSpace, ignoreSpace, ignoreCase)); // The B-Version of the data (modified data) to be compared. var dataB = new DiffData(this.DiffCodes(textB, h, trimSpace, ignoreSpace, ignoreCase)); var max = dataA.Length + dataB.Length + 1; // vector for the (0,0) to (x,y) search var downVector = new int[(2 * max) + 2]; // vector for the (u,v) to (N,M) search var upVector = new int[(2 * max) + 2]; this.LongestCommonSubsequence(dataA, 0, dataA.Length, dataB, 0, dataB.Length, downVector, upVector); this.Optimize(dataA); this.Optimize(dataB); return this.CreateDiffs(dataA, dataB); }
/// <summary> /// This is the algorithm to find the Shortest Middle Snake (SMS). /// </summary> /// <param name="dataA">sequence A</param> /// <param name="lowerA">lower bound of the actual range in DataA</param> /// <param name="upperA">upper bound of the actual range in DataA (exclusive)</param> /// <param name="dataB">sequence B</param> /// <param name="lowerB">lower bound of the actual range in DataB</param> /// <param name="upperB">upper bound of the actual range in DataB (exclusive)</param> /// <param name="downVector">a vector for the (0,0) to (x,y) search. Passed as a parameter for speed reasons.</param> /// <param name="upVector">a vector for the (u,v) to (N,M) search. Passed as a parameter for speed reasons.</param> /// <returns>a MiddleSnakeData record containing x,y and u,v</returns> private ShortestMiddleSnakeReturnData ShortestMiddleSnake( DiffData dataA, int lowerA, int upperA, DiffData dataB, int lowerB, int upperB, int[] downVector, int[] upVector) { var ret = default(ShortestMiddleSnakeReturnData); int max = dataA.Length + dataB.Length + 1; int downK = lowerA - lowerB; // the k-line to start the forward search int upK = upperA - upperB; // the k-line to start the reverse search int delta = (upperA - lowerA) - (upperB - lowerB); bool oddDelta = (delta & 1) != 0; // The vectors in the publication accepts negative indexes. the vectors implemented here are 0-based // and are access using a specific offset: UpOffset UpVector and DownOffset for DownVektor int downOffset = max - downK; int upOffset = max - upK; int maxD = ((upperA - lowerA + upperB - lowerB) / 2) + 1; // Debug.Write(2, "SMS", String.Format("Search the box: A[{0}-{1}] to B[{2}-{3}]", LowerA, UpperA, LowerB, UpperB)); // init vectors downVector[downOffset + downK + 1] = lowerA; upVector[upOffset + upK - 1] = upperA; for (int d = 0; d <= maxD; d++) { // Extend the forward path. for (int k = downK - d; k <= downK + d; k += 2) { // Debug.Write(0, "SMS", "extend forward path " + k.ToString()); // find the only or better starting point int x; if (k == downK - d) { x = downVector[downOffset + k + 1]; // down } else { x = downVector[downOffset + k - 1] + 1; // a step to the right if ((k < downK + d) && (downVector[downOffset + k + 1] >= x)) { x = downVector[downOffset + k + 1]; // down } } int y = x - k; // find the end of the furthest reaching forward D-path in diagonal k. while ((x < upperA) && (y < upperB) && (dataA.Data[x] == dataB.Data[y])) { x++; y++; } downVector[downOffset + k] = x; // overlap ? if (oddDelta && (upK - d < k) && (k < upK + d)) { if (upVector[upOffset + k] <= downVector[downOffset + k]) { ret.X = downVector[downOffset + k]; ret.Y = downVector[downOffset + k] - k; return ret; } } } // Extend the reverse path. for (int k = upK - d; k <= upK + d; k += 2) { // Debug.Write(0, "SMS", "extend reverse path " + k.ToString()); // find the only or better starting point int x; if (k == upK + d) { x = upVector[upOffset + k - 1]; // up } else { x = upVector[upOffset + k + 1] - 1; // left if ((k > upK - d) && (upVector[upOffset + k - 1] < x)) { x = upVector[upOffset + k - 1]; // up } } var y = x - k; while ((x > lowerA) && (y > lowerB) && (dataA.Data[x - 1] == dataB.Data[y - 1])) { x--; y--; // diagonal } upVector[upOffset + k] = x; // overlap ? if (!oddDelta && (downK - d <= k) && (k <= downK + d)) { if (upVector[upOffset + k] <= downVector[downOffset + k]) { ret.X = downVector[downOffset + k]; ret.Y = downVector[downOffset + k] - k; return ret; } } } } throw new Exception("the algorithm should never come here."); }
/// <summary> /// If a sequence of modified lines starts with a line that contains the same content /// as the line that appends the changes, the difference sequence is modified so that the /// appended line and not the starting line is marked as modified. /// This leads to more readable diff sequences when comparing text files. /// </summary> /// <param name="data">A Diff data buffer containing the identified changes.</param> private void Optimize(DiffData data) { int startPos = 0; while (startPos < data.Length) { while ((startPos < data.Length) && (data.Modified[startPos] == false)) { startPos++; } int endPos = startPos; while ((endPos < data.Length) && data.Modified[endPos]) { endPos++; } if ((endPos < data.Length) && (data.Data[startPos] == data.Data[endPos])) { data.Modified[startPos] = false; data.Modified[endPos] = true; } else { startPos = endPos; } } }
/// <summary> /// This is the divide-and-conquer implementation of the longest common-subsequence (LCS) /// algorithm. /// The published algorithm passes recursively parts of the A and B sequences. /// To avoid copying these arrays the lower and upper bounds are passed while the sequences stay constant. /// </summary> /// <param name="dataA">sequence A</param> /// <param name="lowerA">lower bound of the actual range in DataA</param> /// <param name="upperA">upper bound of the actual range in DataA (exclusive)</param> /// <param name="dataB">sequence B</param> /// <param name="lowerB">lower bound of the actual range in DataB</param> /// <param name="upperB">upper bound of the actual range in DataB (exclusive)</param> /// <param name="downVector">a vector for the (0,0) to (x,y) search. Passed as a parameter for speed reasons.</param> /// <param name="upVector">a vector for the (u,v) to (N,M) search. Passed as a parameter for speed reasons.</param> private void LongestCommonSubsequence( DiffData dataA, int lowerA, int upperA, DiffData dataB, int lowerB, int upperB, int[] downVector, int[] upVector) { // Debug.Write(2, "LCS", String.Format("Analyse the box: A[{0}-{1}] to B[{2}-{3}]", LowerA, UpperA, LowerB, UpperB)); // Fast walkthrough equal lines at the start while (lowerA < upperA && lowerB < upperB && dataA.Data[lowerA] == dataB.Data[lowerB]) { lowerA++; lowerB++; } // Fast walkthrough equal lines at the end while (lowerA < upperA && lowerB < upperB && dataA.Data[upperA - 1] == dataB.Data[upperB - 1]) { --upperA; --upperB; } if (lowerA == upperA) { // mark as inserted lines. while (lowerB < upperB) { dataB.Modified[lowerB++] = true; } } else if (lowerB == upperB) { // mark as deleted lines. while (lowerA < upperA) { dataA.Modified[lowerA++] = true; } } else { // Find the middle snake and length of an optimal path for A and B var smsrd = this.ShortestMiddleSnake(dataA, lowerA, upperA, dataB, lowerB, upperB, downVector, upVector); // Debug.Write(2, "MiddleSnakeData", String.Format("{0},{1}", smsrd.x, smsrd.y)); // The path is from LowerX to (x,y) and (x,y) to UpperX this.LongestCommonSubsequence(dataA, lowerA, smsrd.X, dataB, lowerB, smsrd.Y, downVector, upVector); this.LongestCommonSubsequence(dataA, smsrd.X, upperA, dataB, smsrd.Y, upperB, downVector, upVector); } }
/// <summary>Scan the tables of which lines are inserted and deleted, /// producing an edit script in forward order. /// </summary> /// dynamic array private Difference[] CreateDiffs(DiffData dataA, DiffData dataB) { var differences = new ArrayList(); var lineA = 0; var lineB = 0; while (lineA < dataA.Length || lineB < dataB.Length) { if ((lineA < dataA.Length) && (!dataA.Modified[lineA]) && (lineB < dataB.Length) && (!dataB.Modified[lineB])) { // equal lines lineA++; lineB++; } else { // maybe deleted and/or inserted lines var startA = lineA; var startB = lineB; // while (LineA < DataA.Length && DataA.modified[LineA]) while (lineA < dataA.Length && (lineB >= dataB.Length || dataA.Modified[lineA])) { lineA++; } // while (LineB < DataB.Length && DataB.modified[LineB]) while (lineB < dataB.Length && (lineA >= dataA.Length || dataB.Modified[lineB])) { lineB++; } if ((startA < lineA) || (startB < lineB)) { // store a new difference-item var item = new Difference { StartA = startA, StartB = startB, DeletedA = lineA - startA, InsertedB = lineB - startB }; differences.Add(item); } } } var result = new Difference[differences.Count]; differences.CopyTo(result); return result; }
/// <summary> /// This is the algorithm to find the Shortest Middle Snake (SMS). /// </summary> /// <param name="dataA">sequence A</param> /// <param name="lowerA">lower bound of the actual range in DataA</param> /// <param name="upperA">upper bound of the actual range in DataA (exclusive)</param> /// <param name="dataB">sequence B</param> /// <param name="lowerB">lower bound of the actual range in DataB</param> /// <param name="upperB">upper bound of the actual range in DataB (exclusive)</param> /// <param name="downVector">a vector for the (0,0) to (x,y) search. Passed as a parameter for speed reasons.</param> /// <param name="upVector">a vector for the (u,v) to (N,M) search. Passed as a parameter for speed reasons.</param> /// <returns>a MiddleSnakeData record containing x,y and u,v</returns> private ShortestMiddleSnakeReturnData ShortestMiddleSnake( DiffData dataA, int lowerA, int upperA, DiffData dataB, int lowerB, int upperB, int[] downVector, int[] upVector) { var ret = new ShortestMiddleSnakeReturnData(); int max = dataA.Length + dataB.Length + 1; int downK = lowerA - lowerB; // the k-line to start the forward search int upK = upperA - upperB; // the k-line to start the reverse search int delta = (upperA - lowerA) - (upperB - lowerB); bool oddDelta = (delta & 1) != 0; // The vectors in the publication accepts negative indexes. the vectors implemented here are 0-based // and are access using a specific offset: UpOffset UpVector and DownOffset for DownVektor int downOffset = max - downK; int upOffset = max - upK; int maxD = ((upperA - lowerA + upperB - lowerB) / 2) + 1; // Debug.Write(2, "SMS", String.Format("Search the box: A[{0}-{1}] to B[{2}-{3}]", LowerA, UpperA, LowerB, UpperB)); // init vectors downVector[downOffset + downK + 1] = lowerA; upVector[upOffset + upK - 1] = upperA; for (int d = 0; d <= maxD; d++) { // Extend the forward path. for (int k = downK - d; k <= downK + d; k += 2) { // Debug.Write(0, "SMS", "extend forward path " + k.ToString()); // find the only or better starting point int x; if (k == downK - d) { x = downVector[downOffset + k + 1]; // down } else { x = downVector[downOffset + k - 1] + 1; // a step to the right if ((k < downK + d) && (downVector[downOffset + k + 1] >= x)) { x = downVector[downOffset + k + 1]; // down } } int y = x - k; // find the end of the furthest reaching forward D-path in diagonal k. while ((x < upperA) && (y < upperB) && (dataA.Data[x] == dataB.Data[y])) { x++; y++; } downVector[downOffset + k] = x; // overlap ? if (oddDelta && (upK - d < k) && (k < upK + d)) { if (upVector[upOffset + k] <= downVector[downOffset + k]) { ret.X = downVector[downOffset + k]; ret.Y = downVector[downOffset + k] - k; return(ret); } } } // Extend the reverse path. for (int k = upK - d; k <= upK + d; k += 2) { // Debug.Write(0, "SMS", "extend reverse path " + k.ToString()); // find the only or better starting point int x, y; if (k == upK + d) { x = upVector[upOffset + k - 1]; // up } else { x = upVector[upOffset + k + 1] - 1; // left if ((k > upK - d) && (upVector[upOffset + k - 1] < x)) { x = upVector[upOffset + k - 1]; // up } } y = x - k; while ((x > lowerA) && (y > lowerB) && (dataA.Data[x - 1] == dataB.Data[y - 1])) { x--; y--; // diagonal } upVector[upOffset + k] = x; // overlap ? if (!oddDelta && (downK - d <= k) && (k <= downK + d)) { if (upVector[upOffset + k] <= downVector[downOffset + k]) { ret.X = downVector[downOffset + k]; ret.Y = downVector[downOffset + k] - k; return(ret); } } } } throw new Exception("the algorithm should never come here."); }