/// <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.");
}
