public void Extract2(int index, int length, string expectedToString)
{
Substring substring = new Substring("abcde", new Range(1, 3));
Assert.AreEqual(expectedToString, substring.Extract(index, length).ToString());
}
// Determines the longest common subsequence between two sequences and populates the
// list of diffs derived from the result as we go. Each recursive step identifies
// a middle "snake" (a common sequence) then splits the problem until nothing remains.
private void ComputeLCS(Substring left, Substring right)
{
int n = left.Length;
int m = right.Length;
if (n != 0 && m != 0)
{
int middleSnakeLeftStartIndex, middleSnakeRightStartIndex, middleSnakeLength;
int ses = FindMiddleSnake(left, right, out middleSnakeLeftStartIndex, out middleSnakeRightStartIndex, out middleSnakeLength);
if (ses > 1)
{
// If SES >= 2 then the edit script includes at least 2 differences, so we divide the problem.
ComputeLCS(
left.Extract(0, middleSnakeLeftStartIndex),
right.Extract(0, middleSnakeRightStartIndex));
EmitDiffsFromCommonSequence(
left.Range.StartIndex + middleSnakeLeftStartIndex,
right.Range.StartIndex + middleSnakeRightStartIndex,
middleSnakeLength);
ComputeLCS(
left.Extract(middleSnakeLeftStartIndex + middleSnakeLength),
right.Extract(middleSnakeRightStartIndex + middleSnakeLength));
}
else
{
// If SES = 1, then exactly one symbol needs to be added or deleted from either sequence.
// If SES = 0, then both sequences are equal.
if (ses != 0)
{
// The middle snake is the common part after the change so we just need to grab the
// common part before the change.
EmitDiffsFromCommonSequence(
left.Range.StartIndex,
right.Range.StartIndex,
Math.Min(middleSnakeLeftStartIndex, middleSnakeRightStartIndex));
}
EmitDiffsFromCommonSequence(
left.Range.StartIndex + middleSnakeLeftStartIndex,
right.Range.StartIndex + middleSnakeRightStartIndex,
middleSnakeLength);
}
}
}
private static void FastDiff(IList<Diff> diffs, Substring left, Substring right, bool boundRuntime)
{
// If either document is empty, then the change covers the whole document.
if (left.Length == 0 || right.Length == 0)
{
diffs.Add(new Diff(DiffKind.Change, left.Range, right.Range));
return;
}
// Reduce the problem size by identifying a common prefix and suffix, if any.
int commonPrefixLength = left.FindCommonPrefixLength(right);
if (commonPrefixLength != 0)
{
if (commonPrefixLength == left.Length && commonPrefixLength == right.Length)
{
diffs.Add(new Diff(DiffKind.NoChange, left.Range, right.Range));
return;
}
diffs.Add(new Diff(DiffKind.NoChange, new Range(left.Range.StartIndex, commonPrefixLength),
new Range(right.Range.StartIndex, commonPrefixLength)));
}
int commonSuffixLength = left.Extract(commonPrefixLength).FindCommonSuffixLength(right.Extract(commonPrefixLength));
// Now work on the middle part.
Substring leftMiddle = left.Extract(commonPrefixLength, left.Length - commonPrefixLength - commonSuffixLength);
Substring rightMiddle = right.Extract(commonPrefixLength, right.Length - commonPrefixLength - commonSuffixLength);
SlowDiff(diffs, leftMiddle, rightMiddle, boundRuntime);
// Tack on the final diff for the common suffix, if any.
if (commonSuffixLength != 0)
{
diffs.Add(new Diff(DiffKind.NoChange,
new Range(leftMiddle.Range.EndIndex, commonSuffixLength),
new Range(rightMiddle.Range.EndIndex, commonSuffixLength)));
}
}
private static void WriteContext(MarkupStreamWriter writer, Substring context, int maxContextLength)
{
if (context.Length < maxContextLength)
{
writer.Write(context.ToString());
}
else
{
int split = maxContextLength / 2;
if (split > 0)
{
writer.Write(context.Extract(0, split).ToString());
writer.WriteEllipsis();
writer.Write(context.Extract(context.Length - split));
}
}
}
public void Extract2(int index, int length, string expectedToString)
{
Substring substring = new Substring("abcde", new Range(1, 3));
Assert.AreEqual(expectedToString, substring.Extract(index, length).ToString());
}
