/// <summary>
/// Increase the context until it is unique,
/// but don't let the pattern expand beyond Match_MaxBits.</summary>
/// <param name="text">Source text</param>
/// <param name="patchMargin"></param>
internal void AddContext(string text, short patchMargin = 4)
{
if (text.Length == 0)
{
return;
}
var pattern = text.Substring(Start2, Length1);
var padding = 0;
// Look for the first and last matches of pattern in text. If two
// different matches are found, increase the pattern length.
while (text.IndexOf(pattern, StringComparison.Ordinal)
!= text.LastIndexOf(pattern, StringComparison.Ordinal) &&
pattern.Length < Constants.MatchMaxBits - patchMargin - patchMargin)
{
padding += patchMargin;
var begin = Math.Max(0, Start2 - padding);
pattern = text.Substring(begin, Math.Min(text.Length, Start2 + Length1 + padding) - begin);
}
// Add one chunk for good luck.
padding += patchMargin;
// Add the prefix.
var begin1 = Math.Max(0, Start2 - padding);
var prefix = text.Substring(begin1, Start2 - begin1);
if (prefix.Length != 0)
{
Diffs.Insert(0, Diff.Equal(prefix));
}
// Add the suffix.
var begin2 = Start2 + Length1;
var length = Math.Min(text.Length, Start2 + Length1 + padding) - begin2;
var suffix = text.Substring(begin2, length);
if (suffix.Length != 0)
{
Diffs.Add(Diff.Equal(suffix));
}
// Roll back the start points.
Start1 -= prefix.Length;
Start2 -= prefix.Length;
// Extend the lengths.
Length1 += prefix.Length + suffix.Length;
Length2 += prefix.Length + suffix.Length;
}
public void AddPaddingBeforeFirstDiff(string nullPadding)
{
if (Diffs.Count == 0 || Diffs[0].Operation != Operation.Equal)
{
// Add nullPadding equality.
Diffs.Insert(0, Diff.Equal(nullPadding));
Start1 -= nullPadding.Length; // Should be 0.
Start2 -= nullPadding.Length; // Should be 0.
Length1 += nullPadding.Length;
Length2 += nullPadding.Length;
}
else if (nullPadding.Length > Diffs[0].Text.Length)
{
// Grow first equality.
var firstDiff = Diffs[0];
var extraLength = nullPadding.Length - firstDiff.Text.Length;
Diffs[0] = firstDiff.Replace(nullPadding.Substring(firstDiff.Text.Length) + firstDiff.Text);
Start1 -= extraLength;
Start2 -= extraLength;
Length1 += extraLength;
Length2 += extraLength;
}
}