/// <summary>
/// Parse a textual represenation of patches and return a List of PatchOp objects.
/// </summary>
/// <param name="textline">Text representation of patches</param>
/// <returns>List of PatchOp objects.</returns>
public static List <PatchOp> PatchFromText(this string textline)
{
List <PatchOp> res = new List <PatchOp>();
if (string.IsNullOrEmpty(textline) || textline == "<null>")
{
return(res);
}
string[] text = textline.Split('\n');
int pos = 0;
while (pos < text.Length)
{
if (!PatchOp.TryParse(text[pos], out PatchOp patch))
{
throw new ArgumentException($"Invalid path string: {text[pos]}");
}
res.Add(patch);
pos++;
while (pos < text.Length)
{
if (string.IsNullOrEmpty(text[pos]))
{
// Blank line; continue.
pos++;
continue;
}
if (text[pos].StartsWith("@")) // Start next patch.
{
break;
}
if (DiffOp.TryParse(text[pos], out DiffOp diff))
{
patch.Diffs.AddIfNotNull(diff);
pos++;
}
else
{
break;
}
}
}
return(res);
}
/// <summary>
/// Increase the context until it is unique, but don't let the pattern expand beyond MAX_BITS
/// </summary>
/// <param name="patch">The patch to grow</param>
/// <param name="text">Source text</param>
/// <param name="margin">Chunk size for context length.</param>
private static void AddContext(this PatchOp patch, string text, short margin = 4)
{
if (string.IsNullOrEmpty(text))
{
return;
}
string pattern = text.Substring(patch.Start2, patch.Length1);
int 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 < MAX_BITS - margin - margin)
{
padding += margin;
pattern = text.JavaSubstring(Math.Max(0, patch.Start2 - padding), Math.Min(text.Length, patch.Start2 + patch.Length1 + padding));
}
// Add one chunk for good luck
padding += margin;
// Add the prefix.
string prefix = text.JavaSubstring(Math.Max(0, patch.Start2 - padding), patch.Start2);
if (prefix.Length > 0)
{
patch.Diffs.Insert(0, new DiffOp(Operation.EQUAL, prefix));
}
// Add the suffix.
string suffix = text.JavaSubstring(patch.Start2 + patch.Length1, Math.Min(text.Length, patch.Start2 + patch.Length1 + padding));
if (suffix.Length > 0)
{
patch.Diffs.Add(new DiffOp(Operation.EQUAL, suffix));
}
// Roll back the start points.
patch.Start1 -= prefix.Length;
patch.Start2 -= prefix.Length;
// Extend the lengths
patch.Length1 += prefix.Length + suffix.Length;
patch.Length2 += prefix.Length + suffix.Length;
}
internal static bool TryParse(string s, out PatchOp res)
{
Match m = PATCH_HEADER.Match(s);
if (!m.Success)
{
res = null;
return(false);
}
int[] coords = new int[4];
for (int i = 1; i < 5; i++)
{
if (i % 2 == 1) // odd (start)
{
coords[i - 1] = int.Parse(m.Groups[i].Value);
}
else //even (length)
{
if (m.Groups[i].Length == 0)
{
coords[i - 2]--;
coords[i - 1] = 1;
}
else if (m.Groups[i].Value == "0")
{
coords[i - 1] = 0;
}
else
{
coords[i - 2]--;
coords[i - 1] = int.Parse(m.Groups[i].Value);
}
}
}
res = new PatchOp(coords);
return(true);
}
/// <summary>
/// Add some padding on text start and end so that edges can match something.
/// </summary>
/// <param name="patches">List of PatchOp objects</param>
/// <param name="margin">Chuck size for context length.</param>
/// <returns>The padding added to each side.</returns>
private static string AddPadding(this List <PatchOp> patches, short margin = 4)
{
string padding = string.Empty;
for (short x = 1; x <= margin; x++)
{
padding += (char)x;
}
// Bump all the patches forward.
foreach (var aPatch in patches)
{
aPatch.Start1 += margin;
aPatch.Start2 += margin;
}
// Add some padding on start of first diff.
PatchOp patch = patches.First();
if (patch.Diffs.Count == 0 || patch.Diffs.First().Operation != Operation.EQUAL)
{
// Add padding equality.
patch.Diffs.Insert(0, new DiffOp(Operation.EQUAL, padding));
patch.Start1 -= margin; // should be 0;
patch.Start2 -= margin; // should be 0;
patch.Length1 += margin;
patch.Length2 += margin;
}
else if (margin > patch.Diffs.First().Text.Length)
{
// Grow first equality.
DiffOp fDif = patch.Diffs.First();
int extraLen = margin - fDif.Text.Length;
fDif.Text = padding.Substring(fDif.Text.Length) + fDif.Text;
patch.Start1 -= extraLen;
patch.Start2 -= extraLen;
patch.Length1 += extraLen;
patch.Length2 += extraLen;
}
// Add some padding on end of last diff.
patch = patches.Last();
if (patch.Diffs.Count == 0 || patch.Diffs.Last().Operation != Operation.EQUAL)
{
// Add padding equality
patch.Diffs.Add(new DiffOp(Operation.EQUAL, padding));
patch.Length1 += margin;
patch.Length2 += margin;
}
else if (margin > patch.Diffs.Last().Text.Length)
{
// Grow last equality.
DiffOp lDif = patch.Diffs.Last();
int extaLen = margin - lDif.Text.Length;
lDif.Text += padding.Substring(0, extaLen);
patch.Length1 += extaLen;
patch.Length2 += extaLen;
}
return(padding);
}
/// <summary>
/// Compute a list of patches to turn original into current text.
/// </summary>
/// <remarks>Current text is not provided, it is inferred from the DiffOps</remarks>
/// <param name="original">Original text.</param>
/// <param name="diffs">List of DiffOp objects between original and current text.</param>
/// <param name="margin">Chuck size for context length (default = 4).</param>
/// <returns>List of PatchOp objects.</returns>
public static List <PatchOp> MakePatch(this string original, List <DiffOp> diffs, short margin = 4)
{
List <PatchOp> res = new List <PatchOp>();
if (diffs == null || diffs.Count < 1)
{
return(res); // Get rid of the null case.
}
PatchOp patch = new PatchOp();
int cChar1 = 0; // Number of characters in the text1 string.
int cChar2 = 0; // Number of characters in the text2 string.
// Start with text1 (prepatch) and apply the diffs until we arrive at text2 (postpatch).
// We recreate the patches one-by-one to determine the contact info.
string prepatch = original;
string postpatch = original;
foreach (DiffOp aDiff in diffs)
{
if (patch.Diffs.Count == 0 && aDiff.Operation != Operation.EQUAL)
{
// A new patch starts here.
patch.Start1 = cChar1;
patch.Start2 = cChar2;
}
switch (aDiff.Operation)
{
case Operation.INSERT: {
patch.Diffs.Add(aDiff);
patch.Length2 += aDiff.Text.Length;
postpatch = postpatch.Insert(cChar2, aDiff.Text);
break;
}
case Operation.DELETE: {
patch.Length1 += aDiff.Text.Length;
patch.Diffs.Add(aDiff);
postpatch = postpatch.Remove(cChar2, aDiff.Text.Length);
break;
}
default: {
if (aDiff.Text.Length <= 2 * margin && patch.Diffs.Count != 0 && aDiff != diffs.Last())
{
// Small equality inside a patch
patch.Diffs.Add(aDiff);
patch.Length1 += aDiff.Text.Length;
patch.Length2 += aDiff.Text.Length;
}
if (aDiff.Text.Length >= 2 * margin)
{
// Time for a new patch.
if (patch.Diffs.Count > 0)
{
patch.AddContext(prepatch);
res.Add(patch);
patch = new PatchOp();
// Unlike UniDiff, our patch lists have a rolling context. https://github.com/google/diff-match-patch/wiki/unidiff
// Update prepatch text & pos to reflect the application of the just completed patch.
prepatch = postpatch;
cChar1 = cChar2;
}
}
break;
}
}
// Update the current character count;
if (aDiff.Operation != Operation.INSERT)
{
cChar1 += aDiff.Text.Length;
}
if (aDiff.Operation != Operation.DELETE)
{
cChar2 += aDiff.Text.Length;
}
}
// Pick up the leftover patch if not empty
if (patch.Diffs.Count != 0)
{
patch.AddContext(prepatch);
res.Add(patch);
}
return(res);
}
/// <summary>
/// Look through the patches and break up any which are longer than the maximum limit of the match algorithm.
/// </summary>
/// <param name="patches">List of PatchOp objects.</param>
private static void SplitMax(this List <PatchOp> patches, short margin = 4)
{
for (int x = 0; x < patches.Count; x++)
{
if (patches[x].Length1 <= MAX_BITS)
{
continue;
}
PatchOp bigPatch = patches[x];
// Remove the big old patch.
patches.Splice(x--, 1);
int start1 = bigPatch.Start1;
int start2 = bigPatch.Start2;
string precontext = string.Empty;
while (bigPatch.Diffs.Count != 0)
{
// Create one of several small patches
PatchOp nPatch = new PatchOp();
bool empty = true;
nPatch.Start1 = start1 - precontext.Length;
nPatch.Start2 = start2 - precontext.Length;
if (precontext.Length > 0)
{
nPatch.Length1 = precontext.Length;
nPatch.Length2 = precontext.Length;
nPatch.Diffs.Add(new DiffOp(Operation.EQUAL, precontext));
}
while (bigPatch.Diffs.Count != 0 && nPatch.Length1 < MAX_BITS - margin)
{
Operation diffType = bigPatch.Diffs[0].Operation;
string diffText = bigPatch.Diffs[0].Text;
if (diffType == Operation.INSERT)
{
// Insertions are harmless
nPatch.Length2 = diffText.Length;
start2 += diffText.Length;
nPatch.Diffs.Add(bigPatch.Diffs[0].Clone());
bigPatch.Diffs.RemoveAt(0);
}
else if (diffType == Operation.DELETE && nPatch.Diffs.Count == 1 &&
nPatch.Diffs.First().Operation == Operation.EQUAL && diffText.Length > 2 * MAX_BITS)
{
// This is a large deletion. Let it pass in one chunk.
nPatch.Length1 += diffText.Length;
start1 += diffText.Length;
empty = false;
nPatch.Diffs.Add(new DiffOp(diffType, diffText));
bigPatch.Diffs.RemoveAt(0);
}
else
{
//Deletion or equality. Only take as much as we can stomach.
diffText = diffText.Substring(0, Math.Min(diffText.Length, MAX_BITS - nPatch.Length1 - margin));
nPatch.Length1 = diffText.Length;
start1 += diffText.Length;
if (diffType == Operation.EQUAL)
{
nPatch.Length2 += diffText.Length;
start2 += diffText.Length;
}
else
{
empty = false;
}
nPatch.Diffs.Add(new DiffOp(diffType, diffText));
if (diffText == bigPatch.Diffs[0].Text)
{
bigPatch.Diffs.RemoveAt(0);
}
else
{
bigPatch.Diffs[0].Text = bigPatch.Diffs[0].Text.Substring(diffText.Length);
}
}
}
// Compute the head context for the next patch.
precontext = nPatch.Diffs.CurrentText();
precontext = precontext.Substring(Math.Max(0, precontext.Length - margin));
// Append the end context for this patch.
string orig = bigPatch.Diffs.OriginalText();
string postContext;
if (orig.Length > margin)
{
postContext = orig.Substring(0, margin);
}
else
{
postContext = orig;
}
if (postContext.Length > 0)
{
nPatch.Length1 += postContext.Length;
nPatch.Length2 += postContext.Length;
if (nPatch.Diffs.Count > 0 && nPatch.Diffs[nPatch.Diffs.Count - 1].Operation == Operation.EQUAL)
{
nPatch.Diffs[nPatch.Diffs.Count - 1].Text += postContext;
}
else
{
nPatch.Diffs.Add(new DiffOp(Operation.EQUAL, postContext));
}
}
if (!empty)
{
patches.Splice(++x, 0, nPatch);
}
}
}
}
