/**
* Performs a multi-pass diff between the base and witness documents provided. This first performs
* a normal diff, and then takes all the ares that are marked as change blocks and diffs them
* against one another. The differences are integrated into a single set of differences, providing
* a much higher resolution result set.
*
* @return A <code>DifferenceSet</code> containing the differences between the two documents.
*/
public MultiPassDiff(DocumentModel baseDocument, DocumentModel witnessDocument) {
diff = new DiffAlgorithm();
DifferenceSet diffSet = diff.diffDocuments(baseDocument, witnessDocument);
DifferenceConsolidator differenceConsolidator =
new DifferenceConsolidator(baseDocument, witnessDocument);
differenceConsolidator.consolidateDifferences(diffSet);
/**
* Keeps doing a diff on the change blocks as long as a large change block is getting broken
* down, and the max number of passes haven't been made.
*/
previousLargestChangeBlock = Integer.MAX_VALUE;
int iterationCount = 0;
while (iterationCount < MAX_DIFF_PASSES
&& diffSet.getLargestChangeBlock() < previousLargestChangeBlock) {
iterationCount++;
// System.out.println("Iteration number: " + iterationCount);
// System.out.println("Largest Change Block: " + diffSet.getLargestChangeBlock());
// System.out.println("Previous Largest Change Block: " + previousLargestChangeBlock);
differenceSet = makeAdditionalPass(diffSet, baseDocument, witnessDocument);
differenceConsolidator.consolidateDifferences(differenceSet);
differenceConsolidator.consolidateInsertDelete(differenceSet);
// if we are going to look at these differences later,
// the real diff algorithm needs the latest version of the changes.
diff.updateDifferenceSet(differenceSet);
previousLargestChangeBlock = diffSet.getLargestChangeBlock();
diffSet = differenceSet;
}
differenceConsolidator.consolidateDifferences(differenceSet);
differenceConsolidator.consolidateInsertDelete(differenceSet);
}
/**
* Set the repository the formatter can load object contents from.
*
* <p>Once a repository has been set, the formatter must be released to ensure the internal
* ObjectReader is able to release its resources.
*
* @param repository source repository holding referenced objects.
*/
public void setRepository(Repository repository) {
if (reader != null) reader.release();
db = repository;
reader = db.newObjectReader();
ContentSource cs = ContentSource.create(reader);
source = new ContentSource.Pair(cs, cs);
DiffConfig dc = db.getConfig().get(DiffConfig.KEY);
if (dc.isNoPrefix()) {
setOldPrefix(""); // $NON-NLS-1$
setNewPrefix(""); // $NON-NLS-1$
}
setDetectRenames(dc.isRenameDetectionEnabled());
diffAlgorithm =
DiffAlgorithm.getAlgorithm(
db.getConfig()
.getEnum(
ConfigConstants.CONFIG_DIFF_SECTION,
null,
ConfigConstants.CONFIG_KEY_ALGORITHM,
SupportedAlgorithm.HISTOGRAM));
}
private DifferenceSet makeAdditionalPass(
DifferenceSet originalDifferenceSet,
DocumentModel baseDocument,
DocumentModel witnessDocument) {
DifferenceSet refinedDifferenceSet = new DifferenceSet();
refinedDifferenceSet.setBaseDocument(baseDocument);
refinedDifferenceSet.setWitnessDocument(witnessDocument);
refinedDifferenceSet.setNumberOfSymbols(originalDifferenceSet.getNumberOfSymbols());
for (Iterator i = originalDifferenceSet.getDifferenceList().iterator(); i.hasNext(); ) {
Difference difference = (Difference) i.next();
DiffAlgorithm subdiff = new DiffAlgorithm();
if (difference.getType() == Difference.CHANGE) {
// SubdocumentModel represents a substring of an original DocumentModel with its xml source
// metadata (if it exists)
DocumentModel subBaseText =
new DocumentModel(
baseDocument,
difference.getOffset(Difference.BASE),
difference.getOffset(Difference.BASE) + difference.getLength(Difference.BASE));
DocumentModel subWitnessText =
new DocumentModel(
witnessDocument,
difference.getOffset(Difference.WITNESS),
difference.getOffset(Difference.WITNESS)
+ difference.getLength(Difference.WITNESS));
// perform a diff on the text with the change blocks
subBaseText.tokenize(baseDocument.getTokenizerSettings());
subWitnessText.tokenize(witnessDocument.getTokenizerSettings());
DifferenceSet subDifferences = subdiff.diffDocuments(subBaseText, subWitnessText);
// add the resulting differences to the new difference set.
addSubDifferences(refinedDifferenceSet, subDifferences, difference);
} else {
refinedDifferenceSet.addDifference(difference);
}
}
return refinedDifferenceSet;
}
private EditList diff(RawText a, RawText b) {
return diffAlgorithm.diff(comparator, a, b);
}
public int getWitnessOffset(int baseOffset, boolean getEnd) {
return diff.getCorrespondingWitnessOffset(baseOffset, getEnd);
}
// Given the offset in one document, this finds the offset of that character in the other
// document.
// If there is a perfect match, then it is easy to know what to return.
// If it doesn't appear in the other document, then return it's insert point.
// If it is part of a change, return -1.
public int getBaseOffset(int witnessOffset, boolean getEnd) {
return diff.getCorrespondingBaseOffset(witnessOffset, getEnd);
}
/**
* compute the difference between the original and a revision.
*
* @param rev the revision to compare with the original.
* @return a Revision describing the differences
*/
public Revision diff(Object[] rev) throws DifferentiationFailedException {
if (orig.length == 0 && rev.length == 0) return new Revision();
else return algorithm.diff(orig, rev);
}
