/**
* Find the differences between two texts. Simplifies the problem by stripping any common prefix
* or suffix off the texts before diffing.
*
* @return List of Difference objects
*/
public List<Difference> compare() {
// Check for equality (speedup)
List<Difference> diffs;
if (source.equals(target)) {
diffs = new ArrayList<Difference>();
diffs.add(new Difference(EditType.EQUAL, source));
return diffs;
}
// Trim off common prefix (speedup)
int commonLength = Commonality.prefix(source, target);
String commonPrefix = source.substring(0, commonLength);
source = source.substring(commonLength);
target = target.substring(commonLength);
// Trim off common suffix (speedup)
commonLength = Commonality.suffix(source, target);
String commonSuffix = source.substring(source.length() - commonLength);
source = source.substring(0, source.length() - commonLength);
target = target.substring(0, target.length() - commonLength);
// Compute the diff on the middle block
diffs = compute();
// Restore the prefix and suffix
if (!"".equals(commonPrefix)) {
diffs.add(0, new Difference(EditType.EQUAL, commonPrefix));
}
if (!"".equals(commonSuffix)) {
diffs.add(new Difference(EditType.EQUAL, commonSuffix));
}
DiffCleanup.cleanupMerge(diffs);
return diffs;
}
