diff function

List<Diff> diff(String text1, String text2, { double timeout = 1.0, bool checklines = true, DateTime? deadline, })

Find the differences between two texts. Simplifies the problem by stripping any common prefix or suffix off the texts before diffing.

• text1 is the old string to be diffed.
• text2 is the new string to be diffed.
• timeout is an optional number of seconds to map a diff before giving up (0 for infinity).
• checklines is an optional speedup flag. If false, then don't run a line-level diff first to identify the changed areas. Defaults to true, which does a faster, slightly less optimal diff.
• deadline is an optional time when the diff should be complete by. Used internally for recursive calls. Users should set diffTimeout instead.

Returns a List of Diff objects.

Implementation

List<Diff> diff(String text1, String text2,
                {double timeout: 1.0, bool checklines: true,
                 DateTime? deadline}) {
  // Set a deadline by which time the diff must be complete.
  if (deadline == null) {
    deadline = new DateTime.now();
    if (timeout <= 0) {
      // One year should be sufficient for 'infinity'.
      deadline = deadline.add(new Duration(days: 365));
    } else {
      deadline = deadline.add(new Duration(
          milliseconds: (timeout * 1000).toInt()));
    }
  }

  // Check for equality (speedup).
  List<Diff> diffs;
  if (text1 == text2) {
    diffs = [];
    if (!text1.isEmpty) {
      diffs.add(new Diff(DIFF_EQUAL, text1));
    }
    return diffs;
  }

  // Trim off common prefix (speedup).
  int commonlength = commonPrefix(text1, text2);
  String commonprefix = text1.substring(0, commonlength);
  text1 = text1.substring(commonlength);
  text2 = text2.substring(commonlength);

  // Trim off common suffix (speedup).
  commonlength = commonSuffix(text1, text2);
  String commonsuffix = text1.substring(text1.length - commonlength);
  text1 = text1.substring(0, text1.length - commonlength);
  text2 = text2.substring(0, text2.length - commonlength);

  // Compute the diff on the middle block.
  diffs = _diffCompute(text1, text2, timeout, checklines, deadline);

  // Restore the prefix and suffix.
  if (!commonprefix.isEmpty) {
    diffs.insert(0, new Diff(DIFF_EQUAL, commonprefix));
  }
  if (!commonsuffix.isEmpty) {
    diffs.add(new Diff(DIFF_EQUAL, commonsuffix));
  }

  cleanupMerge(diffs);
  return diffs;
}