diff_match_patch.prototype.diff_cleanupEfficiency = function()

in kitsune/sumo/static/sumo/js/libs/diff_match_patch_uncompressed.js [977:1051]

• 71 lines of code
• 18 McCabe index (conditional complexity)

diff_match_patch.prototype.diff_cleanupEfficiency = function(diffs) {
  var changes = false;
  var equalities = [];  // Stack of indices where equalities are found.
  var equalitiesLength = 0;  // Keeping our own length var is faster in JS.
  /** @type {?string} */
  var lastequality = null;
  // Always equal to diffs[equalities[equalitiesLength - 1]][1]
  var pointer = 0;  // Index of current position.
  // Is there an insertion operation before the last equality.
  var pre_ins = false;
  // Is there a deletion operation before the last equality.
  var pre_del = false;
  // Is there an insertion operation after the last equality.
  var post_ins = false;
  // Is there a deletion operation after the last equality.
  var post_del = false;
  while (pointer < diffs.length) {
    if (diffs[pointer][0] == DIFF_EQUAL) {  // Equality found.
      if (diffs[pointer][1].length < this.Diff_EditCost &&
          (post_ins || post_del)) {
        // Candidate found.
        equalities[equalitiesLength++] = pointer;
        pre_ins = post_ins;
        pre_del = post_del;
        lastequality = diffs[pointer][1];
      } else {
        // Not a candidate, and can never become one.
        equalitiesLength = 0;
        lastequality = null;
      }
      post_ins = post_del = false;
    } else {  // An insertion or deletion.
      if (diffs[pointer][0] == DIFF_DELETE) {
        post_del = true;
      } else {
        post_ins = true;
      }
      /*
       * Five types to be split:
       * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
       * <ins>A</ins>X<ins>C</ins><del>D</del>
       * <ins>A</ins><del>B</del>X<ins>C</ins>
       * <ins>A</del>X<ins>C</ins><del>D</del>
       * <ins>A</ins><del>B</del>X<del>C</del>
       */
      if (lastequality && ((pre_ins && pre_del && post_ins && post_del) ||
                           ((lastequality.length < this.Diff_EditCost / 2) &&
                            (pre_ins + pre_del + post_ins + post_del) == 3))) {
        // Duplicate record.
        diffs.splice(equalities[equalitiesLength - 1], 0,
                     [DIFF_DELETE, lastequality]);
        // Change second copy to insert.
        diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
        equalitiesLength--;  // Throw away the equality we just deleted;
        lastequality = null;
        if (pre_ins && pre_del) {
          // No changes made which could affect previous entry, keep going.
          post_ins = post_del = true;
          equalitiesLength = 0;
        } else {
          equalitiesLength--;  // Throw away the previous equality.
          pointer = equalitiesLength > 0 ?
              equalities[equalitiesLength - 1] : -1;
          post_ins = post_del = false;
        }
        changes = true;
      }
    }
    pointer++;
  }

  if (changes) {
    this.diff_cleanupMerge(diffs);
  }
};