Added the sources.

Change-Id: Ifd46f7bc83306f9e16ec2a725c2300f584068e59

2 files changed, 3373 insertions, 0 deletions

diff --git a/name/fraser/neil/plaintext/diff_match_patch.java b/name/fraser/neil/plaintext/diff_match_patch.java
new file mode 100644
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+++ b/name/fraser/neil/plaintext/diff_match_patch.java
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+/*
+ * Diff Match and Patch
+ *
+ * Copyright 2006 Google Inc.
+ * http://code.google.com/p/google-diff-match-patch/
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package name.fraser.neil.plaintext;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+import java.net.URLDecoder;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.Map;
+import java.util.Set;
+import java.util.Stack;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+
+/*
+ * Functions for diff, match and patch.
+ * Computes the difference between two texts to create a patch.
+ * Applies the patch onto another text, allowing for errors.
+ *
+ * @author fraser@google.com (Neil Fraser)
+ */
+
+/**
+ * Class containing the diff, match and patch methods.
+ * Also contains the behaviour settings.
+ */
+public class diff_match_patch {
+
+  // Defaults.
+  // Set these on your diff_match_patch instance to override the defaults.
+
+  /**
+   * Number of seconds to map a diff before giving up (0 for infinity).
+   */
+  public float Diff_Timeout = 1.0f;
+  /**
+   * Cost of an empty edit operation in terms of edit characters.
+   */
+  public short Diff_EditCost = 4;
+  /**
+   * The size beyond which the double-ended diff activates.
+   * Double-ending is twice as fast, but less accurate.
+   */
+  public short Diff_DualThreshold = 32;
+  /**
+   * At what point is no match declared (0.0 = perfection, 1.0 = very loose).
+   */
+  public float Match_Threshold = 0.5f;
+  /**
+   * How far to search for a match (0 = exact location, 1000+ = broad match).
+   * A match this many characters away from the expected location will add
+   * 1.0 to the score (0.0 is a perfect match).
+   */
+  public int Match_Distance = 1000;
+  /**
+   * When deleting a large block of text (over ~64 characters), how close does
+   * the contents have to match the expected contents. (0.0 = perfection,
+   * 1.0 = very loose).  Note that Match_Threshold controls how closely the
+   * end points of a delete need to match.
+   */
+  public float Patch_DeleteThreshold = 0.5f;
+  /**
+   * Chunk size for context length.
+   */
+  public short Patch_Margin = 4;
+
+  /**
+   * The number of bits in an int.
+   */
+  private int Match_MaxBits = 32;
+
+  /**
+   * Internal class for returning results from diff_linesToChars().
+   * Other less paranoid languages just use a three-element array.
+   */
+  protected static class LinesToCharsResult {
+    protected String chars1;
+    protected String chars2;
+    protected List<String> lineArray;
+
+    protected LinesToCharsResult(String chars1, String chars2,
+        List<String> lineArray) {
+      this.chars1 = chars1;
+      this.chars2 = chars2;
+      this.lineArray = lineArray;
+    }
+  }
+
+
+  //  DIFF FUNCTIONS
+
+
+  /**
+   * The data structure representing a diff is a Linked list of Diff objects:
+   * {Diff(Operation.DELETE, "Hello"), Diff(Operation.INSERT, "Goodbye"),
+   *  Diff(Operation.EQUAL, " world.")}
+   * which means: delete "Hello", add "Goodbye" and keep " world."
+   */
+  public enum Operation {
+    DELETE, INSERT, EQUAL
+  }
+
+
+  /**
+   * Find the differences between two texts.
+   * Run a faster slightly less optimal diff
+   * This method allows the 'checklines' of diff_main() to be optional.
+   * Most of the time checklines is wanted, so default to true.
+   * @param text1 Old string to be diffed.
+   * @param text2 New string to be diffed.
+   * @return Linked List of Diff objects.
+   */
+  public LinkedList<Diff> diff_main(String text1, String text2) {
+    return diff_main(text1, text2, true);
+  }
+
+  /**
+   * Find the differences between two texts.  Simplifies the problem by
+   * stripping any common prefix or suffix off the texts before diffing.
+   * @param text1 Old string to be diffed.
+   * @param text2 New string to be diffed.
+   * @param checklines Speedup flag.  If false, then don't run a
+   *     line-level diff first to identify the changed areas.
+   *     If true, then run a faster slightly less optimal diff
+   * @return Linked List of Diff objects.
+   */
+  public LinkedList<Diff> diff_main(String text1, String text2,
+                                    boolean checklines) {
+    // Check for null inputs.
+    if (text1 == null || text2 == null) {
+      throw new IllegalArgumentException("Null inputs. (diff_main)");
+    }
+
+    // Check for equality (speedup).
+    LinkedList<Diff> diffs;
+    if (text1.equals(text2)) {
+      diffs = new LinkedList<Diff>();
+      diffs.add(new Diff(Operation.EQUAL, text1));
+      return diffs;
+    }
+
+    // Trim off common prefix (speedup).
+    int commonlength = diff_commonPrefix(text1, text2);
+    String commonprefix = text1.substring(0, commonlength);
+    text1 = text1.substring(commonlength);
+    text2 = text2.substring(commonlength);
+
+    // Trim off common suffix (speedup).
+    commonlength = diff_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 = diff_compute(text1, text2, checklines);
+
+    // Restore the prefix and suffix.
+    if (commonprefix.length() != 0) {
+      diffs.addFirst(new Diff(Operation.EQUAL, commonprefix));
+    }
+    if (commonsuffix.length() != 0) {
+      diffs.addLast(new Diff(Operation.EQUAL, commonsuffix));
+    }
+
+    diff_cleanupMerge(diffs);
+    return diffs;
+  }
+
+
+  /**
+   * Find the differences between two texts.  Assumes that the texts do not
+   * have any common prefix or suffix.
+   * @param text1 Old string to be diffed.
+   * @param text2 New string to be diffed.
+   * @param checklines Speedup flag.  If false, then don't run a
+   *     line-level diff first to identify the changed areas.
+   *     If true, then run a faster slightly less optimal diff
+   * @return Linked List of Diff objects.
+   */
+  protected LinkedList<Diff> diff_compute(String text1, String text2,
+                                          boolean checklines) {
+    LinkedList<Diff> diffs = new LinkedList<Diff>();
+
+    if (text1.length() == 0) {
+      // Just add some text (speedup).
+      diffs.add(new Diff(Operation.INSERT, text2));
+      return diffs;
+    }
+
+    if (text2.length() == 0) {
+      // Just delete some text (speedup).
+      diffs.add(new Diff(Operation.DELETE, text1));
+      return diffs;
+    }
+
+    String longtext = text1.length() > text2.length() ? text1 : text2;
+    String shorttext = text1.length() > text2.length() ? text2 : text1;
+    int i = longtext.indexOf(shorttext);
+    if (i != -1) {
+      // Shorter text is inside the longer text (speedup).
+      Operation op = (text1.length() > text2.length()) ?
+                     Operation.DELETE : Operation.INSERT;
+      diffs.add(new Diff(op, longtext.substring(0, i)));
+      diffs.add(new Diff(Operation.EQUAL, shorttext));
+      diffs.add(new Diff(op, longtext.substring(i + shorttext.length())));
+      return diffs;
+    }
+    longtext = shorttext = null;  // Garbage collect.
+
+    // Check to see if the problem can be split in two.
+    String[] hm = diff_halfMatch(text1, text2);
+    if (hm != null) {
+      // A half-match was found, sort out the return data.
+      String text1_a = hm[0];
+      String text1_b = hm[1];
+      String text2_a = hm[2];
+      String text2_b = hm[3];
+      String mid_common = hm[4];
+      // Send both pairs off for separate processing.
+      LinkedList<Diff> diffs_a = diff_main(text1_a, text2_a, checklines);
+      LinkedList<Diff> diffs_b = diff_main(text1_b, text2_b, checklines);
+      // Merge the results.
+      diffs = diffs_a;
+      diffs.add(new Diff(Operation.EQUAL, mid_common));
+      diffs.addAll(diffs_b);
+      return diffs;
+    }
+
+    // Perform a real diff.
+    if (checklines && (text1.length() < 100 || text2.length() < 100)) {
+      checklines = false;  // Too trivial for the overhead.
+    }
+    List<String> linearray = null;
+    if (checklines) {
+      // Scan the text on a line-by-line basis first.
+      LinesToCharsResult b = diff_linesToChars(text1, text2);
+      text1 = b.chars1;
+      text2 = b.chars2;
+      linearray = b.lineArray;
+    }
+
+    diffs = diff_map(text1, text2);
+    if (diffs == null) {
+      // No acceptable result.
+      diffs = new LinkedList<Diff>();
+      diffs.add(new Diff(Operation.DELETE, text1));
+      diffs.add(new Diff(Operation.INSERT, text2));
+    }
+
+    if (checklines) {
+      // Convert the diff back to original text.
+      diff_charsToLines(diffs, linearray);
+      // Eliminate freak matches (e.g. blank lines)
+      diff_cleanupSemantic(diffs);
+
+      // Rediff any replacement blocks, this time character-by-character.
+      // Add a dummy entry at the end.
+      diffs.add(new Diff(Operation.EQUAL, ""));
+      int count_delete = 0;
+      int count_insert = 0;
+      String text_delete = "";
+      String text_insert = "";
+      ListIterator<Diff> pointer = diffs.listIterator();
+      Diff thisDiff = pointer.next();
+      while (thisDiff != null) {
+        switch (thisDiff.operation) {
+        case INSERT:
+          count_insert++;
+          text_insert += thisDiff.text;
+          break;
+        case DELETE:
+          count_delete++;
+          text_delete += thisDiff.text;
+          break;
+        case EQUAL:
+          // Upon reaching an equality, check for prior redundancies.
+          if (count_delete >= 1 && count_insert >= 1) {
+            // Delete the offending records and add the merged ones.
+            pointer.previous();
+            for (int j = 0; j < count_delete + count_insert; j++) {
+              pointer.previous();
+              pointer.remove();
+            }
+            for (Diff newDiff : diff_main(text_delete, text_insert, false)) {
+              pointer.add(newDiff);
+            }
+          }
+          count_insert = 0;
+          count_delete = 0;
+          text_delete = "";
+          text_insert = "";
+          break;
+        }
+        thisDiff = pointer.hasNext() ? pointer.next() : null;
+      }
+      diffs.removeLast();  // Remove the dummy entry at the end.
+    }
+    return diffs;
+  }
+
+
+  /**
+   * Split two texts into a list of strings.  Reduce the texts to a string of
+   * hashes where each Unicode character represents one line.
+   * @param text1 First string.
+   * @param text2 Second string.
+   * @return An object containing the encoded text1, the encoded text2 and
+   *     the List of unique strings.  The zeroth element of the List of
+   *     unique strings is intentionally blank.
+   */
+  protected LinesToCharsResult diff_linesToChars(String text1, String text2) {
+    List<String> lineArray = new ArrayList<String>();
+    Map<String, Integer> lineHash = new HashMap<String, Integer>();
+    // e.g. linearray[4] == "Hello\n"
+    // e.g. linehash.get("Hello\n") == 4
+
+    // "\x00" is a valid character, but various debuggers don't like it.
+    // So we'll insert a junk entry to avoid generating a null character.
+    lineArray.add("");
+
+    String chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash);
+    String chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash);
+    return new LinesToCharsResult(chars1, chars2, lineArray);
+  }
+
+
+  /**
+   * Split a text into a list of strings.  Reduce the texts to a string of
+   * hashes where each Unicode character represents one line.
+   * @param text String to encode.
+   * @param lineArray List of unique strings.
+   * @param lineHash Map of strings to indices.
+   * @return Encoded string.
+   */
+  private String diff_linesToCharsMunge(String text, List<String> lineArray,
+                                        Map<String, Integer> lineHash) {
+    int lineStart = 0;
+    int lineEnd = -1;
+    String line;
+    StringBuilder chars = new StringBuilder();
+    // Walk the text, pulling out a substring for each line.
+    // text.split('\n') would would temporarily double our memory footprint.
+    // Modifying text would create many large strings to garbage collect.
+    while (lineEnd < text.length() - 1) {
+      lineEnd = text.indexOf('\n', lineStart);
+      if (lineEnd == -1) {
+        lineEnd = text.length() - 1;
+      }
+      line = text.substring(lineStart, lineEnd + 1);
+      lineStart = lineEnd + 1;
+
+      if (lineHash.containsKey(line)) {
+        chars.append(String.valueOf((char) (int) lineHash.get(line)));
+      } else {
+        lineArray.add(line);
+        lineHash.put(line, lineArray.size() - 1);
+        chars.append(String.valueOf((char) (lineArray.size() - 1)));
+      }
+    }
+    return chars.toString();
+  }
+
+
+  /**
+   * Rehydrate the text in a diff from a string of line hashes to real lines of
+   * text.
+   * @param diffs LinkedList of Diff objects.
+   * @param lineArray List of unique strings.
+   */
+  protected void diff_charsToLines(LinkedList<Diff> diffs,
+                                  List<String> lineArray) {
+    StringBuilder text;
+    for (Diff diff : diffs) {
+      text = new StringBuilder();
+      for (int y = 0; y < diff.text.length(); y++) {
+        text.append(lineArray.get(diff.text.charAt(y)));
+      }
+      diff.text = text.toString();
+    }
+  }
+
+
+  /**
+   * Explore the intersection points between the two texts.
+   * @param text1 Old string to be diffed.
+   * @param text2 New string to be diffed.
+   * @return LinkedList of Diff objects or null if no diff available.
+   */
+  protected LinkedList<Diff> diff_map(String text1, String text2) {
+    long ms_end = System.currentTimeMillis() + (long) (Diff_Timeout * 1000);
+    // Cache the text lengths to prevent multiple calls.
+    int text1_length = text1.length();
+    int text2_length = text2.length();
+    int max_d = text1_length + text2_length - 1;
+    boolean doubleEnd = Diff_DualThreshold * 2 < max_d;
+    List<Set<Long>> v_map1 = new ArrayList<Set<Long>>();
+    List<Set<Long>> v_map2 = new ArrayList<Set<Long>>();
+    Map<Integer, Integer> v1 = new HashMap<Integer, Integer>();
+    Map<Integer, Integer> v2 = new HashMap<Integer, Integer>();
+    v1.put(1, 0);
+    v2.put(1, 0);
+    int x, y;
+    Long footstep = 0L;  // Used to track overlapping paths.
+    Map<Long, Integer> footsteps = new HashMap<Long, Integer>();
+    boolean done = false;
+    // If the total number of characters is odd, then the front path will
+    // collide with the reverse path.
+    boolean front = ((text1_length + text2_length) % 2 == 1);
+    for (int d = 0; d < max_d; d++) {
+      // Bail out if timeout reached.
+      if (Diff_Timeout > 0 && System.currentTimeMillis() > ms_end) {
+        return null;
+      }
+
+      // Walk the front path one step.
+      v_map1.add(new HashSet<Long>());  // Adds at index 'd'.
+      for (int k = -d; k <= d; k += 2) {
+        if (k == -d || k != d && v1.get(k - 1) < v1.get(k + 1)) {
+          x = v1.get(k + 1);
+        } else {
+          x = v1.get(k - 1) + 1;
+        }
+        y = x - k;
+        if (doubleEnd) {
+          footstep = diff_footprint(x, y);
+          if (front && (footsteps.containsKey(footstep))) {
+            done = true;
+          }
+          if (!front) {
+            footsteps.put(footstep, d);
+          }
+        }
+        while (!done && x < text1_length && y < text2_length
+               && text1.charAt(x) == text2.charAt(y)) {
+          x++;
+          y++;
+          if (doubleEnd) {
+            footstep = diff_footprint(x, y);
+            if (front && (footsteps.containsKey(footstep))) {
+              done = true;
+            }
+            if (!front) {
+              footsteps.put(footstep, d);
+            }
+          }
+        }
+        v1.put(k, x);
+        v_map1.get(d).add(diff_footprint(x, y));
+        if (x == text1_length && y == text2_length) {
+          // Reached the end in single-path mode.
+          return diff_path1(v_map1, text1, text2);
+        } else if (done) {
+          // Front path ran over reverse path.
+          v_map2 = v_map2.subList(0, footsteps.get(footstep) + 1);
+          LinkedList<Diff> a = diff_path1(v_map1, text1.substring(0, x),
+                                          text2.substring(0, y));
+          a.addAll(diff_path2(v_map2, text1.substring(x), text2.substring(y)));
+          return a;
+        }
+      }
+
+      if (doubleEnd) {
+        // Walk the reverse path one step.
+        v_map2.add(new HashSet<Long>());  // Adds at index 'd'.
+        for (int k = -d; k <= d; k += 2) {
+          if (k == -d || k != d && v2.get(k - 1) < v2.get(k + 1)) {
+            x = v2.get(k + 1);
+          } else {
+            x = v2.get(k - 1) + 1;
+          }
+          y = x - k;
+          footstep = diff_footprint(text1_length - x, text2_length - y);
+          if (!front && (footsteps.containsKey(footstep))) {
+            done = true;
+          }
+          if (front) {
+            footsteps.put(footstep, d);
+          }
+          while (!done && x < text1_length && y < text2_length
+                 && text1.charAt(text1_length - x - 1)
+                 == text2.charAt(text2_length - y - 1)) {
+            x++;
+            y++;
+            footstep = diff_footprint(text1_length - x, text2_length - y);
+            if (!front && (footsteps.containsKey(footstep))) {
+              done = true;
+            }
+            if (front) {
+              footsteps.put(footstep, d);
+            }
+          }
+          v2.put(k, x);
+          v_map2.get(d).add(diff_footprint(x, y));
+          if (done) {
+            // Reverse path ran over front path.
+            v_map1 = v_map1.subList(0, footsteps.get(footstep) + 1);
+            LinkedList<Diff> a
+                = diff_path1(v_map1, text1.substring(0, text1_length - x),
+                             text2.substring(0, text2_length - y));
+            a.addAll(diff_path2(v_map2, text1.substring(text1_length - x),
+                                text2.substring(text2_length - y)));
+            return a;
+          }
+        }
+      }
+    }
+    // Number of diffs equals number of characters, no commonality at all.
+    return null;
+  }
+
+
+  /**
+   * Work from the middle back to the start to determine the path.
+   * @param v_map List of path sets.
+   * @param text1 Old string fragment to be diffed.
+   * @param text2 New string fragment to be diffed.
+   * @return LinkedList of Diff objects.
+   */
+  protected LinkedList<Diff> diff_path1(List<Set<Long>> v_map,
+                                        String text1, String text2) {
+    LinkedList<Diff> path = new LinkedList<Diff>();
+    int x = text1.length();
+    int y = text2.length();
+    Operation last_op = null;
+    for (int d = v_map.size() - 2; d >= 0; d--) {
+      while (true) {
+        if (v_map.get(d).contains(diff_footprint(x - 1, y))) {
+          x--;
+          if (last_op == Operation.DELETE) {
+            path.getFirst().text = text1.charAt(x) + path.getFirst().text;
+          } else {
+            path.addFirst(new Diff(Operation.DELETE,
+                                   text1.substring(x, x + 1)));
+          }
+          last_op = Operation.DELETE;
+          break;
+        } else if (v_map.get(d).contains(diff_footprint(x, y - 1))) {
+          y--;
+          if (last_op == Operation.INSERT) {
+            path.getFirst().text = text2.charAt(y) + path.getFirst().text;
+          } else {
+            path.addFirst(new Diff(Operation.INSERT,
+                                   text2.substring(y, y + 1)));
+          }
+          last_op = Operation.INSERT;
+          break;
+        } else {
+          x--;
+          y--;
+          assert (text1.charAt(x) == text2.charAt(y))
+                 : "No diagonal.  Can't happen. (diff_path1)";
+          if (last_op == Operation.EQUAL) {
+            path.getFirst().text = text1.charAt(x) + path.getFirst().text;
+          } else {
+            path.addFirst(new Diff(Operation.EQUAL, text1.substring(x, x + 1)));
+          }
+          last_op = Operation.EQUAL;
+        }
+      }
+    }
+    return path;
+  }
+
+
+  /**
+   * Work from the middle back to the end to determine the path.
+   * @param v_map List of path sets.
+   * @param text1 Old string fragment to be diffed.
+   * @param text2 New string fragment to be diffed.
+   * @return LinkedList of Diff objects.
+   */
+  protected LinkedList<Diff> diff_path2(List<Set<Long>> v_map,
+                                        String text1, String text2) {
+    LinkedList<Diff> path = new LinkedList<Diff>();
+    int x = text1.length();
+    int y = text2.length();
+    Operation last_op = null;
+    for (int d = v_map.size() - 2; d >= 0; d--) {
+      while (true) {
+        if (v_map.get(d).contains(diff_footprint(x - 1, y))) {
+          x--;
+          if (last_op == Operation.DELETE) {
+            path.getLast().text += text1.charAt(text1.length() - x - 1);
+          } else {
+            path.addLast(new Diff(Operation.DELETE,
+                text1.substring(text1.length() - x - 1, text1.length() - x)));
+          }
+          last_op = Operation.DELETE;
+          break;
+        } else if (v_map.get(d).contains(diff_footprint(x, y - 1))) {
+          y--;
+          if (last_op == Operation.INSERT) {
+            path.getLast().text += text2.charAt(text2.length() - y - 1);
+          } else {
+            path.addLast(new Diff(Operation.INSERT,
+                text2.substring(text2.length() - y - 1, text2.length() - y)));
+          }
+          last_op = Operation.INSERT;
+          break;
+        } else {
+          x--;
+          y--;
+          assert (text1.charAt(text1.length() - x - 1)
+                  == text2.charAt(text2.length() - y - 1))
+                 : "No diagonal.  Can't happen. (diff_path2)";
+          if (last_op == Operation.EQUAL) {
+            path.getLast().text += text1.charAt(text1.length() - x - 1);
+          } else {
+            path.addLast(new Diff(Operation.EQUAL,
+                text1.substring(text1.length() - x - 1, text1.length() - x)));
+          }
+          last_op = Operation.EQUAL;
+        }
+      }
+    }
+    return path;
+  }
+
+
+  /**
+   * Compute a good hash of two integers.
+   * @param x First int.
+   * @param y Second int.
+   * @return A long made up of both ints.
+   */
+  protected long diff_footprint(int x, int y) {
+    // The maximum size for a long is 9,223,372,036,854,775,807
+    // The maximum size for an int is 2,147,483,647
+    // Two ints fit nicely in one long.
+    long result = x;
+    result = result << 32;
+    result += y;
+    return result;
+  }
+
+
+  /**
+   * Determine the common prefix of two strings
+   * @param text1 First string.
+   * @param text2 Second string.
+   * @return The number of characters common to the start of each string.
+   */
+  public int diff_commonPrefix(String text1, String text2) {
+    // Performance analysis: http://neil.fraser.name/news/2007/10/09/
+    int n = Math.min(text1.length(), text2.length());
+    for (int i = 0; i < n; i++) {
+      if (text1.charAt(i) != text2.charAt(i)) {
+        return i;
+      }
+    }
+    return n;
+  }
+
+
+  /**
+   * Determine the common suffix of two strings
+   * @param text1 First string.
+   * @param text2 Second string.
+   * @return The number of characters common to the end of each string.
+   */
+  public int diff_commonSuffix(String text1, String text2) {
+    // Performance analysis: http://neil.fraser.name/news/2007/10/09/
+    int text1_length = text1.length();
+    int text2_length = text2.length();
+    int n = Math.min(text1_length, text2_length);
+    for (int i = 1; i <= n; i++) {
+      if (text1.charAt(text1_length - i) != text2.charAt(text2_length - i)) {
+        return i - 1;
+      }
+    }
+    return n;
+  }
+
+
+  /**
+   * Do the two texts share a substring which is at least half the length of
+   * the longer text?
+   * @param text1 First string.
+   * @param text2 Second string.
+   * @return Five element String array, containing the prefix of text1, the
+   *     suffix of text1, the prefix of text2, the suffix of text2 and the
+   *     common middle.  Or null if there was no match.
+   */
+  protected String[] diff_halfMatch(String text1, String text2) {
+    String longtext = text1.length() > text2.length() ? text1 : text2;
+    String shorttext = text1.length() > text2.length() ? text2 : text1;
+    if (longtext.length() < 10 || shorttext.length() < 1) {
+      return null;  // Pointless.
+    }
+
+    // First check if the second quarter is the seed for a half-match.
+    String[] hm1 = diff_halfMatchI(longtext, shorttext,
+                                   (longtext.length() + 3) / 4);
+    // Check again based on the third quarter.
+    String[] hm2 = diff_halfMatchI(longtext, shorttext,
+                                   (longtext.length() + 1) / 2);
+    String[] hm;
+    if (hm1 == null && hm2 == null) {
+      return null;
+    } else if (hm2 == null) {
+      hm = hm1;
+    } else if (hm1 == null) {
+      hm = hm2;
+    } else {
+      // Both matched.  Select the longest.
+      hm = hm1[4].length() > hm2[4].length() ? hm1 : hm2;
+    }
+
+    // A half-match was found, sort out the return data.
+    if (text1.length() > text2.length()) {
+      return hm;
+      //return new String[]{hm[0], hm[1], hm[2], hm[3], hm[4]};
+    } else {
+      return new String[]{hm[2], hm[3], hm[0], hm[1], hm[4]};
+    }
+  }
+
+
+  /**
+   * Does a substring of shorttext exist within longtext such that the
+   * substring is at least half the length of longtext?
+   * @param longtext Longer string.
+   * @param shorttext Shorter string.
+   * @param i Start index of quarter length substring within longtext.
+   * @return Five element String array, containing the prefix of longtext, the
+   *     suffix of longtext, the prefix of shorttext, the suffix of shorttext
+   *     and the common middle.  Or null if there was no match.
+   */
+  private String[] diff_halfMatchI(String longtext, String shorttext, int i) {
+    // Start with a 1/4 length substring at position i as a seed.
+    String seed = longtext.substring(i, i + longtext.length() / 4);
+    int j = -1;
+    String best_common = "";
+    String best_longtext_a = "", best_longtext_b = "";
+    String best_shorttext_a = "", best_shorttext_b = "";
+    while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
+      int prefixLength = diff_commonPrefix(longtext.substring(i),
+                                           shorttext.substring(j));
+      int suffixLength = diff_commonSuffix(longtext.substring(0, i),
+                                           shorttext.substring(0, j));
+      if (best_common.length() < suffixLength + prefixLength) {
+        best_common = shorttext.substring(j - suffixLength, j)
+            + shorttext.substring(j, j + prefixLength);
+        best_longtext_a = longtext.substring(0, i - suffixLength);
+        best_longtext_b = longtext.substring(i + prefixLength);
+        best_shorttext_a = shorttext.substring(0, j - suffixLength);
+        best_shorttext_b = shorttext.substring(j + prefixLength);
+      }
+    }
+    if (best_common.length() >= longtext.length() / 2) {
+      return new String[]{best_longtext_a, best_longtext_b,
+                          best_shorttext_a, best_shorttext_b, best_common};
+    } else {
+      return null;
+    }
+  }
+
+
+  /**
+   * Reduce the number of edits by eliminating semantically trivial equalities.
+   * @param diffs LinkedList of Diff objects.
+   */
+  public void diff_cleanupSemantic(LinkedList<Diff> diffs) {
+    if (diffs.isEmpty()) {
+      return;
+    }
+    boolean changes = false;
+    Stack<Diff> equalities = new Stack<Diff>();  // Stack of qualities.
+    String lastequality = null; // Always equal to equalities.lastElement().text
+    ListIterator<Diff> pointer = diffs.listIterator();
+    // Number of characters that changed prior to the equality.
+    int length_changes1 = 0;
+    // Number of characters that changed after the equality.
+    int length_changes2 = 0;
+    Diff thisDiff = pointer.next();
+    while (thisDiff != null) {
+      if (thisDiff.operation == Operation.EQUAL) {
+        // equality found
+        equalities.push(thisDiff);
+        length_changes1 = length_changes2;
+        length_changes2 = 0;
+        lastequality = thisDiff.text;
+      } else {
+        // an insertion or deletion
+        length_changes2 += thisDiff.text.length();
+        if (lastequality != null && (lastequality.length() <= length_changes1)
+            && (lastequality.length() <= length_changes2)) {
+          //System.out.println("Splitting: '" + lastequality + "'");
+          // Walk back to offending equality.
+          while (thisDiff != equalities.lastElement()) {
+            thisDiff = pointer.previous();
+          }
+          pointer.next();
+
+          // Replace equality with a delete.
+          pointer.set(new Diff(Operation.DELETE, lastequality));
+          // Insert a corresponding an insert.
+          pointer.add(new Diff(Operation.INSERT, lastequality));
+
+          equalities.pop();  // Throw away the equality we just deleted.
+          if (!equalities.empty()) {
+            // Throw away the previous equality (it needs to be reevaluated).
+            equalities.pop();
+          }
+          if (equalities.empty()) {
+            // There are no previous equalities, walk back to the start.
+            while (pointer.hasPrevious()) {
+              pointer.previous();
+            }
+          } else {
+            // There is a safe equality we can fall back to.
+            thisDiff = equalities.lastElement();
+            while (thisDiff != pointer.previous()) {
+              // Intentionally empty loop.
+            }
+          }
+
+          length_changes1 = 0;  // Reset the counters.
+          length_changes2 = 0;
+          lastequality = null;
+          changes = true;
+        }
+      }
+      thisDiff = pointer.hasNext() ? pointer.next() : null;
+    }
+
+    if (changes) {
+      diff_cleanupMerge(diffs);
+    }
+    diff_cleanupSemanticLossless(diffs);
+  }
+
+
+  /**
+   * Look for single edits surrounded on both sides by equalities
+   * which can be shifted sideways to align the edit to a word boundary.
+   * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
+   * @param diffs LinkedList of Diff objects.
+   */
+  public void diff_cleanupSemanticLossless(LinkedList<Diff> diffs) {
+    String equality1, edit, equality2;
+    String commonString;
+    int commonOffset;
+    int score, bestScore;
+    String bestEquality1, bestEdit, bestEquality2;
+    // Create a new iterator at the start.
+    ListIterator<Diff> pointer = diffs.listIterator();
+    Diff prevDiff = pointer.hasNext() ? pointer.next() : null;
+    Diff thisDiff = pointer.hasNext() ? pointer.next() : null;
+    Diff nextDiff = pointer.hasNext() ? pointer.next() : null;
+    // Intentionally ignore the first and last element (don't need checking).
+    while (nextDiff != null) {
+      if (prevDiff.operation == Operation.EQUAL &&
+          nextDiff.operation == Operation.EQUAL) {
+        // This is a single edit surrounded by equalities.
+        equality1 = prevDiff.text;
+        edit = thisDiff.text;
+        equality2 = nextDiff.text;
+
+        // First, shift the edit as far left as possible.
+        commonOffset = diff_commonSuffix(equality1, edit);
+        if (commonOffset != 0) {
+          commonString = edit.substring(edit.length() - commonOffset);
+          equality1 = equality1.substring(0, equality1.length() - commonOffset);
+          edit = commonString + edit.substring(0, edit.length() - commonOffset);
+          equality2 = commonString + equality2;
+        }
+
+        // Second, step character by character right, looking for the best fit.
+        bestEquality1 = equality1;
+        bestEdit = edit;
+        bestEquality2 = equality2;
+        bestScore = diff_cleanupSemanticScore(equality1, edit)
+            + diff_cleanupSemanticScore(edit, equality2);
+        while (edit.length() != 0 && equality2.length() != 0
+            && edit.charAt(0) == equality2.charAt(0)) {
+          equality1 += edit.charAt(0);
+          edit = edit.substring(1) + equality2.charAt(0);
+          equality2 = equality2.substring(1);
+          score = diff_cleanupSemanticScore(equality1, edit)
+              + diff_cleanupSemanticScore(edit, equality2);
+          // The >= encourages trailing rather than leading whitespace on edits.
+          if (score >= bestScore) {
+            bestScore = score;
+            bestEquality1 = equality1;
+            bestEdit = edit;
+            bestEquality2 = equality2;
+          }
+        }
+
+        if (!prevDiff.text.equals(bestEquality1)) {
+          // We have an improvement, save it back to the diff.
+          if (bestEquality1.length() != 0) {
+            prevDiff.text = bestEquality1;
+          } else {
+            pointer.previous(); // Walk past nextDiff.
+            pointer.previous(); // Walk past thisDiff.
+            pointer.previous(); // Walk past prevDiff.
+            pointer.remove(); // Delete prevDiff.
+            pointer.next(); // Walk past thisDiff.
+            pointer.next(); // Walk past nextDiff.
+          }
+          thisDiff.text = bestEdit;
+          if (bestEquality2.length() != 0) {
+            nextDiff.text = bestEquality2;
+          } else {
+            pointer.remove(); // Delete nextDiff.
+            nextDiff = thisDiff;
+            thisDiff = prevDiff;
+          }
+        }
+      }
+      prevDiff = thisDiff;
+      thisDiff = nextDiff;
+      nextDiff = pointer.hasNext() ? pointer.next() : null;
+    }
+  }
+
+
+  /**
+   * Given two strings, compute a score representing whether the internal
+   * boundary falls on logical boundaries.
+   * Scores range from 5 (best) to 0 (worst).
+   * @param one First string.
+   * @param two Second string.
+   * @return The score.
+   */
+  private int diff_cleanupSemanticScore(String one, String two) {
+    if (one.length() == 0 || two.length() == 0) {
+      // Edges are the best.
+      return 5;
+    }
+
+    // Each port of this function behaves slightly differently due to
+    // subtle differences in each language's definition of things like
+    // 'whitespace'.  Since this function's purpose is largely cosmetic,
+    // the choice has been made to use each language's native features
+    // rather than force total conformity.
+    int score = 0;
+    // One point for non-alphanumeric.
+    if (!Character.isLetterOrDigit(one.charAt(one.length() - 1))
+        || !Character.isLetterOrDigit(two.charAt(0))) {
+      score++;
+      // Two points for whitespace.
+      if (Character.isWhitespace(one.charAt(one.length() - 1))
+          || Character.isWhitespace(two.charAt(0))) {
+        score++;
+        // Three points for line breaks.
+        if (Character.getType(one.charAt(one.length() - 1)) == Character.CONTROL
+            || Character.getType(two.charAt(0)) == Character.CONTROL) {
+          score++;
+          // Four points for blank lines.
+          if (BLANKLINEEND.matcher(one).find()
+              || BLANKLINESTART.matcher(two).find()) {
+            score++;
+          }
+        }
+      }
+    }
+    return score;
+  }
+
+
+  private Pattern BLANKLINEEND
+      = Pattern.compile("\\n\\r?\\n\\Z", Pattern.DOTALL);
+  private Pattern BLANKLINESTART
+      = Pattern.compile("\\A\\r?\\n\\r?\\n", Pattern.DOTALL);
+
+
+  /**
+   * Reduce the number of edits by eliminating operationally trivial equalities.
+   * @param diffs LinkedList of Diff objects.
+   */
+  public void diff_cleanupEfficiency(LinkedList<Diff> diffs) {
+    if (diffs.isEmpty()) {
+      return;
+    }
+    boolean changes = false;
+    Stack<Diff> equalities = new Stack<Diff>();  // Stack of equalities.
+    String lastequality = null; // Always equal to equalities.lastElement().text
+    ListIterator<Diff> pointer = diffs.listIterator();
+    // Is there an insertion operation before the last equality.
+    boolean pre_ins = false;
+    // Is there a deletion operation before the last equality.
+    boolean pre_del = false;
+    // Is there an insertion operation after the last equality.
+    boolean post_ins = false;
+    // Is there a deletion operation after the last equality.
+    boolean post_del = false;
+    Diff thisDiff = pointer.next();
+    Diff safeDiff = thisDiff;  // The last Diff that is known to be unsplitable.
+    while (thisDiff != null) {
+      if (thisDiff.operation == Operation.EQUAL) {
+        // equality found
+        if (thisDiff.text.length() < Diff_EditCost && (post_ins || post_del)) {
+          // Candidate found.
+          equalities.push(thisDiff);
+          pre_ins = post_ins;
+          pre_del = post_del;
+          lastequality = thisDiff.text;
+        } else {
+          // Not a candidate, and can never become one.
+          equalities.clear();
+          lastequality = null;
+          safeDiff = thisDiff;
+        }
+        post_ins = post_del = false;
+      } else {
+        // an insertion or deletion
+        if (thisDiff.operation == Operation.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 != null
+            && ((pre_ins && pre_del && post_ins && post_del)
+                || ((lastequality.length() < Diff_EditCost / 2)
+                    && ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0)
+                        + (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3))) {
+          //System.out.println("Splitting: '" + lastequality + "'");
+          // Walk back to offending equality.
+          while (thisDiff != equalities.lastElement()) {
+            thisDiff = pointer.previous();
+          }
+          pointer.next();
+
+          // Replace equality with a delete.
+          pointer.set(new Diff(Operation.DELETE, lastequality));
+          // Insert a corresponding an insert.
+          pointer.add(thisDiff = new Diff(Operation.INSERT, lastequality));
+
+          equalities.pop();  // 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;
+            equalities.clear();
+            safeDiff = thisDiff;
+          } else {
+            if (!equalities.empty()) {
+              // Throw away the previous equality (it needs to be reevaluated).
+              equalities.pop();
+            }
+            if (equalities.empty()) {
+              // There are no previous questionable equalities,
+              // walk back to the last known safe diff.
+              thisDiff = safeDiff;
+            } else {
+              // There is an equality we can fall back to.
+              thisDiff = equalities.lastElement();
+            }
+            while (thisDiff != pointer.previous()) {
+              // Intentionally empty loop.
+            }
+            post_ins = post_del = false;
+          }
+
+          changes = true;
+        }
+      }
+      thisDiff = pointer.hasNext() ? pointer.next() : null;
+    }
+
+    if (changes) {
+      diff_cleanupMerge(diffs);
+    }
+  }
+
+
+  /**
+   * Reorder and merge like edit sections.  Merge equalities.
+   * Any edit section can move as long as it doesn't cross an equality.
+   * @param diffs LinkedList of Diff objects.
+   */
+  public void diff_cleanupMerge(LinkedList<Diff> diffs) {
+    diffs.add(new Diff(Operation.EQUAL, ""));  // Add a dummy entry at the end.
+    ListIterator<Diff> pointer = diffs.listIterator();
+    int count_delete = 0;
+    int count_insert = 0;
+    String text_delete = "";
+    String text_insert = "";
+    Diff thisDiff = pointer.next();
+    Diff prevEqual = null;
+    int commonlength;
+    while (thisDiff != null) {
+      switch (thisDiff.operation) {
+      case INSERT:
+        count_insert++;
+        text_insert += thisDiff.text;
+        prevEqual = null;
+        break;
+      case DELETE:
+        count_delete++;
+        text_delete += thisDiff.text;
+        prevEqual = null;
+        break;
+      case EQUAL:
+        if (count_delete != 0 || count_insert != 0) {
+          // Delete the offending records.
+          pointer.previous();  // Reverse direction.
+          while (count_delete-- > 0) {
+            pointer.previous();
+            pointer.remove();
+          }
+          while (count_insert-- > 0) {
+            pointer.previous();
+            pointer.remove();
+          }
+          if (count_delete != 0 && count_insert != 0) {
+            // Factor out any common prefixies.
+            commonlength = diff_commonPrefix(text_insert, text_delete);
+            if (commonlength != 0) {
+              if (pointer.hasPrevious()) {
+                thisDiff = pointer.previous();
+                assert thisDiff.operation == Operation.EQUAL
+                       : "Previous diff should have been an equality.";
+                thisDiff.text += text_insert.substring(0, commonlength);
+                pointer.next();
+              } else {
+                pointer.add(new Diff(Operation.EQUAL,
+                    text_insert.substring(0, commonlength)));
+              }
+              text_insert = text_insert.substring(commonlength);
+              text_delete = text_delete.substring(commonlength);
+            }
+            // Factor out any common suffixies.
+            commonlength = diff_commonSuffix(text_insert, text_delete);
+            if (commonlength != 0) {
+              thisDiff = pointer.next();
+              thisDiff.text = text_insert.substring(text_insert.length()
+                  - commonlength) + thisDiff.text;
+              text_insert = text_insert.substring(0, text_insert.length()
+                  - commonlength);
+              text_delete = text_delete.substring(0, text_delete.length()
+                  - commonlength);
+              pointer.previous();
+            }
+          }
+          // Insert the merged records.
+          if (text_delete.length() != 0) {
+            pointer.add(new Diff(Operation.DELETE, text_delete));
+          }
+          if (text_insert.length() != 0) {
+            pointer.add(new Diff(Operation.INSERT, text_insert));
+          }
+          // Step forward to the equality.
+          thisDiff = pointer.hasNext() ? pointer.next() : null;
+        } else if (prevEqual != null) {
+          // Merge this equality with the previous one.
+          prevEqual.text += thisDiff.text;
+          pointer.remove();
+          thisDiff = pointer.previous();
+          pointer.next();  // Forward direction
+        }
+        count_insert = 0;
+        count_delete = 0;
+        text_delete = "";
+        text_insert = "";
+        prevEqual = thisDiff;
+        break;
+      }
+      thisDiff = pointer.hasNext() ? pointer.next() : null;
+    }
+    // System.out.println(diff);
+    if (diffs.getLast().text.length() == 0) {
+      diffs.removeLast();  // Remove the dummy entry at the end.
+    }
+
+    /*
+     * Second pass: look for single edits surrounded on both sides by equalities
+     * which can be shifted sideways to eliminate an equality.
+     * e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
+     */
+    boolean changes = false;
+    // Create a new iterator at the start.
+    // (As opposed to walking the current one back.)
+    pointer = diffs.listIterator();
+    Diff prevDiff = pointer.hasNext() ? pointer.next() : null;
+    thisDiff = pointer.hasNext() ? pointer.next() : null;
+    Diff nextDiff = pointer.hasNext() ? pointer.next() : null;
+    // Intentionally ignore the first and last element (don't need checking).
+    while (nextDiff != null) {
+      if (prevDiff.operation == Operation.EQUAL &&
+          nextDiff.operation == Operation.EQUAL) {
+        // This is a single edit surrounded by equalities.
+        if (thisDiff.text.endsWith(prevDiff.text)) {
+          // Shift the edit over the previous equality.
+          thisDiff.text = prevDiff.text
+              + thisDiff.text.substring(0, thisDiff.text.length()
+                                           - prevDiff.text.length());
+          nextDiff.text = prevDiff.text + nextDiff.text;
+          pointer.previous(); // Walk past nextDiff.
+          pointer.previous(); // Walk past thisDiff.
+          pointer.previous(); // Walk past prevDiff.
+          pointer.remove(); // Delete prevDiff.
+          pointer.next(); // Walk past thisDiff.
+          thisDiff = pointer.next(); // Walk past nextDiff.
+          nextDiff = pointer.hasNext() ? pointer.next() : null;
+          changes = true;
+        } else if (thisDiff.text.startsWith(nextDiff.text)) {
+          // Shift the edit over the next equality.
+          prevDiff.text += nextDiff.text;
+          thisDiff.text = thisDiff.text.substring(nextDiff.text.length())
+              + nextDiff.text;
+          pointer.remove(); // Delete nextDiff.
+          nextDiff = pointer.hasNext() ? pointer.next() : null;
+          changes = true;
+        }
+      }
+      prevDiff = thisDiff;
+      thisDiff = nextDiff;
+      nextDiff = pointer.hasNext() ? pointer.next() : null;
+    }
+    // If shifts were made, the diff needs reordering and another shift sweep.
+    if (changes) {
+      diff_cleanupMerge(diffs);
+    }
+  }
+
+
+  /**
+   * loc is a location in text1, compute and return the equivalent location in
+   * text2.
+   * e.g. "The cat" vs "The big cat", 1->1, 5->8
+   * @param diffs LinkedList of Diff objects.
+   * @param loc Location within text1.
+   * @return Location within text2.
+   */
+  public int diff_xIndex(LinkedList<Diff> diffs, int loc) {
+    int chars1 = 0;
+    int chars2 = 0;
+    int last_chars1 = 0;
+    int last_chars2 = 0;
+    Diff lastDiff = null;
+    for (Diff aDiff : diffs) {
+      if (aDiff.operation != Operation.INSERT) {
+        // Equality or deletion.
+        chars1 += aDiff.text.length();
+      }
+      if (aDiff.operation != Operation.DELETE) {
+        // Equality or insertion.
+        chars2 += aDiff.text.length();
+      }
+      if (chars1 > loc) {
+        // Overshot the location.
+        lastDiff = aDiff;
+        break;
+      }
+      last_chars1 = chars1;
+      last_chars2 = chars2;
+    }
+    if (lastDiff != null && lastDiff.operation == Operation.DELETE) {
+      // The location was deleted.
+      return last_chars2;
+    }
+    // Add the remaining character length.
+    return last_chars2 + (loc - last_chars1);
+  }
+
+
+  /**
+   * Convert a Diff list into a pretty HTML report.
+   * @param diffs LinkedList of Diff objects.
+   * @return HTML representation.
+   */
+  public String diff_prettyHtml(LinkedList<Diff> diffs) {
+    StringBuilder html = new StringBuilder();
+    int i = 0;
+    for (Diff aDiff : diffs) {
+      String text = aDiff.text.replace("&", "&amp;").replace("<", "&lt;")
+          .replace(">", "&gt;").replace("\n", "&para;<BR>");
+      switch (aDiff.operation) {
+      case INSERT:
+        html.append("<INS STYLE=\"background:#E6FFE6;\" TITLE=\"i=").append(i)
+            .append("\">").append(text).append("</INS>");
+        break;
+      case DELETE:
+        html.append("<DEL STYLE=\"background:#FFE6E6;\" TITLE=\"i=").append(i)
+            .append("\">").append(text).append("</DEL>");
+        break;
+      case EQUAL:
+        html.append("<SPAN TITLE=\"i=").append(i).append("\">").append(text)
+            .append("</SPAN>");
+        break;
+      }
+      if (aDiff.operation != Operation.DELETE) {
+        i += aDiff.text.length();
+      }
+    }
+    return html.toString();
+  }
+
+
+  /**
+   * Compute and return the source text (all equalities and deletions).
+   * @param diffs LinkedList of Diff objects.
+   * @return Source text.
+   */
+  public String diff_text1(LinkedList<Diff> diffs) {
+    StringBuilder text = new StringBuilder();
+    for (Diff aDiff : diffs) {
+      if (aDiff.operation != Operation.INSERT) {
+        text.append(aDiff.text);
+      }
+    }
+    return text.toString();
+  }
+
+
+  /**
+   * Compute and return the destination text (all equalities and insertions).
+   * @param diffs LinkedList of Diff objects.
+   * @return Destination text.
+   */
+  public String diff_text2(LinkedList<Diff> diffs) {
+    StringBuilder text = new StringBuilder();
+    for (Diff aDiff : diffs) {
+      if (aDiff.operation != Operation.DELETE) {
+        text.append(aDiff.text);
+      }
+    }
+    return text.toString();
+  }
+
+
+  /**
+   * Compute the Levenshtein distance; the number of inserted, deleted or
+   * substituted characters.
+   * @param diffs LinkedList of Diff objects.
+   * @return Number of changes.
+   */
+  public int diff_levenshtein(LinkedList<Diff> diffs) {
+    int levenshtein = 0;
+    int insertions = 0;
+    int deletions = 0;
+    for (Diff aDiff : diffs) {
+      switch (aDiff.operation) {
+      case INSERT:
+        insertions += aDiff.text.length();
+        break;
+      case DELETE:
+        deletions += aDiff.text.length();
+        break;
+      case EQUAL:
+        // A deletion and an insertion is one substitution.
+        levenshtein += Math.max(insertions, deletions);
+        insertions = 0;
+        deletions = 0;
+        break;
+      }
+    }
+    levenshtein += Math.max(insertions, deletions);
+    return levenshtein;
+  }
+
+
+  /**
+   * Crush the diff into an encoded string which describes the operations
+   * required to transform text1 into text2.
+   * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
+   * Operations are tab-separated.  Inserted text is escaped using %xx notation.
+   * @param diffs Array of diff tuples.
+   * @return Delta text.
+   */
+  public String diff_toDelta(LinkedList<Diff> diffs) {
+    StringBuilder text = new StringBuilder();
+    for (Diff aDiff : diffs) {
+      switch (aDiff.operation) {
+      case INSERT:
+        try {
+          text.append("+").append(URLEncoder.encode(aDiff.text, "UTF-8")
+                                            .replace('+', ' ')).append("\t");
+        } catch (UnsupportedEncodingException e) {
+          // Not likely on modern system.
+          throw new Error("This system does not support UTF-8.", e);
+        }
+        break;
+      case DELETE:
+        text.append("-").append(aDiff.text.length()).append("\t");
+        break;
+      case EQUAL:
+        text.append("=").append(aDiff.text.length()).append("\t");
+        break;
+      }
+    }
+    String delta = text.toString();
+    if (delta.length() != 0) {
+      // Strip off trailing tab character.
+      delta = delta.substring(0, delta.length() - 1);
+      delta = unescapeForEncodeUriCompatability(delta);
+    }
+    return delta;
+  }
+
+
+  /**
+   * Given the original text1, and an encoded string which describes the
+   * operations required to transform text1 into text2, compute the full diff.
+   * @param text1 Source string for the diff.
+   * @param delta Delta text.
+   * @return Array of diff tuples or null if invalid.
+   * @throws IllegalArgumentException If invalid input.
+   */
+  public LinkedList<Diff> diff_fromDelta(String text1, String delta)
+      throws IllegalArgumentException {
+    LinkedList<Diff> diffs = new LinkedList<Diff>();
+    int pointer = 0;  // Cursor in text1
+    String[] tokens = delta.split("\t");
+    for (String token : tokens) {
+      if (token.length() == 0) {
+        // Blank tokens are ok (from a trailing \t).
+        continue;
+      }
+      // Each token begins with a one character parameter which specifies the
+      // operation of this token (delete, insert, equality).
+      String param = token.substring(1);
+      switch (token.charAt(0)) {
+      case '+':
+        // decode would change all "+" to " "
+        param = param.replace("+", "%2B");
+        try {
+          param = URLDecoder.decode(param, "UTF-8");
+        } catch (UnsupportedEncodingException e) {
+          // Not likely on modern system.
+          throw new Error("This system does not support UTF-8.", e);
+        } catch (IllegalArgumentException e) {
+          // Malformed URI sequence.
+          throw new IllegalArgumentException(
+              "Illegal escape in diff_fromDelta: " + param, e);
+        }
+        diffs.add(new Diff(Operation.INSERT, param));
+        break;
+      case '-':
+        // Fall through.
+      case '=':
+        int n;
+        try {
+          n = Integer.parseInt(param);
+        } catch (NumberFormatException e) {
+          throw new IllegalArgumentException(
+              "Invalid number in diff_fromDelta: " + param, e);
+        }
+        if (n < 0) {
+          throw new IllegalArgumentException(
+              "Negative number in diff_fromDelta: " + param);
+        }
+        String text;
+        try {
+          text = text1.substring(pointer, pointer += n);
+        } catch (StringIndexOutOfBoundsException e) {
+          throw new IllegalArgumentException("Delta length (" + pointer
+              + ") larger than source text length (" + text1.length()
+              + ").", e);
+        }
+        if (token.charAt(0) == '=') {
+          diffs.add(new Diff(Operation.EQUAL, text));
+        } else {
+          diffs.add(new Diff(Operation.DELETE, text));
+        }
+        break;
+      default:
+        // Anything else is an error.
+        throw new IllegalArgumentException(
+            "Invalid diff operation in diff_fromDelta: " + token.charAt(0));
+      }
+    }
+    if (pointer != text1.length()) {
+      throw new IllegalArgumentException("Delta length (" + pointer
+          + ") smaller than source text length (" + text1.length() + ").");
+    }
+    return diffs;
+  }
+
+
+  //  MATCH FUNCTIONS
+
+
+  /**
+   * Locate the best instance of 'pattern' in 'text' near 'loc'.
+   * Returns -1 if no match found.
+   * @param text The text to search.
+   * @param pattern The pattern to search for.
+   * @param loc The location to search around.
+   * @return Best match index or -1.
+   */
+  public int match_main(String text, String pattern, int loc) {
+    // Check for null inputs.
+    if (text == null || pattern == null) {
+      throw new IllegalArgumentException("Null inputs. (match_main)");
+    }
+
+    loc = Math.max(0, Math.min(loc, text.length()));
+    if (text.equals(pattern)) {
+      // Shortcut (potentially not guaranteed by the algorithm)
+      return 0;
+    } else if (text.length() == 0) {
+      // Nothing to match.
+      return -1;
+    } else if (loc + pattern.length() <= text.length()
+        && text.substring(loc, loc + pattern.length()).equals(pattern)) {
+      // Perfect match at the perfect spot!  (Includes case of null pattern)
+      return loc;
+    } else {
+      // Do a fuzzy compare.
+      return match_bitap(text, pattern, loc);
+    }
+  }
+
+
+  /**
+   * Locate the best instance of 'pattern' in 'text' near 'loc' using the
+   * Bitap algorithm.  Returns -1 if no match found.
+   * @param text The text to search.
+   * @param pattern The pattern to search for.
+   * @param loc The location to search around.
+   * @return Best match index or -1.
+   */
+  protected int match_bitap(String text, String pattern, int loc) {
+    assert (Match_MaxBits == 0 || pattern.length() <= Match_MaxBits)
+        : "Pattern too long for this application.";
+
+    // Initialise the alphabet.
+    Map<Character, Integer> s = match_alphabet(pattern);
+
+    // Highest score beyond which we give up.
+    double score_threshold = Match_Threshold;
+    // Is there a nearby exact match? (speedup)
+    int best_loc = text.indexOf(pattern, loc);
+    if (best_loc != -1) {
+      score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),
+          score_threshold);
+      // What about in the other direction? (speedup)
+      best_loc = text.lastIndexOf(pattern, loc + pattern.length());
+      if (best_loc != -1) {
+        score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),
+            score_threshold);
+      }
+    }
+
+    // Initialise the bit arrays.
+    int matchmask = 1 << (pattern.length() - 1);
+    best_loc = -1;
+
+    int bin_min, bin_mid;
+    int bin_max = pattern.length() + text.length();
+    // Empty initialization added to appease Java compiler.
+    int[] last_rd = new int[0];
+    for (int d = 0; d < pattern.length(); d++) {
+      // Scan for the best match; each iteration allows for one more error.
+      // Run a binary search to determine how far from 'loc' we can stray at
+      // this error level.
+      bin_min = 0;
+      bin_mid = bin_max;
+      while (bin_min < bin_mid) {
+        if (match_bitapScore(d, loc + bin_mid, loc, pattern)
+            <= score_threshold) {
+          bin_min = bin_mid;
+        } else {
+          bin_max = bin_mid;
+        }
+        bin_mid = (bin_max - bin_min) / 2 + bin_min;
+      }
+      // Use the result from this iteration as the maximum for the next.
+      bin_max = bin_mid;
+      int start = Math.max(1, loc - bin_mid + 1);
+      int finish = Math.min(loc + bin_mid, text.length()) + pattern.length();
+
+      int[] rd = new int[finish + 2];
+      rd[finish + 1] = (1 << d) - 1;
+      for (int j = finish; j >= start; j--) {
+        int charMatch;
+        if (text.length() <= j - 1 || !s.containsKey(text.charAt(j - 1))) {
+          // Out of range.
+          charMatch = 0;
+        } else {
+          charMatch = s.get(text.charAt(j - 1));
+        }
+        if (d == 0) {
+          // First pass: exact match.
+          rd[j] = ((rd[j + 1] << 1) | 1) & charMatch;
+        } else {
+          // Subsequent passes: fuzzy match.
+          rd[j] = ((rd[j + 1] << 1) | 1) & charMatch
+              | (((last_rd[j + 1] | last_rd[j]) << 1) | 1) | last_rd[j + 1];
+        }
+        if ((rd[j] & matchmask) != 0) {
+          double score = match_bitapScore(d, j - 1, loc, pattern);
+          // This match will almost certainly be better than any existing
+          // match.  But check anyway.
+          if (score <= score_threshold) {
+            // Told you so.
+            score_threshold = score;
+            best_loc = j - 1;
+            if (best_loc > loc) {
+              // When passing loc, don't exceed our current distance from loc.
+              start = Math.max(1, 2 * loc - best_loc);
+            } else {
+              // Already passed loc, downhill from here on in.
+              break;
+            }
+          }
+        }
+      }
+      if (match_bitapScore(d + 1, loc, loc, pattern) > score_threshold) {
+        // No hope for a (better) match at greater error levels.
+        break;
+      }
+      last_rd = rd;
+    }
+    return best_loc;
+  }
+
+
+  /**
+   * Compute and return the score for a match with e errors and x location.
+   * @param e Number of errors in match.
+   * @param x Location of match.
+   * @param loc Expected location of match.
+   * @param pattern Pattern being sought.
+   * @return Overall score for match (0.0 = good, 1.0 = bad).
+   */
+  private double match_bitapScore(int e, int x, int loc, String pattern) {
+    float accuracy = (float) e / pattern.length();
+    int proximity = Math.abs(loc - x);
+    if (Match_Distance == 0) {
+      // Dodge divide by zero error.
+      return proximity == 0 ? accuracy : 1.0;
+    }
+    return accuracy + (proximity / (float) Match_Distance);
+  }
+
+
+  /**
+   * Initialise the alphabet for the Bitap algorithm.
+   * @param pattern The text to encode.
+   * @return Hash of character locations.
+   */
+  protected Map<Character, Integer> match_alphabet(String pattern) {
+    Map<Character, Integer> s = new HashMap<Character, Integer>();
+    char[] char_pattern = pattern.toCharArray();
+    for (char c : char_pattern) {
+      s.put(c, 0);
+    }
+    int i = 0;
+    for (char c : char_pattern) {
+      s.put(c, s.get(c) | (1 << (pattern.length() - i - 1)));
+      i++;
+    }
+    return s;
+  }
+
+
+  //  PATCH FUNCTIONS
+
+
+  /**
+   * Increase the context until it is unique,
+   * but don't let the pattern expand beyond Match_MaxBits.
+   * @param patch The patch to grow.
+   * @param text Source text.
+   */
+  protected void patch_addContext(Patch patch, String text) {
+    if (text.length() == 0) {
+      return;
+    }
+    String pattern = text.substring(patch.start2, 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) != text.lastIndexOf(pattern)
+        && pattern.length() < Match_MaxBits - Patch_Margin - Patch_Margin) {
+      padding += Patch_Margin;
+      pattern = text.substring(Math.max(0, patch.start2 - padding),
+          Math.min(text.length(), patch.start2 + patch.length1 + padding));
+    }
+    // Add one chunk for good luck.
+    padding += Patch_Margin;
+
+    // Add the prefix.
+    String prefix = text.substring(Math.max(0, patch.start2 - padding),
+        patch.start2);
+    if (prefix.length() != 0) {
+      patch.diffs.addFirst(new Diff(Operation.EQUAL, prefix));
+    }
+    // Add the suffix.
+    String suffix = text.substring(patch.start2 + patch.length1,
+        Math.min(text.length(), patch.start2 + patch.length1 + padding));
+    if (suffix.length() != 0) {
+      patch.diffs.addLast(new Diff(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();
+  }
+
+
+  /**
+   * Compute a list of patches to turn text1 into text2.
+   * A set of diffs will be computed.
+   * @param text1 Old text.
+   * @param text2 New text.
+   * @return LinkedList of Patch objects.
+   */
+  public LinkedList<Patch> patch_make(String text1, String text2) {
+    if (text1 == null || text2 == null) {
+      throw new IllegalArgumentException("Null inputs. (patch_make)");
+    }
+    // No diffs provided, compute our own.
+    LinkedList<Diff> diffs = diff_main(text1, text2, true);
+    if (diffs.size() > 2) {
+      diff_cleanupSemantic(diffs);
+      diff_cleanupEfficiency(diffs);
+    }
+    return patch_make(text1, diffs);
+  }
+
+
+  /**
+   * Compute a list of patches to turn text1 into text2.
+   * text1 will be derived from the provided diffs.
+   * @param diffs Array of diff tuples for text1 to text2.
+   * @return LinkedList of Patch objects.
+   */
+  public LinkedList<Patch> patch_make(LinkedList<Diff> diffs) {
+    if (diffs == null) {
+      throw new IllegalArgumentException("Null inputs. (patch_make)");
+    }
+    // No origin string provided, compute our own.
+    String text1 = diff_text1(diffs);
+    return patch_make(text1, diffs);
+  }
+
+
+  /**
+   * Compute a list of patches to turn text1 into text2.
+   * text2 is ignored, diffs are the delta between text1 and text2.
+   * @param text1 Old text
+   * @param text2 Ignored.
+   * @param diffs Array of diff tuples for text1 to text2.
+   * @return LinkedList of Patch objects.
+   * @deprecated Prefer patch_make(String text1, LinkedList<Diff> diffs).
+   */
+  public LinkedList<Patch> patch_make(String text1, String text2,
+      LinkedList<Diff> diffs) {
+    return patch_make(text1, diffs);
+  }
+
+
+  /**
+   * Compute a list of patches to turn text1 into text2.
+   * text2 is not provided, diffs are the delta between text1 and text2.
+   * @param text1 Old text.
+   * @param diffs Array of diff tuples for text1 to text2.
+   * @return LinkedList of Patch objects.
+   */
+  public LinkedList<Patch> patch_make(String text1, LinkedList<Diff> diffs) {
+    if (text1 == null || diffs == null) {
+      throw new IllegalArgumentException("Null inputs. (patch_make)");
+    }
+
+    LinkedList<Patch> patches = new LinkedList<Patch>();
+    if (diffs.isEmpty()) {
+      return patches;  // Get rid of the null case.
+    }
+    Patch patch = new Patch();
+    int char_count1 = 0;  // Number of characters into the text1 string.
+    int char_count2 = 0;  // Number of characters into the text2 string.
+    // Start with text1 (prepatch_text) and apply the diffs until we arrive at
+    // text2 (postpatch_text). We recreate the patches one by one to determine
+    // context info.
+    String prepatch_text = text1;
+    String postpatch_text = text1;
+    for (Diff aDiff : diffs) {
+      if (patch.diffs.isEmpty() && aDiff.operation != Operation.EQUAL) {
+        // A new patch starts here.
+        patch.start1 = char_count1;
+        patch.start2 = char_count2;
+      }
+
+      switch (aDiff.operation) {
+      case INSERT:
+        patch.diffs.add(aDiff);
+        patch.length2 += aDiff.text.length();
+        postpatch_text = postpatch_text.substring(0, char_count2)
+            + aDiff.text + postpatch_text.substring(char_count2);
+        break;
+      case DELETE:
+        patch.length1 += aDiff.text.length();
+        patch.diffs.add(aDiff);
+        postpatch_text = postpatch_text.substring(0, char_count2)
+            + postpatch_text.substring(char_count2 + aDiff.text.length());
+        break;
+      case EQUAL:
+        if (aDiff.text.length() <= 2 * Patch_Margin
+            && !patch.diffs.isEmpty() && aDiff != diffs.getLast()) {
+          // Small equality inside a patch.
+          patch.diffs.add(aDiff);
+          patch.length1 += aDiff.text.length();
+          patch.length2 += aDiff.text.length();
+        }
+
+        if (aDiff.text.length() >= 2 * Patch_Margin) {
+          // Time for a new patch.
+          if (!patch.diffs.isEmpty()) {
+            patch_addContext(patch, prepatch_text);
+            patches.add(patch);
+            patch = new Patch();
+            // Unlike Unidiff, our patch lists have a rolling context.
+            // http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
+            // Update prepatch text & pos to reflect the application of the
+            // just completed patch.
+            prepatch_text = postpatch_text;
+            char_count1 = char_count2;
+          }
+        }
+        break;
+      }
+
+      // Update the current character count.
+      if (aDiff.operation != Operation.INSERT) {
+        char_count1 += aDiff.text.length();
+      }
+      if (aDiff.operation != Operation.DELETE) {
+        char_count2 += aDiff.text.length();
+      }
+    }
+    // Pick up the leftover patch if not empty.
+    if (!patch.diffs.isEmpty()) {
+      patch_addContext(patch, prepatch_text);
+      patches.add(patch);
+    }
+
+    return patches;
+  }
+
+
+  /**
+   * Given an array of patches, return another array that is identical.
+   * @param patches Array of patch objects.
+   * @return Array of patch objects.
+   */
+  public LinkedList<Patch> patch_deepCopy(LinkedList<Patch> patches) {
+    LinkedList<Patch> patchesCopy = new LinkedList<Patch>();
+    for (Patch aPatch : patches) {
+      Patch patchCopy = new Patch();
+      for (Diff aDiff : aPatch.diffs) {
+        Diff diffCopy = new Diff(aDiff.operation, aDiff.text);
+        patchCopy.diffs.add(diffCopy);
+      }
+      patchCopy.start1 = aPatch.start1;
+      patchCopy.start2 = aPatch.start2;
+      patchCopy.length1 = aPatch.length1;
+      patchCopy.length2 = aPatch.length2;
+      patchesCopy.add(patchCopy);
+    }
+    return patchesCopy;
+  }
+
+
+  /**
+   * Merge a set of patches onto the text.  Return a patched text, as well
+   * as an array of true/false values indicating which patches were applied.
+   * @param patches Array of patch objects
+   * @param text Old text.
+   * @return Two element Object array, containing the new text and an array of
+   *      boolean values.
+   */
+  public Object[] patch_apply(LinkedList<Patch> patches, String text) {
+    if (patches.isEmpty()) {
+      return new Object[]{text, new boolean[0]};
+    }
+
+    // Deep copy the patches so that no changes are made to originals.
+    patches = patch_deepCopy(patches);
+
+    String nullPadding = patch_addPadding(patches);
+    text = nullPadding + text + nullPadding;
+    patch_splitMax(patches);
+
+    int x = 0;
+    // delta keeps track of the offset between the expected and actual location
+    // of the previous patch.  If there are patches expected at positions 10 and
+    // 20, but the first patch was found at 12, delta is 2 and the second patch
+    // has an effective expected position of 22.
+    int delta = 0;
+    boolean[] results = new boolean[patches.size()];
+    for (Patch aPatch : patches) {
+      int expected_loc = aPatch.start2 + delta;
+      String text1 = diff_text1(aPatch.diffs);
+      int start_loc;
+      int end_loc = -1;
+      if (text1.length() > this.Match_MaxBits) {
+        // patch_splitMax will only provide an oversized pattern in the case of
+        // a monster delete.
+        start_loc = match_main(text,
+            text1.substring(0, this.Match_MaxBits), expected_loc);
+        if (start_loc != -1) {
+          end_loc = match_main(text,
+              text1.substring(text1.length() - this.Match_MaxBits),
+              expected_loc + text1.length() - this.Match_MaxBits);
+          if (end_loc == -1 || start_loc >= end_loc) {
+            // Can't find valid trailing context.  Drop this patch.
+            start_loc = -1;
+          }
+        }
+      } else {
+        start_loc = match_main(text, text1, expected_loc);
+      }
+      if (start_loc == -1) {
+        // No match found.  :(
+        results[x] = false;
+        // Subtract the delta for this failed patch from subsequent patches.
+        delta -= aPatch.length2 - aPatch.length1;
+      } else {
+        // Found a match.  :)
+        results[x] = true;
+        delta = start_loc - expected_loc;
+        String text2;
+        if (end_loc == -1) {
+          text2 = text.substring(start_loc,
+              Math.min(start_loc + text1.length(), text.length()));
+        } else {
+          text2 = text.substring(start_loc,
+              Math.min(end_loc + this.Match_MaxBits, text.length()));
+        }
+        if (text1.equals(text2)) {
+          // Perfect match, just shove the replacement text in.
+          text = text.substring(0, start_loc) + diff_text2(aPatch.diffs)
+              + text.substring(start_loc + text1.length());
+        } else {
+          // Imperfect match.  Run a diff to get a framework of equivalent
+          // indices.
+          LinkedList<Diff> diffs = diff_main(text1, text2, false);
+          if (text1.length() > this.Match_MaxBits
+              && diff_levenshtein(diffs) / (float) text1.length()
+              > this.Patch_DeleteThreshold) {
+            // The end points match, but the content is unacceptably bad.
+            results[x] = false;
+          } else {
+            diff_cleanupSemanticLossless(diffs);
+            int index1 = 0;
+            for (Diff aDiff : aPatch.diffs) {
+              if (aDiff.operation != Operation.EQUAL) {
+                int index2 = diff_xIndex(diffs, index1);
+                if (aDiff.operation == Operation.INSERT) {
+                  // Insertion
+                  text = text.substring(0, start_loc + index2) + aDiff.text
+                      + text.substring(start_loc + index2);
+                } else if (aDiff.operation == Operation.DELETE) {
+                  // Deletion
+                  text = text.substring(0, start_loc + index2)
+                      + text.substring(start_loc + diff_xIndex(diffs,
+                      index1 + aDiff.text.length()));
+                }
+              }
+              if (aDiff.operation != Operation.DELETE) {
+                index1 += aDiff.text.length();
+              }
+            }
+          }
+        }
+      }
+      x++;
+    }
+    // Strip the padding off.
+    text = text.substring(nullPadding.length(), text.length()
+        - nullPadding.length());
+    return new Object[]{text, results};
+  }
+
+
+  /**
+   * Add some padding on text start and end so that edges can match something.
+   * Intended to be called only from within patch_apply.
+   * @param patches Array of patch objects.
+   * @return The padding string added to each side.
+   */
+  public String patch_addPadding(LinkedList<Patch> patches) {
+    int paddingLength = this.Patch_Margin;
+    String nullPadding = "";
+    for (int x = 1; x <= paddingLength; x++) {
+      nullPadding += String.valueOf((char) x);
+    }
+
+    // Bump all the patches forward.
+    for (Patch aPatch : patches) {
+      aPatch.start1 += paddingLength;
+      aPatch.start2 += paddingLength;
+    }
+
+    // Add some padding on start of first diff.
+    Patch patch = patches.getFirst();
+    LinkedList<Diff> diffs = patch.diffs;
+    if (diffs.isEmpty() || diffs.getFirst().operation != Operation.EQUAL) {
+      // Add nullPadding equality.
+      diffs.addFirst(new Diff(Operation.EQUAL, nullPadding));
+      patch.start1 -= paddingLength;  // Should be 0.
+      patch.start2 -= paddingLength;  // Should be 0.
+      patch.length1 += paddingLength;
+      patch.length2 += paddingLength;
+    } else if (paddingLength > diffs.getFirst().text.length()) {
+      // Grow first equality.
+      Diff firstDiff = diffs.getFirst();
+      int extraLength = paddingLength - firstDiff.text.length();
+      firstDiff.text = nullPadding.substring(firstDiff.text.length())
+          + firstDiff.text;
+      patch.start1 -= extraLength;
+      patch.start2 -= extraLength;
+      patch.length1 += extraLength;
+      patch.length2 += extraLength;
+    }
+
+    // Add some padding on end of last diff.
+    patch = patches.getLast();
+    diffs = patch.diffs;
+    if (diffs.isEmpty() || diffs.getLast().operation != Operation.EQUAL) {
+      // Add nullPadding equality.
+      diffs.addLast(new Diff(Operation.EQUAL, nullPadding));
+      patch.length1 += paddingLength;
+      patch.length2 += paddingLength;
+    } else if (paddingLength > diffs.getLast().text.length()) {
+      // Grow last equality.
+      Diff lastDiff = diffs.getLast();
+      int extraLength = paddingLength - lastDiff.text.length();
+      lastDiff.text += nullPadding.substring(0, extraLength);
+      patch.length1 += extraLength;
+      patch.length2 += extraLength;
+    }
+
+    return nullPadding;
+  }
+
+
+  /**
+   * Look through the patches and break up any which are longer than the
+   * maximum limit of the match algorithm.
+   * @param patches LinkedList of Patch objects.
+   */
+  public void patch_splitMax(LinkedList<Patch> patches) {
+    int patch_size;
+    String precontext, postcontext;
+    Patch patch;
+    int start1, start2;
+    boolean empty;
+    Operation diff_type;
+    String diff_text;
+    ListIterator<Patch> pointer = patches.listIterator();
+    Patch bigpatch = pointer.hasNext() ? pointer.next() : null;
+    while (bigpatch != null) {
+      if (bigpatch.length1 <= Match_MaxBits) {
+        bigpatch = pointer.hasNext() ? pointer.next() : null;
+        continue;
+      }
+      // Remove the big old patch.
+      pointer.remove();
+      patch_size = Match_MaxBits;
+      start1 = bigpatch.start1;
+      start2 = bigpatch.start2;
+      precontext = "";
+      while (!bigpatch.diffs.isEmpty()) {
+        // Create one of several smaller patches.
+        patch = new Patch();
+        empty = true;
+        patch.start1 = start1 - precontext.length();
+        patch.start2 = start2 - precontext.length();
+        if (precontext.length() != 0) {
+          patch.length1 = patch.length2 = precontext.length();
+          patch.diffs.add(new Diff(Operation.EQUAL, precontext));
+        }
+        while (!bigpatch.diffs.isEmpty()
+            && patch.length1 < patch_size - Patch_Margin) {
+          diff_type = bigpatch.diffs.getFirst().operation;
+          diff_text = bigpatch.diffs.getFirst().text;
+          if (diff_type == Operation.INSERT) {
+            // Insertions are harmless.
+            patch.length2 += diff_text.length();
+            start2 += diff_text.length();
+            patch.diffs.addLast(bigpatch.diffs.removeFirst());
+            empty = false;
+          } else if (diff_type == Operation.DELETE && patch.diffs.size() == 1
+              && patch.diffs.getFirst().operation == Operation.EQUAL
+              && diff_text.length() > 2 * patch_size) {
+            // This is a large deletion.  Let it pass in one chunk.
+            patch.length1 += diff_text.length();
+            start1 += diff_text.length();
+            empty = false;
+            patch.diffs.add(new Diff(diff_type, diff_text));
+            bigpatch.diffs.removeFirst();
+          } else {
+            // Deletion or equality.  Only take as much as we can stomach.
+            diff_text = diff_text.substring(0, Math.min(diff_text.length(),
+                patch_size - patch.length1 - Patch_Margin));
+            patch.length1 += diff_text.length();
+            start1 += diff_text.length();
+            if (diff_type == Operation.EQUAL) {
+              patch.length2 += diff_text.length();
+              start2 += diff_text.length();
+            } else {
+              empty = false;
+            }
+            patch.diffs.add(new Diff(diff_type, diff_text));
+            if (diff_text.equals(bigpatch.diffs.getFirst().text)) {
+              bigpatch.diffs.removeFirst();
+            } else {
+              bigpatch.diffs.getFirst().text = bigpatch.diffs.getFirst().text
+                  .substring(diff_text.length());
+            }
+          }
+        }
+        // Compute the head context for the next patch.
+        precontext = diff_text2(patch.diffs);
+        precontext = precontext.substring(Math.max(0, precontext.length()
+            - Patch_Margin));
+        // Append the end context for this patch.
+        if (diff_text1(bigpatch.diffs).length() > Patch_Margin) {
+          postcontext = diff_text1(bigpatch.diffs).substring(0, Patch_Margin);
+        } else {
+          postcontext = diff_text1(bigpatch.diffs);
+        }
+        if (postcontext.length() != 0) {
+          patch.length1 += postcontext.length();
+          patch.length2 += postcontext.length();
+          if (!patch.diffs.isEmpty()
+              && patch.diffs.getLast().operation == Operation.EQUAL) {
+            patch.diffs.getLast().text += postcontext;
+          } else {
+            patch.diffs.add(new Diff(Operation.EQUAL, postcontext));
+          }
+        }
+        if (!empty) {
+          pointer.add(patch);
+        }
+      }
+      bigpatch = pointer.hasNext() ? pointer.next() : null;
+    }
+  }
+
+
+  /**
+   * Take a list of patches and return a textual representation.
+   * @param patches List of Patch objects.
+   * @return Text representation of patches.
+   */
+  public String patch_toText(List<Patch> patches) {
+    StringBuilder text = new StringBuilder();
+    for (Patch aPatch : patches) {
+      text.append(aPatch);
+    }
+    return text.toString();
+  }
+
+
+  /**
+   * Parse a textual representation of patches and return a List of Patch
+   * objects.
+   * @param textline Text representation of patches.
+   * @return List of Patch objects.
+   * @throws IllegalArgumentException If invalid input.
+   */
+  public List<Patch> patch_fromText(String textline)
+      throws IllegalArgumentException {
+    List<Patch> patches = new LinkedList<Patch>();
+    if (textline.length() == 0) {
+      return patches;
+    }
+    List<String> textList = Arrays.asList(textline.split("\n"));
+    LinkedList<String> text = new LinkedList<String>(textList);
+    Patch patch;
+    Pattern patchHeader
+        = Pattern.compile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$");
+    Matcher m;
+    char sign;
+    String line;
+    while (!text.isEmpty()) {
+      m = patchHeader.matcher(text.getFirst());
+      if (!m.matches()) {
+        throw new IllegalArgumentException(
+            "Invalid patch string: " + text.getFirst());
+      }
+      patch = new Patch();
+      patches.add(patch);
+      patch.start1 = Integer.parseInt(m.group(1));
+      if (m.group(2).length() == 0) {
+        patch.start1--;
+        patch.length1 = 1;
+      } else if (m.group(2).equals("0")) {
+        patch.length1 = 0;
+      } else {
+        patch.start1--;
+        patch.length1 = Integer.parseInt(m.group(2));
+      }
+
+      patch.start2 = Integer.parseInt(m.group(3));
+      if (m.group(4).length() == 0) {
+        patch.start2--;
+        patch.length2 = 1;
+      } else if (m.group(4).equals("0")) {
+        patch.length2 = 0;
+      } else {
+        patch.start2--;
+        patch.length2 = Integer.parseInt(m.group(4));
+      }
+      text.removeFirst();
+
+      while (!text.isEmpty()) {
+        try {
+          sign = text.getFirst().charAt(0);
+        } catch (IndexOutOfBoundsException e) {
+          // Blank line?  Whatever.
+          text.removeFirst();
+          continue;
+        }
+        line = text.getFirst().substring(1);
+        line = line.replace("+", "%2B");  // decode would change all "+" to " "
+        try {
+          line = URLDecoder.decode(line, "UTF-8");
+        } catch (UnsupportedEncodingException e) {
+          // Not likely on modern system.
+          throw new Error("This system does not support UTF-8.", e);
+        } catch (IllegalArgumentException e) {
+          // Malformed URI sequence.
+          throw new IllegalArgumentException(
+              "Illegal escape in patch_fromText: " + line, e);
+        }
+        if (sign == '-') {
+          // Deletion.
+          patch.diffs.add(new Diff(Operation.DELETE, line));
+        } else if (sign == '+') {
+          // Insertion.
+          patch.diffs.add(new Diff(Operation.INSERT, line));
+        } else if (sign == ' ') {
+          // Minor equality.
+          patch.diffs.add(new Diff(Operation.EQUAL, line));
+        } else if (sign == '@') {
+          // Start of next patch.
+          break;
+        } else {
+          // WTF?
+          throw new IllegalArgumentException(
+              "Invalid patch mode '" + sign + "' in: " + line);
+        }
+        text.removeFirst();
+      }
+    }
+    return patches;
+  }
+
+
+  /**
+   * Class representing one diff operation.
+   */
+  public static class Diff {
+    /**
+     * One of: INSERT, DELETE or EQUAL.
+     */
+    public Operation operation;
+    /**
+     * The text associated with this diff operation.
+     */
+    public String text;
+
+    /**
+     * Constructor.  Initializes the diff with the provided values.
+     * @param operation One of INSERT, DELETE or EQUAL.
+     * @param text The text being applied.
+     */
+    public Diff(Operation operation, String text) {
+      // Construct a diff with the specified operation and text.
+      this.operation = operation;
+      this.text = text;
+    }
+
+
+    /**
+     * Display a human-readable version of this Diff.
+     * @return text version.
+     */
+    public String toString() {
+      String prettyText = this.text.replace('\n', '\u00b6');
+      return "Diff(" + this.operation + ",\"" + prettyText + "\")";
+    }
+
+
+    /**
+     * Is this Diff equivalent to another Diff?
+     * @param d Another Diff to compare against.
+     * @return true or false.
+     */
+    public boolean equals(Object d) {
+      try {
+        return (((Diff) d).operation == this.operation)
+               && (((Diff) d).text.equals(this.text));
+      } catch (ClassCastException e) {
+        return false;
+      }
+    }
+  }
+
+
+  /**
+   * Class representing one patch operation.
+   */
+  public static class Patch {
+    public LinkedList<Diff> diffs;
+    public int start1;
+    public int start2;
+    public int length1;
+    public int length2;
+
+
+    /**
+     * Constructor.  Initializes with an empty list of diffs.
+     */
+    public Patch() {
+      this.diffs = new LinkedList<Diff>();
+    }
+
+
+    /**
+     * Emmulate GNU diff's format.
+     * Header: @@ -382,8 +481,9 @@
+     * Indicies are printed as 1-based, not 0-based.
+     * @return The GNU diff string.
+     */
+    public String toString() {
+      String coords1, coords2;
+      if (this.length1 == 0) {
+        coords1 = this.start1 + ",0";
+      } else if (this.length1 == 1) {
+        coords1 = Integer.toString(this.start1 + 1);
+      } else {
+        coords1 = (this.start1 + 1) + "," + this.length1;
+      }
+      if (this.length2 == 0) {
+        coords2 = this.start2 + ",0";
+      } else if (this.length2 == 1) {
+        coords2 = Integer.toString(this.start2 + 1);
+      } else {
+        coords2 = (this.start2 + 1) + "," + this.length2;
+      }
+      StringBuilder text = new StringBuilder();
+      text.append("@@ -").append(coords1).append(" +").append(coords2)
+          .append(" @@\n");
+      // Escape the body of the patch with %xx notation.
+      for (Diff aDiff : this.diffs) {
+        switch (aDiff.operation) {
+        case INSERT:
+          text.append('+');
+          break;
+        case DELETE:
+          text.append('-');
+          break;
+        case EQUAL:
+          text.append(' ');
+          break;
+        }
+        try {
+          text.append(URLEncoder.encode(aDiff.text, "UTF-8").replace('+', ' '))
+              .append("\n");
+        } catch (UnsupportedEncodingException e) {
+          // Not likely on modern system.
+          throw new Error("This system does not support UTF-8.", e);
+        }
+      }
+      return unescapeForEncodeUriCompatability(text.toString());
+    }
+  }
+
+
+  /**
+   * Unescape selected chars for compatability with JavaScript's encodeURI.
+   * In speed critical applications this could be dropped since the
+   * receiving application will certainly decode these fine.
+   * Note that this function is case-sensitive.  Thus "%3f" would not be
+   * unescaped.  But this is ok because it is only called with the output of
+   * URLEncoder.encode which returns uppercase hex.
+   *
+   * Example: "%3F" -> "?", "%24" -> "$", etc.
+   *
+   * @param str The string to escape.
+   * @return The escaped string.
+   */
+  private static String unescapeForEncodeUriCompatability(String str) {
+    return str.replace("%21", "!").replace("%7E", "~")
+        .replace("%27", "'").replace("%28", "(").replace("%29", ")")
+        .replace("%3B", ";").replace("%2F", "/").replace("%3F", "?")
+        .replace("%3A", ":").replace("%40", "@").replace("%26", "&")
+        .replace("%3D", "=").replace("%2B", "+").replace("%24", "$")
+        .replace("%2C", ",").replace("%23", "#");
+  }
+}
diff --git a/name/fraser/neil/plaintext/diff_match_patch_test.java b/name/fraser/neil/plaintext/diff_match_patch_test.java
new file mode 100644
index 0000000..a920315
--- /dev/null
+++ b/name/fraser/neil/plaintext/diff_match_patch_test.java
@@ -0,0 +1,945 @@
+/*
+ * Test harness for diff_match_patch.java
+ *
+ * Copyright 2006 Google Inc.
+ * http://code.google.com/p/google-diff-match-patch/
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package name.fraser.neil.plaintext;
+
+import junit.framework.TestCase;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import name.fraser.neil.plaintext.diff_match_patch.Diff;
+import name.fraser.neil.plaintext.diff_match_patch.LinesToCharsResult;
+import name.fraser.neil.plaintext.diff_match_patch.Patch;
+
+public class diff_match_patch_test extends TestCase {
+
+  private diff_match_patch dmp;
+  private diff_match_patch.Operation DELETE = diff_match_patch.Operation.DELETE;
+  private diff_match_patch.Operation EQUAL = diff_match_patch.Operation.EQUAL;
+  private diff_match_patch.Operation INSERT = diff_match_patch.Operation.INSERT;
+
+  protected void setUp() {
+    // Create an instance of the diff_match_patch object.
+    dmp = new diff_match_patch();
+  }
+
+
+  //  DIFF TEST FUNCTIONS
+
+
+  public void testDiffCommonPrefix() {
+    // Detect and remove any common prefix.
+    assertEquals("diff_commonPrefix: Null case.", 0, dmp.diff_commonPrefix("abc", "xyz"));
+
+    assertEquals("diff_commonPrefix: Non-null case.", 4, dmp.diff_commonPrefix("1234abcdef", "1234xyz"));
+
+    assertEquals("diff_commonPrefix: Whole case.", 4, dmp.diff_commonPrefix("1234", "1234xyz"));
+  }
+
+  public void testDiffCommonSuffix() {
+    // Detect and remove any common suffix.
+    assertEquals("diff_commonSuffix: Null case.", 0, dmp.diff_commonSuffix("abc", "xyz"));
+
+    assertEquals("diff_commonSuffix: Non-null case.", 4, dmp.diff_commonSuffix("abcdef1234", "xyz1234"));
+
+    assertEquals("diff_commonSuffix: Whole case.", 4, dmp.diff_commonSuffix("1234", "xyz1234"));
+  }
+
+  public void testDiffHalfmatch() {
+    // Detect a halfmatch.
+    assertNull("diff_halfMatch: No match.", dmp.diff_halfMatch("1234567890", "abcdef"));
+
+    assertArrayEquals("diff_halfMatch: Single Match #1.", new String[]{"12", "90", "a", "z", "345678"}, dmp.diff_halfMatch("1234567890", "a345678z"));
+
+    assertArrayEquals("diff_halfMatch: Single Match #2.", new String[]{"a", "z", "12", "90", "345678"}, dmp.diff_halfMatch("a345678z", "1234567890"));
+
+    assertArrayEquals("diff_halfMatch: Multiple Matches #1.", new String[]{"12123", "123121", "a", "z", "1234123451234"}, dmp.diff_halfMatch("121231234123451234123121", "a1234123451234z"));
+
+    assertArrayEquals("diff_halfMatch: Multiple Matches #2.", new String[]{"", "-=-=-=-=-=", "x", "", "x-=-=-=-=-=-=-="}, dmp.diff_halfMatch("x-=-=-=-=-=-=-=-=-=-=-=-=", "xx-=-=-=-=-=-=-="));
+
+    assertArrayEquals("diff_halfMatch: Multiple Matches #3.", new String[]{"-=-=-=-=-=", "", "", "y", "-=-=-=-=-=-=-=y"}, dmp.diff_halfMatch("-=-=-=-=-=-=-=-=-=-=-=-=y", "-=-=-=-=-=-=-=yy"));
+  }
+
+  public void testDiffLinesToChars() {
+    // Convert lines down to characters.
+    ArrayList<String> tmpVector = new ArrayList<String>();
+    tmpVector.add("");
+    tmpVector.add("alpha\n");
+    tmpVector.add("beta\n");
+    assertLinesToCharsResultEquals("diff_linesToChars:", new LinesToCharsResult("\u0001\u0002\u0001", "\u0002\u0001\u0002", tmpVector), dmp.diff_linesToChars("alpha\nbeta\nalpha\n", "beta\nalpha\nbeta\n"));
+
+    tmpVector.clear();
+    tmpVector.add("");
+    tmpVector.add("alpha\r\n");
+    tmpVector.add("beta\r\n");
+    tmpVector.add("\r\n");
+    assertLinesToCharsResultEquals("diff_linesToChars:", new LinesToCharsResult("", "\u0001\u0002\u0003\u0003", tmpVector), dmp.diff_linesToChars("", "alpha\r\nbeta\r\n\r\n\r\n"));
+
+    tmpVector.clear();
+    tmpVector.add("");
+    tmpVector.add("a");
+    tmpVector.add("b");
+    assertLinesToCharsResultEquals("diff_linesToChars:", new LinesToCharsResult("\u0001", "\u0002", tmpVector), dmp.diff_linesToChars("a", "b"));
+
+    // More than 256 to reveal any 8-bit limitations.
+    int n = 300;
+    tmpVector.clear();
+    StringBuilder lineList = new StringBuilder();
+    StringBuilder charList = new StringBuilder();
+    for (int x = 1; x < n + 1; x++) {
+      tmpVector.add(x + "\n");
+      lineList.append(x + "\n");
+      charList.append(String.valueOf((char) x));
+    }
+    assertEquals(n, tmpVector.size());
+    String lines = lineList.toString();
+    String chars = charList.toString();
+    assertEquals(n, chars.length());
+    tmpVector.add(0, "");
+    assertLinesToCharsResultEquals("diff_linesToChars: More than 256.", new LinesToCharsResult(chars, "", tmpVector), dmp.diff_linesToChars(lines, ""));
+  }
+
+  public void testDiffCharsToLines() {
+    // First check that Diff equality works.
+    assertTrue("diff_charsToLines:", new Diff(EQUAL, "a").equals(new Diff(EQUAL, "a")));
+
+    assertEquals("diff_charsToLines:", new Diff(EQUAL, "a"), new Diff(EQUAL, "a"));
+
+    // Convert chars up to lines
+    LinkedList<Diff> diffs = diffList(new Diff(EQUAL, "\u0001\u0002\u0001"), new Diff(INSERT, "\u0002\u0001\u0002"));
+    ArrayList<String> tmpVector = new ArrayList<String>();
+    tmpVector.add("");
+    tmpVector.add("alpha\n");
+    tmpVector.add("beta\n");
+    dmp.diff_charsToLines(diffs, tmpVector);
+    assertEquals("diff_charsToLines:", diffList(new Diff(EQUAL, "alpha\nbeta\nalpha\n"), new Diff(INSERT, "beta\nalpha\nbeta\n")), diffs);
+
+    // More than 256 to reveal any 8-bit limitations.
+    int n = 300;
+    tmpVector.clear();
+    StringBuilder lineList = new StringBuilder();
+    StringBuilder charList = new StringBuilder();
+    for (int x = 1; x < n + 1; x++) {
+      tmpVector.add(x + "\n");
+      lineList.append(x + "\n");
+      charList.append(String.valueOf((char) x));
+    }
+    assertEquals(n, tmpVector.size());
+    String lines = lineList.toString();
+    String chars = charList.toString();
+    assertEquals(n, chars.length());
+    tmpVector.add(0, "");
+    diffs = diffList(new Diff(DELETE, chars));
+    dmp.diff_charsToLines(diffs, tmpVector);
+    assertEquals("diff_charsToLines: More than 256.", diffList(new Diff(DELETE, lines)), diffs);
+  }
+
+  public void testDiffCleanupMerge() {
+    // Cleanup a messy diff.
+    LinkedList<Diff> diffs = diffList();
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Null case.", diffList(), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "b"), new Diff(INSERT, "c"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: No change case.", diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "b"), new Diff(INSERT, "c")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(EQUAL, "b"), new Diff(EQUAL, "c"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Merge equalities.", diffList(new Diff(EQUAL, "abc")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(DELETE, "b"), new Diff(DELETE, "c"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Merge deletions.", diffList(new Diff(DELETE, "abc")), diffs);
+
+    diffs = diffList(new Diff(INSERT, "a"), new Diff(INSERT, "b"), new Diff(INSERT, "c"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Merge insertions.", diffList(new Diff(INSERT, "abc")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(INSERT, "b"), new Diff(DELETE, "c"), new Diff(INSERT, "d"), new Diff(EQUAL, "e"), new Diff(EQUAL, "f"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Merge interweave.", diffList(new Diff(DELETE, "ac"), new Diff(INSERT, "bd"), new Diff(EQUAL, "ef")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(INSERT, "abc"), new Diff(DELETE, "dc"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Prefix and suffix detection.", diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "d"), new Diff(INSERT, "b"), new Diff(EQUAL, "c")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(INSERT, "ba"), new Diff(EQUAL, "c"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Slide edit left.", diffList(new Diff(INSERT, "ab"), new Diff(EQUAL, "ac")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "c"), new Diff(INSERT, "ab"), new Diff(EQUAL, "a"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Slide edit right.", diffList(new Diff(EQUAL, "ca"), new Diff(INSERT, "ba")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "b"), new Diff(EQUAL, "c"), new Diff(DELETE, "ac"), new Diff(EQUAL, "x"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Slide edit left recursive.", diffList(new Diff(DELETE, "abc"), new Diff(EQUAL, "acx")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "x"), new Diff(DELETE, "ca"), new Diff(EQUAL, "c"), new Diff(DELETE, "b"), new Diff(EQUAL, "a"));
+    dmp.diff_cleanupMerge(diffs);
+    assertEquals("diff_cleanupMerge: Slide edit right recursive.", diffList(new Diff(EQUAL, "xca"), new Diff(DELETE, "cba")), diffs);
+  }
+
+  public void testDiffCleanupSemanticLossless() {
+    // Slide diffs to match logical boundaries.
+    LinkedList<Diff> diffs = diffList();
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Null case.", diffList(), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "AAA\r\n\r\nBBB"), new Diff(INSERT, "\r\nDDD\r\n\r\nBBB"), new Diff(EQUAL, "\r\nEEE"));
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Blank lines.", diffList(new Diff(EQUAL, "AAA\r\n\r\n"), new Diff(INSERT, "BBB\r\nDDD\r\n\r\n"), new Diff(EQUAL, "BBB\r\nEEE")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "AAA\r\nBBB"), new Diff(INSERT, " DDD\r\nBBB"), new Diff(EQUAL, " EEE"));
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Line boundaries.", diffList(new Diff(EQUAL, "AAA\r\n"), new Diff(INSERT, "BBB DDD\r\n"), new Diff(EQUAL, "BBB EEE")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "The c"), new Diff(INSERT, "ow and the c"), new Diff(EQUAL, "at."));
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Word boundaries.", diffList(new Diff(EQUAL, "The "), new Diff(INSERT, "cow and the "), new Diff(EQUAL, "cat.")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "The-c"), new Diff(INSERT, "ow-and-the-c"), new Diff(EQUAL, "at."));
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Alphanumeric boundaries.", diffList(new Diff(EQUAL, "The-"), new Diff(INSERT, "cow-and-the-"), new Diff(EQUAL, "cat.")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "a"), new Diff(EQUAL, "ax"));
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Hitting the start.", diffList(new Diff(DELETE, "a"), new Diff(EQUAL, "aax")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "xa"), new Diff(DELETE, "a"), new Diff(EQUAL, "a"));
+    dmp.diff_cleanupSemanticLossless(diffs);
+    assertEquals("diff_cleanupSemanticLossless: Hitting the end.", diffList(new Diff(EQUAL, "xaa"), new Diff(DELETE, "a")), diffs);
+  }
+
+  public void testDiffCleanupSemantic() {
+    // Cleanup semantically trivial equalities.
+    LinkedList<Diff> diffs = diffList();
+    dmp.diff_cleanupSemantic(diffs);
+    assertEquals("diff_cleanupSemantic: Null case.", diffList(), diffs);
+
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(INSERT, "b"), new Diff(EQUAL, "cd"), new Diff(DELETE, "e"));
+    dmp.diff_cleanupSemantic(diffs);
+    assertEquals("diff_cleanupSemantic: No elimination.", diffList(new Diff(DELETE, "a"), new Diff(INSERT, "b"), new Diff(EQUAL, "cd"), new Diff(DELETE, "e")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(EQUAL, "b"), new Diff(DELETE, "c"));
+    dmp.diff_cleanupSemantic(diffs);
+    assertEquals("diff_cleanupSemantic: Simple elimination.", diffList(new Diff(DELETE, "abc"), new Diff(INSERT, "b")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "ab"), new Diff(EQUAL, "cd"), new Diff(DELETE, "e"), new Diff(EQUAL, "f"), new Diff(INSERT, "g"));
+    dmp.diff_cleanupSemantic(diffs);
+    assertEquals("diff_cleanupSemantic: Backpass elimination.", diffList(new Diff(DELETE, "abcdef"), new Diff(INSERT, "cdfg")), diffs);
+
+    diffs = diffList(new Diff(INSERT, "1"), new Diff(EQUAL, "A"), new Diff(DELETE, "B"), new Diff(INSERT, "2"), new Diff(EQUAL, "_"), new Diff(INSERT, "1"), new Diff(EQUAL, "A"), new Diff(DELETE, "B"), new Diff(INSERT, "2"));
+    dmp.diff_cleanupSemantic(diffs);
+    assertEquals("diff_cleanupSemantic: Multiple elimination.", diffList(new Diff(DELETE, "AB_AB"), new Diff(INSERT, "1A2_1A2")), diffs);
+
+    diffs = diffList(new Diff(EQUAL, "The c"), new Diff(DELETE, "ow and the c"), new Diff(EQUAL, "at."));
+    dmp.diff_cleanupSemantic(diffs);
+    assertEquals("diff_cleanupSemantic: Word boundaries.", diffList(new Diff(EQUAL, "The "), new Diff(DELETE, "cow and the "), new Diff(EQUAL, "cat.")), diffs);
+  }
+
+  public void testDiffCleanupEfficiency() {
+    // Cleanup operationally trivial equalities.
+    dmp.Diff_EditCost = 4;
+    LinkedList<Diff> diffs = diffList();
+    dmp.diff_cleanupEfficiency(diffs);
+    assertEquals("diff_cleanupEfficiency: Null case.", diffList(), diffs);
+
+    diffs = diffList(new Diff(DELETE, "ab"), new Diff(INSERT, "12"), new Diff(EQUAL, "wxyz"), new Diff(DELETE, "cd"), new Diff(INSERT, "34"));
+    dmp.diff_cleanupEfficiency(diffs);
+    assertEquals("diff_cleanupEfficiency: No elimination.", diffList(new Diff(DELETE, "ab"), new Diff(INSERT, "12"), new Diff(EQUAL, "wxyz"), new Diff(DELETE, "cd"), new Diff(INSERT, "34")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "ab"), new Diff(INSERT, "12"), new Diff(EQUAL, "xyz"), new Diff(DELETE, "cd"), new Diff(INSERT, "34"));
+    dmp.diff_cleanupEfficiency(diffs);
+    assertEquals("diff_cleanupEfficiency: Four-edit elimination.", diffList(new Diff(DELETE, "abxyzcd"), new Diff(INSERT, "12xyz34")), diffs);
+
+    diffs = diffList(new Diff(INSERT, "12"), new Diff(EQUAL, "x"), new Diff(DELETE, "cd"), new Diff(INSERT, "34"));
+    dmp.diff_cleanupEfficiency(diffs);
+    assertEquals("diff_cleanupEfficiency: Three-edit elimination.", diffList(new Diff(DELETE, "xcd"), new Diff(INSERT, "12x34")), diffs);
+
+    diffs = diffList(new Diff(DELETE, "ab"), new Diff(INSERT, "12"), new Diff(EQUAL, "xy"), new Diff(INSERT, "34"), new Diff(EQUAL, "z"), new Diff(DELETE, "cd"), new Diff(INSERT, "56"));
+    dmp.diff_cleanupEfficiency(diffs);
+    assertEquals("diff_cleanupEfficiency: Backpass elimination.", diffList(new Diff(DELETE, "abxyzcd"), new Diff(INSERT, "12xy34z56")), diffs);
+
+    dmp.Diff_EditCost = 5;
+    diffs = diffList(new Diff(DELETE, "ab"), new Diff(INSERT, "12"), new Diff(EQUAL, "wxyz"), new Diff(DELETE, "cd"), new Diff(INSERT, "34"));
+    dmp.diff_cleanupEfficiency(diffs);
+    assertEquals("diff_cleanupEfficiency: High cost elimination.", diffList(new Diff(DELETE, "abwxyzcd"), new Diff(INSERT, "12wxyz34")), diffs);
+    dmp.Diff_EditCost = 4;
+  }
+
+  public void testDiffPrettyHtml() {
+    // Pretty print.
+    LinkedList<Diff> diffs = diffList(new Diff(EQUAL, "a\n"), new Diff(DELETE, "<B>b</B>"), new Diff(INSERT, "c&d"));
+    assertEquals("diff_prettyHtml:", "<SPAN TITLE=\"i=0\">a&para;<BR></SPAN><DEL STYLE=\"background:#FFE6E6;\" TITLE=\"i=2\">&lt;B&gt;b&lt;/B&gt;</DEL><INS STYLE=\"background:#E6FFE6;\" TITLE=\"i=2\">c&amp;d</INS>", dmp.diff_prettyHtml(diffs));
+  }
+
+  public void testDiffText() {
+    // Compute the source and destination texts.
+    LinkedList<Diff> diffs = diffList(new Diff(EQUAL, "jump"), new Diff(DELETE, "s"), new Diff(INSERT, "ed"), new Diff(EQUAL, " over "), new Diff(DELETE, "the"), new Diff(INSERT, "a"), new Diff(EQUAL, " lazy"));
+    assertEquals("diff_text1:", "jumps over the lazy", dmp.diff_text1(diffs));
+    assertEquals("diff_text2:", "jumped over a lazy", dmp.diff_text2(diffs));
+  }
+
+  public void testDiffDelta() {
+    // Convert a diff into delta string.
+    LinkedList<Diff> diffs = diffList(new Diff(EQUAL, "jump"), new Diff(DELETE, "s"), new Diff(INSERT, "ed"), new Diff(EQUAL, " over "), new Diff(DELETE, "the"), new Diff(INSERT, "a"), new Diff(EQUAL, " lazy"), new Diff(INSERT, "old dog"));
+    String text1 = dmp.diff_text1(diffs);
+    assertEquals("diff_text1: Base text.", "jumps over the lazy", text1);
+
+    String delta = dmp.diff_toDelta(diffs);
+    assertEquals("diff_toDelta:", "=4\t-1\t+ed\t=6\t-3\t+a\t=5\t+old dog", delta);
+
+    // Convert delta string into a diff.
+    assertEquals("diff_fromDelta: Normal.", diffs, dmp.diff_fromDelta(text1, delta));
+
+    // Generates error (19 < 20).
+    try {
+      dmp.diff_fromDelta(text1 + "x", delta);
+      fail("diff_fromDelta: Too long.");
+    } catch (IllegalArgumentException ex) {
+      // Exception expected.
+    }
+
+    // Generates error (19 > 18).
+    try {
+      dmp.diff_fromDelta(text1.substring(1), delta);
+      fail("diff_fromDelta: Too short.");
+    } catch (IllegalArgumentException ex) {
+      // Exception expected.
+    }
+
+    // Generates error (%c3%xy invalid Unicode).
+    try {
+      dmp.diff_fromDelta("", "+%c3%xy");
+      fail("diff_fromDelta: Invalid character.");
+    } catch (IllegalArgumentException ex) {
+      // Exception expected.
+    }
+
+    // Test deltas with special characters.
+    diffs = diffList(new Diff(EQUAL, "\u0680 \000 \t %"), new Diff(DELETE, "\u0681 \001 \n ^"), new Diff(INSERT, "\u0682 \002 \\ |"));
+    text1 = dmp.diff_text1(diffs);
+    assertEquals("diff_text1: Unicode text.", "\u0680 \000 \t %\u0681 \001 \n ^", text1);
+
+    delta = dmp.diff_toDelta(diffs);
+    assertEquals("diff_toDelta: Unicode.", "=7\t-7\t+%DA%82 %02 %5C %7C", delta);
+
+    assertEquals("diff_fromDelta: Unicode.", diffs, dmp.diff_fromDelta(text1, delta));
+
+    // Verify pool of unchanged characters.
+    diffs = diffList(new Diff(INSERT, "A-Z a-z 0-9 - _ . ! ~ * ' ( ) ; / ? : @ & = + $ , # "));
+    String text2 = dmp.diff_text2(diffs);
+    assertEquals("diff_text2: Unchanged characters.", "A-Z a-z 0-9 - _ . ! ~ * \' ( ) ; / ? : @ & = + $ , # ", text2);
+
+    delta = dmp.diff_toDelta(diffs);
+    assertEquals("diff_toDelta: Unchanged characters.", "+A-Z a-z 0-9 - _ . ! ~ * \' ( ) ; / ? : @ & = + $ , # ", delta);
+
+    // Convert delta string into a diff.
+    assertEquals("diff_fromDelta: Unchanged characters.", diffs, dmp.diff_fromDelta("", delta));
+  }
+
+  public void testDiffXIndex() {
+    // Translate a location in text1 to text2.
+    LinkedList<Diff> diffs = diffList(new Diff(DELETE, "a"), new Diff(INSERT, "1234"), new Diff(EQUAL, "xyz"));
+    assertEquals("diff_xIndex: Translation on equality.", 5, dmp.diff_xIndex(diffs, 2));
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "1234"), new Diff(EQUAL, "xyz"));
+    assertEquals("diff_xIndex: Translation on deletion.", 1, dmp.diff_xIndex(diffs, 3));
+  }
+
+  public void testDiffLevenshtein() {
+    LinkedList<Diff> diffs = diffList(new Diff(DELETE, "abc"), new Diff(INSERT, "1234"), new Diff(EQUAL, "xyz"));
+    assertEquals("Levenshtein with trailing equality.", 4, dmp.diff_levenshtein(diffs));
+
+    diffs = diffList(new Diff(EQUAL, "xyz"), new Diff(DELETE, "abc"), new Diff(INSERT, "1234"));
+    assertEquals("Levenshtein with leading equality.", 4, dmp.diff_levenshtein(diffs));
+
+    diffs = diffList(new Diff(DELETE, "abc"), new Diff(EQUAL, "xyz"), new Diff(INSERT, "1234"));
+    assertEquals("Levenshtein with middle equality.", 7, dmp.diff_levenshtein(diffs));
+  }
+
+  public void testDiffPath() {
+    // First, check footprints are different.
+    assertTrue("diff_footprint:", dmp.diff_footprint(1, 10) != dmp.diff_footprint(10, 1));
+
+    // Single letters.
+    // Trace a path from back to front.
+    List<Set<Long>> v_map;
+    Set<Long> row_set;
+    v_map = new ArrayList<Set<Long>>();
+    {
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 1));
+      row_set.add(dmp.diff_footprint(1, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 2));
+      row_set.add(dmp.diff_footprint(2, 0));
+      row_set.add(dmp.diff_footprint(2, 2));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 3));
+      row_set.add(dmp.diff_footprint(2, 3));
+      row_set.add(dmp.diff_footprint(3, 0));
+      row_set.add(dmp.diff_footprint(4, 3));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 4));
+      row_set.add(dmp.diff_footprint(2, 4));
+      row_set.add(dmp.diff_footprint(4, 0));
+      row_set.add(dmp.diff_footprint(4, 4));
+      row_set.add(dmp.diff_footprint(5, 3));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 5));
+      row_set.add(dmp.diff_footprint(2, 5));
+      row_set.add(dmp.diff_footprint(4, 5));
+      row_set.add(dmp.diff_footprint(5, 0));
+      row_set.add(dmp.diff_footprint(6, 3));
+      row_set.add(dmp.diff_footprint(6, 5));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 6));
+      row_set.add(dmp.diff_footprint(2, 6));
+      row_set.add(dmp.diff_footprint(4, 6));
+      row_set.add(dmp.diff_footprint(6, 6));
+      row_set.add(dmp.diff_footprint(7, 5));
+      v_map.add(row_set);
+    }
+    LinkedList<Diff> diffs = diffList(new Diff(INSERT, "W"), new Diff(DELETE, "A"), new Diff(EQUAL, "1"), new Diff(DELETE, "B"), new Diff(EQUAL, "2"), new Diff(INSERT, "X"), new Diff(DELETE, "C"), new Diff(EQUAL, "3"), new Diff(DELETE, "D"));
+    assertEquals("diff_path1: Single letters.", diffs, dmp.diff_path1(v_map, "A1B2C3D", "W12X3"));
+
+    // Trace a path from front to back.
+    v_map.remove(v_map.size() - 1);
+    diffs = diffList(new Diff(EQUAL, "4"), new Diff(DELETE, "E"), new Diff(INSERT, "Y"), new Diff(EQUAL, "5"), new Diff(DELETE, "F"), new Diff(EQUAL, "6"), new Diff(DELETE, "G"), new Diff(INSERT, "Z"));
+    assertEquals("diff_path2: Single letters.", diffs, dmp.diff_path2(v_map, "4E5F6G", "4Y56Z"));
+
+    // Double letters.
+    // Trace a path from back to front.
+    v_map = new ArrayList<Set<Long>>();
+    {
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 1));
+      row_set.add(dmp.diff_footprint(1, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 2));
+      row_set.add(dmp.diff_footprint(1, 1));
+      row_set.add(dmp.diff_footprint(2, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 3));
+      row_set.add(dmp.diff_footprint(1, 2));
+      row_set.add(dmp.diff_footprint(2, 1));
+      row_set.add(dmp.diff_footprint(3, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 4));
+      row_set.add(dmp.diff_footprint(1, 3));
+      row_set.add(dmp.diff_footprint(3, 1));
+      row_set.add(dmp.diff_footprint(4, 0));
+      row_set.add(dmp.diff_footprint(4, 4));
+      v_map.add(row_set);
+    }
+    diffs = diffList(new Diff(INSERT, "WX"), new Diff(DELETE, "AB"), new Diff(EQUAL, "12"));
+    assertEquals("diff_path1: Double letters.", diffs, dmp.diff_path1(v_map, "AB12", "WX12"));
+
+    // Trace a path from front to back.
+    v_map = new ArrayList<Set<Long>>();
+    {
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(0, 1));
+      row_set.add(dmp.diff_footprint(1, 0));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(1, 1));
+      row_set.add(dmp.diff_footprint(2, 0));
+      row_set.add(dmp.diff_footprint(2, 4));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(2, 1));
+      row_set.add(dmp.diff_footprint(2, 5));
+      row_set.add(dmp.diff_footprint(3, 0));
+      row_set.add(dmp.diff_footprint(3, 4));
+      v_map.add(row_set);
+      row_set = new HashSet<Long>();
+      row_set.add(dmp.diff_footprint(2, 6));
+      row_set.add(dmp.diff_footprint(3, 5));
+      row_set.add(dmp.diff_footprint(4, 4));
+      v_map.add(row_set);
+    }
+    diffs = diffList(new Diff(DELETE, "CD"), new Diff(EQUAL, "34"), new Diff(INSERT, "YZ"));
+    assertEquals("diff_path2: Double letters.", diffs, dmp.diff_path2(v_map, "CD34", "34YZ"));
+  }
+
+  public void testDiffMain() {
+    // Perform a trivial diff.
+    LinkedList<Diff> diffs = diffList(new Diff(EQUAL, "abc"));
+    assertEquals("diff_main: Null case.", diffs, dmp.diff_main("abc", "abc", false));
+
+    diffs = diffList(new Diff(EQUAL, "ab"), new Diff(INSERT, "123"), new Diff(EQUAL, "c"));
+    assertEquals("diff_main: Simple insertion.", diffs, dmp.diff_main("abc", "ab123c", false));
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "123"), new Diff(EQUAL, "bc"));
+    assertEquals("diff_main: Simple deletion.", diffs, dmp.diff_main("a123bc", "abc", false));
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(INSERT, "123"), new Diff(EQUAL, "b"), new Diff(INSERT, "456"), new Diff(EQUAL, "c"));
+    assertEquals("diff_main: Two insertions.", diffs, dmp.diff_main("abc", "a123b456c", false));
+
+    diffs = diffList(new Diff(EQUAL, "a"), new Diff(DELETE, "123"), new Diff(EQUAL, "b"), new Diff(DELETE, "456"), new Diff(EQUAL, "c"));
+    assertEquals("diff_main: Two deletions.", diffs, dmp.diff_main("a123b456c", "abc", false));
+
+    // Perform a real diff.
+    // Switch off the timeout.
+    dmp.Diff_Timeout = 0;
+    dmp.Diff_DualThreshold = 32;
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(INSERT, "b"));
+    assertEquals("diff_main: Simple case #1.", diffs, dmp.diff_main("a", "b", false));
+
+    diffs = diffList(new Diff(DELETE, "Apple"), new Diff(INSERT, "Banana"), new Diff(EQUAL, "s are a"), new Diff(INSERT, "lso"), new Diff(EQUAL, " fruit."));
+    assertEquals("diff_main: Simple case #2.", diffs, dmp.diff_main("Apples are a fruit.", "Bananas are also fruit.", false));
+
+    diffs = diffList(new Diff(DELETE, "a"), new Diff(INSERT, "\u0680"), new Diff(EQUAL, "x"), new Diff(DELETE, "\t"), new Diff(INSERT, "\000"));
+    assertEquals("diff_main: Simple case #3.", diffs, dmp.diff_main("ax\t", "\u0680x\000", false));
+
+    diffs = diffList(new Diff(DELETE, "1"), new Diff(EQUAL, "a"), new Diff(DELETE, "y"), new Diff(EQUAL, "b"), new Diff(DELETE, "2"), new Diff(INSERT, "xab"));
+    assertEquals("diff_main: Overlap #1.", diffs, dmp.diff_main("1ayb2", "abxab", false));
+
+    diffs = diffList(new Diff(INSERT, "xaxcx"), new Diff(EQUAL, "abc"), new Diff(DELETE, "y"));
+    assertEquals("diff_main: Overlap #2.", diffs, dmp.diff_main("abcy", "xaxcxabc", false));
+
+    // Sub-optimal double-ended diff.
+    dmp.Diff_DualThreshold = 2;
+    diffs = diffList(new Diff(INSERT, "x"), new Diff(EQUAL, "a"), new Diff(DELETE, "b"), new Diff(INSERT, "x"), new Diff(EQUAL, "c"), new Diff(DELETE, "y"), new Diff(INSERT, "xabc"));
+    assertEquals("diff_main: Overlap #3.", diffs, dmp.diff_main("abcy", "xaxcxabc", false));
+
+    dmp.Diff_DualThreshold = 32;
+    dmp.Diff_Timeout = 0.001f;  // 1ms
+    String a = "`Twas brillig, and the slithy toves\nDid gyre and gimble in the wabe:\nAll mimsy were the borogoves,\nAnd the mome raths outgrabe.\n";
+    String b = "I am the very model of a modern major general,\nI've information vegetable, animal, and mineral,\nI know the kings of England, and I quote the fights historical,\nFrom Marathon to Waterloo, in order categorical.\n";
+    // Increase the text lengths by 1024 times to ensure a timeout.
+    for (int x = 0; x < 10; x++) {
+      a = a + a;
+      b = b + b;
+    }
+    assertNull("diff_main: Timeout.", dmp.diff_map(a, b));
+    dmp.Diff_Timeout = 0;
+
+    // Test the linemode speedup.
+    // Must be long to pass the 200 char cutoff.
+    a = "1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n";
+    b = "abcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\nabcdefghij\n";
+    assertEquals("diff_main: Simple.", dmp.diff_main(a, b, true), dmp.diff_main(a, b, false));
+
+    a = "1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n1234567890\n";
+    b = "abcdefghij\n1234567890\n1234567890\n1234567890\nabcdefghij\n1234567890\n1234567890\n1234567890\nabcdefghij\n1234567890\n1234567890\n1234567890\nabcdefghij\n";
+    String[] texts_linemode = diff_rebuildtexts(dmp.diff_main(a, b, true));
+    String[] texts_textmode = diff_rebuildtexts(dmp.diff_main(a, b, false));
+    assertArrayEquals("diff_main: Overlap.", texts_textmode, texts_linemode);
+
+    // Test null inputs.
+    try {
+      dmp.diff_main(null, null);
+      fail("diff_main: Null inputs.");
+    } catch (IllegalArgumentException ex) {
+      // Error expected.
+    }
+  }
+
+
+  //  MATCH TEST FUNCTIONS
+
+
+  public void testMatchAlphabet() {
+    // Initialise the bitmasks for Bitap.
+    Map<Character, Integer> bitmask;
+    bitmask = new HashMap<Character, Integer>();
+    bitmask.put('a', 4); bitmask.put('b', 2); bitmask.put('c', 1);
+    assertEquals("match_alphabet: Unique.", bitmask, dmp.match_alphabet("abc"));
+
+    bitmask = new HashMap<Character, Integer>();
+    bitmask.put('a', 37); bitmask.put('b', 18); bitmask.put('c', 8);
+    assertEquals("match_alphabet: Duplicates.", bitmask, dmp.match_alphabet("abcaba"));
+  }
+
+  public void testMatchBitap() {
+    // Bitap algorithm.
+    dmp.Match_Distance = 100;
+    dmp.Match_Threshold = 0.5f;
+    assertEquals("match_bitap: Exact match #1.", 5, dmp.match_bitap("abcdefghijk", "fgh", 5));
+
+    assertEquals("match_bitap: Exact match #2.", 5, dmp.match_bitap("abcdefghijk", "fgh", 0));
+
+    assertEquals("match_bitap: Fuzzy match #1.", 4, dmp.match_bitap("abcdefghijk", "efxhi", 0));
+
+    assertEquals("match_bitap: Fuzzy match #2.", 2, dmp.match_bitap("abcdefghijk", "cdefxyhijk", 5));
+
+    assertEquals("match_bitap: Fuzzy match #3.", -1, dmp.match_bitap("abcdefghijk", "bxy", 1));
+
+    assertEquals("match_bitap: Overflow.", 2, dmp.match_bitap("123456789xx0", "3456789x0", 2));
+
+    assertEquals("match_bitap: Before start match.", 0, dmp.match_bitap("abcdef", "xxabc", 4));
+
+    assertEquals("match_bitap: Beyond end match.", 3, dmp.match_bitap("abcdef", "defyy", 4));
+
+    assertEquals("match_bitap: Oversized pattern.", 0, dmp.match_bitap("abcdef", "xabcdefy", 0));
+
+    dmp.Match_Threshold = 0.4f;
+    assertEquals("match_bitap: Threshold #1.", 4, dmp.match_bitap("abcdefghijk", "efxyhi", 1));
+
+    dmp.Match_Threshold = 0.3f;
+    assertEquals("match_bitap: Threshold #2.", -1, dmp.match_bitap("abcdefghijk", "efxyhi", 1));
+
+    dmp.Match_Threshold = 0.0f;
+    assertEquals("match_bitap: Threshold #3.", 1, dmp.match_bitap("abcdefghijk", "bcdef", 1));
+
+    dmp.Match_Threshold = 0.5f;
+    assertEquals("match_bitap: Multiple select #1.", 0, dmp.match_bitap("abcdexyzabcde", "abccde", 3));
+
+    assertEquals("match_bitap: Multiple select #2.", 8, dmp.match_bitap("abcdexyzabcde", "abccde", 5));
+
+    dmp.Match_Distance = 10;  // Strict location.
+    assertEquals("match_bitap: Distance test #1.", -1, dmp.match_bitap("abcdefghijklmnopqrstuvwxyz", "abcdefg", 24));
+
+    assertEquals("match_bitap: Distance test #2.", 0, dmp.match_bitap("abcdefghijklmnopqrstuvwxyz", "abcdxxefg", 1));
+
+    dmp.Match_Distance = 1000;  // Loose location.
+    assertEquals("match_bitap: Distance test #3.", 0, dmp.match_bitap("abcdefghijklmnopqrstuvwxyz", "abcdefg", 24));
+  }
+
+  public void testMatchMain() {
+    // Full match.
+    assertEquals("match_main: Equality.", 0, dmp.match_main("abcdef", "abcdef", 1000));
+
+    assertEquals("match_main: Null text.", -1, dmp.match_main("", "abcdef", 1));
+
+    assertEquals("match_main: Null pattern.", 3, dmp.match_main("abcdef", "", 3));
+
+    assertEquals("match_main: Exact match.", 3, dmp.match_main("abcdef", "de", 3));
+
+    assertEquals("match_main: Beyond end match.", 3, dmp.match_main("abcdef", "defy", 4));
+
+    assertEquals("match_main: Oversized pattern.", 0, dmp.match_main("abcdef", "abcdefy", 0));
+
+    dmp.Match_Threshold = 0.7f;
+    assertEquals("match_main: Complex match.", 4, dmp.match_main("I am the very model of a modern major general.", " that berry ", 5));
+    dmp.Match_Threshold = 0.5f;
+
+    // Test null inputs.
+    try {
+      dmp.match_main(null, null, 0);
+      fail("match_main: Null inputs.");
+    } catch (IllegalArgumentException ex) {
+      // Error expected.
+    }
+  }
+
+
+  //  PATCH TEST FUNCTIONS
+
+
+  public void testPatchObj() {
+    // Patch Object.
+    Patch p = new Patch();
+    p.start1 = 20;
+    p.start2 = 21;
+    p.length1 = 18;
+    p.length2 = 17;
+    p.diffs = diffList(new Diff(EQUAL, "jump"), new Diff(DELETE, "s"), new Diff(INSERT, "ed"), new Diff(EQUAL, " over "), new Diff(DELETE, "the"), new Diff(INSERT, "a"), new Diff(EQUAL, "\nlaz"));
+    String strp = "@@ -21,18 +22,17 @@\n jump\n-s\n+ed\n  over \n-the\n+a\n %0Alaz\n";
+    assertEquals("Patch: toString.", strp, p.toString());
+  }
+
+  public void testPatchFromText() {
+    assertTrue("patch_fromText: #0.", dmp.patch_fromText("").isEmpty());
+
+    String strp = "@@ -21,18 +22,17 @@\n jump\n-s\n+ed\n  over \n-the\n+a\n %0Alaz\n";
+    assertEquals("patch_fromText: #1.", strp, dmp.patch_fromText(strp).get(0).toString());
+
+    assertEquals("patch_fromText: #2.", "@@ -1 +1 @@\n-a\n+b\n", dmp.patch_fromText("@@ -1 +1 @@\n-a\n+b\n").get(0).toString());
+
+    assertEquals("patch_fromText: #3.", "@@ -1,3 +0,0 @@\n-abc\n", dmp.patch_fromText("@@ -1,3 +0,0 @@\n-abc\n").get(0).toString());
+
+    assertEquals("patch_fromText: #4.", "@@ -0,0 +1,3 @@\n+abc\n", dmp.patch_fromText("@@ -0,0 +1,3 @@\n+abc\n").get(0).toString());
+
+    // Generates error.
+    try {
+      dmp.patch_fromText("Bad\nPatch\n");
+      fail("patch_fromText: #5.");
+    } catch (IllegalArgumentException ex) {
+      // Exception expected.
+    }
+  }
+
+  public void testPatchToText() {
+    String strp = "@@ -21,18 +22,17 @@\n jump\n-s\n+ed\n  over \n-the\n+a\n  laz\n";
+    List<Patch> patches;
+    patches = dmp.patch_fromText(strp);
+    assertEquals("patch_toText: Single", strp, dmp.patch_toText(patches));
+
+    strp = "@@ -1,9 +1,9 @@\n-f\n+F\n oo+fooba\n@@ -7,9 +7,9 @@\n obar\n-,\n+.\n  tes\n";
+    patches = dmp.patch_fromText(strp);
+    assertEquals("patch_toText: Dual", strp, dmp.patch_toText(patches));
+  }
+
+  public void testPatchAddContext() {
+    dmp.Patch_Margin = 4;
+    Patch p;
+    p = dmp.patch_fromText("@@ -21,4 +21,10 @@\n-jump\n+somersault\n").get(0);
+    dmp.patch_addContext(p, "The quick brown fox jumps over the lazy dog.");
+    assertEquals("patch_addContext: Simple case.", "@@ -17,12 +17,18 @@\n fox \n-jump\n+somersault\n s ov\n", p.toString());
+
+    p = dmp.patch_fromText("@@ -21,4 +21,10 @@\n-jump\n+somersault\n").get(0);
+    dmp.patch_addContext(p, "The quick brown fox jumps.");
+    assertEquals("patch_addContext: Not enough trailing context.", "@@ -17,10 +17,16 @@\n fox \n-jump\n+somersault\n s.\n", p.toString());
+
+    p = dmp.patch_fromText("@@ -3 +3,2 @@\n-e\n+at\n").get(0);
+    dmp.patch_addContext(p, "The quick brown fox jumps.");
+    assertEquals("patch_addContext: Not enough leading context.", "@@ -1,7 +1,8 @@\n Th\n-e\n+at\n  qui\n", p.toString());
+
+    p = dmp.patch_fromText("@@ -3 +3,2 @@\n-e\n+at\n").get(0);
+    dmp.patch_addContext(p, "The quick brown fox jumps.  The quick brown fox crashes.");
+    assertEquals("patch_addContext: Ambiguity.", "@@ -1,27 +1,28 @@\n Th\n-e\n+at\n  quick brown fox jumps. \n", p.toString());
+  }
+
+  @SuppressWarnings("deprecation")
+  public void testPatchMake() {
+    LinkedList<Patch> patches;
+    String text1 = "The quick brown fox jumps over the lazy dog.";
+    String text2 = "That quick brown fox jumped over a lazy dog.";
+    String expectedPatch = "@@ -1,8 +1,7 @@\n Th\n-at\n+e\n  qui\n@@ -21,17 +21,18 @@\n jump\n-ed\n+s\n  over \n-a\n+the\n  laz\n";
+    // The second patch must be "-21,17 +21,18", not "-22,17 +21,18" due to rolling context.
+    patches = dmp.patch_make(text2, text1);
+    assertEquals("patch_make: Text2+Text1 inputs", expectedPatch, dmp.patch_toText(patches));
+
+    expectedPatch = "@@ -1,11 +1,12 @@\n Th\n-e\n+at\n  quick b\n@@ -22,18 +22,17 @@\n jump\n-s\n+ed\n  over \n-the\n+a\n  laz\n";
+    patches = dmp.patch_make(text1, text2);
+    assertEquals("patch_make: Text1+Text2 inputs", expectedPatch, dmp.patch_toText(patches));
+
+    LinkedList<Diff> diffs = dmp.diff_main(text1, text2, false);
+    patches = dmp.patch_make(diffs);
+    assertEquals("patch_make: Diff input", expectedPatch, dmp.patch_toText(patches));
+
+    patches = dmp.patch_make(text1, diffs);
+    assertEquals("patch_make: Text1+Diff inputs", expectedPatch, dmp.patch_toText(patches));
+
+    patches = dmp.patch_make(text1, text2, diffs);
+    assertEquals("patch_make: Text1+Text2+Diff inputs (deprecated)", expectedPatch, dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("`1234567890-=[]\\;',./", "~!@#$%^&*()_+{}|:\"<>?");
+    assertEquals("patch_toText: Character encoding.", "@@ -1,21 +1,21 @@\n-%601234567890-=%5B%5D%5C;',./\n+~!@#$%25%5E&*()_+%7B%7D%7C:%22%3C%3E?\n", dmp.patch_toText(patches));
+
+    diffs = diffList(new Diff(DELETE, "`1234567890-=[]\\;',./"), new Diff(INSERT, "~!@#$%^&*()_+{}|:\"<>?"));
+    assertEquals("patch_fromText: Character decoding.", diffs, dmp.patch_fromText("@@ -1,21 +1,21 @@\n-%601234567890-=%5B%5D%5C;',./\n+~!@#$%25%5E&*()_+%7B%7D%7C:%22%3C%3E?\n").get(0).diffs);
+
+    text1 = "";
+    for (int x = 0; x < 100; x++) {
+      text1 += "abcdef";
+    }
+    text2 = text1 + "123";
+    expectedPatch = "@@ -573,28 +573,31 @@\n cdefabcdefabcdefabcdefabcdef\n+123\n";
+    patches = dmp.patch_make(text1, text2);
+    assertEquals("patch_make: Long string with repeats.", expectedPatch, dmp.patch_toText(patches));
+
+    // Test null inputs.
+    try {
+      dmp.patch_make(null);
+      fail("patch_make: Null inputs.");
+    } catch (IllegalArgumentException ex) {
+      // Error expected.
+    }
+  }
+
+  public void testPatchSplitMax() {
+    // Assumes that Match_MaxBits is 32.
+    LinkedList<Patch> patches;
+    patches = dmp.patch_make("abcdefghijklmnopqrstuvwxyz01234567890", "XabXcdXefXghXijXklXmnXopXqrXstXuvXwxXyzX01X23X45X67X89X0");
+    dmp.patch_splitMax(patches);
+    assertEquals("patch_splitMax: #1.", "@@ -1,32 +1,46 @@\n+X\n ab\n+X\n cd\n+X\n ef\n+X\n gh\n+X\n ij\n+X\n kl\n+X\n mn\n+X\n op\n+X\n qr\n+X\n st\n+X\n uv\n+X\n wx\n+X\n yz\n+X\n 012345\n@@ -25,13 +39,18 @@\n zX01\n+X\n 23\n+X\n 45\n+X\n 67\n+X\n 89\n+X\n 0\n", dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("abcdef1234567890123456789012345678901234567890123456789012345678901234567890uvwxyz", "abcdefuvwxyz");
+    String oldToText = dmp.patch_toText(patches);
+    dmp.patch_splitMax(patches);
+    assertEquals("patch_splitMax: #2.", oldToText, dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("1234567890123456789012345678901234567890123456789012345678901234567890", "abc");
+    dmp.patch_splitMax(patches);
+    assertEquals("patch_splitMax: #3.", "@@ -1,32 +1,4 @@\n-1234567890123456789012345678\n 9012\n@@ -29,32 +1,4 @@\n-9012345678901234567890123456\n 7890\n@@ -57,14 +1,3 @@\n-78901234567890\n+abc\n", dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("abcdefghij , h : 0 , t : 1 abcdefghij , h : 0 , t : 1 abcdefghij , h : 0 , t : 1", "abcdefghij , h : 1 , t : 1 abcdefghij , h : 1 , t : 1 abcdefghij , h : 0 , t : 1");
+    dmp.patch_splitMax(patches);
+    assertEquals("patch_splitMax: #4.", "@@ -2,32 +2,32 @@\n bcdefghij , h : \n-0\n+1\n  , t : 1 abcdef\n@@ -29,32 +29,32 @@\n bcdefghij , h : \n-0\n+1\n  , t : 1 abcdef\n", dmp.patch_toText(patches));
+  }
+
+  public void testPatchAddPadding() {
+    LinkedList<Patch> patches;
+    patches = dmp.patch_make("", "test");
+    assertEquals("patch_addPadding: Both edges full.", "@@ -0,0 +1,4 @@\n+test\n", dmp.patch_toText(patches));
+    dmp.patch_addPadding(patches);
+    assertEquals("patch_addPadding: Both edges full.", "@@ -1,8 +1,12 @@\n %01%02%03%04\n+test\n %01%02%03%04\n", dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("XY", "XtestY");
+    assertEquals("patch_addPadding: Both edges partial.", "@@ -1,2 +1,6 @@\n X\n+test\n Y\n", dmp.patch_toText(patches));
+    dmp.patch_addPadding(patches);
+    assertEquals("patch_addPadding: Both edges partial.", "@@ -2,8 +2,12 @@\n %02%03%04X\n+test\n Y%01%02%03\n", dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("XXXXYYYY", "XXXXtestYYYY");
+    assertEquals("patch_addPadding: Both edges none.", "@@ -1,8 +1,12 @@\n XXXX\n+test\n YYYY\n", dmp.patch_toText(patches));
+    dmp.patch_addPadding(patches);
+    assertEquals("patch_addPadding: Both edges none.", "@@ -5,8 +5,12 @@\n XXXX\n+test\n YYYY\n", dmp.patch_toText(patches));
+  }
+
+  public void testPatchApply() {
+    dmp.Match_Distance = 1000;
+    dmp.Match_Threshold = 0.5f;
+    dmp.Patch_DeleteThreshold = 0.5f;
+    LinkedList<Patch> patches;
+    patches = dmp.patch_make("The quick brown fox jumps over the lazy dog.", "That quick brown fox jumped over a lazy dog.");
+    Object[] results = dmp.patch_apply(patches, "The quick brown fox jumps over the lazy dog.");
+    boolean[] boolArray = (boolean[]) results[1];
+    String resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("patch_apply: Exact match.", "That quick brown fox jumped over a lazy dog.\ttrue\ttrue", resultStr);
+
+    results = dmp.patch_apply(patches, "The quick red rabbit jumps over the tired tiger.");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("patch_apply: Partial match.", "That quick red rabbit jumped over a tired tiger.\ttrue\ttrue", resultStr);
+
+    results = dmp.patch_apply(patches, "I am the very model of a modern major general.");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("patch_apply: Failed match.", "I am the very model of a modern major general.\tfalse\tfalse", resultStr);
+
+    patches = dmp.patch_make("x1234567890123456789012345678901234567890123456789012345678901234567890y", "xabcy");
+    results = dmp.patch_apply(patches, "x123456789012345678901234567890-----++++++++++-----123456789012345678901234567890y");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("patch_apply: Big delete, small change.", "xabcy\ttrue\ttrue", resultStr);
+
+    patches = dmp.patch_make("x1234567890123456789012345678901234567890123456789012345678901234567890y", "xabcy");
+    results = dmp.patch_apply(patches, "x12345678901234567890---------------++++++++++---------------12345678901234567890y");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("patch_apply: Big delete, big change 1.", "xabc12345678901234567890---------------++++++++++---------------12345678901234567890y\tfalse\ttrue", resultStr);
+
+    dmp.Patch_DeleteThreshold = 0.6f;
+    patches = dmp.patch_make("x1234567890123456789012345678901234567890123456789012345678901234567890y", "xabcy");
+    results = dmp.patch_apply(patches, "x12345678901234567890---------------++++++++++---------------12345678901234567890y");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("patch_apply: Big delete, big change 2.", "xabcy\ttrue\ttrue", resultStr);
+    dmp.Patch_DeleteThreshold = 0.5f;
+
+    // Compensate for failed patch.
+    dmp.Match_Threshold = 0.0f;
+    dmp.Match_Distance = 0;
+    patches = dmp.patch_make("abcdefghijklmnopqrstuvwxyz--------------------1234567890", "abcXXXXXXXXXXdefghijklmnopqrstuvwxyz--------------------1234567YYYYYYYYYY890");
+    results = dmp.patch_apply(patches, "ABCDEFGHIJKLMNOPQRSTUVWXYZ--------------------1234567890");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0] + "\t" + boolArray[1];
+    assertEquals("ABCDEFGHIJKLMNOPQRSTUVWXYZ--------------------1234567YYYYYYYYYY890\tfalse\ttrue", resultStr);
+    dmp.Match_Threshold = 0.5f;
+    dmp.Match_Distance = 1000;
+
+    patches = dmp.patch_make("", "test");
+    String patchStr = dmp.patch_toText(patches);
+    dmp.patch_apply(patches, "");
+    assertEquals("patch_apply: No side effects.", patchStr, dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("The quick brown fox jumps over the lazy dog.", "Woof");
+    patchStr = dmp.patch_toText(patches);
+    dmp.patch_apply(patches, "The quick brown fox jumps over the lazy dog.");
+    assertEquals("patch_apply: No side effects with major delete.", patchStr, dmp.patch_toText(patches));
+
+    patches = dmp.patch_make("", "test");
+    results = dmp.patch_apply(patches, "");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0];
+    assertEquals("patch_apply: Edge exact match.", "test\ttrue", resultStr);
+
+    patches = dmp.patch_make("XY", "XtestY");
+    results = dmp.patch_apply(patches, "XY");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0];
+    assertEquals("patch_apply: Near edge exact match.", "XtestY\ttrue", resultStr);
+
+    patches = dmp.patch_make("y", "y123");
+    results = dmp.patch_apply(patches, "x");
+    boolArray = (boolean[]) results[1];
+    resultStr = results[0] + "\t" + boolArray[0];
+    assertEquals("patch_apply: Edge partial match.", "x123\ttrue", resultStr);
+  }
+
+
+  private void assertArrayEquals(String error_msg, Object[] a, Object[] b) {
+    List<Object> list_a = Arrays.asList(a);
+    List<Object> list_b = Arrays.asList(b);
+    assertEquals(error_msg, list_a, list_b);
+  }
+
+
+  private void assertLinesToCharsResultEquals(String error_msg,
+      LinesToCharsResult a, LinesToCharsResult b) {
+    assertEquals(error_msg, a.chars1, b.chars1);
+    assertEquals(error_msg, a.chars2, b.chars2);
+    assertEquals(error_msg, a.lineArray, b.lineArray);
+  }
+
+  // Construct the two texts which made up the diff originally.
+  private static String[] diff_rebuildtexts(LinkedList<Diff> diffs) {
+    String[] text = {"", ""};
+    for (Diff myDiff : diffs) {
+      if (myDiff.operation != diff_match_patch.Operation.INSERT) {
+        text[0] += myDiff.text;
+      }
+      if (myDiff.operation != diff_match_patch.Operation.DELETE) {
+        text[1] += myDiff.text;
+      }
+    }
+    return text;
+  }
+
+
+  // Private function for quickly building lists of diffs.
+  private static LinkedList<Diff> diffList(Diff... diffs) {
+    LinkedList<Diff> myDiffList = new LinkedList<Diff>();
+    for (Diff myDiff : diffs) {
+      myDiffList.add(myDiff);
+    }
+    return myDiffList;
+  }
+}