Introduce TextBuffer as Output Type of copyTextTo() for Text Iterators

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 648 matching lines @@
 static VisiblePositionTemplate<Strategy> previousBoundary(const VisiblePositionTemplate<Strategy>& c, BoundarySearchFunction searchFunction)
 {
     const PositionTemplate<Strategy> pos = c.deepEquivalent();
     Node* boundary = parentEditingBoundary(pos);
     if (!boundary)
         return VisiblePositionTemplate<Strategy>();
 
     const PositionTemplate<Strategy> start = PositionTemplate<Strategy>::editingPositionOf(boundary, 0).parentAnchoredEquivalent();
     const PositionTemplate<Strategy> end = pos.parentAnchoredEquivalent();
 
-    Vector<UChar, 1024> string;
+    ForwardsTextBuffer suffixString;
     unsigned suffixLength = 0;
 
     if (requiresContextForWordBoundary(characterBefore(c))) {
         TextIteratorAlgorithm<Strategy> forwardsIterator(end, PositionTemplate<Strategy>::afterNode(boundary));
         while (!forwardsIterator.atEnd()) {
-            Vector<UChar, 1024> characters;
+            // TODO(xiaochengh): Eliminate this intermediate buffer.
+            ForwardsTextBuffer characters;
             forwardsIterator.copyTextTo(characters);
             int i = endOfFirstWordBoundaryContext(characters.data(), characters.size());
-            string.append(characters.data(), i);
+            suffixString.pushRange(characters.data(), i);
             suffixLength += i;
             if (static_cast<unsigned>(i) < characters.size())
                 break;
             forwardsIterator.advance();
         }
     }
 
+    BackwardsTextBuffer string;
+    string.pushRange(suffixString.data(), suffixString.size());
+
     SimplifiedBackwardsTextIteratorAlgorithm<Strategy> it(start, end);
     unsigned next = 0;
     bool needMoreContext = false;
     while (!it.atEnd()) {
         bool inTextSecurityMode = it.isInTextSecurityMode();
         // iterate to get chunks until the searchFunction returns a non-zero
         // value.
-        // TODO(xiaochengh): Iterative prepending has quadratic running time
-        // in the worst case. Should improve it to linear.
         if (!inTextSecurityMode) {
             it.copyTextTo(string);
         } else {
             // Treat bullets used in the text security mode as regular
             // characters when looking for boundaries
-            Vector<UChar, 1024> iteratorString;
-            iteratorString.fill('x', it.length());
-            string.prepend(iteratorString.data(), iteratorString.size());
+            string.pushCharacters('x', it.length());
         }
         // TODO(xiaochengh): The following line takes O(string.size()) time,
         // which makes the while loop take quadratic time in the worst case.
         // Should improve it in some way.
         next = searchFunction(string.data(), string.size(), string.size() - suffixLength, MayHaveMoreContext, needMoreContext);
         if (next)
             break;
         it.advance();
     }
     if (needMoreContext) {
@@ skipping 26 matching lines @@
 static VisiblePositionTemplate<Strategy> nextBoundary(const VisiblePositionTemplate<Strategy>& c, BoundarySearchFunction searchFunction)
 {
     PositionTemplate<Strategy> pos = c.deepEquivalent();
     Node* boundary = parentEditingBoundary(pos);
     if (!boundary)
         return VisiblePositionTemplate<Strategy>();
 
     Document& d = boundary->document();
     const PositionTemplate<Strategy> start(pos.parentAnchoredEquivalent());
 
-    Vector<UChar, 1024> string;
+    BackwardsTextBuffer prefixString;
     unsigned prefixLength = 0;
 
     if (requiresContextForWordBoundary(characterAfter(c))) {
         SimplifiedBackwardsTextIteratorAlgorithm<Strategy> backwardsIterator(PositionTemplate<Strategy>::firstPositionInNode(&d), start);
         while (!backwardsIterator.atEnd()) {
-            Vector<UChar, 1024> characters;
+            // TODO(xiaochengh): Eliminate this intermediate buffer.
+            BackwardsTextBuffer characters;
             backwardsIterator.copyTextTo(characters);
             int length = characters.size();
             int i = startOfLastWordBoundaryContext(characters.data(), length);
-            // TODO(xiaochengh): Iterative prepending has quadratic running
-            // time in the worst case. Should improve it to linear.
-            string.prepend(characters.data() + i, length - i);
+            prefixString.pushRange(characters.data() + i, length - i);
             prefixLength += length - i;
             if (i > 0)
                 break;
             backwardsIterator.advance();
         }
     }
 
+    ForwardsTextBuffer string;
+    string.pushRange(prefixString.data(), prefixString.size());
+
     const PositionTemplate<Strategy> searchStart = PositionTemplate<Strategy>::editingPositionOf(start.anchorNode(), start.offsetInContainerNode());
     const PositionTemplate<Strategy> searchEnd = PositionTemplate<Strategy>::lastPositionInNode(boundary);
     TextIteratorAlgorithm<Strategy> it(searchStart, searchEnd, TextIteratorEmitsCharactersBetweenAllVisiblePositions);
     const unsigned invalidOffset = static_cast<unsigned>(-1);
     unsigned next = invalidOffset;
     unsigned offset = prefixLength;
     bool needMoreContext = false;
     while (!it.atEnd()) {
         // Keep asking the iterator for chunks until the search function
         // returns an end value not equal to the length of the string passed to
         // it.
         bool inTextSecurityMode = it.isInTextSecurityMode();
         if (!inTextSecurityMode) {
             it.copyTextTo(string);
         } else {
             // Treat bullets used in the text security mode as regular
             // characters when looking for boundaries
-            Vector<UChar, 1024> iteratorString;
-            iteratorString.fill('x', it.length());
-            string.append(iteratorString.data(), iteratorString.size());
+            string.pushCharacters('x', it.length());
         }
         next = searchFunction(string.data(), string.size(), offset, MayHaveMoreContext, needMoreContext);
         if (next != string.size())
             break;
         it.advance();
         if (!needMoreContext) {
             // When the search does not need more context, skip all examined
             // characters except the last one, in case it is a boundary.
             offset = string.size();
             U16_BACK_1(string.data(), 0, offset);
@@ skipping 2528 matching lines @@
 {
     return previousPositionOfAlgorithm<EditingStrategy>(visiblePosition, rule);
 }
 
 VisiblePositionInComposedTree previousPositionOf(const VisiblePositionInComposedTree& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     return previousPositionOfAlgorithm<EditingInComposedTreeStrategy>(visiblePosition, rule);
 }
 
 } // namespace blink