ALL-IN-ONE: Optimization to previousBoundary() and nextBoundary()

third_party/WebKit/Source/core/editing/iterators/ProgressiveTextAccumulator.cpp

Index: third_party/WebKit/Source/core/editing/iterators/ProgressiveTextAccumulator.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/ProgressiveTextAccumulator.cpp b/third_party/WebKit/Source/core/editing/iterators/ProgressiveTextAccumulator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6c4c7e4f505134afb14e495f398ef2017a408524
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/iterators/ProgressiveTextAccumulator.cpp
@@ -0,0 +1,57 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/editing/iterators/ProgressiveTextAccumulator.h"
+
+namespace blink {
+
+template<typename Iterator>
+ProgressiveTextAccumulator<Iterator>::ProgressiveTextAccumulator(const PositionType& start, const PositionType& end, TextIteratorBehaviorFlags behavior)
+    : m_iterator(start, end, behavior)
+    , m_maxAccumulate(1024)
+    , m_accumulatedInCurrentNode(0)
+{
+}
+
+template<typename Iterator>
+void ProgressiveTextAccumulator<Iterator>::advance()
+{
+    ASSERT(!m_iterator.atEnd());
+    ASSERT(m_accumulatedInCurrentNode <= m_iterator.length());
+
+    if (m_accumulatedInCurrentNode == m_iterator.length()) {
+        m_accumulatedInCurrentNode = 0;
+        m_iterator.advance();
+    }
+}
+
+template<typename Iterator>
+int ProgressiveTextAccumulator<Iterator>::expandToValidLength(int accumulateLength)
+{
+    int ans = accumulateLength;
+    // Make sure we copy whole code points (on well-formed UTF-16).
+    if (m_accumulatedInCurrentNode + accumulateLength < m_iterator.length()) {
+        UChar last = m_iterator.characterAt(m_accumulatedInCurrentNode + accumulateLength - 1);
+        UChar next = m_iterator.characterAt(m_accumulatedInCurrentNode + accumulateLength);
+        if (arePairingSurrogates(last, next))
+            ans = accumulateLength + 1;
+    }
+    // TODO(xiaochengh): Do we have to copy whole grapheme clusters?
+    return ans;
+}
+
+template<typename Iterator>
+bool ProgressiveTextAccumulator<Iterator>::arePairingSurrogates(UChar first, UChar second)
+{
+    if (Iterator::direction == TextIteratorDirection::TextIteratorForward)
+        return U16_IS_LEAD(first) && U16_IS_TRAIL(second);
+    return U16_IS_TRAIL(first) && U16_IS_LEAD(second);
+}
+
+template class CORE_TEMPLATE_EXPORT ProgressiveTextAccumulator<TextIteratorAlgorithm<EditingStrategy>>;
+template class CORE_TEMPLATE_EXPORT ProgressiveTextAccumulator<TextIteratorAlgorithm<EditingInComposedTreeStrategy>>;
+template class CORE_TEMPLATE_EXPORT ProgressiveTextAccumulator<SimplifiedBackwardsTextIteratorAlgorithm<EditingStrategy>>;
+template class CORE_TEMPLATE_EXPORT ProgressiveTextAccumulator<SimplifiedBackwardsTextIteratorAlgorithm<EditingInComposedTreeStrategy>>;
+
+} // namespace blink