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

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

Index: third_party/WebKit/Source/core/editing/iterators/TextBuffer.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/TextBuffer.cpp b/third_party/WebKit/Source/core/editing/iterators/TextBuffer.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..d84b7412dae2b8f045bd8a5f7935676bb7a24d4b
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/iterators/TextBuffer.cpp
@@ -0,0 +1,67 @@
+// 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/TextBuffer.h"
+
+namespace blink {
+
+TextBufferBase::TextBufferBase()
+{
+    m_buffer.resize(m_buffer.capacity());
+}
+
+void TextBufferBase::pushCharacters(UChar ch, size_t length)
+{
+    if (length == 0)
+        return;
+    std::fill_n(pushInternal(length), length, ch);
+}
+
+UChar* TextBufferBase::pushInternal(size_t length)

[yosin_UTC9, 2016/01/28 09:06:17]

s/pushInternal/ensureDestination/ or another, this function allocates
destination in buffer.

+{
+    if (m_size + length > m_buffer.capacity())
+        grow(m_size + length);
+    UChar* ans = pushDestination(length);

[yosin_UTC9, 2016/01/28 09:06:17]

nit: s/pushDestination/computeDestination/ or another. It doesn't add data, it
returns destination.

+    m_size += length;
+    return ans;
+}
+
+void TextBufferBase::grow(size_t demand)
+{
+    size_t oldCapacity = m_buffer.capacity();
+    m_buffer.resize(demand);
+    m_buffer.resize(m_buffer.capacity());
+    shiftData(oldCapacity);
+}
+
+const UChar* ForwardsTextBuffer::data() const
+{
+    return m_buffer.begin();
+}
+
+UChar* ForwardsTextBuffer::pushDestination(size_t length)
+{
+    ASSERT(m_size + length <= m_buffer.capacity());
+    return m_buffer.begin() + m_size;
+}
+
+const UChar* BackwardsTextBuffer::data() const
+{
+    return m_buffer.end() - m_size;
+}
+
+UChar* BackwardsTextBuffer::pushDestination(size_t length)
+{
+    ASSERT(m_size + length <= m_buffer.capacity());
+    return m_buffer.end() - m_size - length;
+}
+
+void BackwardsTextBuffer::shiftData(size_t oldCapacity)
+{
+    ASSERT(oldCapacity <= m_buffer.capacity());
+    ASSERT(m_size <= oldCapacity);
+    std::copy_backward(m_buffer.begin() + oldCapacity - m_size, m_buffer.begin() + oldCapacity, m_buffer.end());
+}
+
+} // namespace blink