[All-In-One] Introduce BackspaceStateMachine

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

Index: third_party/WebKit/Source/core/editing/BackspaceStateMachine.cpp
diff --git a/third_party/WebKit/Source/core/editing/BackspaceStateMachine.cpp b/third_party/WebKit/Source/core/editing/BackspaceStateMachine.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5c054ee21c5b48bd1536a42b4ccbba34decd2544
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/BackspaceStateMachine.cpp
@@ -0,0 +1,63 @@
+// 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/BackspaceStateMachine.h"
+
+#include <unicode/utf16.h>

[yosin_UTC9, 2016/03/25 10:01:05]

nit: s/<unicode/utf16.h>/"third_party/icu/source/common/unicode/utf16.h"/

We'll see what PRESUBMIT says. If PRESUBMIT complains, we need to update DEPS.

[Seigo Nonaka, 2016/03/25 10:26:32]

Done and also updated DEPS.

+
+namespace blink {
+
+BackspaceStateMachine::BackspaceStateMachine()
+{
+}
+
+int BackspaceStateMachine::finalizeAndGetCodeUnitCountToBeDeleted()
+{
+    if (m_TrailSurrogate != 0) {
+        // Unpaired trail surrogate. Removing broken surrogate.
+        ++m_CodeUnitsToBeDeleted;
+        m_TrailSurrogate = 0;
+    }
+    return m_CodeUnitsToBeDeleted;
+}
+
+bool BackspaceStateMachine::updateState(uint16_t codeUnit)
+{
+    uint32_t codePoint = codeUnit;
+    if (U16_IS_LEAD(codeUnit)) {
+        if (m_TrailSurrogate == 0) {
+            // Unpaired lead surrogate. Aborting with deleting broken surrogate.
+            ++m_CodeUnitsToBeDeleted;
+            return true;
+        }
+        codePoint = U16_GET_SUPPLEMENTARY(codeUnit, m_TrailSurrogate);
+        m_TrailSurrogate = 0;
+    } else if (U16_IS_TRAIL(codeUnit)) {
+        if (m_TrailSurrogate != 0) {
+            // Unpaired trail surrogate. Aborting with deleting broken
+            // surrogate.
+            return true;
+        }
+        m_TrailSurrogate = codeUnit;
+        return false; // Needs surrogate lead.
+    } else {
+        if (m_TrailSurrogate != 0) {
+            // Unpaired trail surrogate. Aborting with deleting broken
+            // surrogate.
+            return true;
+        }
+    }
+
+    // TODO(nona): Handle emoji sequences.
+    m_CodeUnitsToBeDeleted = U16_LENGTH(codePoint);
+    return true;
+}
+
+void BackspaceStateMachine::reset()
+{
+    m_CodeUnitsToBeDeleted = 0;
+    m_TrailSurrogate = 0;
+}
+
+} // namespace blink