[All-In-One] Introduce BackspaceStateMachine

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

+// 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>
+
+namespace blink {
+
+BackspaceStateMachine::BackspaceStateMachine()
+    : mCodeUnitsToBeDeleted(0)
+    , mTrailSurrogate(0)
+{
+}
+
+int BackspaceStateMachine::FinalizeAndGetCodeUnitCountToBeDeleted()
+{
+    if (mTrailSurrogate != 0) {
+        // Unpaired trail surrogate. Removing broken surrogate.
+        ++mCodeUnitsToBeDeleted;

[yosin_UTC9, 2016/03/25 04:37:23]

It seems we should reset |mTrailSurogate| too.

[Seigo Nonaka, 2016/03/25 06:59:06]

Done.

+    }
+    return mCodeUnitsToBeDeleted;
+}
+
+bool BackspaceStateMachine::ComputeNextState(uint16_t codeUnit)

[yosin_UTC9, 2016/03/25 04:37:22]

|updateState()| or |moveToNextState()| or another?

I feel |compute| is const function and returning |bool| doesn't not seem to be
"next state".

[Seigo Nonaka, 2016/03/25 06:59:06]

Sure, updated.

+{
+    uint32_t cp = codeUnit;

[yosin_UTC9, 2016/03/25 04:37:23]

s/cp/codePoint/

[Seigo Nonaka, 2016/03/25 06:59:06]

Done.

+    if (U16_IS_LEAD(codeUnit)) {
+        if (mTrailSurrogate == 0) {
+            // Unpaired lead surrogate. Aborting with deleting broken surrogate.
+            ++mCodeUnitsToBeDeleted;
+            return true;
+        }
+        cp = U16_GET_SUPPLEMENTARY(codeUnit, mTrailSurrogate);
+        mTrailSurrogate = 0;
+    } else if (U16_IS_TRAIL(codeUnit)) {
+        if (mTrailSurrogate != 0) {
+            // Unpaired trail surrogate. Aborting with deleting broken
+            // surrogate.
+            ++mCodeUnitsToBeDeleted;
+            return true;
+        }
+        mTrailSurrogate = codeUnit;
+        return false; // Needs surrogate lead.
+    } else {
+        if (mTrailSurrogate != 0) {
+            // Unpaired trail surrogate. Aborting with deleting broken
+            // surrogate.
+            ++mCodeUnitsToBeDeleted;
+            return true;
+        }
+    }
+
+    // TODO(nona): Handle emoji sequences.
+    mCodeUnitsToBeDeleted = U16_LENGTH(cp);
+    return true;
+}
+
+} // namespace blink