Introduce ForwardCodePointStateMachine to traverse chars in code points

third_party/WebKit/Source/core/editing/state_machines/ForwardCodePointStateMachine.cpp

+// Copyright 2017 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/state_machines/ForwardCodePointStateMachine.h"
+
+namespace blink {
+
+enum class ForwardCodePointStateMachine::ForwardCodePointState {
+  NotSurrogate,
+  LeadSurrogate,
+  Invalid,
+};
+
+ForwardCodePointStateMachine::ForwardCodePointStateMachine()
+    : m_state(ForwardCodePointState::NotSurrogate) {}
+
+TextSegmentationMachineState
+ForwardCodePointStateMachine::feedFollowingCodeUnit(UChar codeUnit) {
+  switch (m_state) {
+    case ForwardCodePointState::NotSurrogate:
+      if (U16_IS_TRAIL(codeUnit)) {
+        m_codeUnitsToBeDeleted = 0;
+        m_state = ForwardCodePointState::Invalid;
+        return TextSegmentationMachineState::Invalid;
+      }
+      ++m_codeUnitsToBeDeleted;
+      if (U16_IS_LEAD(codeUnit)) {
+        m_state = ForwardCodePointState::LeadSurrogate;
+        return TextSegmentationMachineState::NeedMoreCodeUnit;
+      }
+      return TextSegmentationMachineState::Finished;
+    case ForwardCodePointState::LeadSurrogate:
+      if (U16_IS_TRAIL(codeUnit)) {
+        ++m_codeUnitsToBeDeleted;
+        m_state = ForwardCodePointState::NotSurrogate;
+        return TextSegmentationMachineState::Finished;
+      }
+      m_codeUnitsToBeDeleted = 0;
+      m_state = ForwardCodePointState::Invalid;
+      return TextSegmentationMachineState::Invalid;
+    case ForwardCodePointState::Invalid:
+      m_codeUnitsToBeDeleted = 0;
+      return TextSegmentationMachineState::Invalid;
+  }
+  NOTREACHED();
+  return TextSegmentationMachineState::Invalid;
+}
+
+TextSegmentationMachineState
+ForwardCodePointStateMachine::feedPrecedingCodeUnit(UChar codeUnit) {
+  NOTREACHED();
+  return TextSegmentationMachineState::Invalid;
+}
+
+bool ForwardCodePointStateMachine::atCodePointBoundary() {
+  return m_state == ForwardCodePointState::NotSurrogate;
+}
+
+int ForwardCodePointStateMachine::getBoundaryOffset() {
+  return m_codeUnitsToBeDeleted;
+}
+
+void ForwardCodePointStateMachine::reset() {
+  m_codeUnitsToBeDeleted = 0;
+  m_state = ForwardCodePointState::NotSurrogate;
+}
+
+}  // namespace blink