Add spellcheck and word suggestion to the prediction service

third_party/prediction/suggest/policyimpl/utils/damerau_levenshtein_edit_distance_policy.h

+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DAEMARU_LEVENSHTEIN_EDIT_DISTANCE_POLICY_H
+#define LATINIME_DAEMARU_LEVENSHTEIN_EDIT_DISTANCE_POLICY_H
+
+#include "third_party/prediction/suggest/policyimpl/utils/edit_distance_policy.h"
+#include "third_party/prediction/utils/char_utils.h"
+
+namespace latinime {
+
+class DamerauLevenshteinEditDistancePolicy : public EditDistancePolicy {
+ public:
+  DamerauLevenshteinEditDistancePolicy(const int* const string0,
+                                       const int length0,
+                                       const int* const string1,
+                                       const int length1)
+      : mString0(string0),
+        mString0Length(length0),
+        mString1(string1),
+        mString1Length(length1) {}
+  ~DamerauLevenshteinEditDistancePolicy() {}
+
+  AK_FORCE_INLINE float getSubstitutionCost(const int index0,
+                                            const int index1) const {
+    const int c0 = CharUtils::toBaseLowerCase(mString0[index0]);
+    const int c1 = CharUtils::toBaseLowerCase(mString1[index1]);
+    return (c0 == c1) ? 0.0f : 1.0f;
+  }
+
+  AK_FORCE_INLINE float getDeletionCost(const int index0,
+                                        const int index1) const {
+    return 1.0f;
+  }
+
+  AK_FORCE_INLINE float getInsertionCost(const int index0,
+                                         const int index1) const {
+    return 1.0f;
+  }
+
+  AK_FORCE_INLINE bool allowTransposition(const int index0,
+                                          const int index1) const {
+    const int c0 = CharUtils::toBaseLowerCase(mString0[index0]);
+    const int c1 = CharUtils::toBaseLowerCase(mString1[index1]);
+    if (index0 > 0 && index1 > 0 &&
+        c0 == CharUtils::toBaseLowerCase(mString1[index1 - 1]) &&
+        c1 == CharUtils::toBaseLowerCase(mString0[index0 - 1])) {
+      return true;
+    }
+    return false;
+  }
+
+  AK_FORCE_INLINE float getTranspositionCost(const int index0,
+                                             const int index1) const {
+    return getSubstitutionCost(index0, index1);
+  }
+
+  AK_FORCE_INLINE int getString0Length() const { return mString0Length; }
+
+  AK_FORCE_INLINE int getString1Length() const { return mString1Length; }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DamerauLevenshteinEditDistancePolicy);
+
+  const int* const mString0;
+  const int mString0Length;
+  const int* const mString1;
+  const int mString1Length;
+};
+}  // namespace latinime
+
+#endif  // LATINIME_DAEMARU_LEVENSHTEIN_EDIT_DISTANCE_POLICY_H