Add spellcheck and word suggestion to the prediction service

third_party/android_prediction/suggest/core/dictionary/multi_bigram_map.h

Index: third_party/android_prediction/suggest/core/dictionary/multi_bigram_map.h
diff --git a/third_party/android_prediction/suggest/core/dictionary/multi_bigram_map.h b/third_party/android_prediction/suggest/core/dictionary/multi_bigram_map.h
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+/*
+ * 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_MULTI_BIGRAM_MAP_H
+#define LATINIME_MULTI_BIGRAM_MAP_H
+
+#include <cstddef>
+#include <unordered_map>
+
+#include "third_party/android_prediction/defines.h"
+#include "third_party/android_prediction/suggest/core/dictionary/binary_dictionary_bigrams_iterator.h"
+#include "third_party/android_prediction/suggest/core/dictionary/bloom_filter.h"
+#include "third_party/android_prediction/suggest/core/dictionary/ngram_listener.h"
+#include "third_party/android_prediction/suggest/core/policy/dictionary_structure_with_buffer_policy.h"
+
+namespace latinime {
+
+// Class for caching bigram maps for multiple previous word contexts. This is useful since the
+// algorithm needs to look up the set of bigrams for every word pair that occurs in every
+// multi-word suggestion.
+class MultiBigramMap {
+ public:
+    MultiBigramMap() : mBigramMaps() {}
+    ~MultiBigramMap() {}
+
+    // Look up the bigram probability for the given word pair from the cached bigram maps.
+    // Also caches the bigrams if there is space remaining and they have not been cached already.
+    int getBigramProbability(const DictionaryStructureWithBufferPolicy *const structurePolicy,
+            const int *const prevWordsPtNodePos, const int nextWordPosition,
+            const int unigramProbability);
+
+    void clear() {
+        mBigramMaps.clear();
+    }
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(MultiBigramMap);
+
+    class BigramMap : public NgramListener {
+     public:
+        BigramMap() : mBigramMap(DEFAULT_HASH_MAP_SIZE_FOR_EACH_BIGRAM_MAP), mBloomFilter() {}
+        // Copy constructor needed for std::unordered_map.
+        BigramMap(const BigramMap &bigramMap)
+                : mBigramMap(bigramMap.mBigramMap), mBloomFilter(bigramMap.mBloomFilter) {}
+        virtual ~BigramMap() {}
+
+        void init(const DictionaryStructureWithBufferPolicy *const structurePolicy,
+                const int *const prevWordsPtNodePos);
+        int getBigramProbability(
+                const DictionaryStructureWithBufferPolicy *const structurePolicy,
+                const int nextWordPosition, const int unigramProbability) const;
+        virtual void onVisitEntry(const int ngramProbability, const int targetPtNodePos);
+
+     private:
+        static const int DEFAULT_HASH_MAP_SIZE_FOR_EACH_BIGRAM_MAP;
+        std::unordered_map<int, int> mBigramMap;
+        BloomFilter mBloomFilter;
+    };
+
+    void addBigramsForWordPosition(
+            const DictionaryStructureWithBufferPolicy *const structurePolicy,
+            const int *const prevWordsPtNodePos);
+
+    int readBigramProbabilityFromBinaryDictionary(
+            const DictionaryStructureWithBufferPolicy *const structurePolicy,
+            const int *const prevWordsPtNodePos, const int nextWordPosition,
+            const int unigramProbability);
+
+    static const size_t MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP;
+    std::unordered_map<int, BigramMap> mBigramMaps;
+};
+} // namespace latinime
+#endif // LATINIME_MULTI_BIGRAM_MAP_H