Use enum to specify ngram type.

Change-Id: Ie28768ceadcd7a2d940c57eb30be7d4c364e509f

1 files changed, 62 insertions, 0 deletions

diff --git a/native/jni/src/utils/ngram_utils.h b/native/jni/src/utils/ngram_utils.h
new file mode 100644
index 000000000..6227812d4
--- /dev/null
+++ b/native/jni/src/utils/ngram_utils.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2014, 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_NGRAM_UTILS_H
+#define LATINIME_NGRAM_UTILS_H
+
+#include "defines.h"
+
+namespace latinime {
+
+enum class NgramType : int {
+    Unigram = 0,
+    Bigram = 1,
+    Trigram = 2,
+    NotANgramType = -1,
+};
+
+namespace AllNgramTypes {
+// Use anonymous namespace to avoid ODR (One Definition Rule) violation.
+namespace {
+
+const NgramType ASCENDING[] = {
+   NgramType::Unigram, NgramType::Bigram, NgramType::Trigram
+};
+
+const NgramType DESCENDING[] = {
+   NgramType::Trigram, NgramType::Bigram, NgramType::Unigram
+};
+
+}  // namespace
+}  // namespace AllNgramTypes
+
+class NgramUtils final {
+ public:
+    static AK_FORCE_INLINE NgramType getNgramTypeFromWordCount(const int wordCount) {
+        // Max supported ngram is (MAX_PREV_WORD_COUNT_FOR_N_GRAM + 1)-gram.
+        if (wordCount <= 0 || wordCount > MAX_PREV_WORD_COUNT_FOR_N_GRAM + 1) {
+            return NgramType::NotANgramType;
+        }
+        // Convert word count to 0-origin enum value.
+        return static_cast<NgramType>(wordCount - 1);
+    }
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(NgramUtils);
+
+};
+}
+#endif /* LATINIME_NGRAM_UTILS_H */