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diff --git a/native/jni/src/dictionary/utils/buffer_with_extendable_buffer.h b/native/jni/src/dictionary/utils/buffer_with_extendable_buffer.h
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+++ b/native/jni/src/dictionary/utils/buffer_with_extendable_buffer.h
@@ -0,0 +1,125 @@
+/*
+ * 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_BUFFER_WITH_EXTENDABLE_BUFFER_H
+#define LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+#include "defines.h"
+#include "dictionary/utils/byte_array_utils.h"
+#include "utils/byte_array_view.h"
+
+namespace latinime {
+
+// This is used as a buffer that can be extended for updatable dictionaries.
+// To optimize performance, raw pointer is directly used for reading buffer. The position has to be
+// adjusted to access additional buffer. On the other hand, this class does not provide writable
+// raw pointer but provides several methods that handle boundary checking for writing data.
+class BufferWithExtendableBuffer {
+ public:
+    static const size_t DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE;
+
+    BufferWithExtendableBuffer(const ReadWriteByteArrayView originalBuffer,
+            const int maxAdditionalBufferSize)
+            : mOriginalBuffer(originalBuffer), mAdditionalBuffer(), mUsedAdditionalBufferSize(0),
+              mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
+
+    // Without original buffer.
+    BufferWithExtendableBuffer(const int maxAdditionalBufferSize)
+            : mOriginalBuffer(), mAdditionalBuffer(), mUsedAdditionalBufferSize(0),
+              mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
+
+    AK_FORCE_INLINE int getTailPosition() const {
+        return mOriginalBuffer.size() + mUsedAdditionalBufferSize;
+    }
+
+    AK_FORCE_INLINE int getUsedAdditionalBufferSize() const {
+        return mUsedAdditionalBufferSize;
+    }
+
+    /**
+     * For reading.
+     */
+    AK_FORCE_INLINE bool isInAdditionalBuffer(const int position) const {
+        return position >= static_cast<int>(mOriginalBuffer.size());
+    }
+
+    // TODO: Resolve the issue that the address can be changed when the vector is resized.
+    // CAVEAT!: Be careful about array out of bound access with buffers
+    AK_FORCE_INLINE const uint8_t *getBuffer(const bool usesAdditionalBuffer) const {
+        if (usesAdditionalBuffer) {
+            return mAdditionalBuffer.data();
+        } else {
+            return mOriginalBuffer.data();
+        }
+    }
+
+    uint32_t readUint(const int size, const int pos) const;
+
+    uint32_t readUintAndAdvancePosition(const int size, int *const pos) const;
+
+    void readCodePointsAndAdvancePosition(const int maxCodePointCount,
+            int *const outCodePoints, int *outCodePointCount, int *const pos) const;
+
+    AK_FORCE_INLINE int getOriginalBufferSize() const {
+        return mOriginalBuffer.size();
+    }
+
+    AK_FORCE_INLINE bool isNearSizeLimit() const {
+        return mAdditionalBuffer.size() >= ((mMaxAdditionalBufferSize
+                * NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE) / 100);
+    }
+
+    bool extend(const int size);
+
+    /**
+     * For writing.
+     *
+     * Writing is allowed for original buffer, already written region of additional buffer and the
+     * tail of additional buffer.
+     */
+    bool writeUint(const uint32_t data, const int size, const int pos);
+
+    bool writeUintAndAdvancePosition(const uint32_t data, const int size, int *const pos);
+
+    bool writeCodePointsAndAdvancePosition(const int *const codePoints, const int codePointCount,
+            const bool writesTerminator, int *const pos);
+
+    bool copy(const BufferWithExtendableBuffer *const sourceBuffer);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(BufferWithExtendableBuffer);
+
+    static const int NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE;
+    static const size_t EXTEND_ADDITIONAL_BUFFER_SIZE_STEP;
+
+    const ReadWriteByteArrayView mOriginalBuffer;
+    std::vector<uint8_t> mAdditionalBuffer;
+    int mUsedAdditionalBufferSize;
+    const size_t mMaxAdditionalBufferSize;
+
+    // Return if the buffer is successfully extended or not.
+    bool extendBuffer(const size_t size);
+
+    // Returns if it is possible to write size-bytes from pos. When pos is at the tail position of
+    // the additional buffer, try extending the buffer.
+    bool checkAndPrepareWriting(const int pos, const int size);
+};
+}
+#endif /* LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H */