diff --git a/native/jni/Android.mk b/native/jni/Android.mk
index a51fe3c03..bf188971e 100644
--- a/native/jni/Android.mk
+++ b/native/jni/Android.mk
@@ -71,14 +71,16 @@ LATIN_IME_CORE_SRC_FILES := \
         header/header_policy.cpp \
         header/header_reading_utils.cpp \
         shortcut/shortcut_list_reading_utils.cpp \
-        utils/byte_array_utils.cpp \
-        utils/format_utils.cpp \
         dictionary_structure_with_buffer_policy_factory.cpp \
         dynamic_patricia_trie_node_reader.cpp \
         dynamic_patricia_trie_policy.cpp \
         dynamic_patricia_trie_reading_utils.cpp \
         patricia_trie_policy.cpp \
         patricia_trie_reading_utils.cpp) \
+    $(addprefix suggest/policyimpl/dictionary/utils/, \
+        byte_array_utils.cpp \
+        extendable_buffer.cpp \
+        format_utils.cpp) \
     suggest/policyimpl/gesture/gesture_suggest_policy_factory.cpp \
     $(addprefix suggest/policyimpl/typing/, \
         scoring_params.cpp \
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
index 8ba057b20..0e5920f42 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
@@ -24,6 +24,7 @@
 #include "suggest/policyimpl/dictionary/bigram/bigram_list_policy.h"
 #include "suggest/policyimpl/dictionary/header/header_policy.h"
 #include "suggest/policyimpl/dictionary/shortcut/shortcut_list_policy.h"
+#include "suggest/policyimpl/dictionary/utils/extendable_buffer.h"
 #include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
 
 namespace latinime {
@@ -34,7 +35,7 @@ class DicNodeVector;
 class DynamicPatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
  public:
     DynamicPatriciaTriePolicy(const MmappedBuffer *const buffer)
-            : mBuffer(buffer), mHeaderPolicy(mBuffer->getBuffer()),
+            : mBuffer(buffer), mExtendableBuffer(), mHeaderPolicy(mBuffer->getBuffer()),
               mDictRoot(mBuffer->getBuffer() + mHeaderPolicy.getSize()),
               mBigramListPolicy(mDictRoot), mShortcutListPolicy(mDictRoot) {}
 
@@ -87,8 +88,10 @@ class DynamicPatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
     static const int MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP;
 
     const MmappedBuffer *const mBuffer;
+    const ExtendableBuffer mExtendableBuffer;
     const HeaderPolicy mHeaderPolicy;
     // TODO: Consolidate mDictRoot.
+    // CAVEAT!: Be careful about array out of bound access with mDictRoot
     const uint8_t *const mDictRoot;
     const BigramListPolicy mBigramListPolicy;
     const ShortcutListPolicy mShortcutListPolicy;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/extendable_buffer.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/extendable_buffer.cpp
new file mode 100644
index 000000000..e55cc2410
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/extendable_buffer.cpp
@@ -0,0 +1,25 @@
+/*
+ * 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.
+ */
+
+#include "suggest/policyimpl/dictionary/utils/extendable_buffer.h"
+
+namespace latinime {
+
+const size_t ExtendableBuffer::INITIAL_BUFFER_SIZE = 16 * 1024;
+const size_t ExtendableBuffer::MAX_BUFFER_SIZE = 1024 * 1024;
+const size_t ExtendableBuffer::EXTEND_BUFFER_SIZE_STEP = 16 * 1024;
+
+}
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/extendable_buffer.h b/native/jni/src/suggest/policyimpl/dictionary/utils/extendable_buffer.h
new file mode 100644
index 000000000..d902d19c8
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/extendable_buffer.h
@@ -0,0 +1,70 @@
+/*
+ * 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_EXTENDABLE_BUFFER_H
+#define LATINIME_EXTENDABLE_BUFFER_H
+
+#include <cstddef>
+#include <stdint.h>
+#include <vector>
+
+#include "defines.h"
+
+namespace latinime {
+
+// This is used as a buffer that can be extended for updatable dictionaries.
+class ExtendableBuffer {
+ public:
+    ExtendableBuffer() : mBuffer(INITIAL_BUFFER_SIZE), mUsedSize(0) {}
+
+   AK_FORCE_INLINE uint8_t *getBuffer() {
+        return  &mBuffer[0];
+    }
+
+    // Return if the buffer is successfully extended or not.
+   AK_FORCE_INLINE bool extendBuffer() {
+        if (mBuffer.size() + EXTEND_BUFFER_SIZE_STEP > MAX_BUFFER_SIZE) {
+            return false;
+        }
+        mBuffer.resize(mBuffer.size() + EXTEND_BUFFER_SIZE_STEP);
+        return true;
+    }
+
+    AK_FORCE_INLINE int getAllocatedSize() const {
+        return mBuffer.size();
+    }
+
+    AK_FORCE_INLINE int getUsedSize() const {
+        return mUsedSize;
+    }
+
+    AK_FORCE_INLINE void clear() {
+        mUsedSize = 0;
+        mBuffer.clear();
+    }
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(ExtendableBuffer);
+
+    static const size_t INITIAL_BUFFER_SIZE;
+    static const size_t MAX_BUFFER_SIZE;
+    static const size_t EXTEND_BUFFER_SIZE_STEP;
+
+    std::vector<uint8_t> mBuffer;
+    int mUsedSize;
+};
+}
+#endif /* LATINIME_MMAPED_BUFFER_H */