Implement ver4 dict PtNode reading methods.

Bug: 11073222
Change-Id: I03af717ff02a621d9be8eb554d8f1438a500339b

12 files changed, 302 insertions, 19 deletions

diff --git a/native/jni/Android.mk b/native/jni/Android.mk
index f4c8f7a40..d73862eb6 100644
--- a/native/jni/Android.mk
+++ b/native/jni/Android.mk
@@ -87,6 +87,7 @@ LATIN_IME_CORE_SRC_FILES := \
         dynamic_patricia_trie_writing_utils.cpp) \
     $(addprefix suggest/policyimpl/dictionary/structure/v4/, \
         ver4_dict_constants.cpp \
+        ver4_patricia_trie_node_reader.cpp \
         ver4_patricia_trie_policy.cpp \
         ver4_patricia_trie_reading_utils.cpp ) \
     $(addprefix suggest/policyimpl/dictionary/utils/, \
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h
index 7bdd829cd..edc7b954c 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h
@@ -32,7 +32,7 @@ class PtNodeParams {
     // Invalid PtNode.
     PtNodeParams() : mHeadPos(NOT_A_DICT_POS), mFlags(0), mParentPos(NOT_A_DICT_POS),
             mCodePointCount(0), mCodePoints(), mTerminalIdFieldPos(NOT_A_DICT_POS),
-            mTerminalId(Ver4DictConstants::NOT_A_TERMINAL), mProbabilityFieldPos(NOT_A_DICT_POS),
+            mTerminalId(Ver4DictConstants::NOT_A_TERMINAL_ID), mProbabilityFieldPos(NOT_A_DICT_POS),
             mProbability(NOT_A_PROBABILITY), mChildrenPosFieldPos(NOT_A_DICT_POS),
             mChildrenPos(NOT_A_DICT_POS), mBigramLinkedNodePos(NOT_A_DICT_POS),
             mShortcutPos(NOT_A_DICT_POS), mBigramPos(NOT_A_DICT_POS),
@@ -53,6 +53,7 @@ class PtNodeParams {
         memcpy(mCodePoints, ptNodeParams.getCodePoints(), sizeof(int) * mCodePointCount);
     }
 
+    // PtNode without terminal id.
     PtNodeParams(const int headPos, const PatriciaTrieReadingUtils::NodeFlags flags,
             const int parentPos, const int codePointCount, const int *const codePoints,
             const int probabilityFieldPos, const int probability, const int childrenPosFieldPos,
@@ -60,7 +61,8 @@ class PtNodeParams {
             const int bigramPos, const int siblingPos)
             : mHeadPos(headPos), mFlags(flags), mParentPos(parentPos),
               mCodePointCount(codePointCount), mCodePoints(),
-              mTerminalIdFieldPos(NOT_A_DICT_POS), mTerminalId(Ver4DictConstants::NOT_A_TERMINAL),
+              mTerminalIdFieldPos(NOT_A_DICT_POS),
+              mTerminalId(Ver4DictConstants::NOT_A_TERMINAL_ID),
               mProbabilityFieldPos(probabilityFieldPos), mProbability(probability),
               mChildrenPosFieldPos(childrenPosFieldPos), mChildrenPos(childrenPos),
               mBigramLinkedNodePos(bigramLinkedNodePos), mShortcutPos(shortcutPos),
@@ -68,6 +70,22 @@ class PtNodeParams {
         memcpy(mCodePoints, codePoints, sizeof(int) * mCodePointCount);
     }
 
+    // PtNode with a terminal id.
+    PtNodeParams(const int headPos, const PatriciaTrieReadingUtils::NodeFlags flags,
+            const int parentPos, const int codePointCount, const int *const codePoints,
+            const int terminalIdFieldPos, const int terminalId, const int probability,
+            const int childrenPosFieldPos, const int childrenPos, const int bigramLinkedNodePos,
+            const int siblingPos)
+            : mHeadPos(headPos), mFlags(flags), mParentPos(parentPos),
+              mCodePointCount(codePointCount), mCodePoints(),
+              mTerminalIdFieldPos(terminalIdFieldPos), mTerminalId(terminalId),
+              mProbabilityFieldPos(NOT_A_DICT_POS), mProbability(probability),
+              mChildrenPosFieldPos(childrenPosFieldPos), mChildrenPos(childrenPos),
+              mBigramLinkedNodePos(bigramLinkedNodePos), mShortcutPos(terminalId),
+              mBigramPos(terminalId), mSiblingPos(siblingPos) {
+        memcpy(mCodePoints, codePoints, sizeof(int) * mCodePointCount);
+    }
+
     AK_FORCE_INLINE bool isValid() const {
         return mCodePointCount > 0;
     }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h
index b5abffeda..ef0067b48 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h
@@ -55,7 +55,7 @@ class DynamicPatriciaTrieNodeReader : public PtNodeReader {
     const DictionaryBigramsStructurePolicy *const mBigramsPolicy;
     const DictionaryShortcutsStructurePolicy *const mShortcutsPolicy;
 
-   const  PtNodeParams fetchPtNodeInfoFromBufferAndProcessMovedPtNode(const int ptNodePos,
+    const PtNodeParams fetchPtNodeInfoFromBufferAndProcessMovedPtNode(const int ptNodePos,
             const int siblingNodePos, const int bigramLinkedNodePos) const;
 };
 } // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
index 160259afc..3e21399fd 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
@@ -30,7 +30,7 @@ const char *const Ver4DictConstants::SHORTCUT_LOOKUP_TABLE_FILE_EXTENSION = ".sh
 const char *const Ver4DictConstants::SHORTCUT_CONTENT_TABLE_FILE_EXTENSION =
         ".shortcut_index_shortcut";
 
-const int Ver4DictConstants::NOT_A_TERMINAL = -1;
+const int Ver4DictConstants::NOT_A_TERMINAL_ID = -1;
 const int Ver4DictConstants::PROBABILITY_SIZE = 1;
 const int Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE = 1;
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
index dcc36d1dc..47a6990f8 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
@@ -34,7 +34,7 @@ class Ver4DictConstants {
     static const char *const SHORTCUT_LOOKUP_TABLE_FILE_EXTENSION;
     static const char *const SHORTCUT_CONTENT_TABLE_FILE_EXTENSION;
 
-    static const int NOT_A_TERMINAL;
+    static const int NOT_A_TERMINAL_ID;
     static const int PROBABILITY_SIZE;
     static const int FLAGS_IN_PROBABILITY_FILE_SIZE;
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.cpp
new file mode 100644
index 000000000..b18bdc943
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.cpp
@@ -0,0 +1,95 @@
+/*
+ * 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/structure/v4/ver4_patricia_trie_node_reader.h"
+
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+const PtNodeParams Ver4PatriciaTrieNodeReader::fetchPtNodeInfoFromBufferAndProcessMovedPtNode(
+        const int ptNodePos, const int siblingNodePos, const int bigramLinkedNodePos) const {
+    if (ptNodePos < 0 || ptNodePos >= mBuffer->getTailPosition()) {
+        // Reading invalid position because of bug or broken dictionary.
+        AKLOGE("Fetching PtNode info from invalid dictionary position: %d, dictionary size: %d",
+                ptNodePos, mBuffer->getTailPosition());
+        ASSERT(false);
+        return PtNodeParams();
+    }
+    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(ptNodePos);
+    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
+    int pos = ptNodePos;
+    const int headPos = ptNodePos;
+    if (usesAdditionalBuffer) {
+        pos -= mBuffer->getOriginalBufferSize();
+    }
+    const PatriciaTrieReadingUtils::NodeFlags flags =
+            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
+    const int parentPosOffset =
+            DynamicPatriciaTrieReadingUtils::getParentPtNodePosOffsetAndAdvancePosition(
+                    dictBuf, &pos);
+    const int parentPos =
+            DynamicPatriciaTrieReadingUtils::getParentPtNodePos(parentPosOffset, headPos);
+    int codePoints[MAX_WORD_LENGTH];
+    const int codePonitCount = PatriciaTrieReadingUtils::getCharsAndAdvancePosition(
+            dictBuf, flags, MAX_WORD_LENGTH, codePoints, &pos);
+    int terminalIdFieldPos = NOT_A_DICT_POS;
+    int terminalId = Ver4DictConstants::NOT_A_TERMINAL_ID;
+    int probability = NOT_A_PROBABILITY;
+    if (PatriciaTrieReadingUtils::isTerminal(flags)) {
+        terminalIdFieldPos = pos;
+        if (usesAdditionalBuffer) {
+            terminalIdFieldPos += mBuffer->getOriginalBufferSize();
+        }
+        terminalId = Ver4PatriciaTrieReadingUtils::getTerminalIdAndAdvancePosition(dictBuf, &pos);
+        probability = mProbabilityDictContent->getProbability(terminalId);
+    }
+    int childrenPosFieldPos = pos;
+    if (usesAdditionalBuffer) {
+        childrenPosFieldPos += mBuffer->getOriginalBufferSize();
+    }
+    int childrenPos = DynamicPatriciaTrieReadingUtils::readChildrenPositionAndAdvancePosition(
+            dictBuf, &pos);
+    if (usesAdditionalBuffer && childrenPos != NOT_A_DICT_POS) {
+        childrenPos += mBuffer->getOriginalBufferSize();
+    }
+    int newBigramLinkedNodePos = bigramLinkedNodePos;
+    if (siblingNodePos == NOT_A_DICT_POS) {
+        if (DynamicPatriciaTrieReadingUtils::isMoved(flags)) {
+            newBigramLinkedNodePos = childrenPos;
+        }
+    }
+    if (usesAdditionalBuffer) {
+        pos += mBuffer->getOriginalBufferSize();
+    }
+    // Sibling position is the tail position of original PtNode.
+    int newSiblingNodePos = (siblingNodePos == NOT_A_DICT_POS) ? pos : siblingNodePos;
+    // Read destination node if the read node is a moved node.
+    if (DynamicPatriciaTrieReadingUtils::isMoved(flags)) {
+        // The destination position is stored at the same place as the parent position.
+        return fetchPtNodeInfoFromBufferAndProcessMovedPtNode(parentPos, newSiblingNodePos,
+                newBigramLinkedNodePos);
+    } else {
+        return PtNodeParams(headPos, flags, parentPos, codePonitCount, codePoints,
+                terminalIdFieldPos, terminalId, probability, childrenPosFieldPos, childrenPos,
+                newBigramLinkedNodePos, newSiblingNodePos);
+    }
+}
+
+}
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h
new file mode 100644
index 000000000..bdae0de7e
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h
@@ -0,0 +1,58 @@
+/*
+ * 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_VER4_PATRICIA_TRIE_NODE_READER_H
+#define LATINIME_VER4_PATRICIA_TRIE_NODE_READER_H
+
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+class ProbabilityDictContent;
+
+/*
+ * This class is used for helping to read nodes of ver4 patricia trie. This class handles moved
+ * node and reads node attributes including probability form probabilityBuffer.
+ */
+class Ver4PatriciaTrieNodeReader : public PtNodeReader {
+ public:
+    Ver4PatriciaTrieNodeReader(const BufferWithExtendableBuffer *const buffer,
+            const ProbabilityDictContent *const probabilityDictContent)
+            : mBuffer(buffer), mProbabilityDictContent(probabilityDictContent) {}
+
+    ~Ver4PatriciaTrieNodeReader() {}
+
+    virtual const PtNodeParams fetchNodeInfoInBufferFromPtNodePos(const int ptNodePos) const {
+        return fetchPtNodeInfoFromBufferAndProcessMovedPtNode(ptNodePos,
+                NOT_A_DICT_POS /* siblingNodePos */, NOT_A_DICT_POS /* bigramLinkedNodePos */);
+    }
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(Ver4PatriciaTrieNodeReader);
+
+    const BufferWithExtendableBuffer *const mBuffer;
+    const ProbabilityDictContent *const mProbabilityDictContent;
+
+    const PtNodeParams fetchPtNodeInfoFromBufferAndProcessMovedPtNode(const int ptNodePos,
+            const int siblingNodePos, const int bigramLinkedNodePos) const;
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_PATRICIA_TRIE_NODE_READER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
index b9ee4891c..33f738413 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
@@ -16,45 +16,110 @@
 
 #include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h"
 
+#include "suggest/core/dicnode/dic_node.h"
+#include "suggest/core/dicnode/dic_node_vector.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_helper.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+#include "suggest/policyimpl/dictionary/utils/probability_utils.h"
+
 namespace latinime {
 
 void Ver4PatriciaTriePolicy::createAndGetAllChildDicNodes(const DicNode *const dicNode,
         DicNodeVector *const childDicNodes) const {
-    // TODO: Implement.
+    if (!dicNode->hasChildren()) {
+        return;
+    }
+    DynamicPatriciaTrieReadingHelper readingHelper(&mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodeArrayPos(dicNode->getChildrenPtNodeArrayPos());
+    while (!readingHelper.isEnd()) {
+        const PtNodeParams ptNodeParams = readingHelper.getPtNodeParams();
+        if (!ptNodeParams.isValid()) {
+            break;
+        }
+        bool isTerminal = ptNodeParams.isTerminal() && !ptNodeParams.isDeleted();
+        if (isTerminal && mHeaderPolicy.isDecayingDict()) {
+            // A DecayingDict may have a terminal PtNode that has a terminal DicNode whose
+            // probability is NOT_A_PROBABILITY. In such case, we don't want to treat it as a
+            // valid terminal DicNode.
+            isTerminal = getProbability(ptNodeParams.getProbability(), NOT_A_PROBABILITY)
+                    != NOT_A_PROBABILITY;
+        }
+        childDicNodes->pushLeavingChild(dicNode, ptNodeParams.getHeadPos(),
+                ptNodeParams.getChildrenPos(), ptNodeParams.getProbability(), isTerminal,
+                ptNodeParams.hasChildren(),
+                ptNodeParams.isBlacklisted()
+                        || ptNodeParams.isNotAWord() /* isBlacklistedOrNotAWord */,
+                ptNodeParams.getCodePointCount(), ptNodeParams.getCodePoints());
+        readingHelper.readNextSiblingNode(ptNodeParams);
+    }
 }
 
 int Ver4PatriciaTriePolicy::getCodePointsAndProbabilityAndReturnCodePointCount(
         const int ptNodePos, const int maxCodePointCount, int *const outCodePoints,
         int *const outUnigramProbability) const {
-    // TODO: Implement.
-    return 0;
+    DynamicPatriciaTrieReadingHelper readingHelper(&mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodePos(ptNodePos);
+    return readingHelper.getCodePointsAndProbabilityAndReturnCodePointCount(
+            maxCodePointCount, outCodePoints, outUnigramProbability);
 }
 
 int Ver4PatriciaTriePolicy::getTerminalPtNodePositionOfWord(const int *const inWord,
         const int length, const bool forceLowerCaseSearch) const {
-    // TODO: Implement.
-    return NOT_A_DICT_POS;
+    DynamicPatriciaTrieReadingHelper readingHelper(&mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodeArrayPos(getRootPosition());
+    return readingHelper.getTerminalPtNodePositionOfWord(inWord, length, forceLowerCaseSearch);
 }
 
 int Ver4PatriciaTriePolicy::getProbability(const int unigramProbability,
         const int bigramProbability) const {
-    // TODO: Implement.
-    return NOT_A_PROBABILITY;
+    if (mHeaderPolicy.isDecayingDict()) {
+        // Both probabilities are encoded. Decode them and get probability.
+        return ForgettingCurveUtils::getProbability(unigramProbability, bigramProbability);
+    } else {
+        if (unigramProbability == NOT_A_PROBABILITY) {
+            return NOT_A_PROBABILITY;
+        } else if (bigramProbability == NOT_A_PROBABILITY) {
+            return ProbabilityUtils::backoff(unigramProbability);
+        } else {
+            // bigramProbability is a bigram probability delta.
+            return ProbabilityUtils::computeProbabilityForBigram(unigramProbability,
+                    bigramProbability);
+        }
+    }
 }
 
 int Ver4PatriciaTriePolicy::getUnigramProbabilityOfPtNode(const int ptNodePos) const {
-    // TODO: Implement.
-    return NOT_A_PROBABILITY;
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return NOT_A_PROBABILITY;
+    }
+    const PtNodeParams ptNodeParams(mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos));
+    if (ptNodeParams.isDeleted() || ptNodeParams.isBlacklisted() || ptNodeParams.isNotAWord()) {
+        return NOT_A_PROBABILITY;
+    }
+    return getProbability(ptNodeParams.getProbability(), NOT_A_PROBABILITY);
 }
 
 int Ver4PatriciaTriePolicy::getShortcutPositionOfPtNode(const int ptNodePos) const {
-    // TODO: Implement.
-    return NOT_A_DICT_POS;
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return NOT_A_DICT_POS;
+    }
+    const PtNodeParams ptNodeParams(mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos));
+    if (ptNodeParams.isDeleted()) {
+        return NOT_A_DICT_POS;
+    }
+    return ptNodeParams.getTerminalId();
 }
 
 int Ver4PatriciaTriePolicy::getBigramsPositionOfPtNode(const int ptNodePos) const {
-    // TODO: Implement.
-    return NOT_A_DICT_POS;
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return NOT_A_DICT_POS;
+    }
+    const PtNodeParams ptNodeParams(mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos));
+    if (ptNodeParams.isDeleted()) {
+        return NOT_A_DICT_POS;
+    }
+    return ptNodeParams.getTerminalId();
 }
 
 bool Ver4PatriciaTriePolicy::addUnigramWord(const int *const word, const int length,
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h
index f7bfb3b0d..2f577f741 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h
@@ -21,6 +21,7 @@
 #include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
 #include "suggest/policyimpl/dictionary/header/header_policy.h"
 #include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
 #include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
 
 namespace latinime {
@@ -33,7 +34,11 @@ class Ver4PatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
  public:
     Ver4PatriciaTriePolicy(const Ver4DictBuffers::Ver4DictBuffersPtr &buffers)
             : mBuffers(buffers),
-              mHeaderPolicy(mBuffers.get()->getRawDictBuffer(), FormatUtils::VERSION_4) {};
+              mHeaderPolicy(mBuffers.get()->getRawDictBuffer(), FormatUtils::VERSION_4),
+              mDictBuffer(mBuffers.get()->getRawDictBuffer() + mHeaderPolicy.getSize(),
+                      mBuffers.get()->getRawDictBufferSize() - mHeaderPolicy.getSize(),
+                      BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+              mNodeReader(&mDictBuffer, mBuffers.get()->getProbabilityDictContent()) {};
 
     AK_FORCE_INLINE int getRootPosition() const {
         return 0;
@@ -91,6 +96,8 @@ class Ver4PatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
 
     const Ver4DictBuffers::Ver4DictBuffersPtr mBuffers;
     const HeaderPolicy mHeaderPolicy;
+    BufferWithExtendableBuffer mDictBuffer;
+    Ver4PatriciaTrieNodeReader mNodeReader;
 };
 } // namespace latinime
 #endif // LATINIME_VER4_PATRICIA_TRIE_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp
index 3304f1521..fd8a3ba55 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp
@@ -18,9 +18,15 @@
 
 #include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
 #include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/byte_array_utils.h"
 
 namespace latinime {
 
+/* static */ int Ver4PatriciaTrieReadingUtils::getTerminalIdAndAdvancePosition(
+        const uint8_t *const buffer, int *pos) {
+    return ByteArrayUtils::readUint32AndAdvancePosition(buffer, pos);
+}
+
 /* static */ int Ver4PatriciaTrieReadingUtils::getProbability(
         const BufferWithExtendableBuffer *const probabilityBuffer, const int terminalId) {
     int pos = terminalId * (Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h
index ee369d1e1..19e6dd331 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h
@@ -27,6 +27,9 @@ class BufferWithExtendableBuffer;
 
 class Ver4PatriciaTrieReadingUtils {
  public:
+    static int getTerminalIdAndAdvancePosition(const uint8_t *const buffer,
+            int *const pos);
+
     static int getProbability(const BufferWithExtendableBuffer *const probabilityBuffer,
             const int terminalId);
 
diff --git a/tests/src/com/android/inputmethod/latin/Ver4BinaryDictionaryTests.java b/tests/src/com/android/inputmethod/latin/Ver4BinaryDictionaryTests.java
index 25fb1c2a8..f48a4296a 100644
--- a/tests/src/com/android/inputmethod/latin/Ver4BinaryDictionaryTests.java
+++ b/tests/src/com/android/inputmethod/latin/Ver4BinaryDictionaryTests.java
@@ -33,6 +33,7 @@ import java.io.IOException;
 import java.util.HashMap;
 import java.util.Locale;
 
+// TODO: Add a test to evaluate the speed of operations of Ver4 dictionary.
 @LargeTest
 public class Ver4BinaryDictionaryTests extends AndroidTestCase {
     private static final String TAG = Ver4BinaryDictionaryTests.class.getSimpleName();
@@ -90,4 +91,33 @@ public class Ver4BinaryDictionaryTests extends AndroidTestCase {
                 Locale.getDefault(), TEST_LOCALE, true /* isUpdatable */);
         assertTrue(binaryDictionary.isValidDictionary());
     }
+
+    // TODO: Add large tests.
+    public void testReadProbability() {
+        final String dictVersion = Long.toString(System.currentTimeMillis());
+        final FusionDictionary dict = new FusionDictionary(new PtNodeArray(),
+                getDictionaryOptions(TEST_LOCALE, dictVersion));
+
+        final int frequency = 100;
+        dict.add("a", frequency, null, false /* isNotAWord */);
+        dict.add("aaa", frequency, null, false /* isNotAWord */);
+        dict.add("ab", frequency, null, false /* isNotAWord */);
+
+        DictEncoder encoder = new Ver4DictEncoder(getContext().getCacheDir());
+        try {
+            encoder.writeDictionary(dict, FORMAT_OPTIONS);
+        } catch (IOException e) {
+            Log.e(TAG, "IOException while writing dictionary", e);
+        } catch (UnsupportedFormatException e) {
+            Log.e(TAG, "Unsupported format", e);
+        }
+        File trieFile = getTrieFile(TEST_LOCALE, dictVersion);
+        BinaryDictionary binaryDictionary = new BinaryDictionary(trieFile.getAbsolutePath(),
+                0 /* offset */, trieFile.length(), true /* useFullEditDistance */,
+                Locale.getDefault(), TEST_LOCALE, true /* isUpdatable */);
+        assertTrue(binaryDictionary.isValidDictionary());
+        assertEquals(frequency, binaryDictionary.getFrequency("a"));
+        assertEquals(frequency, binaryDictionary.getFrequency("aaa"));
+        assertEquals(frequency, binaryDictionary.getFrequency("ab"));
+    }
 }