diff --git a/src/HMMSegment.cpp b/src/HMMSegment.cpp
index 04f813a..dcede07 100644
--- a/src/HMMSegment.cpp
+++ b/src/HMMSegment.cpp
@@ -149,9 +149,13 @@ namespace CppJieba
             return false;
         }
         res.clear();
+        string tmp;
         for(uint i = 0; i < words.size(); i++)
         {
-            res.push_back(TransCode::encode(words[i].begin(), words[i].end()));
+            if(TransCode::encode(words[i], tmp))
+            {
+                res.push_back(tmp);
+            }
         }
 		return true;
 	}
diff --git a/src/KeyWordExt.cpp b/src/KeyWordExt.cpp
index 1b7c2b1..979f9e1 100644
--- a/src/KeyWordExt.cpp
+++ b/src/KeyWordExt.cpp
@@ -27,30 +27,6 @@ namespace CppJieba
 		return true;
 	}
 
-	//bool KeyWordExt::_loadPriorSubWords(const char * const filePath)
-	//{
-	//	LogInfo(string_format("_loadPriorSubWords(%s) start", filePath));
-	//	if(!checkFileExist(filePath))
-	//	{
-	//		LogError(string_format("cann't find file[%s].",filePath));
-	//		return false;
-	//	}
-	//	if(!_priorSubWords.empty())
-	//	{
-	//		LogError("_priorSubWords has been initted before");
-	//		return false;
-	//	}
-	//	ifstream infile(filePath);
-	//	string subword;
-	//	while(getline(infile, subword))
-	//	{
-	//		_priorSubWords.push_back(subword);
-	//	}
-	//	LogInfo(string_format("_loadPriorSubWords(%s) end", filePath));
-	//	infile.close();
-	//	return true;
-	//}
-
 	bool KeyWordExt::loadStopWords(const char * const filePath)
 	{
 
diff --git a/src/MPSegment.cpp b/src/MPSegment.cpp
index 643bd8b..4db524b 100644
--- a/src/MPSegment.cpp
+++ b/src/MPSegment.cpp
@@ -44,9 +44,17 @@ namespace CppJieba
 			return false;
 		}
 		res.clear();
+        string tmp;
 		for(uint i = 0; i < segWordInfos.size(); i++)
 		{
-			res.push_back(TransCode::encode(segWordInfos[i].word.begin(), segWordInfos[i].word.end()));
+			if(TransCode::encode(segWordInfos[i].word, tmp))
+            {
+                res.push_back(tmp);
+            }
+            else
+            {
+                LogError("encode failed.");
+            }
 		}
 		return true;
 	}
diff --git a/src/MixSegment.cpp b/src/MixSegment.cpp
index 39c54af..d9a763e 100644
--- a/src/MixSegment.cpp
+++ b/src/MixSegment.cpp
@@ -43,6 +43,7 @@ namespace CppJieba
         res.clear();
         Unicode unico;
         vector<Unicode> hmmRes;
+        string tmp;
         for(uint i= 0; i < infos.size(); i++)
         {
             if(1 == infos[i].word.size())
@@ -60,12 +61,14 @@ namespace CppJieba
                     }
                     for(uint j = 0; j < hmmRes.size(); j++)
                     {
-                        res.push_back(TransCode::encode(hmmRes[j]));
+                        TransCode::encode(hmmRes[j], tmp);
+                        res.push_back(tmp);
                     }
                 }
                 unico.clear();
 
-                res.push_back(TransCode::encode(infos[i].word));
+                TransCode::encode(infos[i].word, tmp);
+                res.push_back(tmp);
             }
             
         }
@@ -78,7 +81,8 @@ namespace CppJieba
             }
             for(uint j = 0; j < hmmRes.size(); j++)
             {
-                res.push_back(TransCode::encode(hmmRes[j]));
+                TransCode::encode(hmmRes[j], tmp);
+                res.push_back(tmp);
             }
         }
         
diff --git a/src/TransCode.cpp b/src/TransCode.cpp
index 80ab080..8ced090 100644
--- a/src/TransCode.cpp
+++ b/src/TransCode.cpp
@@ -34,14 +34,6 @@ namespace CppJieba
 		_pf_encode = vecToUtf8;
 	}
 	
-	bool TransCode::decode(const string& str, vector<uint16_t>& vec)
-	{
-		if(NULL == _pf_decode)
-		{
-			return false;
-		}
-		return _pf_decode(str, vec);
-	}
 
 	bool TransCode::utf8ToVec(const string& str, vector<uint16_t>& vec)
 	{
@@ -112,27 +104,14 @@ namespace CppJieba
 		return true;
 	}
     
-    string TransCode::encode(const Unicode& sentence)
-    {
-        return encode(sentence.begin(), sentence.end());
-    }
-	
-	string TransCode::encode(Unicode::const_iterator begin, Unicode::const_iterator end)
-	{
-		if(!_pf_encode)
-		{
-			return "";
-		}
-		return _pf_encode(begin, end);
-	}
 
-	string TransCode::vecToUtf8(Unicode::const_iterator begin, Unicode::const_iterator end)
+	bool TransCode::vecToUtf8(Unicode::const_iterator begin, Unicode::const_iterator end, string& res)
 	{
 		if(begin >= end)
 		{
-			return "";
+			return false;
 		}
-		string res;
+        res.clear();
 		uint16_t ui;
 		while(begin != end)
 		{
@@ -154,17 +133,17 @@ namespace CppJieba
 			}
 			begin ++;
 		}
-		return res;
+		return true;
 	}
 
-	string TransCode::vecToGbk(Unicode::const_iterator begin, Unicode::const_iterator end)
+	bool TransCode::vecToGbk(Unicode::const_iterator begin, Unicode::const_iterator end, string& res)
 	{
 		if(begin >= end)
 		{
-			return "";
+			return false;
 		}
+        res.clear();
 		pair<char, char> pa;
-		string res;
 		while(begin != end)
 		{
 			pa = uint16ToChar2(*begin);
@@ -179,21 +158,8 @@ namespace CppJieba
 			}
 			begin++;
 		}
-		return res;
+		return true;
 	}
-
-	//size_t TransCode::getWordLength(const string& str)
-	//{
-	//	vector<uint16_t> vec;
-	//	if(!decode(str, vec))
-	//	{
-	//		return 0;
-	//	}
-	//	else
-	//	{
-	//		return vec.size();
-	//	}
-	//}
 }
 
 
@@ -202,27 +168,6 @@ using namespace CPPCOMMON;
 using namespace CppJieba;
 int main()
 {
-	//ifstream ifile("/home/wuyanyi/code/SevKeyword/log.2.txt");
-	//string line;
-	//Unicode vec;
-	//while(getline(ifile, line))
-	//{
-	//	
-	//	cout<<line<<endl;
-	//	cout<<line.size()<<endl;
-	//	if(!TransCode::decode(line, vec))
-	//	{
-	//		cout<<"error"<<endl;
-	//	}
-	//	PRINT_VECTOR(vec);
-	//	cout<<TransCode::encode(vec)<<endl;
-	//}
-	//ifile.close();
-	//typedef bool (* pf)(const string& , vector<uint16_t>&);
-	//pf tmp = TransCode::a;
-	//vector<uint16_t> vec;
-	//tmp("1",vec);
-
 	string a("abd你好世界!a");
 	vector<uint16_t> vec;
 	//TransCode::setUtf8Enc();
diff --git a/src/TransCode.h b/src/TransCode.h
index 5627941..817aa79 100644
--- a/src/TransCode.h
+++ b/src/TransCode.h
@@ -17,38 +17,56 @@ namespace CppJieba
 	{
 		public:
 			typedef bool (*pf_decode_t)(const string&, vector<uint16_t>&);
-			typedef string (*pf_encode_t)(Unicode::const_iterator begin, Unicode::const_iterator end);
-			typedef size_t (*pf_getWordLength_t)(const string& str);
+			typedef bool (*pf_encode_t)(Unicode::const_iterator begin, Unicode::const_iterator end, string& res);
 		private:
 			static vector<string> _encVec;
 			static bool _isInitted;
 			static pf_decode_t _pf_decode;
 			static pf_encode_t _pf_encode;
-			static pf_getWordLength_t _pf_getWordLength;
 			
 		public:
 			static void setGbkEnc();
 			static void setUtf8Enc();
 			
-		public:
+		private:
 			TransCode();
 			~TransCode();
 		public:
 			static bool init();
 		public:
-			static bool decode(const string& str, vector<uint16_t>& vec);
-			static string encode(Unicode::const_iterator begin, Unicode::const_iterator end);
-            static string encode(const Unicode& sentence);
-			//static size_t getWordLength(const string& str);
+			static inline bool decode(const string& str, vector<uint16_t>& vec);
+			static inline bool encode(Unicode::const_iterator begin, Unicode::const_iterator end, string& res);
+            static inline bool encode(const Unicode& sentence, string& res);
+
 		public:
 			static bool gbkToVec(const string& str, vector<uint16_t>& vec);
-			static string vecToGbk(Unicode::const_iterator begin, Unicode::const_iterator end);
-			//static size_t getGbkLength(const string& str);
+			static bool vecToGbk(Unicode::const_iterator begin, Unicode::const_iterator end, string& res);
 		public:
 			static bool utf8ToVec(const string& str, vector<uint16_t>& vec);
-			static string vecToUtf8(Unicode::const_iterator begin, Unicode::const_iterator end);
-			//static size_t getUtf8Length(const string& str);
+			static bool vecToUtf8(Unicode::const_iterator begin, Unicode::const_iterator end, string& res);
 	};
+
+	inline bool TransCode::decode(const string& str, vector<uint16_t>& vec)
+	{
+		if(NULL == _pf_decode)
+		{
+			return false;
+		}
+		return _pf_decode(str, vec);
+	}
+    inline bool TransCode::encode(const Unicode& sentence, string& res)
+    {
+        return encode(sentence.begin(), sentence.end(), res);
+    }
+	
+	inline bool TransCode::encode(Unicode::const_iterator begin, Unicode::const_iterator end, string& res)
+	{
+		if(!_pf_encode)
+		{
+			return false;
+		}
+		return _pf_encode(begin, end, res);
+	}
 }
 
 #endif
diff --git a/src/structs.h b/src/structs.h
index 13e4d9c..6cb4ed0 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -82,9 +82,11 @@ namespace CppJieba
 		KeyWordInfo(const TrieNodeInfo& trieNodeInfo):TrieNodeInfo(trieNodeInfo)
 		{
 		}
-		string toString() const
+		inline string toString() const
 		{
-			return string_format("{word:%s,weight:%lf, idf:%lf}", TransCode::encode(word.begin(), word.end()).c_str(), weight, idf);
+            string tmp;
+            TransCode::encode(word, tmp);
+			return string_format("{word:%s,weight:%lf, idf:%lf}", tmp.c_str(), weight, idf);
 		}
 		KeyWordInfo& operator = (const TrieNodeInfo& trieNodeInfo)
 		{