diff --git a/ChangeLog b/ChangeLog
index 89f70ede..20e9c627 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,72 @@
+2009-03-13  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	Refactored BtMessage subclasses. BtCancelMessage, BtRequestMessage
+	and BtRejectMessage are derived from RangeBtMessage class.
+	BtAllowedFastMessage, BtHaveMessage and BtSuggestPieceMessage are
+	derived from IndexBtMessage class. BtChokeMessage,
+	BtHaveAllMessage, BtHaveNoneMessage, BtInterestedMessage,
+	BtNotInterestedMessage and BtUnchokeMessage are derived from
+	ZeroBtMessage class.
+	* src/AbstractBtMessage.cc
+	* src/AbstractBtMessage.h
+	* src/BtAllowedFastMessage.cc
+	* src/BtAllowedFastMessage.h
+	* src/BtAllowedFastMessageValidator.h: Removed
+	* src/BtBitfieldMessage.cc
+	* src/BtBitfieldMessage.h
+	* src/BtCancelMessage.cc
+	* src/BtCancelMessage.h
+	* src/BtCancelMessageValidator.h: Removed
+	* src/BtChokeMessage.cc
+	* src/BtChokeMessage.h
+	* src/BtExtendedMessage.cc
+	* src/BtExtendedMessage.h
+	* src/BtHandshakeMessage.cc
+	* src/BtHandshakeMessage.h
+	* src/BtHaveAllMessage.cc
+	* src/BtHaveAllMessage.h
+	* src/BtHaveMessage.cc
+	* src/BtHaveMessage.h
+	* src/BtHaveMessageValidator.h: Removed
+	* src/BtHaveNoneMessage.cc
+	* src/BtHaveNoneMessage.h
+	* src/BtInterestedMessage.cc
+	* src/BtInterestedMessage.h
+	* src/BtKeepAliveMessage.cc
+	* src/BtKeepAliveMessage.h
+	* src/BtNotInterestedMessage.cc
+	* src/BtNotInterestedMessage.h
+	* src/BtPieceMessage.cc
+	* src/BtPieceMessage.h
+	* src/BtPortMessage.cc
+	* src/BtPortMessage.h
+	* src/BtRejectMessage.cc
+	* src/BtRejectMessage.h
+	* src/BtRejectMessageValidator.h: Removed
+	* src/BtRequestMessage.cc
+	* src/BtRequestMessage.h
+	* src/BtRequestMessageValidator.h: Removed
+	* src/BtSuggestPieceMessage.cc
+	* src/BtSuggestPieceMessage.h
+	* src/BtSuggestPieceMessageValidator.h: Removed
+	* src/BtUnchokeMessage.cc
+	* src/BtUnchokeMessage.h
+	* src/DefaultBtMessageFactory.cc
+	* src/IndexBtMessage.cc
+	* src/IndexBtMessage.h
+	* src/IndexBtMessageValidator.h
+	* src/Makefile.am
+	* src/PeerMessageUtil.cc
+	* src/PeerMessageUtil.h
+	* src/RangeBtMessage.cc
+	* src/RangeBtMessage.h
+	* src/RangeBtMessageValidator.h
+	* src/SimpleBtMessage.cc
+	* src/SimpleBtMessage.h
+	* src/ZeroBtMessage.cc
+	* src/ZeroBtMessage.h
+	* test/BtRequestMessageTest.cc
+
 2009-03-12  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Reverted usage_text.h to r1093 to avoid to lose translated
diff --git a/src/AbstractBtMessage.cc b/src/AbstractBtMessage.cc
index 455dbc7b..eb339ac5 100644
--- a/src/AbstractBtMessage.cc
+++ b/src/AbstractBtMessage.cc
@@ -43,12 +43,13 @@
 
 namespace aria2 {
 
-AbstractBtMessage::AbstractBtMessage(uint8_t id):
+AbstractBtMessage::AbstractBtMessage(uint8_t id, const std::string& name):
   BtMessage(id),
   sendingInProgress(false),
   invalidate(false),
   uploading(false),
   cuid(0),
+  _name(name),
   logger(LogFactory::getInstance())
 {}
 
@@ -132,4 +133,9 @@ void AbstractBtMessage::setBtRequestFactory(const WeakHandle<BtRequestFactory>&
   this->requestFactory = factory;
 }
 
+const std::string& AbstractBtMessage::getName() const
+{
+  return _name;
+}
+
 } // namespace aria2
diff --git a/src/AbstractBtMessage.h b/src/AbstractBtMessage.h
index 3acb1c5b..5c1fffff 100644
--- a/src/AbstractBtMessage.h
+++ b/src/AbstractBtMessage.h
@@ -58,6 +58,8 @@ protected:
   bool uploading;
   int32_t cuid;
 
+  std::string _name;
+
   SharedHandle<BtContext> btContext;
 
   SharedHandle<PieceStorage> pieceStorage;
@@ -78,7 +80,7 @@ protected:
 
   Logger* logger;
 public:
-  AbstractBtMessage(uint8_t id);
+  AbstractBtMessage(uint8_t id, const std::string& name);
 
   virtual ~AbstractBtMessage();
 
@@ -145,6 +147,8 @@ public:
   void setBtMessageFactory(const WeakHandle<BtMessageFactory>& factory);
 
   void setBtRequestFactory(const WeakHandle<BtRequestFactory>& factory);
+
+  const std::string& getName() const;
 };
 
 typedef SharedHandle<AbstractBtMessage> AbstractBtMessageHandle;
diff --git a/src/BtAllowedFastMessage.cc b/src/BtAllowedFastMessage.cc
index b9d557fe..a3e81350 100644
--- a/src/BtAllowedFastMessage.cc
+++ b/src/BtAllowedFastMessage.cc
@@ -33,28 +33,18 @@
  */
 /* copyright --> */
 #include "BtAllowedFastMessage.h"
-#include "PeerMessageUtil.h"
-#include "Util.h"
 #include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
 #include "StringFormat.h"
 
 namespace aria2 {
 
-BtAllowedFastMessageHandle BtAllowedFastMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 5) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "allowed fast", dataLength, 5).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "allowed fast", ID).str());
-  }
-  BtAllowedFastMessageHandle message(new BtAllowedFastMessage());
-  message->setIndex(PeerMessageUtil::getIntParam(data, 1));
-  return message;
+const std::string BtAllowedFastMessage::NAME("allowed fast");
+
+SharedHandle<BtAllowedFastMessage> BtAllowedFastMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return IndexBtMessage::create<BtAllowedFastMessage>(data, dataLength);
 }
 
 void BtAllowedFastMessage::doReceivedAction() {
@@ -63,34 +53,11 @@ void BtAllowedFastMessage::doReceivedAction() {
       (StringFormat("%s received while fast extension is disabled",
 		    toString().c_str()).str());
   }
-  peer->addPeerAllowedIndex(index);
-}
-
-const unsigned char* BtAllowedFastMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 5, 4bytes
-     * id --- 17, 1byte
-     * piece index --- index, 4bytes
-     * total: 9bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 5, ID);
-    PeerMessageUtil::setIntParam(&msg[5], index);
-  }
-  return msg;
-}
-
-size_t BtAllowedFastMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
+  peer->addPeerAllowedIndex(getIndex());
 }
 
 void BtAllowedFastMessage::onSendComplete() {
-  peer->addAmAllowedIndex(index);
-}
-
-std::string BtAllowedFastMessage::toString() const {
-  return "allowed fast index="+Util::itos(index);
+  peer->addAmAllowedIndex(getIndex());
 }
 
 } // namespace aria2
diff --git a/src/BtAllowedFastMessage.h b/src/BtAllowedFastMessage.h
index 8d25d388..ab22f0a7 100644
--- a/src/BtAllowedFastMessage.h
+++ b/src/BtAllowedFastMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_ALLOWED_FAST_MESSAGE_H_
 #define _D_BT_ALLOWED_FAST_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "IndexBtMessage.h"
 
 namespace aria2 {
 
@@ -43,39 +43,20 @@ class BtAllowedFastMessage;
 
 typedef SharedHandle<BtAllowedFastMessage> BtAllowedFastMessageHandle;
 
-class BtAllowedFastMessage : public SimpleBtMessage {
-private:
-  size_t index;
-  unsigned char* msg;
-
-  static const size_t MESSAGE_LENGTH = 9;
+class BtAllowedFastMessage : public IndexBtMessage {
 public:
   BtAllowedFastMessage(size_t index = 0)
-    :SimpleBtMessage(ID),
-     index(index),
-     msg(0) {}
-
-  virtual ~BtAllowedFastMessage() {
-    delete [] msg;
-  }
+    :IndexBtMessage(ID, NAME, index) {}
 
   static const uint8_t ID = 17;
 
-  void setIndex(size_t index) {
-    this->index = index;
-  }
-  size_t getIndex() const { return index; }
+  static const std::string NAME;
 
-  static BtAllowedFastMessageHandle create(const unsigned char* data, size_t dataLength);
+  static SharedHandle<BtAllowedFastMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
 
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
-
   virtual void onSendComplete();
 
 };
diff --git a/src/BtBitfieldMessage.cc b/src/BtBitfieldMessage.cc
index 13541777..dc5ea786 100644
--- a/src/BtBitfieldMessage.cc
+++ b/src/BtBitfieldMessage.cc
@@ -33,6 +33,9 @@
  */
 /* copyright --> */
 #include "BtBitfieldMessage.h"
+
+#include <cstring>
+
 #include "PeerMessageUtil.h"
 #include "Util.h"
 #include "DlAbortEx.h"
@@ -40,10 +43,11 @@
 #include "Peer.h"
 #include "StringFormat.h"
 #include "PieceStorage.h"
-#include <cstring>
 
 namespace aria2 {
 
+const std::string BtBitfieldMessage::NAME("bitfield");
+
 void BtBitfieldMessage::setBitfield(const unsigned char* bitfield, size_t bitfieldLength) {
   if(this->bitfield == bitfield) {
     return;
@@ -58,15 +62,8 @@ void BtBitfieldMessage::setBitfield(const unsigned char* bitfield, size_t bitfie
 BtBitfieldMessageHandle
 BtBitfieldMessage::create(const unsigned char* data, size_t dataLength)
 {
-  if(dataLength <= 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "bitfield", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "bitfield", ID).str());
-  }
+  PeerMessageUtil::assertPayloadLengthGreater(1,dataLength, NAME);
+  PeerMessageUtil::assertID(ID, data, NAME);
   BtBitfieldMessageHandle message(new BtBitfieldMessage());
   message->setBitfield((unsigned char*)data+1, dataLength-1);
   return message;
@@ -100,7 +97,7 @@ size_t BtBitfieldMessage::getMessageLength() {
 }
 
 std::string BtBitfieldMessage::toString() const {
-  return "bitfield "+Util::toHex(bitfield, bitfieldLength);
+  return NAME+" "+Util::toHex(bitfield, bitfieldLength);
 }
 
 } // namespace aria2
diff --git a/src/BtBitfieldMessage.h b/src/BtBitfieldMessage.h
index 03fe02a8..2a05471e 100644
--- a/src/BtBitfieldMessage.h
+++ b/src/BtBitfieldMessage.h
@@ -57,13 +57,13 @@ private:
     msgLength = 0;
   }
 public:
-  BtBitfieldMessage():SimpleBtMessage(ID)
+  BtBitfieldMessage():SimpleBtMessage(ID, NAME)
   {
     init();
   }
 
   BtBitfieldMessage(const unsigned char* bitfield,
-		    size_t bitfieldLength):SimpleBtMessage(ID)
+		    size_t bitfieldLength):SimpleBtMessage(ID, NAME)
   {
     init();
     setBitfield(bitfield, bitfieldLength);
@@ -76,6 +76,8 @@ public:
 
   static const uint8_t ID = 5;
 
+  static const std::string NAME;
+
   void setBitfield(const unsigned char* bitfield, size_t bitfieldLength);
 
   const unsigned char* getBitfield() const { return bitfield; }
diff --git a/src/BtCancelMessage.cc b/src/BtCancelMessage.cc
index a87e904c..536f4b58 100644
--- a/src/BtCancelMessage.cc
+++ b/src/BtCancelMessage.cc
@@ -33,62 +33,21 @@
  */
 /* copyright --> */
 #include "BtCancelMessage.h"
-#include "PeerMessageUtil.h"
-#include "Util.h"
-#include "DlAbortEx.h"
-#include "message.h"
 #include "BtMessageDispatcher.h"
-#include "StringFormat.h"
 
 namespace aria2 {
 
-BtCancelMessageHandle BtCancelMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 13) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "cancel", dataLength, 13).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "cancel", ID).str());
-  }
-  BtCancelMessageHandle message(new BtCancelMessage());
-  message->setIndex(PeerMessageUtil::getIntParam(data, 1));
-  message->setBegin(PeerMessageUtil::getIntParam(data, 5));
-  message->setLength(PeerMessageUtil::getIntParam(data, 9));
-  return message;
+const std::string BtCancelMessage::NAME("cancel");
+
+SharedHandle<BtCancelMessage> BtCancelMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return RangeBtMessage::create<BtCancelMessage>(data, dataLength);
 }
 
-void BtCancelMessage::doReceivedAction() {
-  dispatcher->doCancelSendingPieceAction(index, begin, length);
-}
-
-const unsigned char* BtCancelMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 13, 4bytes
-     * id --- 8, 1byte
-     * index --- index, 4bytes
-     * begin --- begin, 4bytes
-     * length -- length, 4bytes
-     * total: 17bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 13, ID);
-    PeerMessageUtil::setIntParam(&msg[5], index);
-    PeerMessageUtil::setIntParam(&msg[9], begin);
-    PeerMessageUtil::setIntParam(&msg[13], length);
-  }
-  return msg;
-}
-
-size_t BtCancelMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtCancelMessage::toString() const {
-  return "cancel index="+Util::uitos(index)+", begin="+Util::uitos(begin)+
-    ", length="+Util::uitos(length);
+void BtCancelMessage::doReceivedAction()
+{
+  dispatcher->doCancelSendingPieceAction(getIndex(), getBegin(), getLength());
 }
 
 } // namespace aria2
diff --git a/src/BtCancelMessage.h b/src/BtCancelMessage.h
index 8dd6f12c..e78cb892 100644
--- a/src/BtCancelMessage.h
+++ b/src/BtCancelMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_CANCEL_MESSAGE_H_
 #define _D_BT_CANCEL_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "RangeBtMessage.h"
 
 namespace aria2 {
 
@@ -43,49 +43,18 @@ class BtCancelMessage;
 
 typedef SharedHandle<BtCancelMessage> BtCancelMessageHandle;
 
-class BtCancelMessage : public SimpleBtMessage {
-private:
-  size_t index;
-  uint32_t begin;
-  size_t length;
-  unsigned char* msg;
-
-  static const size_t MESSAGE_LENGTH = 17;
+class BtCancelMessage : public RangeBtMessage {
 public:
   BtCancelMessage(size_t index = 0, uint32_t begin = 0, size_t length = 0)
-    :SimpleBtMessage(ID),
-     index(index),
-     begin(begin),
-     length(length),
-     msg(0) {}
-
-  virtual ~BtCancelMessage() {
-    delete [] msg;
-  }
+    :RangeBtMessage(ID, NAME, index, begin, length) {}
 
   static const int8_t ID = 8;
 
-  size_t getIndex() const { return index; }
-
-  void setIndex(size_t index) { this->index = index; }
-
-  uint32_t getBegin() const { return begin; }
-
-  void setBegin(uint32_t begin) { this->begin = begin; }
-
-  size_t getLength() const { return length; }
-
-  void setLength(size_t length) { this->length = length; }
+  static const std::string NAME;
 
   static BtCancelMessageHandle create(const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
-
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
 };
 
 } // namespace aria2
diff --git a/src/BtChokeMessage.cc b/src/BtChokeMessage.cc
index 6854386b..85cad16e 100644
--- a/src/BtChokeMessage.cc
+++ b/src/BtChokeMessage.cc
@@ -33,65 +33,36 @@
  */
 /* copyright --> */
 #include "BtChokeMessage.h"
-#include "PeerMessageUtil.h"
-#include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
 #include "BtMessageDispatcher.h"
 #include "BtRequestFactory.h"
-#include "StringFormat.h"
 
 namespace aria2 {
 
-BtChokeMessageHandle BtChokeMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "choke", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "choke", ID).str());
-  }
-  BtChokeMessageHandle chokeMessage(new BtChokeMessage());
-  return chokeMessage;
+const std::string BtChokeMessage::NAME("choke");
+
+SharedHandle<BtChokeMessage> BtChokeMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return ZeroBtMessage::create<BtChokeMessage>(data, dataLength);
 }
 
-void BtChokeMessage::doReceivedAction() {
+void BtChokeMessage::doReceivedAction()
+{
   peer->peerChoking(true);
   dispatcher->doChokedAction();
   requestFactory->doChokedAction();
 }
 
-bool BtChokeMessage::sendPredicate() const {
+bool BtChokeMessage::sendPredicate() const
+{
   return !peer->amChoking();
 }
 
-const unsigned char* BtChokeMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 1, 4bytes
-     * id --- 0, 1byte
-     * total: 5bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 1, ID);
-  }
-  return msg;
-}
-
-size_t BtChokeMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-void BtChokeMessage::onSendComplete() {
+void BtChokeMessage::onSendComplete()
+{
   peer->amChoking(true);
   dispatcher->doChokingAction();
 }
 
-std::string BtChokeMessage::toString() const {
-  static const std::string CHOKE("choke");
-  return CHOKE;
-}
-
 } // namespace aria2
diff --git a/src/BtChokeMessage.h b/src/BtChokeMessage.h
index 442097fe..b3445e86 100644
--- a/src/BtChokeMessage.h
+++ b/src/BtChokeMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_CHOKE_MESSAGE_H_
 #define _D_BT_CHOKE_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "ZeroBtMessage.h"
 
 namespace aria2 {
 
@@ -43,29 +43,18 @@ class BtChokeMessage;
 
 typedef SharedHandle<BtChokeMessage> BtChokeMessageHandle;
 
-class BtChokeMessage : public SimpleBtMessage {
-private:
-  unsigned char* msg;
-
-  static const size_t MESSAGE_LENGTH = 5;
+class BtChokeMessage : public ZeroBtMessage {
 public:
-  BtChokeMessage():SimpleBtMessage(ID), msg(0) {}
-
-  virtual ~BtChokeMessage() {
-    delete [] msg;
-  }
+  BtChokeMessage():ZeroBtMessage(ID, NAME) {}
 
   static const uint8_t ID = 0;
 
+  static const std::string NAME;
+
   virtual void doReceivedAction();
 
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
-
-  static BtChokeMessageHandle create(const unsigned char* data, size_t dataLength);
+  static SharedHandle<BtChokeMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual bool sendPredicate() const;
 
diff --git a/src/BtExtendedMessage.cc b/src/BtExtendedMessage.cc
index ec626cf2..0256d9f3 100644
--- a/src/BtExtendedMessage.cc
+++ b/src/BtExtendedMessage.cc
@@ -47,9 +47,11 @@
 
 namespace aria2 {
 
+const std::string BtExtendedMessage::NAME("extended");
+
 BtExtendedMessage::BtExtendedMessage
 (const ExtensionMessageHandle& extensionMessage):
-  SimpleBtMessage(ID),
+  SimpleBtMessage(ID, NAME),
   _extensionMessage(extensionMessage),
   _msg(0),
   _msgLength(0)
@@ -90,7 +92,7 @@ bool BtExtendedMessage::sendPredicate() const
 }
 
 std::string BtExtendedMessage::toString() const {
-  return "extended "+_extensionMessage->toString();
+  return NAME+" "+_extensionMessage->toString();
 }
 
 BtExtendedMessageHandle
@@ -98,15 +100,8 @@ BtExtendedMessage::create(const SharedHandle<ExtensionMessageFactory>& factory,
 			  const PeerHandle& peer,
 			  const unsigned char* data, size_t dataLength)
 {
-  if(dataLength < 2) {
-    throw DlAbortEx
-      (StringFormat(MSG_TOO_SMALL_PAYLOAD_SIZE, "extended", dataLength).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "extended", ID).str());
-  }
+  PeerMessageUtil::assertPayloadLengthGreater(1, dataLength, NAME);
+  PeerMessageUtil::assertID(ID, data, NAME);
   assert(!factory.isNull());
   ExtensionMessageHandle extmsg = factory->createMessage(data+1,
 							 dataLength-1);
diff --git a/src/BtExtendedMessage.h b/src/BtExtendedMessage.h
index c231c869..63912f92 100644
--- a/src/BtExtendedMessage.h
+++ b/src/BtExtendedMessage.h
@@ -60,6 +60,8 @@ public:
 
   static const uint8_t ID = 20;
 
+  static const std::string NAME;
+
   static BtExtendedMessageHandle create
     (const SharedHandle<ExtensionMessageFactory>& factory,
      const SharedHandle<Peer>& peer,
diff --git a/src/BtHandshakeMessage.cc b/src/BtHandshakeMessage.cc
index 5fd5aff4..ead983b1 100644
--- a/src/BtHandshakeMessage.cc
+++ b/src/BtHandshakeMessage.cc
@@ -40,16 +40,18 @@
 
 namespace aria2 {
 
+const std::string BtHandshakeMessage::NAME("handshake");
+
 const unsigned char* BtHandshakeMessage::BT_PSTR = (const unsigned char*)"BitTorrent protocol";
 
-BtHandshakeMessage::BtHandshakeMessage():SimpleBtMessage(ID)
+BtHandshakeMessage::BtHandshakeMessage():SimpleBtMessage(ID, NAME)
 {
   init();
 }
 
 BtHandshakeMessage::BtHandshakeMessage(const unsigned char* infoHash,
 				       const unsigned char* peerId):
-  SimpleBtMessage(ID)
+  SimpleBtMessage(ID, NAME)
 {
   init();
   memcpy(this->infoHash, infoHash, INFO_HASH_LENGTH);
@@ -100,7 +102,7 @@ size_t BtHandshakeMessage::getMessageLength() {
 }
 
 std::string BtHandshakeMessage::toString() const {
-  return "handshake peerId="+
+  return NAME+" peerId="+
     Util::urlencode(peerId, PEER_ID_LENGTH)+
     ", reserved="+Util::toHex(reserved, RESERVED_LENGTH);
 }
diff --git a/src/BtHandshakeMessage.h b/src/BtHandshakeMessage.h
index ef36a3bb..c8ac4ca7 100644
--- a/src/BtHandshakeMessage.h
+++ b/src/BtHandshakeMessage.h
@@ -74,6 +74,8 @@ public:
 
   static const uint8_t ID = INT8_MAX;
 
+  static const std::string NAME;
+
   virtual void doReceivedAction() {};
 
   virtual const unsigned char* getMessage();
diff --git a/src/BtHaveAllMessage.cc b/src/BtHaveAllMessage.cc
index efdc6f9b..10f6cc3d 100644
--- a/src/BtHaveAllMessage.cc
+++ b/src/BtHaveAllMessage.cc
@@ -34,59 +34,31 @@
 /* copyright --> */
 #include "BtHaveAllMessage.h"
 #include "DlAbortEx.h"
-#include "PeerMessageUtil.h"
-#include "message.h"
 #include "Peer.h"
 #include "StringFormat.h"
 #include "PieceStorage.h"
 
 namespace aria2 {
 
-BtHaveAllMessageHandle BtHaveAllMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "have all", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "have all", ID).str());
-  }
-  BtHaveAllMessageHandle message(new BtHaveAllMessage());
-  return message;
+const std::string BtHaveAllMessage::NAME("have all");
+
+SharedHandle<BtHaveAllMessage> BtHaveAllMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return ZeroBtMessage::create<BtHaveAllMessage>(data, dataLength);
 }
 
-void BtHaveAllMessage::doReceivedAction() {
+void BtHaveAllMessage::doReceivedAction()
+{
   if(!peer->isFastExtensionEnabled()) {
     throw DlAbortEx
       (StringFormat("%s received while fast extension is disabled",
 		    toString().c_str()).str());
   }
-  pieceStorage->subtractPieceStats(peer->getBitfield(), peer->getBitfieldLength());
+  pieceStorage->subtractPieceStats(peer->getBitfield(),
+				   peer->getBitfieldLength());
   peer->setAllBitfield();
   pieceStorage->addPieceStats(peer->getBitfield(), peer->getBitfieldLength());
 }
 
-const unsigned char* BtHaveAllMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 1, 4bytes
-     * id --- 14, 1byte
-     * total: 5bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 1, ID);
-  }
-  return msg;
-}
-
-size_t BtHaveAllMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtHaveAllMessage::toString() const {
-  static const std::string HAVE_ALL("have all");
-  return HAVE_ALL;
-}
-
 } // namespace aria2
diff --git a/src/BtHaveAllMessage.h b/src/BtHaveAllMessage.h
index 4eb79c1f..537bf2de 100644
--- a/src/BtHaveAllMessage.h
+++ b/src/BtHaveAllMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_HAVE_ALL_MESSAGE_H_
 #define _D_BT_HAVE_ALL_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "ZeroBtMessage.h"
 
 namespace aria2 {
 
@@ -43,29 +43,18 @@ class BtHaveAllMessage;
 
 typedef SharedHandle<BtHaveAllMessage> BtHaveAllMessageHandle;
 
-class BtHaveAllMessage : public SimpleBtMessage {
-private:
-  unsigned char* msg;
-
-  static const size_t MESSAGE_LENGTH = 5;
+class BtHaveAllMessage : public ZeroBtMessage {
 public:
-  BtHaveAllMessage():SimpleBtMessage(ID), msg(0) {}
-
-  virtual ~BtHaveAllMessage() {
-    delete [] msg;
-  }
+  BtHaveAllMessage():ZeroBtMessage(ID, NAME) {}
 
   static const uint8_t ID = 14;
 
-  static BtHaveAllMessageHandle create(const unsigned char* data, size_t dataLength);
+  static const std::string NAME;
+
+  static SharedHandle<BtHaveAllMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
-
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
 };
 
 } // namespace aria2
diff --git a/src/BtHaveMessage.cc b/src/BtHaveMessage.cc
index 1afd48df..6641f6a0 100644
--- a/src/BtHaveMessage.cc
+++ b/src/BtHaveMessage.cc
@@ -33,57 +33,23 @@
  */
 /* copyright --> */
 #include "BtHaveMessage.h"
-#include "PeerMessageUtil.h"
-#include "Util.h"
-#include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
-#include "StringFormat.h"
 #include "PieceStorage.h"
 
 namespace aria2 {
 
-BtHaveMessageHandle BtHaveMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 5) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "have", dataLength, 5).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "have", ID).str());
-  }
-  BtHaveMessageHandle message(new BtHaveMessage());
-  message->setIndex(PeerMessageUtil::getIntParam(data, 1));
-  return message;
+const std::string BtHaveMessage::NAME("have");
+
+SharedHandle<BtHaveMessage> BtHaveMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return IndexBtMessage::create<BtHaveMessage>(data, dataLength);
 }
 
-void BtHaveMessage::doReceivedAction() {
-  peer->updateBitfield(index, 1);
-  pieceStorage->addPieceStats(index);
-}
-
-const unsigned char* BtHaveMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 5, 4bytes
-     * id --- 4, 1byte
-     * piece index --- index, 4bytes
-     * total: 9bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 5, ID);
-    PeerMessageUtil::setIntParam(&msg[5], index);
-  }
-  return msg;
-}
-
-size_t BtHaveMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtHaveMessage::toString() const {
-  return "have index="+Util::itos(index);
+void BtHaveMessage::doReceivedAction()
+{
+  peer->updateBitfield(getIndex(), 1);
+  pieceStorage->addPieceStats(getIndex());
 }
 
 } // namespace aria2
diff --git a/src/BtHaveMessage.h b/src/BtHaveMessage.h
index 9ff9423f..51087f2b 100644
--- a/src/BtHaveMessage.h
+++ b/src/BtHaveMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_HAVE_MESSAGE_H_
 #define _D_BT_HAVE_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "IndexBtMessage.h"
 
 namespace aria2 {
 
@@ -43,35 +43,18 @@ class BtHaveMessage;
 
 typedef SharedHandle<BtHaveMessage> BtHaveMessageHandle;
 
-class BtHaveMessage : public SimpleBtMessage {
-private:
-  size_t index;
-  unsigned char* msg;
-  static const size_t MESSAGE_LENGTH = 9;
+class BtHaveMessage : public IndexBtMessage {
 public:
-  BtHaveMessage(size_t index = 0):SimpleBtMessage(ID), index(index), msg(0) {}
-
-  virtual ~BtHaveMessage() {
-    delete [] msg;
-  }
+  BtHaveMessage(size_t index = 0):IndexBtMessage(ID, NAME, index) {}
 
   static const uint8_t ID = 4;
 
-  void setIndex(size_t index) {
-    this->index = index;
-  }
+  static const std::string NAME;
 
-  size_t getIndex() const { return index; }
-
-  static BtHaveMessageHandle create(const unsigned char* data, size_t dataLength);
+  static SharedHandle<BtHaveMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
-
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
 };
 
 } // namespace aria2
diff --git a/src/BtHaveNoneMessage.cc b/src/BtHaveNoneMessage.cc
index 3981a20a..1ff27e06 100644
--- a/src/BtHaveNoneMessage.cc
+++ b/src/BtHaveNoneMessage.cc
@@ -34,28 +34,21 @@
 /* copyright --> */
 #include "BtHaveNoneMessage.h"
 #include "DlAbortEx.h"
-#include "PeerMessageUtil.h"
-#include "message.h"
 #include "Peer.h"
 #include "StringFormat.h"
 
 namespace aria2 {
 
-BtHaveNoneMessageHandle BtHaveNoneMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "have none", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "have none", ID).str());
-  }
-  BtHaveNoneMessageHandle message(new BtHaveNoneMessage());
-  return message;
+const std::string BtHaveNoneMessage::NAME("have none");
+
+SharedHandle<BtHaveNoneMessage> BtHaveNoneMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return ZeroBtMessage::create<BtHaveNoneMessage>(data, dataLength);
 }
 
-void BtHaveNoneMessage::doReceivedAction() {
+void BtHaveNoneMessage::doReceivedAction()
+{
   if(!peer->isFastExtensionEnabled()) {
     throw DlAbortEx
       (StringFormat("%s received while fast extension is disabled",
@@ -63,26 +56,4 @@ void BtHaveNoneMessage::doReceivedAction() {
   }
 }
 
-const unsigned char* BtHaveNoneMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 1, 4bytes
-     * id --- 15, 1byte
-     * total: 5bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 1, ID);
-  }
-  return msg;
-}
-
-size_t BtHaveNoneMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtHaveNoneMessage::toString() const {
-  static const std::string HAVE_NONE("have none");
-  return HAVE_NONE;
-}
-
 } // namespace aria2
diff --git a/src/BtHaveNoneMessage.h b/src/BtHaveNoneMessage.h
index 4aaee64c..90a4619d 100644
--- a/src/BtHaveNoneMessage.h
+++ b/src/BtHaveNoneMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_HAVE_NONE_MESSAGE_H_
 #define _D_BT_HAVE_NONE_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "ZeroBtMessage.h"
 
 namespace aria2 {
 
@@ -43,29 +43,17 @@ class BtHaveNoneMessage;
 
 typedef SharedHandle<BtHaveNoneMessage> BtHaveNoneMessageHandle;
 
-class BtHaveNoneMessage : public SimpleBtMessage {
-private:
-  unsigned char* msg;
-
-  static const size_t MESSAGE_LENGTH = 5;
+class BtHaveNoneMessage : public ZeroBtMessage {
 public:
-  BtHaveNoneMessage():SimpleBtMessage(ID), msg(0) {}
-
-  virtual ~BtHaveNoneMessage() {
-    delete []  msg;
-  }
-  
+  BtHaveNoneMessage():ZeroBtMessage(ID, NAME) {}
   static const uint8_t ID = 15;
 
-  static BtHaveNoneMessageHandle create(const unsigned char* data, size_t dataLength);
+  static const std::string NAME;
+
+  static SharedHandle<BtHaveNoneMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
-
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
 };
 
 } // namespace aria2
diff --git a/src/BtInterestedMessage.cc b/src/BtInterestedMessage.cc
index 18ae56c2..38b23106 100644
--- a/src/BtInterestedMessage.cc
+++ b/src/BtInterestedMessage.cc
@@ -33,67 +33,36 @@
  */
 /* copyright --> */
 #include "BtInterestedMessage.h"
-#include "PeerMessageUtil.h"
-#include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
-#include "BtContext.h"
-#include "StringFormat.h"
 #include "PeerStorage.h"
 
 namespace aria2 {
 
-BtInterestedMessageHandle BtInterestedMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "interested", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "interested", ID).str());
-  }
-  BtInterestedMessageHandle message(new BtInterestedMessage());
-  return message;
+const std::string BtInterestedMessage::NAME("interested");
+
+SharedHandle<BtInterestedMessage> BtInterestedMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return ZeroBtMessage::create<BtInterestedMessage>(data, dataLength);
 }
 
-void BtInterestedMessage::doReceivedAction() {
+void BtInterestedMessage::doReceivedAction()
+{
   peer->peerInterested(true);
   if(!peer->amChoking()) {
     _peerStorage->executeChoke();
   }
 }
 
-bool BtInterestedMessage::sendPredicate() const {
+bool BtInterestedMessage::sendPredicate() const
+{
   return !peer->amInterested();
 }
 
-const unsigned char* BtInterestedMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 1, 4bytes
-     * id --- 2, 1byte
-     * total: 5bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 1, ID);
-  }
-  return msg;
-}
-
-size_t BtInterestedMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
 void BtInterestedMessage::onSendComplete() {
   peer->amInterested(true);
 }
 
-std::string BtInterestedMessage::toString() const {
-  static const std::string INTERESTED("interested");
-  return INTERESTED;
-}
-
 void BtInterestedMessage::setPeerStorage
 (const SharedHandle<PeerStorage>& peerStorage)
 {
diff --git a/src/BtInterestedMessage.h b/src/BtInterestedMessage.h
index 0a3fe8ec..72bd2bf6 100644
--- a/src/BtInterestedMessage.h
+++ b/src/BtInterestedMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_INTERESTED_MESSAGE_H_
 #define _D_BT_INTERESTED_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "ZeroBtMessage.h"
 
 namespace aria2 {
 
@@ -44,32 +44,21 @@ class BtInterestedMessage;
 
 typedef SharedHandle<BtInterestedMessage> BtInterestedMessageHandle;
 
-class BtInterestedMessage : public SimpleBtMessage {
+class BtInterestedMessage : public ZeroBtMessage {
 private:
-  unsigned char* msg;
-
   SharedHandle<PeerStorage> _peerStorage;
-
-  static const size_t MESSAGE_LENGTH = 5;
 public:
-  BtInterestedMessage():SimpleBtMessage(ID), msg(0) {}
-
-  virtual ~BtInterestedMessage() {
-    delete [] msg;
-  }
+  BtInterestedMessage():ZeroBtMessage(ID, NAME) {}
 
   static const uint8_t ID = 2;
 
-  static BtInterestedMessageHandle create(const unsigned char* data, size_t dataLength);
+  static const std::string NAME;
+
+  static SharedHandle<BtInterestedMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
 
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
-
   virtual bool sendPredicate() const;
 
   virtual void onSendComplete();
diff --git a/src/BtKeepAliveMessage.cc b/src/BtKeepAliveMessage.cc
index 6998ba49..b59b9ebb 100644
--- a/src/BtKeepAliveMessage.cc
+++ b/src/BtKeepAliveMessage.cc
@@ -37,6 +37,8 @@
 
 namespace aria2 {
 
+const std::string BtKeepAliveMessage::NAME("keep alive");
+
 const unsigned char* BtKeepAliveMessage::getMessage() {
   if(!msg) {
     /**
diff --git a/src/BtKeepAliveMessage.h b/src/BtKeepAliveMessage.h
index f100c7cb..bec16187 100644
--- a/src/BtKeepAliveMessage.h
+++ b/src/BtKeepAliveMessage.h
@@ -49,7 +49,7 @@ private:
 
   static const size_t MESSAGE_LENGTH = 4;
 public:
-  BtKeepAliveMessage():SimpleBtMessage(ID), msg(0) {}
+  BtKeepAliveMessage():SimpleBtMessage(ID, NAME), msg(0) {}
 
   virtual ~BtKeepAliveMessage() {
     delete [] msg;
@@ -57,6 +57,8 @@ public:
 
   static const uint8_t ID = 99;
 
+  static const std::string NAME;
+
   virtual void doReceivedAction() {}
 
   virtual const unsigned char* getMessage();
@@ -64,7 +66,7 @@ public:
   virtual size_t getMessageLength();
 
   virtual std::string toString() const {
-    return "keep alive";
+    return NAME;
   }
 };
 
diff --git a/src/BtNotInterestedMessage.cc b/src/BtNotInterestedMessage.cc
index 37829be8..a4adc7df 100644
--- a/src/BtNotInterestedMessage.cc
+++ b/src/BtNotInterestedMessage.cc
@@ -33,67 +33,36 @@
  */
 /* copyright --> */
 #include "BtNotInterestedMessage.h"
-#include "PeerMessageUtil.h"
-#include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
-#include "BtContext.h"
 #include "PeerStorage.h"
-#include "StringFormat.h"
 
 namespace aria2 {
 
-BtNotInterestedMessageHandle BtNotInterestedMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "not interested", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "not interested", ID).str());
-  }
-  BtNotInterestedMessageHandle message(new BtNotInterestedMessage());
-  return message;
+const std::string BtNotInterestedMessage::NAME("not interested");
+
+SharedHandle<BtNotInterestedMessage> BtNotInterestedMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return ZeroBtMessage::create<BtNotInterestedMessage>(data, dataLength);
 }
 
-void BtNotInterestedMessage::doReceivedAction() {
+void BtNotInterestedMessage::doReceivedAction()
+{
   peer->peerInterested(false);
   if(!peer->amChoking()) {
     _peerStorage->executeChoke();
   }
 }
 
-bool BtNotInterestedMessage::sendPredicate() const {
+bool BtNotInterestedMessage::sendPredicate() const
+{
   return peer->amInterested();
 }
 
-const unsigned char* BtNotInterestedMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 1, 4bytes
-     * id --- 3, 1byte
-     * total: 5bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 1, ID);
-  }
-  return msg;
-}
-
-size_t BtNotInterestedMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
 void BtNotInterestedMessage::onSendComplete() {
   peer->amInterested(false);
 }
 
-std::string BtNotInterestedMessage::toString() const {
-  static const std::string NOT_INTERESTED("not interested");
-  return NOT_INTERESTED;
-}
-
 void BtNotInterestedMessage::setPeerStorage
 (const SharedHandle<PeerStorage>& peerStorage)
 {
diff --git a/src/BtNotInterestedMessage.h b/src/BtNotInterestedMessage.h
index 329dda1a..630b9fac 100644
--- a/src/BtNotInterestedMessage.h
+++ b/src/BtNotInterestedMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_NOT_INTERESTED_MESSAGE_H_
 #define _D_BT_NOT_INTERESTED_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "ZeroBtMessage.h"
 
 namespace aria2 {
 
@@ -44,32 +44,21 @@ class BtNotInterestedMessage;
 
 typedef SharedHandle<BtNotInterestedMessage> BtNotInterestedMessageHandle;
 
-class BtNotInterestedMessage : public SimpleBtMessage {
+class BtNotInterestedMessage : public ZeroBtMessage {
 private:
-  unsigned char* msg;
-  
   SharedHandle<PeerStorage> _peerStorage;
-
-  static const size_t MESSAGE_LENGTH = 5;
 public:
-  BtNotInterestedMessage():SimpleBtMessage(ID), msg(0) {}
-
-  virtual ~BtNotInterestedMessage() {
-    delete [] msg;
-  }
+  BtNotInterestedMessage():ZeroBtMessage(ID, NAME) {}
 
   static const uint8_t ID = 3;
 
-  static BtNotInterestedMessageHandle create(const unsigned char* data, size_t dataLength);
+  static const std::string NAME;
+
+  static SharedHandle<BtNotInterestedMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
 
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
-
   virtual bool sendPredicate() const;
 
   virtual void onSendComplete();
diff --git a/src/BtPieceMessage.cc b/src/BtPieceMessage.cc
index bba0ca74..f20eb1e6 100644
--- a/src/BtPieceMessage.cc
+++ b/src/BtPieceMessage.cc
@@ -33,6 +33,11 @@
  */
 /* copyright --> */
 #include "BtPieceMessage.h"
+
+#include <cstring>
+#include <cstdlib>
+#include <cassert>
+
 #include "PeerMessageUtil.h"
 #include "Util.h"
 #include "message.h"
@@ -51,12 +56,11 @@
 #include "BtRequestFactory.h"
 #include "PeerConnection.h"
 #include "StringFormat.h"
-#include <cstring>
-#include <cstdlib>
-#include <cassert>
 
 namespace aria2 {
 
+const std::string BtPieceMessage::NAME("piece");
+
 void BtPieceMessage::setBlock(const unsigned char* block, size_t blockLength) {
   delete [] this->block;
   this->blockLength = blockLength;
@@ -65,15 +69,8 @@ void BtPieceMessage::setBlock(const unsigned char* block, size_t blockLength) {
 }
 
 BtPieceMessageHandle BtPieceMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength <= 9) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "piece", dataLength, 9).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "piece", ID).str());
-  }
+  PeerMessageUtil::assertPayloadLengthGreater(9, dataLength, NAME);
+  PeerMessageUtil::assertID(ID, data, NAME);
   BtPieceMessageHandle message(new BtPieceMessage());
   message->setIndex(PeerMessageUtil::getIntParam(data, 1));
   message->setBegin(PeerMessageUtil::getIntParam(data, 5));
@@ -173,7 +170,7 @@ size_t BtPieceMessage::sendPieceData(off_t offset, size_t length) const {
 }
 
 std::string BtPieceMessage::toString() const {
-  return "piece index="+Util::itos(index)+", begin="+Util::itos(begin)+
+  return NAME+" index="+Util::itos(index)+", begin="+Util::itos(begin)+
     ", length="+Util::itos(blockLength);
 }
 
diff --git a/src/BtPieceMessage.h b/src/BtPieceMessage.h
index 3b4a83b5..a2435709 100644
--- a/src/BtPieceMessage.h
+++ b/src/BtPieceMessage.h
@@ -93,7 +93,7 @@ private:
   typedef SharedHandle<BtCancelSendingPieceEventListener> BtCancelSendingPieceEventListenerHandle;
 public:
   BtPieceMessage(size_t index = 0, uint32_t begin = 0, size_t blockLength = 0)
-    :AbstractBtMessage(ID),
+    :AbstractBtMessage(ID, NAME),
      index(index),
      begin(begin),
      blockLength(blockLength),
@@ -118,6 +118,8 @@ public:
 
   static const uint8_t ID = 7;
 
+  static const std::string NAME;
+
   size_t getIndex() const { return index; }
 
   void setIndex(size_t index) { this->index = index; }
diff --git a/src/BtPortMessage.cc b/src/BtPortMessage.cc
index f4d3c6b3..4367ee6a 100644
--- a/src/BtPortMessage.cc
+++ b/src/BtPortMessage.cc
@@ -48,8 +48,10 @@
 
 namespace aria2 {
 
+const std::string BtPortMessage::NAME("port");
+
 BtPortMessage::BtPortMessage(uint16_t port):
-  SimpleBtMessage(ID), _port(port), _msg(0) {}
+  SimpleBtMessage(ID, NAME), _port(port), _msg(0) {}
 
 BtPortMessage::~BtPortMessage()
 {
@@ -58,15 +60,8 @@ BtPortMessage::~BtPortMessage()
 
 SharedHandle<BtPortMessage> BtPortMessage::create(const unsigned char* data, size_t dataLength)
 {
-  if(dataLength != 3) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "port", dataLength, 3).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "piece", ID).str());
-  }
+  PeerMessageUtil::assertPayloadLengthEqual(3, dataLength, NAME);
+  PeerMessageUtil::assertID(ID, data, NAME);
   uint16_t port = PeerMessageUtil::getShortIntParam(data, 1);
   SharedHandle<BtPortMessage> message(new BtPortMessage(port));
   return message;
@@ -114,7 +109,7 @@ size_t BtPortMessage::getMessageLength() {
 }
 
 std::string BtPortMessage::toString() const {
-  return "port port="+Util::uitos(_port);
+  return NAME+" port="+Util::uitos(_port);
 }
 
 void BtPortMessage::setLocalNode(const WeakHandle<DHTNode>& localNode)
diff --git a/src/BtPortMessage.h b/src/BtPortMessage.h
index 47fabaeb..45c8e22d 100644
--- a/src/BtPortMessage.h
+++ b/src/BtPortMessage.h
@@ -64,6 +64,8 @@ public:
 
   static const uint8_t ID = 9;
 
+  static const std::string NAME;
+
   uint16_t getPort() const { return _port; }
 
   static SharedHandle<BtPortMessage> create(const unsigned char* data, size_t dataLength);
diff --git a/src/BtRejectMessage.cc b/src/BtRejectMessage.cc
index 51f796a9..fce49979 100644
--- a/src/BtRejectMessage.cc
+++ b/src/BtRejectMessage.cc
@@ -33,10 +33,7 @@
  */
 /* copyright --> */
 #include "BtRejectMessage.h"
-#include "PeerMessageUtil.h"
-#include "Util.h"
 #include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
 #include "RequestSlot.h"
 #include "BtMessageDispatcher.h"
@@ -44,24 +41,16 @@
 
 namespace aria2 {
 
-BtRejectMessageHandle BtRejectMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 13) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "reject", dataLength, 13).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "reject", ID).str());
-  }
-  BtRejectMessageHandle message(new BtRejectMessage());
-  message->setIndex(PeerMessageUtil::getIntParam(data, 1));
-  message->setBegin(PeerMessageUtil::getIntParam(data, 5));
-  message->setLength(PeerMessageUtil::getIntParam(data, 9));
-  return message;
+const std::string BtRejectMessage::NAME("reject");
+
+SharedHandle<BtRejectMessage> BtRejectMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return RangeBtMessage::create<BtRejectMessage>(data, dataLength);
 }
 
-void BtRejectMessage::doReceivedAction() {
+void BtRejectMessage::doReceivedAction()
+{
   if(!peer->isFastExtensionEnabled()) {
     throw DlAbortEx
       (StringFormat("%s received while fast extension is disabled.",
@@ -69,7 +58,8 @@ void BtRejectMessage::doReceivedAction() {
   }
   // TODO Current implementation does not close a connection even if
   // a request for this reject message has never sent.
-  RequestSlot slot = dispatcher->getOutstandingRequest(index, begin, length);
+  RequestSlot slot =
+    dispatcher->getOutstandingRequest(getIndex(), getBegin(), getLength());
   if(RequestSlot::isNull(slot)) {
     //throw DlAbortEx("reject recieved, but it is not in the request slots.");
   } else {
@@ -78,32 +68,4 @@ void BtRejectMessage::doReceivedAction() {
 
 }
 
-const unsigned char* BtRejectMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 13, 4bytes
-     * id --- 16, 1byte
-     * index --- index, 4bytes
-     * begin --- begin, 4bytes
-     * length -- length, 4bytes
-     * total: 17bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 13, ID);
-    PeerMessageUtil::setIntParam(&msg[5], index);
-    PeerMessageUtil::setIntParam(&msg[9], begin);
-    PeerMessageUtil::setIntParam(&msg[13], length);
-  }
-  return msg;
-}
-
-size_t BtRejectMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtRejectMessage::toString() const {
-  return "reject index="+Util::uitos(index)+", begin="+Util::uitos(begin)+
-    ", length="+Util::uitos(length);
-}
-
 } // namespace aria2
diff --git a/src/BtRejectMessage.h b/src/BtRejectMessage.h
index 50b98ed0..222a18d1 100644
--- a/src/BtRejectMessage.h
+++ b/src/BtRejectMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_REJECT_MESSAGE_H_
 #define _D_BT_REJECT_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "RangeBtMessage.h"
 
 namespace aria2 {
 
@@ -43,45 +43,19 @@ class BtRejectMessage;
 
 typedef SharedHandle<BtRejectMessage> BtRejectMessageHandle;
 
-class BtRejectMessage : public SimpleBtMessage {
-private:
-  size_t index;
-  uint32_t begin;
-  size_t length;
-  unsigned char* msg;
-  static const size_t MESSAGE_LENGTH = 17;
+class BtRejectMessage : public RangeBtMessage {
 public:
   BtRejectMessage(size_t index = 0, uint32_t begin = 0, size_t length = 0)
-    :SimpleBtMessage(ID),
-     index(index),
-     begin(begin),
-     length(length),
-     msg(0) {}
-
-  virtual ~BtRejectMessage() {
-    delete [] msg;
-  }
+    :RangeBtMessage(ID, NAME, index, begin, length) {}
 
   static const uint8_t ID = 16;
 
-  size_t getIndex() const { return index; }
-  void setIndex(size_t index) { this->index = index; }
+  static const std::string NAME;
 
-  uint32_t getBegin() const { return begin; }
-  void setBegin(uint32_t begin) { this->begin = begin; }
-
-  size_t getLength() const { return length; }
-  void setLength(size_t length) { this->length = length; }
-
-  static BtRejectMessageHandle create(const unsigned char* data, size_t dataLength);
+  static SharedHandle<BtRejectMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
-
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
 };
 
 } // namespace aria2
diff --git a/src/BtRequestMessage.cc b/src/BtRequestMessage.cc
index c6b188db..44b504a5 100644
--- a/src/BtRequestMessage.cc
+++ b/src/BtRequestMessage.cc
@@ -33,101 +33,70 @@
  */
 /* copyright --> */
 #include "BtRequestMessage.h"
-#include "PeerMessageUtil.h"
-#include "Util.h"
-#include "DlAbortEx.h"
 #include "BtAbortOutstandingRequestEvent.h"
-#include "message.h"
 #include "Peer.h"
 #include "Piece.h"
-#include "BtContext.h"
 #include "PieceStorage.h"
 #include "BtMessageDispatcher.h"
 #include "BtMessageFactory.h"
-#include "StringFormat.h"
 
 namespace aria2 {
 
-BtRequestMessageHandle BtRequestMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 13) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "request", dataLength, 13).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "request", ID).str());
-  }
-  BtRequestMessageHandle message(new BtRequestMessage());
-  message->setIndex(PeerMessageUtil::getIntParam(data, 1));
-  message->setBegin(PeerMessageUtil::getIntParam(data, 5));
-  message->setLength(PeerMessageUtil::getIntParam(data, 9));
-  return message;
+const std::string BtRequestMessage::NAME("request");
+
+SharedHandle<BtRequestMessage> BtRequestMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return RangeBtMessage::create<BtRequestMessage>(data, dataLength);
 }
 
-void BtRequestMessage::doReceivedAction() {
-  if(pieceStorage->hasPiece(index) &&
+void BtRequestMessage::doReceivedAction()
+{
+  if(pieceStorage->hasPiece(getIndex()) &&
      (!peer->amChoking() ||
-      (peer->amChoking() && peer->isInAmAllowedIndexSet(index)))) {
-    BtMessageHandle msg = messageFactory->createPieceMessage(index,
-							     begin,
-							     length);
+      (peer->amChoking() && peer->isInAmAllowedIndexSet(getIndex())))) {
+    BtMessageHandle msg = messageFactory->createPieceMessage(getIndex(),
+							     getBegin(),
+							     getLength());
     dispatcher->addMessageToQueue(msg);
   } else {
     if(peer->isFastExtensionEnabled()) {
-      BtMessageHandle msg = messageFactory->createRejectMessage(index,
-								begin,
-								length);
+      BtMessageHandle msg = messageFactory->createRejectMessage(getIndex(),
+								getBegin(),
+								getLength());
       dispatcher->addMessageToQueue(msg);
     }
   }
 }
 
-const unsigned char* BtRequestMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 13, 4bytes
-     * id --- 6, 1byte
-     * index --- index, 4bytes
-     * begin --- begin, 4bytes
-     * length --- length, 4bytes
-     * total: 17bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 13, ID);
-    PeerMessageUtil::setIntParam(&msg[5], index);
-    PeerMessageUtil::setIntParam(&msg[9], begin);
-    PeerMessageUtil::setIntParam(&msg[13], length);
-  }
-  return msg;
-}
-
-size_t BtRequestMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtRequestMessage::toString() const {
-  return "request index="+Util::uitos(index)+", begin="+Util::uitos(begin)+
-    ", length="+Util::uitos(length);
-}
-
-void BtRequestMessage::onQueued() {
-  RequestSlot requestSlot(index, begin, length, blockIndex, pieceStorage->getPiece(index));
+void BtRequestMessage::onQueued()
+{
+  RequestSlot requestSlot(getIndex(), getBegin(), getLength(), _blockIndex,
+			  pieceStorage->getPiece(getIndex()));
   dispatcher->addOutstandingRequest(requestSlot);
 }
 
-bool BtRequestMessage::BtAbortOutstandingRequestEventListener::canHandle(const BtEventHandle& event) {
-  BtAbortOutstandingRequestEvent* intEvent = dynamic_cast<BtAbortOutstandingRequestEvent*>(event.get());
+bool BtRequestMessage::
+BtAbortOutstandingRequestEventListener::canHandle(const BtEventHandle& event)
+{
+  BtAbortOutstandingRequestEvent* intEvent =
+    dynamic_cast<BtAbortOutstandingRequestEvent*>(event.get());
   return intEvent != 0;
 }
 
-void BtRequestMessage::BtAbortOutstandingRequestEventListener::handleEventInternal(const BtEventHandle& event) {
+void BtRequestMessage::
+BtAbortOutstandingRequestEventListener::handleEventInternal
+(const BtEventHandle& event)
+{
   message->handleAbortOutstandingRequestEvent(event);
 }
 
-void BtRequestMessage::handleAbortOutstandingRequestEvent(const BtEventHandle& event) {
-  BtAbortOutstandingRequestEvent* intEvent = (BtAbortOutstandingRequestEvent*)event.get();
-  if(index == intEvent->getPiece()->getIndex() &&
+void BtRequestMessage::
+handleAbortOutstandingRequestEvent(const BtEventHandle& event)
+{
+  BtAbortOutstandingRequestEvent* intEvent =
+    (BtAbortOutstandingRequestEvent*)event.get();
+  if(getIndex() == intEvent->getPiece()->getIndex() &&
      !invalidate &&
      !sendingInProgress) {
     invalidate = true;
diff --git a/src/BtRequestMessage.h b/src/BtRequestMessage.h
index 97d66ca3..e7a8d10a 100644
--- a/src/BtRequestMessage.h
+++ b/src/BtRequestMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_REQUEST_MESSAGE_H_
 #define _D_BT_REQUEST_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "RangeBtMessage.h"
 #include "AbstractBtEventListener.h"
 
 namespace aria2 {
@@ -44,75 +44,53 @@ class BtRequestMessage;
 
 typedef SharedHandle<BtRequestMessage> BtRequestMessageHandle;
 
-class BtRequestMessage : public SimpleBtMessage {
+class BtRequestMessage : public RangeBtMessage {
 private:
-  size_t index;
-  uint32_t begin;
-  uint32_t length;
-  size_t blockIndex;
-  unsigned char* msg;
+  size_t _blockIndex;
 
-  static const size_t MESSAGE_LENGTH = 17;
-
-  class BtAbortOutstandingRequestEventListener : public AbstractBtEventListener {
+  class BtAbortOutstandingRequestEventListener:public AbstractBtEventListener {
   private:
     BtRequestMessage* message;
   public:
-    BtAbortOutstandingRequestEventListener(BtRequestMessage* message):message(message) {}
+    BtAbortOutstandingRequestEventListener(BtRequestMessage* message):
+      message(message) {}
 
     virtual bool canHandle(const SharedHandle<BtEvent>& event);
 
     virtual void handleEventInternal(const SharedHandle<BtEvent>& event);
   };
 
-  typedef SharedHandle<BtAbortOutstandingRequestEventListener> BtAbortOutstandingRequestEventListenerHandle;
+  typedef SharedHandle<BtAbortOutstandingRequestEventListener>
+  BtAbortOutstandingRequestEventListenerHandle;
 public:
   BtRequestMessage(size_t index = 0,
 		   uint32_t begin = 0,
 		   uint32_t length = 0,
 		   size_t blockIndex = 0)
-    :SimpleBtMessage(ID),
-     index(index),
-     begin(begin),
-     length(length),
-     blockIndex(blockIndex),
-     msg(0)
+    :RangeBtMessage(ID, NAME, index, begin, length),
+     _blockIndex(blockIndex)
   {
-    SharedHandle<BtEventListener> listener(new BtAbortOutstandingRequestEventListener(this));
+    SharedHandle<BtEventListener> listener
+      (new BtAbortOutstandingRequestEventListener(this));
     addEventListener(listener);
   }
 
-  virtual ~BtRequestMessage() {
-    delete [] msg;
-  }
-
   static const uint8_t ID = 6;
 
-  size_t getIndex() const { return index; }
-  void setIndex(size_t index) { this->index = index; }
+  static const std::string NAME;
 
-  uint32_t getBegin() const { return begin; }
-  void setBegin(uint32_t begin) { this->begin = begin; }
+  size_t getBlockIndex() const { return _blockIndex; }
+  void setBlockIndex(size_t blockIndex) { _blockIndex = blockIndex; }
 
-  uint32_t getLength() const { return length; }
-  void setLength(uint32_t length) { this->length = length; }
-
-  size_t getBlockIndex() const { return blockIndex; }
-  void setBlockIndex(size_t blockIndex) { this->blockIndex = blockIndex; }
-
-  static BtRequestMessageHandle create(const unsigned char* data, size_t dataLength);
+  static SharedHandle<BtRequestMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
 
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
-
   virtual void onQueued();
 
-  virtual void handleAbortOutstandingRequestEvent(const SharedHandle<BtEvent>& event);
+  virtual void handleAbortOutstandingRequestEvent
+  (const SharedHandle<BtEvent>& event);
 };
 
 } // namespace aria2
diff --git a/src/BtRequestMessageValidator.h b/src/BtRequestMessageValidator.h
deleted file mode 100644
index f01b037a..00000000
--- a/src/BtRequestMessageValidator.h
+++ /dev/null
@@ -1,73 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#ifndef _D_BT_REQUEST_MESSAGE_VALIDATOR_H_
-#define _D_BT_REQUEST_MESSAGE_VALIDATOR_H_
-
-#include "BtMessageValidator.h"
-#include "BtRequestMessage.h"
-#include "PeerMessageUtil.h"
-
-namespace aria2 {
-
-class BtRequestMessageValidator : public BtMessageValidator {
-private:
-  const BtRequestMessage* message;
-  size_t numPiece;
-  size_t pieceLength;
-public:
-  BtRequestMessageValidator(const BtRequestMessage* message,
-			   size_t numPiece,
-			   size_t pieceLength):
-    message(message),
-    numPiece(numPiece),
-    pieceLength(pieceLength) {}
-
-  virtual bool validate(Errors& error) {
-    // TODO
-    PeerMessageUtil::checkIndex(message->getIndex(), numPiece);
-    PeerMessageUtil::checkBegin(message->getBegin(), pieceLength);
-    PeerMessageUtil::checkLength(message->getLength());
-    PeerMessageUtil::checkRange(message->getBegin(),
-				message->getLength(),
-				pieceLength);
-    return true;
-  }
-};
-
-typedef SharedHandle<BtRequestMessageValidator> BtRequestMessageValidatorHandle;
-
-} // namespace aria2
-
-#endif // _D_BT_REQUEST_MESSAGE_VALIDATOR_H_
diff --git a/src/BtSuggestPieceMessage.cc b/src/BtSuggestPieceMessage.cc
index e946504d..4e9cedb8 100644
--- a/src/BtSuggestPieceMessage.cc
+++ b/src/BtSuggestPieceMessage.cc
@@ -33,50 +33,15 @@
  */
 /* copyright --> */
 #include "BtSuggestPieceMessage.h"
-#include "PeerMessageUtil.h"
-#include "Util.h"
-#include "DlAbortEx.h"
-#include "message.h"
-#include "StringFormat.h"
 
 namespace aria2 {
 
-BtSuggestPieceMessageHandle BtSuggestPieceMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 5) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "suggest piece", dataLength, 5).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "suggest piece", ID).str());
-  }
-  BtSuggestPieceMessageHandle message(new BtSuggestPieceMessage());
-  message->setIndex(PeerMessageUtil::getIntParam(data, 1));
-  return message;
-}
+const std::string BtSuggestPieceMessage::NAME("suggest piece");
 
-const unsigned char* BtSuggestPieceMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 5, 4bytes
-     * id --- 13, 1byte
-     * piece index --- index, 4bytes
-     * total: 9bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 5, ID);
-    PeerMessageUtil::setIntParam(&msg[5], index);
-  }
-  return msg;
-}
-
-size_t BtSuggestPieceMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
-std::string BtSuggestPieceMessage::toString() const {
-  return "suggest piece index="+Util::itos(index);
+SharedHandle<BtSuggestPieceMessage> BtSuggestPieceMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return IndexBtMessage::create<BtSuggestPieceMessage>(data, dataLength);
 }
 
 } // namespace aria2
diff --git a/src/BtSuggestPieceMessage.h b/src/BtSuggestPieceMessage.h
index b12662ca..820be287 100644
--- a/src/BtSuggestPieceMessage.h
+++ b/src/BtSuggestPieceMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_SUGGEST_PIECE_MESSAGE_H_
 #define _D_BT_SUGGEST_PIECE_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "IndexBtMessage.h"
 
 namespace aria2 {
 
@@ -43,37 +43,20 @@ class BtSuggestPieceMessage;
 
 typedef SharedHandle<BtSuggestPieceMessage> BtSuggestPieceMessageHandle;
 
-class BtSuggestPieceMessage : public SimpleBtMessage {
-private:
-  size_t index;
-  unsigned char* msg;
-  static const size_t MESSAGE_LENGTH = 9;
+class BtSuggestPieceMessage : public IndexBtMessage {
 public:
-  BtSuggestPieceMessage():SimpleBtMessage(ID), index(0), msg(0) {}
-
-  virtual ~BtSuggestPieceMessage() {
-    delete [] msg;
-  }
+  BtSuggestPieceMessage():IndexBtMessage(ID, NAME, 0) {}
 
   static const uint8_t ID = 13;
 
-  void setIndex(size_t index) {
-    this->index = index;
-  }
+  static const std::string NAME;
 
-  size_t getIndex() const { return index; }
-
-  static BtSuggestPieceMessageHandle create(const unsigned char* data, size_t dataLength);
+  static SharedHandle<BtSuggestPieceMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction() {
     // TODO Current implementation ignores this message.
   }
-
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
 };
 
 } // namespace aria2
diff --git a/src/BtUnchokeMessage.cc b/src/BtUnchokeMessage.cc
index 92b73db2..65b419a0 100644
--- a/src/BtUnchokeMessage.cc
+++ b/src/BtUnchokeMessage.cc
@@ -33,60 +33,30 @@
  */
 /* copyright --> */
 #include "BtUnchokeMessage.h"
-#include "PeerMessageUtil.h"
-#include "DlAbortEx.h"
-#include "message.h"
 #include "Peer.h"
-#include "StringFormat.h"
 
 namespace aria2 {
 
-BtUnchokeMessageHandle BtUnchokeMessage::create(const unsigned char* data, size_t dataLength) {
-  if(dataLength != 1) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_PAYLOAD_SIZE, "unchoke", dataLength, 1).str());
-  }
-  uint8_t id = PeerMessageUtil::getId(data);
-  if(id != ID) {
-    throw DlAbortEx
-      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, "unchoke", ID).str());
-  }
-  BtUnchokeMessageHandle message(new BtUnchokeMessage());
-  return message;
+const std::string BtUnchokeMessage::NAME("unchoke");
+
+SharedHandle<BtUnchokeMessage> BtUnchokeMessage::create
+(const unsigned char* data, size_t dataLength)
+{
+  return ZeroBtMessage::create<BtUnchokeMessage>(data, dataLength);
 }
 
-void BtUnchokeMessage::doReceivedAction() {
+void BtUnchokeMessage::doReceivedAction()
+{
   peer->peerChoking(false);
 }
 
-bool BtUnchokeMessage::sendPredicate() const {
+bool BtUnchokeMessage::sendPredicate() const
+{
   return peer->amChoking();
 }
 
-const unsigned char* BtUnchokeMessage::getMessage() {
-  if(!msg) {
-    /**
-     * len --- 1, 4bytes
-     * id --- 1, 1byte
-     * total: 5bytes
-     */
-    msg = new unsigned char[MESSAGE_LENGTH];
-    PeerMessageUtil::createPeerMessageString(msg, MESSAGE_LENGTH, 1, ID);
-  }
-  return msg;
-}
-
-size_t BtUnchokeMessage::getMessageLength() {
-  return MESSAGE_LENGTH;
-}
-
 void BtUnchokeMessage::onSendComplete() {
   peer->amChoking(false);
 }
 
-std::string BtUnchokeMessage::toString() const {
-  static const std::string UNCHOKE("unchoke");
-  return UNCHOKE;
-}
-
 } // namespace aria2
diff --git a/src/BtUnchokeMessage.h b/src/BtUnchokeMessage.h
index d318ba15..0691017f 100644
--- a/src/BtUnchokeMessage.h
+++ b/src/BtUnchokeMessage.h
@@ -35,7 +35,7 @@
 #ifndef _D_BT_UNCHOKE_MESSAGE_H_
 #define _D_BT_UNCHOKE_MESSAGE_H_
 
-#include "SimpleBtMessage.h"
+#include "ZeroBtMessage.h"
 
 namespace aria2 {
 
@@ -43,29 +43,22 @@ class BtUnchokeMessage;
 
 typedef SharedHandle<BtUnchokeMessage> BtUnchokeMessageHandle;
 
-class BtUnchokeMessage : public SimpleBtMessage {
+class BtUnchokeMessage : public ZeroBtMessage {
 private:
   unsigned char* msg;
   static const size_t MESSAGE_LENGTH = 5;
 public:
-  BtUnchokeMessage():SimpleBtMessage(ID), msg(0) {}
-
-  virtual ~BtUnchokeMessage() {
-    delete [] msg;
-  }
+  BtUnchokeMessage():ZeroBtMessage(ID, NAME) {}
 
   static const uint8_t ID = 1;
 
-  static BtUnchokeMessageHandle create(const unsigned char* data, size_t dataLength);
+  static const std::string NAME;
+
+  static SharedHandle<BtUnchokeMessage> create
+  (const unsigned char* data, size_t dataLength);
 
   virtual void doReceivedAction();
 
-  virtual const unsigned char* getMessage();
-
-  virtual size_t getMessageLength();
-
-  virtual std::string toString() const;
-
   virtual bool sendPredicate() const;
 
   virtual void onSendComplete();
diff --git a/src/DefaultBtMessageFactory.cc b/src/DefaultBtMessageFactory.cc
index e480ecad..55a4a97c 100644
--- a/src/DefaultBtMessageFactory.cc
+++ b/src/DefaultBtMessageFactory.cc
@@ -41,24 +41,20 @@
 #include "BtInterestedMessage.h"
 #include "BtNotInterestedMessage.h"
 #include "BtHaveMessage.h"
-#include "BtHaveMessageValidator.h"
 #include "BtBitfieldMessage.h"
 #include "BtBitfieldMessageValidator.h"
+#include "RangeBtMessageValidator.h"
+#include "IndexBtMessageValidator.h"
 #include "BtRequestMessage.h"
-#include "BtRequestMessageValidator.h"
 #include "BtCancelMessage.h"
-#include "BtCancelMessageValidator.h"
 #include "BtPieceMessage.h"
 #include "BtPieceMessageValidator.h"
 #include "BtPortMessage.h"
 #include "BtHaveAllMessage.h"
 #include "BtHaveNoneMessage.h"
 #include "BtRejectMessage.h"
-#include "BtRejectMessageValidator.h"
 #include "BtSuggestPieceMessage.h"
-#include "BtSuggestPieceMessageValidator.h"
 #include "BtAllowedFastMessage.h"
-#include "BtAllowedFastMessageValidator.h"
 #include "BtHandshakeMessage.h"
 #include "BtHandshakeMessageValidator.h"
 #include "BtExtendedMessage.h"
@@ -115,8 +111,8 @@ DefaultBtMessageFactory::createBtMessage(const unsigned char* data, size_t dataL
       msg = BtHaveMessage::create(data, dataLength);
       {
 	SharedHandle<BtMessageValidator> v
-	  (new BtHaveMessageValidator((BtHaveMessage*)msg.get(),
-				      btContext->getNumPieces()));
+	  (new IndexBtMessageValidator((BtHaveMessage*)msg.get(),
+				       btContext->getNumPieces()));
 	msg->setBtMessageValidator(v);
       }
       break;
@@ -131,20 +127,22 @@ DefaultBtMessageFactory::createBtMessage(const unsigned char* data, size_t dataL
       break;
     case BtRequestMessage::ID: {
       BtRequestMessageHandle temp = BtRequestMessage::create(data, dataLength);
-      BtMessageValidatorHandle validator
-	(new BtRequestMessageValidator(temp.get(),
-				      btContext->getNumPieces(),
-				       _pieceStorage->getPieceLength(temp->getIndex())));
+      SharedHandle<BtMessageValidator> validator
+	(new RangeBtMessageValidator
+	 (temp.get(),
+	  btContext->getNumPieces(),
+	  _pieceStorage->getPieceLength(temp->getIndex())));
       temp->setBtMessageValidator(validator);
       msg = temp;
       break;
     }
     case BtCancelMessage::ID: {
       BtCancelMessageHandle temp = BtCancelMessage::create(data, dataLength);
-      BtMessageValidatorHandle validator
-	(new BtCancelMessageValidator(temp.get(),
-				     btContext->getNumPieces(),
-				      _pieceStorage->getPieceLength(temp->getIndex())));
+      SharedHandle<BtMessageValidator> validator
+	(new RangeBtMessageValidator
+	 (temp.get(),
+	  btContext->getNumPieces(),
+	  _pieceStorage->getPieceLength(temp->getIndex())));
       temp->setBtMessageValidator(validator);
       msg = temp;
       break;
@@ -167,28 +165,27 @@ DefaultBtMessageFactory::createBtMessage(const unsigned char* data, size_t dataL
       break;
     case BtRejectMessage::ID: {
       BtRejectMessageHandle temp = BtRejectMessage::create(data, dataLength);
-      BtMessageValidatorHandle validator
-	(new BtRejectMessageValidator(temp.get(),
-				      btContext->getNumPieces(),
-				      _pieceStorage->getPieceLength(temp->getIndex())));
+      SharedHandle<BtMessageValidator> validator
+	(new RangeBtMessageValidator
+	 (temp.get(),
+	  btContext->getNumPieces(),
+	  _pieceStorage->getPieceLength(temp->getIndex())));
       temp->setBtMessageValidator(validator);
       msg = temp;
       break;
     }
     case BtSuggestPieceMessage::ID: {
       BtSuggestPieceMessageHandle temp = BtSuggestPieceMessage::create(data, dataLength);
-      BtMessageValidatorHandle validator
-	(new BtSuggestPieceMessageValidator(temp.get(),
-					    btContext->getNumPieces()));
+      SharedHandle<BtMessageValidator> validator
+	(new IndexBtMessageValidator(temp.get(), btContext->getNumPieces()));
       temp->setBtMessageValidator(validator);
       msg = temp;
       break;
     }
     case BtAllowedFastMessage::ID: {
       BtAllowedFastMessageHandle temp = BtAllowedFastMessage::create(data, dataLength);
-      BtMessageValidatorHandle validator
-	(new BtAllowedFastMessageValidator(temp.get(),
-					  btContext->getNumPieces()));
+      SharedHandle<BtMessageValidator> validator
+	(new IndexBtMessageValidator(temp.get(), btContext->getNumPieces()));
       temp->setBtMessageValidator(validator);
       msg = temp;
       break;
@@ -264,10 +261,11 @@ DefaultBtMessageFactory::createRequestMessage(const PieceHandle& piece, size_t b
 			  blockIndex*piece->getBlockLength(),
 			  piece->getBlockLength(blockIndex),
 			  blockIndex));
-  BtMessageValidatorHandle validator
-    (new BtRequestMessageValidator(msg.get(),
-				   btContext->getNumPieces(),
-				   _pieceStorage->getPieceLength(msg->getIndex())));
+  SharedHandle<BtMessageValidator> validator
+    (new RangeBtMessageValidator
+     (msg.get(),
+      btContext->getNumPieces(),
+      _pieceStorage->getPieceLength(msg->getIndex())));
   msg->setBtMessageValidator(validator);
   setCommonProperty(msg);
   return msg;
@@ -277,10 +275,11 @@ BtMessageHandle
 DefaultBtMessageFactory::createCancelMessage(size_t index, uint32_t begin, size_t length)
 {
   BtCancelMessageHandle msg(new BtCancelMessage(index, begin, length));
-  BtMessageValidatorHandle validator
-    (new BtCancelMessageValidator(msg.get(),
-				  btContext->getNumPieces(),
-				  _pieceStorage->getPieceLength(index)));
+  SharedHandle<BtMessageValidator> validator
+    (new RangeBtMessageValidator
+     (msg.get(),
+      btContext->getNumPieces(),
+      _pieceStorage->getPieceLength(index)));
   msg->setBtMessageValidator(validator);
   setCommonProperty(msg);
   return msg;
@@ -304,8 +303,7 @@ DefaultBtMessageFactory::createHaveMessage(size_t index)
 {
   BtHaveMessageHandle msg(new BtHaveMessage(index));
   SharedHandle<BtMessageValidator> v
-    (new BtHaveMessageValidator(msg.get(),
-				btContext->getNumPieces()));
+    (new IndexBtMessageValidator(msg.get(), btContext->getNumPieces()));
   msg->setBtMessageValidator(v);
   setCommonProperty(msg);
   return msg;
@@ -385,10 +383,11 @@ BtMessageHandle
 DefaultBtMessageFactory::createRejectMessage(size_t index, uint32_t begin, size_t length)
 {
   BtRejectMessageHandle msg(new BtRejectMessage(index, begin, length));
-  BtMessageValidatorHandle validator
-    (new BtRejectMessageValidator(msg.get(),
-				  btContext->getNumPieces(),
-				  _pieceStorage->getPieceLength(index)));
+  SharedHandle<BtMessageValidator> validator
+    (new RangeBtMessageValidator
+     (msg.get(),
+      btContext->getNumPieces(),
+      _pieceStorage->getPieceLength(index)));
   msg->setBtMessageValidator(validator);
   setCommonProperty(msg);
   return msg;
@@ -398,9 +397,8 @@ BtMessageHandle
 DefaultBtMessageFactory::createAllowedFastMessage(size_t index)
 {
   BtAllowedFastMessageHandle msg(new BtAllowedFastMessage(index));
-  BtMessageValidatorHandle validator
-    (new BtAllowedFastMessageValidator(msg.get(),
-				       btContext->getNumPieces()));
+  SharedHandle<BtMessageValidator> validator
+    (new IndexBtMessageValidator(msg.get(), btContext->getNumPieces()));
   msg->setBtMessageValidator(validator);
   setCommonProperty(msg);
   return msg;
diff --git a/src/BtAllowedFastMessageValidator.h b/src/IndexBtMessage.cc
similarity index 67%
rename from src/BtAllowedFastMessageValidator.h
rename to src/IndexBtMessage.cc
index a298ae1f..3c4fce4e 100644
--- a/src/BtAllowedFastMessageValidator.h
+++ b/src/IndexBtMessage.cc
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -32,34 +32,35 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef _D_BT_ALLOWED_FAST_MESSAGE_VALIDATOR_H_
-#define _D_BT_ALLOWED_FAST_MESSAGE_VALIDATOR_H_
-
-#include "BtMessageValidator.h"
-#include "BtAllowedFastMessage.h"
-#include "PeerMessageUtil.h"
+#include "IndexBtMessage.h"
+#include "Util.h"
 
 namespace aria2 {
 
-class BtAllowedFastMessageValidator : public BtMessageValidator {
-private:
-  const BtAllowedFastMessage* message;
-  size_t numPiece;
-public:
-  BtAllowedFastMessageValidator(const BtAllowedFastMessage* message,
-				size_t numPiece):
-    message(message),
-    numPiece(numPiece) {}
-
-  virtual bool validate(Errors& error) {
-    // TODO
-    PeerMessageUtil::checkIndex(message->getIndex(), numPiece);
-    return true;
+const unsigned char* IndexBtMessage::getMessage()
+{
+  if(!_msg) {
+    /**
+     * len --- 5, 4bytes
+     * id --- ?, 1byte
+     * piece index --- index, 4bytes
+     * total: 9bytes
+     */
+    _msg = new unsigned char[MESSAGE_LENGTH];
+    PeerMessageUtil::createPeerMessageString(_msg, MESSAGE_LENGTH, 5, getId());
+    PeerMessageUtil::setIntParam(&_msg[5], _index);
   }
-};
+  return _msg;
+}
 
-typedef SharedHandle<BtAllowedFastMessageValidator> BtAllowedFastMessageValidatorHandle;
+size_t IndexBtMessage::getMessageLength()
+{
+  return MESSAGE_LENGTH;
+}
+
+std::string IndexBtMessage::toString() const
+{
+  return getName()+" index="+Util::itos(_index);
+}
 
 } // namespace aria2
-
-#endif // _D_BT_ALLOWED_FAST_MESSAGE_VALIDATOR_H_
diff --git a/src/BtRejectMessageValidator.h b/src/IndexBtMessage.h
similarity index 60%
rename from src/BtRejectMessageValidator.h
rename to src/IndexBtMessage.h
index a0d5071c..3230baf2 100644
--- a/src/BtRejectMessageValidator.h
+++ b/src/IndexBtMessage.h
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -32,42 +32,52 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef _D_BT_REJECT_MESSAGE_VALIDATOR_H_
-#define _D_BT_REJECT_MESSAGE_VALIDATOR_H_
+#ifndef _D_INDEX_BT_MESSAGE_H_
+#define _D_INDEX_BT_MESSAGE_H_
 
-#include "BtMessageValidator.h"
-#include "BtRejectMessage.h"
+#include "SimpleBtMessage.h"
 #include "PeerMessageUtil.h"
 
 namespace aria2 {
 
-class BtRejectMessageValidator : public BtMessageValidator {
+class IndexBtMessage : public SimpleBtMessage {
 private:
-  const BtRejectMessage* message;
-  size_t numPiece;
-  size_t pieceLength;
-public:
-  BtRejectMessageValidator(const BtRejectMessage* message,
-			   size_t numPiece,
-			   size_t pieceLength):
-    message(message),
-    numPiece(numPiece),
-    pieceLength(pieceLength) {}
+  size_t _index;
+  unsigned char* _msg;
 
-  virtual bool validate(Errors& error) {
-    // TODO
-    PeerMessageUtil::checkIndex(message->getIndex(), numPiece);
-    PeerMessageUtil::checkBegin(message->getBegin(), pieceLength);
-    PeerMessageUtil::checkLength(message->getLength());
-    PeerMessageUtil::checkRange(message->getBegin(),
-				message->getLength(),
-				pieceLength);
-    return true;
+  static const size_t MESSAGE_LENGTH = 9;
+protected:
+  template<typename T>
+  static SharedHandle<T> create(const unsigned char* data, size_t dataLength)
+  {
+    PeerMessageUtil::assertPayloadLengthEqual(5, dataLength, T::NAME);
+    PeerMessageUtil::assertID(T::ID, data, T::NAME);
+    SharedHandle<T> message(new T());
+    message->setIndex(PeerMessageUtil::getIntParam(data, 1));
+    return message;
   }
-};
+public:
+  IndexBtMessage(uint8_t id, const std::string& name, size_t index)
+    :SimpleBtMessage(id, name),
+     _index(index),
+     _msg(0) {}
 
-typedef SharedHandle<BtRejectMessageValidator> BtRejectMessageValidatorHandle;
+  virtual ~IndexBtMessage()
+  {
+    delete [] _msg;
+  }
+
+  void setIndex(size_t index) { _index = index; }
+
+  size_t getIndex() const { return _index; }
+
+  virtual const unsigned char* getMessage();
+
+  virtual size_t getMessageLength();
+
+  virtual std::string toString() const;
+};
 
 } // namespace aria2
 
-#endif // _D_BT_REJECT_MESSAGE_VALIDATOR_H_
+#endif // _D_INDEX_BT_MESSAGE_H_
diff --git a/src/BtHaveMessageValidator.h b/src/IndexBtMessageValidator.h
similarity index 76%
rename from src/BtHaveMessageValidator.h
rename to src/IndexBtMessageValidator.h
index 1fed369c..17bf4fd3 100644
--- a/src/BtHaveMessageValidator.h
+++ b/src/IndexBtMessageValidator.h
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -32,28 +32,29 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef _D_BT_HAVE_MESSAGE_VALIDATOR_H_
-#define _D_BT_HAVE_MESSAGE_VALIDATOR_H_
+#ifndef _D_INDEX_BT_VALIDATOR_H_
+#define _D_INDEX_BT_VALIDATOR_H_
 
 #include "BtMessageValidator.h"
-#include "BtHaveMessage.h"
+#include "IndexBtMessage.h"
 #include "PeerMessageUtil.h"
 
 namespace aria2 {
 
-class BtHaveMessageValidator : public BtMessageValidator {
+class IndexBtMessageValidator : public BtMessageValidator {
 private:
-  const BtHaveMessage* message;
-  size_t numPiece;
+  const IndexBtMessage* _message;
+  size_t _numPiece;
 public:
-  BtHaveMessageValidator(const BtHaveMessage* message,
-			 size_t numPiece):
-    message(message),
-    numPiece(numPiece) {}
+  IndexBtMessageValidator(const IndexBtMessage* message,
+			  size_t numPiece):
+    _message(message),
+    _numPiece(numPiece) {}
 
-  virtual bool validate(Errors& errors) {
+  virtual bool validate(Errors& errors)
+  {
     // TODO
-    PeerMessageUtil::checkIndex(message->getIndex(), numPiece);
+    PeerMessageUtil::checkIndex(_message->getIndex(), _numPiece);
     return true;
   }
 
@@ -61,4 +62,4 @@ public:
 
 } // namespace aria2
 
-#endif // _D_BT_HAVE_MESSAGE_VALIDATOR_H_
+#endif // _D_INDEX_BT_MESSAGE_VALIDATOR_H_
diff --git a/src/Makefile.am b/src/Makefile.am
index 479eb636..231cc9f8 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -296,14 +296,8 @@ SRCS += PeerMessageUtil.cc PeerMessageUtil.h\
 	BtUnchokeMessage.cc BtUnchokeMessage.h\
 	BtHandshakeMessage.cc BtHandshakeMessage.h\
 	BtMessageValidator.h\
-	BtAllowedFastMessageValidator.h\
 	BtBitfieldMessageValidator.h\
-	BtCancelMessageValidator.h\
-	BtHaveMessageValidator.h\
 	BtPieceMessageValidator.h\
-	BtRejectMessageValidator.h\
-	BtRequestMessageValidator.h\
-	BtSuggestPieceMessageValidator.h\
 	BtHandshakeMessageValidator.h\
 	BtMessageFactory.h\
 	DefaultBtMessageFactory.cc DefaultBtMessageFactory.h\
@@ -414,7 +408,11 @@ SRCS += PeerMessageUtil.cc PeerMessageUtil.h\
 	LibsslDHKeyExchange.h\
 	BtConstants.h\
 	BtLeecherStateChoke.cc BtLeecherStateChoke.h\
-	BtSeederStateChoke.cc BtSeederStateChoke.h
+	BtSeederStateChoke.cc BtSeederStateChoke.h\
+	RangeBtMessage.cc RangeBtMessage.h\
+	IndexBtMessage.cc IndexBtMessage.h\
+	ZeroBtMessage.cc ZeroBtMessage.h\
+	RangeBtMessageValidator.h
 endif # ENABLE_BITTORRENT
 
 if ENABLE_METALINK
diff --git a/src/Makefile.in b/src/Makefile.in
index 543bfe44..cd0607ab 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -100,14 +100,8 @@ bin_PROGRAMS = aria2c$(EXEEXT)
 @ENABLE_BITTORRENT_TRUE@	BtUnchokeMessage.cc BtUnchokeMessage.h\
 @ENABLE_BITTORRENT_TRUE@	BtHandshakeMessage.cc BtHandshakeMessage.h\
 @ENABLE_BITTORRENT_TRUE@	BtMessageValidator.h\
-@ENABLE_BITTORRENT_TRUE@	BtAllowedFastMessageValidator.h\
 @ENABLE_BITTORRENT_TRUE@	BtBitfieldMessageValidator.h\
-@ENABLE_BITTORRENT_TRUE@	BtCancelMessageValidator.h\
-@ENABLE_BITTORRENT_TRUE@	BtHaveMessageValidator.h\
 @ENABLE_BITTORRENT_TRUE@	BtPieceMessageValidator.h\
-@ENABLE_BITTORRENT_TRUE@	BtRejectMessageValidator.h\
-@ENABLE_BITTORRENT_TRUE@	BtRequestMessageValidator.h\
-@ENABLE_BITTORRENT_TRUE@	BtSuggestPieceMessageValidator.h\
 @ENABLE_BITTORRENT_TRUE@	BtHandshakeMessageValidator.h\
 @ENABLE_BITTORRENT_TRUE@	BtMessageFactory.h\
 @ENABLE_BITTORRENT_TRUE@	DefaultBtMessageFactory.cc DefaultBtMessageFactory.h\
@@ -218,7 +212,11 @@ bin_PROGRAMS = aria2c$(EXEEXT)
 @ENABLE_BITTORRENT_TRUE@	LibsslDHKeyExchange.h\
 @ENABLE_BITTORRENT_TRUE@	BtConstants.h\
 @ENABLE_BITTORRENT_TRUE@	BtLeecherStateChoke.cc BtLeecherStateChoke.h\
-@ENABLE_BITTORRENT_TRUE@	BtSeederStateChoke.cc BtSeederStateChoke.h
+@ENABLE_BITTORRENT_TRUE@	BtSeederStateChoke.cc BtSeederStateChoke.h\
+@ENABLE_BITTORRENT_TRUE@	RangeBtMessage.cc RangeBtMessage.h\
+@ENABLE_BITTORRENT_TRUE@	IndexBtMessage.cc IndexBtMessage.h\
+@ENABLE_BITTORRENT_TRUE@	ZeroBtMessage.cc ZeroBtMessage.h\
+@ENABLE_BITTORRENT_TRUE@	RangeBtMessageValidator.h
 
 @ENABLE_METALINK_TRUE@am__append_10 = Metalinker.cc Metalinker.h\
 @ENABLE_METALINK_TRUE@	MetalinkEntry.cc MetalinkEntry.h\
@@ -464,10 +462,7 @@ am__libaria2c_a_SOURCES_DIST = Socket.h SocketCore.cc SocketCore.h \
 	BtSuggestPieceMessage.cc BtSuggestPieceMessage.h \
 	BtUnchokeMessage.cc BtUnchokeMessage.h BtHandshakeMessage.cc \
 	BtHandshakeMessage.h BtMessageValidator.h \
-	BtAllowedFastMessageValidator.h BtBitfieldMessageValidator.h \
-	BtCancelMessageValidator.h BtHaveMessageValidator.h \
-	BtPieceMessageValidator.h BtRejectMessageValidator.h \
-	BtRequestMessageValidator.h BtSuggestPieceMessageValidator.h \
+	BtBitfieldMessageValidator.h BtPieceMessageValidator.h \
 	BtHandshakeMessageValidator.h BtMessageFactory.h \
 	DefaultBtMessageFactory.cc DefaultBtMessageFactory.h \
 	BtMessageDispatcher.h DefaultBtMessageDispatcher.cc \
@@ -544,9 +539,11 @@ am__libaria2c_a_SOURCES_DIST = Socket.h SocketCore.cc SocketCore.h \
 	LibsslARC4Decryptor.h LibsslARC4Encryptor.h \
 	LibsslDHKeyExchange.h BtConstants.h BtLeecherStateChoke.cc \
 	BtLeecherStateChoke.h BtSeederStateChoke.cc \
-	BtSeederStateChoke.h Metalinker.cc Metalinker.h \
-	MetalinkEntry.cc MetalinkEntry.h MetalinkResource.cc \
-	MetalinkResource.h MetalinkProcessor.h \
+	BtSeederStateChoke.h RangeBtMessage.cc RangeBtMessage.h \
+	IndexBtMessage.cc IndexBtMessage.h ZeroBtMessage.cc \
+	ZeroBtMessage.h RangeBtMessageValidator.h Metalinker.cc \
+	Metalinker.h MetalinkEntry.cc MetalinkEntry.h \
+	MetalinkResource.cc MetalinkResource.h MetalinkProcessor.h \
 	MetalinkProcessorFactory.cc MetalinkProcessorFactory.h \
 	MetalinkParserController.cc MetalinkParserController.h \
 	MetalinkParserStateMachine.cc MetalinkParserStateMachine.h \
@@ -698,7 +695,10 @@ am__objects_2 =
 @ENABLE_BITTORRENT_TRUE@	ReceiverMSEHandshakeCommand.$(OBJEXT) \
 @ENABLE_BITTORRENT_TRUE@	MSEHandshake.$(OBJEXT) \
 @ENABLE_BITTORRENT_TRUE@	BtLeecherStateChoke.$(OBJEXT) \
-@ENABLE_BITTORRENT_TRUE@	BtSeederStateChoke.$(OBJEXT)
+@ENABLE_BITTORRENT_TRUE@	BtSeederStateChoke.$(OBJEXT) \
+@ENABLE_BITTORRENT_TRUE@	RangeBtMessage.$(OBJEXT) \
+@ENABLE_BITTORRENT_TRUE@	IndexBtMessage.$(OBJEXT) \
+@ENABLE_BITTORRENT_TRUE@	ZeroBtMessage.$(OBJEXT)
 @ENABLE_METALINK_TRUE@am__objects_10 = Metalinker.$(OBJEXT) \
 @ENABLE_METALINK_TRUE@	MetalinkEntry.$(OBJEXT) \
 @ENABLE_METALINK_TRUE@	MetalinkResource.$(OBJEXT) \
@@ -1427,6 +1427,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/HttpServerResponseCommand.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/HttpSkipResponseCommand.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/InOrderURISelector.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/IndexBtMessage.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/InitialMetalinkParserState.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/InitiateConnectionCommand.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/InitiateConnectionCommandFactory.Po@am__quote@
@@ -1484,6 +1485,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/PiecesMetalinkParserState.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/Platform.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/ProtocolDetector.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/RangeBtMessage.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/RarestPieceSelector.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/RealtimeCommand.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/ReceiverMSEHandshakeCommand.Po@am__quote@
@@ -1532,6 +1534,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/VerificationMetalinkParserState.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/VersionMetalinkParserState.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/XML2SAXMetalinkProcessor.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/ZeroBtMessage.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/asctime_r.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/bencode.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/download_helper.Po@am__quote@
diff --git a/src/PeerMessageUtil.cc b/src/PeerMessageUtil.cc
index 325d387f..9ceeceb4 100644
--- a/src/PeerMessageUtil.cc
+++ b/src/PeerMessageUtil.cc
@@ -41,6 +41,8 @@
 #include "a2netcompat.h"
 #include "StringFormat.h"
 #include "BtConstants.h"
+#include "message.h"
+#include "StringFormat.h"
 
 namespace aria2 {
 
@@ -180,4 +182,35 @@ PeerMessageUtil::unpackcompact(const unsigned char* compact)
   return std::pair<std::string, uint16_t>(host, port);
 }
 
+
+void PeerMessageUtil::assertPayloadLengthGreater
+(size_t threshold, size_t actual, const std::string& msgName)
+{
+  if(actual <= threshold) {
+    throw DlAbortEx
+      (StringFormat(MSG_TOO_SMALL_PAYLOAD_SIZE, msgName.c_str(), actual).str());
+  }
+}
+
+void PeerMessageUtil::assertPayloadLengthEqual
+(size_t expected, size_t actual, const std::string& msgName)
+{
+  if(expected != actual) {
+    throw DlAbortEx
+      (StringFormat(EX_INVALID_PAYLOAD_SIZE, msgName.c_str(),
+		    actual, expected).str());
+  }
+}
+
+void PeerMessageUtil::assertID
+(uint8_t expected, const unsigned char* data, const std::string& msgName)
+{
+  uint8_t id = getId(data);
+  if(expected != id) {
+    throw DlAbortEx
+      (StringFormat(EX_INVALID_BT_MESSAGE_ID, id, msgName.c_str(),
+		    expected).str());
+  }
+}
+
 } // namespace aria2
diff --git a/src/PeerMessageUtil.h b/src/PeerMessageUtil.h
index b3de793c..1df121b0 100644
--- a/src/PeerMessageUtil.h
+++ b/src/PeerMessageUtil.h
@@ -79,6 +79,18 @@ public:
   static bool createcompact(unsigned char* compact, const std::string& addr, uint16_t port);
 
   static std::pair<std::string, uint16_t> unpackcompact(const unsigned char* compact);
+
+  // Throws exception if threshold >= actual
+  static void assertPayloadLengthGreater(size_t threshold, size_t actual,
+					 const std::string& msgName);
+
+  // Throws exception if expected != actual
+  static void assertPayloadLengthEqual(size_t expected, size_t actual,
+				       const std::string& msgName);
+
+  // Throws exception if expected is not equal to id from data.
+  static void assertID(uint8_t expected, const unsigned char* data,
+		       const std::string& msgName);
 };
 
 } // namespace aria2
diff --git a/src/RangeBtMessage.cc b/src/RangeBtMessage.cc
new file mode 100644
index 00000000..b0dd9773
--- /dev/null
+++ b/src/RangeBtMessage.cc
@@ -0,0 +1,85 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#include "RangeBtMessage.h"
+#include "Util.h"
+
+namespace aria2 {
+
+RangeBtMessage::RangeBtMessage(uint8_t id,
+			       const std::string& name,
+			       size_t index, uint32_t begin, size_t length)
+  :SimpleBtMessage(id, name),
+   _index(index),
+   _begin(begin),
+   _length(length),
+   _msg(0) {}
+
+RangeBtMessage::~RangeBtMessage()
+{
+  delete [] _msg;
+}
+
+const unsigned char* RangeBtMessage::getMessage()
+{
+  if(!_msg) {
+    /**
+     * len --- 13, 4bytes
+     * id --- ?, 1byte
+     * index --- index, 4bytes
+     * begin --- begin, 4bytes
+     * length -- length, 4bytes
+     * total: 17bytes
+     */
+    _msg = new unsigned char[MESSAGE_LENGTH];
+    PeerMessageUtil::createPeerMessageString(_msg, MESSAGE_LENGTH, 13, getId());
+    PeerMessageUtil::setIntParam(&_msg[5], _index);
+    PeerMessageUtil::setIntParam(&_msg[9], _begin);
+    PeerMessageUtil::setIntParam(&_msg[13], _length);
+  }
+  return _msg;
+}
+
+size_t RangeBtMessage::getMessageLength()
+{
+  return MESSAGE_LENGTH;
+}
+
+std::string RangeBtMessage::toString() const
+{
+  return getName()+" index="+Util::uitos(_index)+", begin="+Util::uitos(_begin)+
+    ", length="+Util::uitos(_length);
+}
+
+} // namespace aria2
diff --git a/src/RangeBtMessage.h b/src/RangeBtMessage.h
new file mode 100644
index 00000000..a0b12df4
--- /dev/null
+++ b/src/RangeBtMessage.h
@@ -0,0 +1,91 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#ifndef _D_RANGE_BT_MESSAGE_H_
+#define _D_RANGE_BT_MESSAGE_H_
+
+#include "SimpleBtMessage.h"
+#include "PeerMessageUtil.h"
+
+namespace aria2 {
+
+class RangeBtMessage : public SimpleBtMessage {
+private:
+  size_t _index;
+  uint32_t _begin;
+  size_t _length;
+  unsigned char* _msg;
+
+  static const size_t MESSAGE_LENGTH = 17;
+protected:
+  template<typename T>
+  static SharedHandle<T> create
+  (const unsigned char* data, size_t dataLength)
+  {
+    PeerMessageUtil::assertPayloadLengthEqual(13, dataLength, T::NAME);
+    PeerMessageUtil::assertID(T::ID, data, T::NAME);
+    SharedHandle<T> message(new T());
+    message->setIndex(PeerMessageUtil::getIntParam(data, 1));
+    message->setBegin(PeerMessageUtil::getIntParam(data, 5));
+    message->setLength(PeerMessageUtil::getIntParam(data, 9));
+    return message;
+  }
+public:
+  RangeBtMessage(uint8_t id, const std::string& name,
+		 size_t index, uint32_t begin, size_t length);
+
+  virtual ~RangeBtMessage();
+
+  size_t getIndex() const { return _index; }
+
+  void setIndex(size_t index) { _index = index; }
+
+  uint32_t getBegin() const { return _begin; }
+
+  void setBegin(uint32_t begin) { _begin = begin; }
+
+  size_t getLength() const { return _length; }
+
+  void setLength(size_t length) { _length = length; }
+
+  virtual const unsigned char* getMessage();
+
+  virtual size_t getMessageLength();
+
+  virtual std::string toString() const;
+};
+
+} // namespace aria2
+
+#endif // _D_RANGE_BT_MESSAGE_H_
diff --git a/src/BtSuggestPieceMessageValidator.h b/src/RangeBtMessageValidator.h
similarity index 66%
rename from src/BtSuggestPieceMessageValidator.h
rename to src/RangeBtMessageValidator.h
index dbfeea87..a6d6cdfa 100644
--- a/src/BtSuggestPieceMessageValidator.h
+++ b/src/RangeBtMessageValidator.h
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -32,35 +32,41 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef _D_BT_SUGGEST_PIECE_MESSAGE_VALIDATOR_H_
-#define _D_BT_SUGGEST_PIECE_MESSAGE_VALIDATOR_H_
+#ifndef _D_RANGE_BT_MESSAGE_VALIDATOR_H_
+#define _D_RANGE_BT_MESSAGE_VALIDATOR_H_
 
 #include "BtMessageValidator.h"
-#include "BtSuggestPieceMessage.h"
+#include "RangeBtMessage.h"
 #include "PeerMessageUtil.h"
 
 namespace aria2 {
 
-class BtSuggestPieceMessageValidator : public BtMessageValidator {
+class RangeBtMessageValidator : public BtMessageValidator {
 private:
-  const BtSuggestPieceMessage* message;
-  size_t numPiece;
+  const RangeBtMessage* _message;
+  size_t _numPiece;
+  size_t _pieceLength;
 public:
-  BtSuggestPieceMessageValidator(const BtSuggestPieceMessage* message,
-				 size_t numPiece):
-    message(message),
-    numPiece(numPiece) {}
+  RangeBtMessageValidator(const RangeBtMessage* message,
+			  size_t numPiece,
+			  size_t pieceLength):
+    _message(message),
+    _numPiece(numPiece),
+    _pieceLength(pieceLength) {}
 
-  virtual bool validate(Errors& errors) {
+  virtual bool validate(Errors& errors)
+  {
     // TODO
-    PeerMessageUtil::checkIndex(message->getIndex(), numPiece);
+    PeerMessageUtil::checkIndex(_message->getIndex(), _numPiece);
+    PeerMessageUtil::checkBegin(_message->getBegin(), _pieceLength);
+    PeerMessageUtil::checkLength(_message->getLength());
+    PeerMessageUtil::checkRange(_message->getBegin(),
+				_message->getLength(),
+				_pieceLength);
     return true;
   }
-
 };
 
-typedef SharedHandle<BtSuggestPieceMessageValidator> BtSuggestPieceMessageValidatorHandle;
-
 } // namespace aria2
 
-#endif // _D_BT_SUGGEST_PIECE_MESSAGE_VALIDATOR_H_
+#endif // _D_RANGE_BT_MESSAGE_VALIDATOR_H_
diff --git a/src/SimpleBtMessage.cc b/src/SimpleBtMessage.cc
index d333adef..b90ad04c 100644
--- a/src/SimpleBtMessage.cc
+++ b/src/SimpleBtMessage.cc
@@ -40,7 +40,8 @@
 
 namespace aria2 {
 
-SimpleBtMessage::SimpleBtMessage(uint8_t id):AbstractBtMessage(id) {}
+SimpleBtMessage::SimpleBtMessage(uint8_t id, const std::string& name):
+  AbstractBtMessage(id, name) {}
 
 SimpleBtMessage::~SimpleBtMessage() {}
 
diff --git a/src/SimpleBtMessage.h b/src/SimpleBtMessage.h
index 3387b810..c5647b93 100644
--- a/src/SimpleBtMessage.h
+++ b/src/SimpleBtMessage.h
@@ -41,7 +41,7 @@ namespace aria2 {
 
 class SimpleBtMessage : public AbstractBtMessage {
 public:
-  SimpleBtMessage(uint8_t id);
+  SimpleBtMessage(uint8_t id, const std::string& name);
 
   virtual ~SimpleBtMessage();
 
diff --git a/src/ZeroBtMessage.cc b/src/ZeroBtMessage.cc
new file mode 100644
index 00000000..153731ae
--- /dev/null
+++ b/src/ZeroBtMessage.cc
@@ -0,0 +1,63 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#include "ZeroBtMessage.h"
+
+namespace aria2 {
+
+const unsigned char* ZeroBtMessage::getMessage()
+{
+  if(!_msg) {
+    /**
+     * len --- 1, 4bytes
+     * id --- ?, 1byte
+     * total: 5bytes
+     */
+    _msg = new unsigned char[MESSAGE_LENGTH];
+    PeerMessageUtil::createPeerMessageString(_msg, MESSAGE_LENGTH, 1, getId());
+  }
+  return _msg;
+}
+
+size_t ZeroBtMessage::getMessageLength()
+{
+  return MESSAGE_LENGTH;
+}
+
+std::string ZeroBtMessage::toString() const
+{
+  return getName();
+}
+
+} // namespace aria2
diff --git a/src/BtCancelMessageValidator.h b/src/ZeroBtMessage.h
similarity index 62%
rename from src/BtCancelMessageValidator.h
rename to src/ZeroBtMessage.h
index 5f75f352..ad2bfc3e 100644
--- a/src/BtCancelMessageValidator.h
+++ b/src/ZeroBtMessage.h
@@ -2,7 +2,7 @@
 /*
  * aria2 - The high speed download utility
  *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ * Copyright (C) 2009 Tatsuhiro Tsujikawa
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -32,41 +32,45 @@
  * files in the program, then also delete it here.
  */
 /* copyright --> */
-#ifndef _D_BT_CANCEL_MESSAGE_VALIDATOR_H_
-#define _D_BT_CANCEL_MESSAGE_VALIDATOR_H_
+#ifndef _D_ZERO_BT_MESSAGE_H_
+#define _D_ZERO_BT_MESSAGE_H_
 
-#include "BtMessageValidator.h"
-#include "BtCancelMessage.h"
+#include "SimpleBtMessage.h"
 #include "PeerMessageUtil.h"
 
 namespace aria2 {
 
-class BtCancelMessageValidator : public BtMessageValidator {
+class ZeroBtMessage : public SimpleBtMessage {
 private:
-  const BtCancelMessage* message;
-  size_t numPiece;
-  size_t pieceLength;
-public:
-  BtCancelMessageValidator(const BtCancelMessage* message,
-			   size_t numPiece,
-			   size_t pieceLength):
-    message(message),
-    numPiece(numPiece),
-    pieceLength(pieceLength) {}
+  unsigned char* _msg;
 
-  virtual bool validate(Errors& error) {
-    // TODO
-    PeerMessageUtil::checkIndex(message->getIndex(), numPiece);
-    PeerMessageUtil::checkBegin(message->getBegin(), pieceLength);
-    PeerMessageUtil::checkLength(message->getLength());
-    PeerMessageUtil::checkRange(message->getBegin(), message->getLength(),
-				pieceLength);
-    return true;
+  static const size_t MESSAGE_LENGTH = 5;
+protected:
+  template<typename T>
+  static SharedHandle<T> create(const unsigned char* data, size_t dataLength)
+  {
+    PeerMessageUtil::assertPayloadLengthEqual(1, dataLength, T::NAME);
+    PeerMessageUtil::assertID(T::ID, data, T::NAME);
+    SharedHandle<T> message(new T());
+    return message;
   }
-};
 
-typedef SharedHandle<BtCancelMessageValidator> BtCancelMessageValidatorHandle;
+public:
+  ZeroBtMessage(uint8_t id, const std::string& name):
+    SimpleBtMessage(id, name), _msg(0) {}
+
+  virtual ~ZeroBtMessage()
+  {
+    delete [] _msg;
+  }
+
+  virtual const unsigned char* getMessage();
+
+  virtual size_t getMessageLength();
+
+  virtual std::string toString() const;
+};
 
 } // namespace aria2
 
-#endif // _D_BT_CANCEL_MESSAGE_VALIDATOR_H_
+#endif // _D_ZERO_BT_MESSAGE_H_
diff --git a/test/BtRequestMessageTest.cc b/test/BtRequestMessageTest.cc
index 2ab4c667..9711dff2 100644
--- a/test/BtRequestMessageTest.cc
+++ b/test/BtRequestMessageTest.cc
@@ -14,7 +14,7 @@
 #include "Peer.h"
 #include "FileEntry.h"
 #include "BtHandshakeMessage.h"
-#include "BtRequestMessageValidator.h"
+#include "RangeBtMessageValidator.h"
 
 namespace aria2 {
 
@@ -144,7 +144,7 @@ void BtRequestMessageTest::testCreate() {
   CPPUNIT_ASSERT_EQUAL((uint8_t)6, pm->getId());
   CPPUNIT_ASSERT_EQUAL((size_t)12345, pm->getIndex());
   CPPUNIT_ASSERT_EQUAL((uint32_t)256, pm->getBegin());
-  CPPUNIT_ASSERT_EQUAL((uint32_t)1024, pm->getLength());
+  CPPUNIT_ASSERT_EQUAL((size_t)1024, pm->getLength());
 
   // case: payload size is wrong
   try {
@@ -289,7 +289,7 @@ void BtRequestMessageTest::testValidate() {
   BtRequestMessage msg(0, 0, 16*1024);
   msg.setBtMessageValidator
     (SharedHandle<BtMessageValidator>
-     (new BtRequestMessageValidator(&msg, 1024, 256*1024)));
+     (new RangeBtMessageValidator(&msg, 1024, 256*1024)));
   std::deque<std::string> errors;
 
   msg.validate(errors);
@@ -299,7 +299,7 @@ void BtRequestMessageTest::testValidate_lengthTooLong() {
   BtRequestMessage msg(0, 0, 16*1024+1);
   msg.setBtMessageValidator
     (SharedHandle<BtMessageValidator>
-     (new BtRequestMessageValidator(&msg, 1024, 256*1024)));
+     (new RangeBtMessageValidator(&msg, 1024, 256*1024)));
   std::deque<std::string> errors;
   try {
     msg.validate(errors);