Allow messages to be designated either by their number or their UID.

Warning: this is an API-breaking change.

20 files changed, 1360 insertions, 982 deletions

diff --git a/SConstruct b/SConstruct
index ed0a4d03..baff95c0 100644
--- a/SConstruct
+++ b/SConstruct
@@ -206,6 +206,7 @@ libvmime_messaging_sources = [
 	'net/folder.cpp', 'net/folder.hpp',
 	'net/folderStatus.hpp',
 	'net/message.cpp', 'net/message.hpp',
+	'net/messageSet.cpp', 'net/messageSet.hpp',
 	'net/securedConnectionInfos.hpp',
 	'net/service.cpp', 'net/service.hpp',
 	'net/serviceFactory.cpp', 'net/serviceFactory.hpp',
@@ -412,6 +413,7 @@ libvmimetest_sources = [
 	'tests/security/digest/md5Test.cpp',
 	'tests/security/digest/sha1Test.cpp',
 	# ===============================  Net  ================================
+	'tests/net/messageSetTest.cpp',
 	'tests/net/pop3/POP3CommandTest.cpp',
 	'tests/net/pop3/POP3ResponseTest.cpp',
 	'tests/net/pop3/POP3UtilsTest.cpp',
diff --git a/doc/book/net.tex b/doc/book/net.tex
index 19a6ccb9..7359c3e3 100644
--- a/doc/book/net.tex
+++ b/doc/book/net.tex
@@ -555,7 +555,9 @@ The following code shows how to list all the messages in a folder, and
 retrieve basic information to show them to the user:
 
 \begin{lstlisting}[caption={Fetching information about multiple messages}]
-std::vector <ref <vmime::net::message> > allMessages = folder->getMessages();
+std::vector <ref <vmime::net::message> > allMessages =
+   folder->getMessages(vmime::net::messageSet::byNumber(1, -1));
+      // -1 is a special value to mean "the number of the last message in the folder"
 
 folder->fetchMessages(allMessages,
    vmime::net::folder::FETCH_FLAGS |
@@ -628,17 +630,17 @@ store.
 \begin{lstlisting}[caption={Deleting messages}]
 vmime::ref <vmime::net::folder> folder = store->getDefaultFolder();
 
-folder->deleteMessage(3);
-folder->deleteMessage(2);
+folder->deleteMessages(vmime::net::messageSet::byNumber(/* from */ 2, /* to */ 3));
 
 // This is equivalent
 std::vector <int> nums;
 nums.push_back(2);
 nums.push_back(3);
-folder->deleteMessages(nums);
+folder->deleteMessages(vmime::net::messageSet::byNumber(nums));
 
-// This is also equivalent
-folder->deleteMessages(/* from */ 2, /* to */ 3);
+// This is also equivalent (but will require 2 roundtrips to server)
+folder->deleteMessages(vmime::net::messageSet::byNumber(2));
+folder->deleteMessages(vmime::net::messageSet::byNumber(2)); // renumbered, 3 becomes 2
 \end{lstlisting}
 
 \subsection{Events} % --------------------------------------------------------
diff --git a/src/net/imap/IMAPFolder.cpp b/src/net/imap/IMAPFolder.cpp
index 3a38182e..dd7f2512 100644
--- a/src/net/imap/IMAPFolder.cpp
+++ b/src/net/imap/IMAPFolder.cpp
@@ -529,135 +529,93 @@ ref <message> IMAPFolder::getMessage(const int num)
 }
 
 
-std::vector <ref <message> > IMAPFolder::getMessages(const int from, const int to)
+std::vector <ref <message> > IMAPFolder::getMessages(const messageSet& msgs)
 {
-	const int messageCount = m_status->getMessageCount();
-	const int to2 = (to == -1 ? messageCount : to);
-
 	if (!isOpen())
 		throw exceptions::illegal_state("Folder not open");
-	else if (to2 < from || from < 1 || to2 < 1 || from > messageCount || to2 > messageCount)
-		throw exceptions::message_not_found();
-
-	std::vector <ref <message> > v;
-	ref <IMAPFolder> thisFolder = thisRef().dynamicCast <IMAPFolder>();
-
-	for (int i = from ; i <= to2 ; ++i)
-		v.push_back(vmime::create <IMAPMessage>(thisFolder, i));
-
-	return (v);
-}
-
-
-std::vector <ref <message> > IMAPFolder::getMessages(const std::vector <int>& nums)
-{
-	if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	std::vector <ref <message> > v;
-	ref <IMAPFolder> thisFolder = thisRef().dynamicCast <IMAPFolder>();
-
-	for (std::vector <int>::const_iterator it = nums.begin() ; it != nums.end() ; ++it)
-		v.push_back(vmime::create <IMAPMessage>(thisFolder, *it));
-
-	return (v);
-}
-
-
-ref <message> IMAPFolder::getMessageByUID(const message::uid& uid)
-{
-	std::vector <message::uid> uids;
-	uids.push_back(uid);
-
-	std::vector <ref <message> > msgs = getMessagesByUID(uids);
-
-	if (msgs.size() == 0)
-		throw exceptions::message_not_found();
-
-	return msgs[0];
-}
-
 
-std::vector <ref <message> > IMAPFolder::getMessagesByUID(const std::vector <message::uid>& uids)
-{
-	if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	if (uids.size() == 0)
+	if (msgs.isEmpty() == 0)
 		return std::vector <ref <message> >();
 
-	//     C: . UID FETCH uuuu1,uuuu2,uuuu3 UID
-	//     S: * nnnn1 FETCH (UID uuuu1)
-	//     S: * nnnn2 FETCH (UID uuuu2)
-	//     S: * nnnn3 FETCH (UID uuuu3)
-	//     S: . OK UID FETCH completed
+	std::vector <ref <message> > messages;
 
-	// Prepare command and arguments
-	std::ostringstream cmd;
-	cmd.imbue(std::locale::classic());
+	if (msgs.isNumberSet())
+	{
+		const std::vector <int> numbers = IMAPUtils::messageSetToNumberList(msgs);
 
-	cmd << "UID FETCH " << uids[0];
+		ref <IMAPFolder> thisFolder = thisRef().dynamicCast <IMAPFolder>();
 
-	for (std::vector <message::uid>::size_type i = 1, n = uids.size() ; i < n ; ++i)
-		cmd << "," << uids[i];
+		for (std::vector <int>::const_iterator it = numbers.begin() ; it != numbers.end() ; ++it)
+			messages.push_back(vmime::create <IMAPMessage>(thisFolder, *it));
+	}
+	else if (msgs.isUIDSet())
+	{
+		//     C: . UID FETCH uuuu1,uuuu2,uuuu3 UID
+		//     S: * nnnn1 FETCH (UID uuuu1)
+		//     S: * nnnn2 FETCH (UID uuuu2)
+		//     S: * nnnn3 FETCH (UID uuuu3)
+		//     S: . OK UID FETCH completed
 
-	cmd << " UID";
+		// Prepare command and arguments
+		std::ostringstream cmd;
+		cmd.imbue(std::locale::classic());
 
-	// Send the request
-	m_connection->send(true, cmd.str(), true);
+		cmd << "UID FETCH " << IMAPUtils::messageSetToSequenceSet(msgs) << " UID";
 
-	// Get the response
-	utility::auto_ptr <IMAPParser::response> resp(m_connection->readResponse());
+		// Send the request
+		m_connection->send(true, cmd.str(), true);
 
-	if (resp->isBad() || resp->response_done()->response_tagged()->
-			resp_cond_state()->status() != IMAPParser::resp_cond_state::OK)
-	{
-		throw exceptions::command_error("UID FETCH ... UID", resp->getErrorLog(), "bad response");
-	}
+		// Get the response
+		utility::auto_ptr <IMAPParser::response> resp(m_connection->readResponse());
 
-	// Process the response
-	const std::vector <IMAPParser::continue_req_or_response_data*>& respDataList =
-		resp->continue_req_or_response_data();
+		if (resp->isBad() || resp->response_done()->response_tagged()->
+				resp_cond_state()->status() != IMAPParser::resp_cond_state::OK)
+		{
+			throw exceptions::command_error("UID FETCH ... UID", resp->getErrorLog(), "bad response");
+		}
 
-	std::vector <ref <message> > messages;
+		// Process the response
+		const std::vector <IMAPParser::continue_req_or_response_data*>& respDataList =
+			resp->continue_req_or_response_data();
 
-	for (std::vector <IMAPParser::continue_req_or_response_data*>::const_iterator
-	     it = respDataList.begin() ; it != respDataList.end() ; ++it)
-	{
-		if ((*it)->response_data() == NULL)
+		for (std::vector <IMAPParser::continue_req_or_response_data*>::const_iterator
+			 it = respDataList.begin() ; it != respDataList.end() ; ++it)
 		{
-			throw exceptions::command_error("UID FETCH ... UID",
-				resp->getErrorLog(), "invalid response");
-		}
+			if ((*it)->response_data() == NULL)
+			{
+				throw exceptions::command_error("UID FETCH ... UID",
+					resp->getErrorLog(), "invalid response");
+			}
 
-		const IMAPParser::message_data* messageData =
-			(*it)->response_data()->message_data();
+			const IMAPParser::message_data* messageData =
+				(*it)->response_data()->message_data();
 
-		// We are only interested in responses of type "FETCH"
-		if (messageData == NULL || messageData->type() != IMAPParser::message_data::FETCH)
-			continue;
+			// We are only interested in responses of type "FETCH"
+			if (messageData == NULL || messageData->type() != IMAPParser::message_data::FETCH)
+				continue;
 
-		// Get Process fetch response for this message
-		const int msgNum = static_cast <int>(messageData->number());
-		message::uid msgUID;
+			// Get Process fetch response for this message
+			const int msgNum = static_cast <int>(messageData->number());
+			message::uid msgUID;
 
-		// Find UID in message attributes
-		const std::vector <IMAPParser::msg_att_item*> atts = messageData->msg_att()->items();
+			// Find UID in message attributes
+			const std::vector <IMAPParser::msg_att_item*> atts = messageData->msg_att()->items();
 
-		for (std::vector <IMAPParser::msg_att_item*>::const_iterator
-		     it = atts.begin() ; it != atts.end() ; ++it)
-		{
-			if ((*it)->type() == IMAPParser::msg_att_item::UID)
+			for (std::vector <IMAPParser::msg_att_item*>::const_iterator
+				 it = atts.begin() ; it != atts.end() ; ++it)
 			{
-				msgUID = (*it)->unique_id()->value();
-				break;
+				if ((*it)->type() == IMAPParser::msg_att_item::UID)
+				{
+					msgUID = (*it)->unique_id()->value();
+					break;
+				}
 			}
-		}
 
-		if (!msgUID.empty())
-		{
-			ref <IMAPFolder> thisFolder = thisRef().dynamicCast <IMAPFolder>();
-			messages.push_back(vmime::create <IMAPMessage>(thisFolder, msgNum, msgUID));
+			if (!msgUID.empty())
+			{
+				ref <IMAPFolder> thisFolder = thisRef().dynamicCast <IMAPFolder>();
+				messages.push_back(vmime::create <IMAPMessage>(thisFolder, msgNum, msgUID));
+			}
 		}
 	}
 
@@ -816,7 +774,9 @@ void IMAPFolder::fetchMessages(std::vector <ref <message> >& msg, const int opti
 	}
 
 	// Send the request
-	const string command = IMAPUtils::buildFetchRequest(m_connection, list, options);
+	const string command = IMAPUtils::buildFetchRequest
+		(m_connection, messageSet::byNumber(list), options);
+
 	m_connection->send(true, command, true);
 
 	// Get the response
@@ -945,17 +905,11 @@ void IMAPFolder::onStoreDisconnected()
 }
 
 
-void IMAPFolder::deleteMessage(const int num)
-{
-	deleteMessages(num, num);
-}
-
-
-void IMAPFolder::deleteMessages(const int from, const int to)
+void IMAPFolder::deleteMessages(const messageSet& msgs)
 {
 	ref <IMAPStore> store = m_store.acquire();
 
-	if (from < 1 || (to < from && to != -1))
+	if (msgs.isEmpty())
 		throw exceptions::invalid_argument();
 
 	if (!store)
@@ -969,19 +923,10 @@ void IMAPFolder::deleteMessages(const int from, const int to)
 	std::ostringstream command;
 	command.imbue(std::locale::classic());
 
-	command << "STORE ";
-
-	if (from == to)
-	{
-		command << from;
-	}
+	if (msgs.isUIDSet())
+		command << "UID STORE" << IMAPUtils::messageSetToSequenceSet(msgs);
 	else
-	{
-		command << from << ":";
-
-		if (to == -1) command << m_status->getMessageCount();
-		else command << to;
-	}
+		command << "STORE" << IMAPUtils::messageSetToSequenceSet(msgs);
 
 	command << " +FLAGS (\\Deleted)";
 
@@ -1002,116 +947,16 @@ void IMAPFolder::deleteMessages(const int from, const int to)
 }
 
 
-void IMAPFolder::deleteMessages(const std::vector <int>& nums)
+void IMAPFolder::setMessageFlags(const messageSet& msgs, const int flags, const int mode)
 {
-	ref <IMAPStore> store = m_store.acquire();
-
-	if (nums.empty())
-		throw exceptions::invalid_argument();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-	else if (m_mode == MODE_READ_ONLY)
-		throw exceptions::illegal_state("Folder is read-only");
-
-	// Sort the list of message numbers
-	std::vector <int> list;
-
-	list.resize(nums.size());
-	std::copy(nums.begin(), nums.end(), list.begin());
-
-	std::sort(list.begin(), list.end());
-
 	// Build the request text
 	std::ostringstream command;
 	command.imbue(std::locale::classic());
 
-	command << "STORE ";
-	command << IMAPUtils::listToSet(list, m_status->getMessageCount(), true);
-	command << " +FLAGS (\\Deleted)";
-
-	// Send the request
-	m_connection->send(true, command.str(), true);
-
-	// Get the response
-	utility::auto_ptr <IMAPParser::response> resp(m_connection->readResponse());
-
-	if (resp->isBad() || resp->response_done()->response_tagged()->
-		resp_cond_state()->status() != IMAPParser::resp_cond_state::OK)
-	{
-		throw exceptions::command_error("STORE",
-			resp->getErrorLog(), "bad response");
-	}
-
-	processStatusUpdate(resp);
-}
-
-
-void IMAPFolder::setMessageFlags(const int from, const int to, const int flags, const int mode)
-{
-	ref <IMAPStore> store = m_store.acquire();
-
-	if (from < 1 || (to < from && to != -1))
-		throw exceptions::invalid_argument();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-	else if (m_mode == MODE_READ_ONLY)
-		throw exceptions::illegal_state("Folder is read-only");
-
-	std::ostringstream oss;
-	oss.imbue(std::locale::classic());
-
-	if (from == to)
-	{
-		oss << from;
-	}
+	if (msgs.isUIDSet())
+		command << "UID STORE " << IMAPUtils::messageSetToSequenceSet(msgs);
 	else
-	{
-		if (to == -1)
-			oss << from << ":*";
-		else
-			oss << from << ":" << to;
-	}
-
-	setMessageFlagsImpl(oss.str(), flags, mode);
-}
-
-
-void IMAPFolder::setMessageFlags(const std::vector <int>& nums, const int flags, const int mode)
-{
-	ref <IMAPStore> store = m_store.acquire();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-	else if (m_mode == MODE_READ_ONLY)
-		throw exceptions::illegal_state("Folder is read-only");
-
-	// Sort the list of message numbers
-	std::vector <int> list;
-
-	list.resize(nums.size());
-	std::copy(nums.begin(), nums.end(), list.begin());
-	std::sort(list.begin(), list.end());
-
-	// Delegates call
-	setMessageFlagsImpl(IMAPUtils::listToSet(list, m_status->getMessageCount(), true), flags, mode);
-}
-
-
-void IMAPFolder::setMessageFlagsImpl(const string& set, const int flags, const int mode)
-{
-	// Build the request text
-	std::ostringstream command;
-	command.imbue(std::locale::classic());
-
-	command << "STORE " << set;
+		command << "STORE " << IMAPUtils::messageSetToSequenceSet(msgs);
 
 	switch (mode)
 	{
@@ -1364,27 +1209,7 @@ void IMAPFolder::rename(const folder::path& newPath)
 }
 
 
-void IMAPFolder::copyMessage(const folder::path& dest, const int num)
-{
-	ref <IMAPStore> store = m_store.acquire();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	// Construct set
-	std::ostringstream set;
-	set.imbue(std::locale::classic());
-
-	set << num;
-
-	// Delegate message copy
-	copyMessagesImpl(set.str(), dest);
-}
-
-
-void IMAPFolder::copyMessages(const folder::path& dest, const int from, const int to)
+void IMAPFolder::copyMessages(const folder::path& dest, const messageSet& set)
 {
 	ref <IMAPStore> store = m_store.acquire();
 
@@ -1392,44 +1217,12 @@ void IMAPFolder::copyMessages(const folder::path& dest, const int from, const in
 		throw exceptions::illegal_state("Store disconnected");
 	else if (!isOpen())
 		throw exceptions::illegal_state("Folder not open");
-	else if (from < 1 || (to < from && to != -1))
-		throw exceptions::invalid_argument();
-
-	// Construct set
-	std::ostringstream set;
-	set.imbue(std::locale::classic());
 
-	if (to == -1)
-		set << from << ":*";
-	else
-		set << from << ":" << to;
-
-	// Delegate message copy
-	copyMessagesImpl(set.str(), dest);
-}
-
-
-void IMAPFolder::copyMessages(const folder::path& dest, const std::vector <int>& nums)
-{
-	ref <IMAPStore> store = m_store.acquire();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	// Delegate message copy
-	copyMessagesImpl(IMAPUtils::listToSet(nums, m_status->getMessageCount()), dest);
-}
-
-
-void IMAPFolder::copyMessagesImpl(const string& set, const folder::path& dest)
-{
 	// Build the request text
 	std::ostringstream command;
 	command.imbue(std::locale::classic());
 
-	command << "COPY " << set << " ";
+	command << "COPY " << IMAPUtils::messageSetToSequenceSet(set) << " ";
 	command << IMAPUtils::quoteString(IMAPUtils::pathToString
 			(m_connection->hierarchySeparator(), dest));
 
@@ -1599,6 +1392,8 @@ std::vector <int> IMAPFolder::getMessageNumbersStartingOnUID(const message::uid&
 		}
 	}
 
+	processStatusUpdate(resp);
+
 	return v;
 }
 
diff --git a/src/net/imap/IMAPMessage.cpp b/src/net/imap/IMAPMessage.cpp
index 96114e94..33599689 100644
--- a/src/net/imap/IMAPMessage.cpp
+++ b/src/net/imap/IMAPMessage.cpp
@@ -531,7 +531,10 @@ void IMAPMessage::setFlags(const int flags, const int mode)
 	if (!folder)
 		throw exceptions::folder_not_found();
 
-	folder->setMessageFlags(m_num, m_num, flags, mode);
+	if (!m_uid.empty())
+		folder->setMessageFlags(messageSet::byUID(m_uid), flags, mode);
+	else
+		folder->setMessageFlags(messageSet::byNumber(m_num), flags, mode);
 }
 
 
diff --git a/src/net/imap/IMAPUtils.cpp b/src/net/imap/IMAPUtils.cpp
index dc583f84..b5f8b38d 100644
--- a/src/net/imap/IMAPUtils.cpp
+++ b/src/net/imap/IMAPUtils.cpp
@@ -472,98 +472,6 @@ const string IMAPUtils::messageFlagList(const int flags)
 
 
 // static
-const string IMAPUtils::listToSet(const std::vector <int>& list, const int max,
-                                  const bool alreadySorted)
-{
-	// Sort a copy of the list (if not already sorted)
-	std::vector <int> temp;
-
-	if (!alreadySorted)
-	{
-		temp.resize(list.size());
-		std::copy(list.begin(), list.end(), temp.begin());
-
-		std::sort(temp.begin(), temp.end());
-	}
-
-	const std::vector <int>& theList = (alreadySorted ? list : temp);
-
-	// Build the set
-	std::ostringstream res;
-	res.imbue(std::locale::classic());
-
-	int previous = -1, setBegin = -1;
-
-	for (std::vector <int>::const_iterator it = theList.begin() ;
-	     it != theList.end() ; ++it)
-	{
-		const int current = *it;
-
-		if (previous == -1)
-		{
-			res << current;
-
-			previous = current;
-			setBegin = current;
-		}
-		else
-		{
-			if (current == previous + 1)
-			{
-				previous = current;
-			}
-			else
-			{
-				if (setBegin != previous)
-				{
-					res << ":" << previous << "," << current;
-
-					previous = current;
-					setBegin = current;
-				}
-				else
-				{
-					if (setBegin != current)  // skip duplicates
-						res << "," << current;
-
-					previous = current;
-					setBegin = current;
-				}
-			}
-		}
-	}
-
-	if (previous != setBegin)
-	{
-		if (previous == max)
-			res << ":*";
-		else
-			res << ":" << previous;
-	}
-
-	return (res.str());
-}
-
-
-// static
-const string IMAPUtils::listToSet(const std::vector <message::uid>& list)
-{
-	if (list.size() == 0)
-		return "";
-
-	std::ostringstream res;
-	res.imbue(std::locale::classic());
-
-	res << list[0];
-
-	for (std::vector <message::uid>::size_type i = 1, n = list.size() ; i < n ; ++i)
-		res << "," << list[i];
-
-	return res.str();
-}
-
-
-// static
 const string IMAPUtils::dateTime(const vmime::datetime& date)
 {
 	std::ostringstream res;
@@ -633,8 +541,8 @@ const string IMAPUtils::dateTime(const vmime::datetime& date)
 
 
 // static
-const string IMAPUtils::buildFetchRequestImpl
-	(ref <IMAPConnection> cnt, const string& mode, const string& set, const int options)
+const string IMAPUtils::buildFetchRequest
+	(ref <IMAPConnection> cnt, const messageSet& msgs, const int options)
 {
 	// Example:
 	//   C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
@@ -702,10 +610,10 @@ const string IMAPUtils::buildFetchRequestImpl
 	std::ostringstream command;
 	command.imbue(std::locale::classic());
 
-	if (mode == "uid")
-		command << "UID FETCH " << set << " (";
+	if (msgs.isUIDSet())
+		command << "UID FETCH " << messageSetToSequenceSet(msgs) << " (";
 	else
-		command << "FETCH " << set << " (";
+		command << "FETCH " << messageSetToSequenceSet(msgs) << " (";
 
 	for (std::vector <string>::const_iterator it = items.begin() ;
 	     it != items.end() ; ++it)
@@ -721,22 +629,6 @@ const string IMAPUtils::buildFetchRequestImpl
 
 
 // static
-const string IMAPUtils::buildFetchRequest
-	(ref <IMAPConnection> cnt, const std::vector <int>& list, const int options)
-{
-	return buildFetchRequestImpl(cnt, "number", listToSet(list, -1, false), options);
-}
-
-
-// static
-const string IMAPUtils::buildFetchRequest
-	(ref <IMAPConnection> cnt, const std::vector <message::uid>& list, const int options)
-{
-	return buildFetchRequestImpl(cnt, "uid", listToSet(list), options);
-}
-
-
-// static
 void IMAPUtils::convertAddressList
 	(const IMAPParser::address_list& src, mailboxList& dest)
 {
@@ -756,6 +648,101 @@ void IMAPUtils::convertAddressList
 }
 
 
+
+class IMAPUIDMessageSetEnumerator : public messageSetEnumerator
+{
+public:
+
+	IMAPUIDMessageSetEnumerator()
+		: m_first(true)
+	{
+	}
+
+	void enumerateNumberMessageRange(const vmime::net::numberMessageRange& range)
+	{
+		if (!m_first)
+			m_oss << ",";
+
+		if (range.getFirst() == range.getLast())
+			m_oss << range.getFirst();
+		else
+			m_oss << range.getFirst() << ":" << range.getLast();
+
+		m_first = false;
+	}
+
+	void enumerateUIDMessageRange(const vmime::net::UIDMessageRange& range)
+	{
+		if (!m_first)
+			m_oss << ",";
+
+		if (range.getFirst() == range.getLast())
+			m_oss << range.getFirst();
+		else
+			m_oss << range.getFirst() << ":" << range.getLast();
+
+		m_first = false;
+	}
+
+	const std::string str() const
+	{
+		return m_oss.str();
+	}
+
+private:
+
+	std::ostringstream m_oss;
+	bool m_first;
+};
+
+
+class IMAPMessageSetEnumerator : public messageSetEnumerator
+{
+public:
+
+	void enumerateNumberMessageRange(const vmime::net::numberMessageRange& range)
+	{
+		for (int i = range.getFirst(), last = range.getLast() ; i <= last ; ++i)
+			m_list.push_back(i);
+	}
+
+	void enumerateUIDMessageRange(const vmime::net::UIDMessageRange& /* range */)
+	{
+		// Not used
+	}
+
+	const std::vector <int>& list() const
+	{
+		return m_list;
+	}
+
+public:
+
+	std::vector <int> m_list;
+};
+
+
+
+// static
+const string IMAPUtils::messageSetToSequenceSet(const messageSet& msgs)
+{
+	IMAPUIDMessageSetEnumerator en;
+	msgs.enumerate(en);
+
+	return en.str();
+}
+
+
+// static
+const std::vector <int> IMAPUtils::messageSetToNumberList(const messageSet& msgs)
+{
+	IMAPMessageSetEnumerator en;
+	msgs.enumerate(en);
+
+	return en.list();
+}
+
+
 } // imap
 } // net
 } // vmime
diff --git a/src/net/maildir/maildirFolder.cpp b/src/net/maildir/maildirFolder.cpp
index 3042d4b5..42a2c5ff 100644
--- a/src/net/maildir/maildirFolder.cpp
+++ b/src/net/maildir/maildirFolder.cpp
@@ -419,49 +419,32 @@ ref <message> maildirFolder::getMessage(const int num)
 }
 
 
-std::vector <ref <message> > maildirFolder::getMessages(const int from, const int to)
-{
-	const int to2 = (to == -1 ? m_messageCount : to);
-
-	if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-	else if (to2 < from || from < 1 || to2 < 1 || from > m_messageCount || to2 > m_messageCount)
-		throw exceptions::message_not_found();
-
-	std::vector <ref <message> > v;
-	ref <maildirFolder> thisFolder = thisRef().dynamicCast <maildirFolder>();
-
-	for (int i = from ; i <= to2 ; ++i)
-		v.push_back(vmime::create <maildirMessage>(thisFolder, i));
-
-	return (v);
-}
-
-
-std::vector <ref <message> > maildirFolder::getMessages(const std::vector <int>& nums)
+std::vector <ref <message> > maildirFolder::getMessages(const messageSet& msgs)
 {
 	if (!isOpen())
 		throw exceptions::illegal_state("Folder not open");
 
-	std::vector <ref <message> > v;
-	ref <maildirFolder> thisFolder = thisRef().dynamicCast <maildirFolder>();
-
-	for (std::vector <int>::const_iterator it = nums.begin() ; it != nums.end() ; ++it)
-		v.push_back(vmime::create <maildirMessage>(thisFolder, *it));
-
-	return (v);
-}
+	if (msgs.isNumberSet())
+	{
+		const std::vector <int> numbers = maildirUtils::messageSetToNumberList(msgs);
 
+		std::vector <ref <message> > messages;
+		ref <maildirFolder> thisFolder = thisRef().dynamicCast <maildirFolder>();
 
-ref <message> maildirFolder::getMessageByUID(const message::uid& /* uid */)
-{
-	throw exceptions::operation_not_supported();
-}
+		for (std::vector <int>::const_iterator it = numbers.begin() ; it != numbers.end() ; ++it)
+		{
+			if (*it < 1|| *it > m_messageCount)
+				throw exceptions::message_not_found();
 
+			messages.push_back(vmime::create <maildirMessage>(thisFolder, *it));
+		}
 
-std::vector <ref <message> > maildirFolder::getMessagesByUID(const std::vector <message::uid>& /* uids */)
-{
-	throw exceptions::operation_not_supported();
+		return messages;
+	}
+	else
+	{
+		throw exceptions::operation_not_supported();
+	}
 }
 
 
@@ -590,35 +573,18 @@ void maildirFolder::rename(const folder::path& newPath)
 }
 
 
-void maildirFolder::deleteMessage(const int num)
-{
-	// Mark messages as deleted
-	setMessageFlags(num, num, message::FLAG_DELETED, message::FLAG_MODE_ADD);
-}
-
-
-void maildirFolder::deleteMessages(const int from, const int to)
-{
-	// Mark messages as deleted
-	setMessageFlags(from, to, message::FLAG_DELETED, message::FLAG_MODE_ADD);
-}
-
-
-void maildirFolder::deleteMessages(const std::vector <int>& nums)
+void maildirFolder::deleteMessages(const messageSet& msgs)
 {
 	// Mark messages as deleted
-	setMessageFlags(nums, message::FLAG_DELETED, message::FLAG_MODE_ADD);
+	setMessageFlags(msgs, message::FLAG_DELETED, message::FLAG_MODE_ADD);
 }
 
 
 void maildirFolder::setMessageFlags
-	(const int from, const int to, const int flags, const int mode)
+	(const messageSet& msgs, const int flags, const int mode)
 {
 	ref <maildirStore> store = m_store.acquire();
 
-	if (from < 1 || (to < from && to != -1))
-		throw exceptions::invalid_argument();
-
 	if (!store)
 		throw exceptions::illegal_state("Store disconnected");
 	else if (!isOpen())
@@ -626,210 +592,116 @@ void maildirFolder::setMessageFlags
 	else if (m_mode == MODE_READ_ONLY)
 		throw exceptions::illegal_state("Folder is read-only");
 
-	// Construct the list of message numbers
-	const int to2 = (to == -1) ? m_messageCount : to;
-	const int count = to - from + 1;
-
-	std::vector <int> nums;
-	nums.resize(count);
+	if (msgs.isNumberSet())
+	{
+		const std::vector <int> nums = maildirUtils::messageSetToNumberList(msgs);
 
-	for (int i = from, j = 0 ; i <= to2 ; ++i, ++j)
-		nums[j] = i;
+		// Change message flags
+		ref <utility::fileSystemFactory> fsf = platform::getHandler()->getFileSystemFactory();
 
-	// Change message flags
-	setMessageFlagsImpl(nums, flags, mode);
+		utility::file::path curDirPath = store->getFormat()->
+			folderPathToFileSystemPath(m_path, maildirFormat::CUR_DIRECTORY);
 
-	// Update local flags
-	switch (mode)
-	{
-	case message::FLAG_MODE_ADD:
-	{
-		for (std::vector <maildirMessage*>::iterator it =
-		     m_messages.begin() ; it != m_messages.end() ; ++it)
-		{
-			if ((*it)->getNumber() >= from && (*it)->getNumber() <= to2 &&
-			    (*it)->m_flags != message::FLAG_UNDEFINED)
-			{
-				(*it)->m_flags |= flags;
-			}
-		}
-
-		break;
-	}
-	case message::FLAG_MODE_REMOVE:
-	{
-		for (std::vector <maildirMessage*>::iterator it =
-		     m_messages.begin() ; it != m_messages.end() ; ++it)
+		for (std::vector <int>::const_iterator it =
+			 nums.begin() ; it != nums.end() ; ++it)
 		{
-			if ((*it)->getNumber() >= from && (*it)->getNumber() <= to2 &&
-			    (*it)->m_flags != message::FLAG_UNDEFINED)
-			{
-				(*it)->m_flags &= ~flags;
-			}
-		}
+			const int num = *it - 1;
 
-		break;
-	}
-	default:
-	case message::FLAG_MODE_SET:
-	{
-		for (std::vector <maildirMessage*>::iterator it =
-		     m_messages.begin() ; it != m_messages.end() ; ++it)
-		{
-			if ((*it)->getNumber() >= from && (*it)->getNumber() <= to2 &&
-			    (*it)->m_flags != message::FLAG_UNDEFINED)
+			try
 			{
-				(*it)->m_flags = flags;
-			}
-		}
-
-		break;
-	}
-
-	}
-
-	// Notify message flags changed
-	ref <events::messageChangedEvent> event =
-		vmime::create <events::messageChangedEvent>
-			(thisRef().dynamicCast <folder>(),
-			 events::messageChangedEvent::TYPE_FLAGS, nums);
-
-	notifyMessageChanged(event);
-
-	// TODO: notify other folders with the same path
-}
-
+				const utility::file::path::component path = m_messageInfos[num].path;
+				ref <utility::file> file = fsf->create(curDirPath / path);
 
-void maildirFolder::setMessageFlags
-	(const std::vector <int>& nums, const int flags, const int mode)
-{
-	ref <maildirStore> store = m_store.acquire();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-	else if (m_mode == MODE_READ_ONLY)
-		throw exceptions::illegal_state("Folder is read-only");
+				int newFlags = maildirUtils::extractFlags(path);
 
-	// Sort the list of message numbers
-	std::vector <int> list;
+				switch (mode)
+				{
+				case message::FLAG_MODE_ADD:    newFlags |= flags; break;
+				case message::FLAG_MODE_REMOVE: newFlags &= ~flags; break;
+				default:
+				case message::FLAG_MODE_SET:    newFlags = flags; break;
+				}
 
-	list.resize(nums.size());
-	std::copy(nums.begin(), nums.end(), list.begin());
+				const utility::file::path::component newPath = maildirUtils::buildFilename
+					(maildirUtils::extractId(path), newFlags);
 
-	std::sort(list.begin(), list.end());
+				file->rename(curDirPath / newPath);
 
-	// Change message flags
-	setMessageFlagsImpl(list, flags, mode);
+				if (flags & message::FLAG_DELETED)
+					m_messageInfos[num].type = messageInfos::TYPE_DELETED;
+				else
+					m_messageInfos[num].type = messageInfos::TYPE_CUR;
 
-	// Update local flags
-	switch (mode)
-	{
-	case message::FLAG_MODE_ADD:
-	{
-		for (std::vector <maildirMessage*>::iterator it =
-		     m_messages.begin() ; it != m_messages.end() ; ++it)
-		{
-			if (std::binary_search(list.begin(), list.end(), (*it)->getNumber()) &&
-			    (*it)->m_flags != message::FLAG_UNDEFINED)
+				m_messageInfos[num].path = newPath;
+			}
+			catch (exceptions::filesystem_exception& e)
 			{
-				(*it)->m_flags |= flags;
+				// Ignore (not important)
 			}
 		}
 
-		break;
-	}
-	case message::FLAG_MODE_REMOVE:
-	{
-		for (std::vector <maildirMessage*>::iterator it =
-		     m_messages.begin() ; it != m_messages.end() ; ++it)
+		// Update local flags
+		switch (mode)
+		{
+		case message::FLAG_MODE_ADD:
 		{
-			if (std::binary_search(list.begin(), list.end(), (*it)->getNumber()) &&
-			    (*it)->m_flags != message::FLAG_UNDEFINED)
+			for (std::vector <maildirMessage*>::iterator it =
+				 m_messages.begin() ; it != m_messages.end() ; ++it)
 			{
-				(*it)->m_flags &= ~flags;
+				if (std::binary_search(nums.begin(), nums.end(), (*it)->getNumber()) &&
+					(*it)->m_flags != message::FLAG_UNDEFINED)
+				{
+					(*it)->m_flags |= flags;
+				}
 			}
-		}
 
-		break;
-	}
-	default:
-	case message::FLAG_MODE_SET:
-	{
-		for (std::vector <maildirMessage*>::iterator it =
-		     m_messages.begin() ; it != m_messages.end() ; ++it)
+			break;
+		}
+		case message::FLAG_MODE_REMOVE:
 		{
-			if (std::binary_search(list.begin(), list.end(), (*it)->getNumber()) &&
-			    (*it)->m_flags != message::FLAG_UNDEFINED)
+			for (std::vector <maildirMessage*>::iterator it =
+				 m_messages.begin() ; it != m_messages.end() ; ++it)
 			{
-				(*it)->m_flags = flags;
+				if (std::binary_search(nums.begin(), nums.end(), (*it)->getNumber()) &&
+					(*it)->m_flags != message::FLAG_UNDEFINED)
+				{
+					(*it)->m_flags &= ~flags;
+				}
 			}
-		}
-
-		break;
-	}
-
-	}
-
-	// Notify message flags changed
-	ref <events::messageChangedEvent> event =
-		vmime::create <events::messageChangedEvent>
-			(thisRef().dynamicCast <folder>(),
-			 events::messageChangedEvent::TYPE_FLAGS, nums);
-
-	notifyMessageChanged(event);
 
-	// TODO: notify other folders with the same path
-}
-
-
-void maildirFolder::setMessageFlagsImpl
-	(const std::vector <int>& nums, const int flags, const int mode)
-{
-	ref <maildirStore> store = m_store.acquire();
-
-	ref <utility::fileSystemFactory> fsf = platform::getHandler()->getFileSystemFactory();
-
-	utility::file::path curDirPath = store->getFormat()->
-		folderPathToFileSystemPath(m_path, maildirFormat::CUR_DIRECTORY);
-
-	for (std::vector <int>::const_iterator it =
-	     nums.begin() ; it != nums.end() ; ++it)
-	{
-		const int num = *it - 1;
-
-		try
+			break;
+		}
+		default:
+		case message::FLAG_MODE_SET:
 		{
-			const utility::file::path::component path = m_messageInfos[num].path;
-			ref <utility::file> file = fsf->create(curDirPath / path);
-
-			int newFlags = maildirUtils::extractFlags(path);
-
-			switch (mode)
+			for (std::vector <maildirMessage*>::iterator it =
+				 m_messages.begin() ; it != m_messages.end() ; ++it)
 			{
-			case message::FLAG_MODE_ADD:    newFlags |= flags; break;
-			case message::FLAG_MODE_REMOVE: newFlags &= ~flags; break;
-			default:
-			case message::FLAG_MODE_SET:    newFlags = flags; break;
+				if (std::binary_search(nums.begin(), nums.end(), (*it)->getNumber()) &&
+					(*it)->m_flags != message::FLAG_UNDEFINED)
+				{
+					(*it)->m_flags = flags;
+				}
 			}
 
-			const utility::file::path::component newPath = maildirUtils::buildFilename
-				(maildirUtils::extractId(path), newFlags);
+			break;
+		}
 
-			file->rename(curDirPath / newPath);
+		}
 
-			if (flags & message::FLAG_DELETED)
-				m_messageInfos[num].type = messageInfos::TYPE_DELETED;
-			else
-				m_messageInfos[num].type = messageInfos::TYPE_CUR;
+		// Notify message flags changed
+		ref <events::messageChangedEvent> event =
+			vmime::create <events::messageChangedEvent>
+				(thisRef().dynamicCast <folder>(),
+				 events::messageChangedEvent::TYPE_FLAGS, nums);
 
-			m_messageInfos[num].path = newPath;
-		}
-		catch (exceptions::filesystem_exception& e)
-		{
-			// Ignore (not important)
-		}
+		notifyMessageChanged(event);
+
+		// TODO: notify other folders with the same path
+	}
+	else
+	{
+		throw exceptions::operation_not_supported();
 	}
 }
 
@@ -1032,46 +904,7 @@ void maildirFolder::copyMessageImpl(const utility::file::path& tmpDirPath,
 }
 
 
-void maildirFolder::copyMessage(const folder::path& dest, const int num)
-{
-	ref <maildirStore> store = m_store.acquire();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	copyMessages(dest, num, num);
-}
-
-
-void maildirFolder::copyMessages(const folder::path& dest, const int from, const int to)
-{
-	ref <maildirStore> store = m_store.acquire();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-	else if (from < 1 || (to < from && to != -1))
-		throw exceptions::invalid_argument();
-
-	// Construct the list of message numbers
-	const int to2 = (to == -1) ? m_messageCount : to;
-	const int count = to - from + 1;
-
-	std::vector <int> nums;
-	nums.resize(count);
-
-	for (int i = from, j = 0 ; i <= to2 ; ++i, ++j)
-		nums[j] = i;
-
-	// Copy messages
-	copyMessagesImpl(dest, nums);
-}
-
-
-void maildirFolder::copyMessages(const folder::path& dest, const std::vector <int>& nums)
+void maildirFolder::copyMessages(const folder::path& dest, const messageSet& msgs)
 {
 	ref <maildirStore> store = m_store.acquire();
 
@@ -1080,15 +913,6 @@ void maildirFolder::copyMessages(const folder::path& dest, const std::vector <in
 	else if (!isOpen())
 		throw exceptions::illegal_state("Folder not open");
 
-	// Copy messages
-	copyMessagesImpl(dest, nums);
-}
-
-
-void maildirFolder::copyMessagesImpl(const folder::path& dest, const std::vector <int>& nums)
-{
-	ref <maildirStore> store = m_store.acquire();
-
 	ref <utility::fileSystemFactory> fsf = platform::getHandler()->getFileSystemFactory();
 
 	utility::file::path curDirPath = store->getFormat()->folderPathToFileSystemPath
@@ -1121,6 +945,8 @@ void maildirFolder::copyMessagesImpl(const folder::path& dest, const std::vector
 	}
 
 	// Copy messages
+	const std::vector <int> nums = maildirUtils::messageSetToNumberList(msgs);
+
 	try
 	{
 		for (std::vector <int>::const_iterator it =
diff --git a/src/net/maildir/maildirMessage.cpp b/src/net/maildir/maildirMessage.cpp
index e63d5edf..a7c2a22f 100644
--- a/src/net/maildir/maildirMessage.cpp
+++ b/src/net/maildir/maildirMessage.cpp
@@ -140,7 +140,7 @@ void maildirMessage::setFlags(const int flags, const int mode)
 	if (!folder)
 		throw exceptions::folder_not_found();
 
-	folder->setMessageFlags(m_num, m_num, flags, mode);
+	folder->setMessageFlags(messageSet::byNumber(m_num), flags, mode);
 }
 
 
diff --git a/src/net/maildir/maildirUtils.cpp b/src/net/maildir/maildirUtils.cpp
index 9028fa59..c4ba2857 100644
--- a/src/net/maildir/maildirUtils.cpp
+++ b/src/net/maildir/maildirUtils.cpp
@@ -214,6 +214,38 @@ void maildirUtils::recursiveFSDelete(ref <utility::file> dir)
 
 
 
+class maildirMessageSetEnumerator : public messageSetEnumerator
+{
+public:
+
+	void enumerateNumberMessageRange(const vmime::net::numberMessageRange& range)
+	{
+		for (int i = range.getFirst(), last = range.getLast() ; i <= last ; ++i)
+			list.push_back(i);
+	}
+
+	void enumerateUIDMessageRange(const vmime::net::UIDMessageRange& /* range */)
+	{
+		// Not supported
+	}
+
+public:
+
+	std::vector <int> list;
+};
+
+
+// static
+const std::vector <int> maildirUtils::messageSetToNumberList(const messageSet& msgs)
+{
+	maildirMessageSetEnumerator en;
+	msgs.enumerate(en);
+
+	return en.list;
+}
+
+
+
 //
 // messageIdComparator
 //
diff --git a/src/net/messageSet.cpp b/src/net/messageSet.cpp
new file mode 100644
index 00000000..04f1debb
--- /dev/null
+++ b/src/net/messageSet.cpp
@@ -0,0 +1,369 @@
+//
+// VMime library (http://www.vmime.org)
+// Copyright (C) 2002-2013 Vincent Richard <[email protected]>
+//
+// 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 3 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.
+//
+// Linking this library statically or dynamically with other modules is making
+// a combined work based on this library.  Thus, the terms and conditions of
+// the GNU General Public License cover the whole combination.
+//
+
+#include "vmime/net/messageSet.hpp"
+
+#include <iterator>
+#include <algorithm>
+#include <typeinfo>
+
+
+namespace vmime {
+namespace net {
+
+
+// messageRange
+
+messageRange::messageRange()
+{
+}
+
+
+messageRange::~messageRange()
+{
+}
+
+
+// numberMessageRange
+
+numberMessageRange::numberMessageRange(const int number)
+	: m_first(number), m_last(number)
+{
+	if (number < 1)
+		throw std::invalid_argument("number");
+}
+
+
+numberMessageRange::numberMessageRange(const int first, const int last)
+	: m_first(first), m_last(last)
+{
+	if (first < 1)
+		throw std::invalid_argument("first");
+	else if (last != -1 && last < first)
+		throw std::invalid_argument("last");
+}
+
+
+numberMessageRange::numberMessageRange(const numberMessageRange& other)
+	: messageRange(), m_first(other.m_first), m_last(other.m_last)
+{
+}
+
+
+int numberMessageRange::getFirst() const
+{
+	return m_first;
+}
+
+
+int numberMessageRange::getLast() const
+{
+	return m_last;
+}
+
+
+void numberMessageRange::enumerate(messageSetEnumerator& en) const
+{
+	en.enumerateNumberMessageRange(*this);
+}
+
+
+messageRange* numberMessageRange::clone() const
+{
+	return new numberMessageRange(*this);
+}
+
+
+// UIDMessageRange
+
+UIDMessageRange::UIDMessageRange(const message::uid& uid)
+	: m_first(uid), m_last(uid)
+{
+}
+
+
+UIDMessageRange::UIDMessageRange(const message::uid& first, const message::uid& last)
+	: m_first(first), m_last(last)
+{
+}
+
+
+UIDMessageRange::UIDMessageRange(const UIDMessageRange& other)
+	: messageRange(), m_first(other.m_first), m_last(other.m_last)
+{
+}
+
+
+const message::uid UIDMessageRange::getFirst() const
+{
+	return m_first;
+}
+
+
+const message::uid UIDMessageRange::getLast() const
+{
+	return m_last;
+}
+
+
+void UIDMessageRange::enumerate(messageSetEnumerator& en) const
+{
+	en.enumerateUIDMessageRange(*this);
+}
+
+
+messageRange* UIDMessageRange::clone() const
+{
+	return new UIDMessageRange(*this);
+}
+
+
+// messageSet
+
+
+messageSet::messageSet()
+{
+}
+
+
+messageSet::messageSet(const messageSet& other)
+	: object()
+{
+	m_ranges.resize(other.m_ranges.size());
+
+	for (unsigned int i = 0, n = other.m_ranges.size() ; i < n ; ++i)
+		m_ranges[i] = other.m_ranges[i]->clone();
+}
+
+
+messageSet::~messageSet()
+{
+	for (unsigned int i = 0, n = m_ranges.size() ; i < n ; ++i)
+		delete m_ranges[i];
+}
+
+
+// static
+messageSet messageSet::byNumber(const int number)
+{
+	messageSet set;
+	set.m_ranges.push_back(new numberMessageRange(number));
+
+	return set;
+}
+
+
+// static
+messageSet messageSet::byNumber(const int first, const int last)
+{
+	messageSet set;
+	set.m_ranges.push_back(new numberMessageRange(first, last));
+
+	return set;
+}
+
+
+// static
+messageSet messageSet::byNumber(const std::vector <int>& numbers)
+{
+	// Sort a copy of the list
+	std::vector <int> sortedNumbers;
+
+	sortedNumbers.resize(numbers.size());
+
+	std::copy(numbers.begin(), numbers.end(), sortedNumbers.begin());
+	std::sort(sortedNumbers.begin(), sortedNumbers.end());
+
+	// Build the set by detecting ranges of continuous numbers
+	int previous = -1, rangeStart = -1;
+	messageSet set;
+
+	for (std::vector <int>::const_iterator it = sortedNumbers.begin() ;
+	     it != sortedNumbers.end() ; ++it)
+	{
+		const int current = *it;
+
+		if (current == previous)
+			continue;  // skip duplicates
+
+		if (previous == -1)
+		{
+			previous = current;
+			rangeStart = current;
+		}
+		else
+		{
+			if (current == previous + 1)
+			{
+				previous = current;
+			}
+			else
+			{
+				set.m_ranges.push_back(new numberMessageRange(rangeStart, previous));
+
+				previous = current;
+				rangeStart = current;
+			}
+		}
+	}
+
+	set.m_ranges.push_back(new numberMessageRange(rangeStart, previous));
+
+	return set;
+}
+
+
+// static
+messageSet messageSet::byUID(const message::uid& uid)
+{
+	messageSet set;
+	set.m_ranges.push_back(new UIDMessageRange(uid));
+
+	return set;
+}
+
+
+messageSet messageSet::byUID(const message::uid& first, const message::uid& last)
+{
+	messageSet set;
+	set.m_ranges.push_back(new UIDMessageRange(first, last));
+
+	return set;
+}
+
+
+messageSet messageSet::byUID(const std::vector <message::uid>& uids)
+{
+	std::vector <vmime_uint32> numericUIDs;
+
+	for (unsigned int i = 0, n = uids.size() ; i < n ; ++i)
+	{
+		const string uid = uids[i];
+		int numericUID = 0;
+
+		const string::value_type* p = uid.c_str();
+
+		for ( ; *p >= '0' && *p <= '9' ; ++p)
+			 numericUID = (numericUID * 10) + (*p - '0');
+
+		if (*p != '\0')
+		{
+			messageSet set;
+
+			// Non-numeric UID, fall back to plain UID list (single-UID ranges)
+			for (unsigned int i = 0, n = uids.size() ; i < n ; ++i)
+				set.m_ranges.push_back(new UIDMessageRange(uids[i]));
+
+			return set;
+		}
+
+		numericUIDs.push_back(numericUID);
+	}
+
+	// Sort a copy of the list
+	std::vector <vmime_uint32> sortedUIDs;
+
+	sortedUIDs.resize(numericUIDs.size());
+
+	std::copy(numericUIDs.begin(), numericUIDs.end(), sortedUIDs.begin());
+	std::sort(sortedUIDs.begin(), sortedUIDs.end());
+
+	// Build the set by detecting ranges of continuous numbers
+	vmime_uint32 previous = -1U, rangeStart = -1U;
+	messageSet set;
+
+	for (std::vector <vmime_uint32>::const_iterator it = sortedUIDs.begin() ;
+	     it != sortedUIDs.end() ; ++it)
+	{
+		const vmime_uint32 current = *it;
+
+		if (current == previous)
+			continue;  // skip duplicates
+
+		if (previous == -1U)
+		{
+			previous = current;
+			rangeStart = current;
+		}
+		else
+		{
+			if (current == previous + 1)
+			{
+				previous = current;
+			}
+			else
+			{
+				set.m_ranges.push_back(new UIDMessageRange
+					(static_cast <std::ostringstream*>(&(std::ostringstream() << rangeStart))->str(),
+					 static_cast <std::ostringstream*>(&(std::ostringstream() << previous))->str()));
+
+				previous = current;
+				rangeStart = current;
+			}
+		}
+	}
+
+	set.m_ranges.push_back(new UIDMessageRange
+		(static_cast <std::ostringstream*>(&(std::ostringstream() << rangeStart))->str(),
+		 static_cast <std::ostringstream*>(&(std::ostringstream() << previous))->str()));
+
+	return set;
+}
+
+
+void messageSet::addRange(const messageRange& range)
+{
+	if (!m_ranges.empty() && typeid(*m_ranges[0]) != typeid(range))
+		throw std::invalid_argument("range");
+
+	m_ranges.push_back(range.clone());
+}
+
+
+void messageSet::enumerate(messageSetEnumerator& en) const
+{
+	for (unsigned int i = 0, n = m_ranges.size() ; i < n ; ++i)
+		m_ranges[i]->enumerate(en);
+}
+
+
+bool messageSet::isEmpty() const
+{
+	return m_ranges.empty();
+}
+
+
+bool messageSet::isNumberSet() const
+{
+	return !isEmpty() && dynamic_cast <numberMessageRange*>(m_ranges[0]) != NULL;
+}
+
+
+bool messageSet::isUIDSet() const
+{
+	return !isEmpty() && dynamic_cast <UIDMessageRange*>(m_ranges[0]) != NULL;
+}
+
+
+} // net
+} // vmime
diff --git a/src/net/pop3/POP3Folder.cpp b/src/net/pop3/POP3Folder.cpp
index 9dc4589b..6a652de0 100644
--- a/src/net/pop3/POP3Folder.cpp
+++ b/src/net/pop3/POP3Folder.cpp
@@ -230,62 +230,36 @@ ref <message> POP3Folder::getMessage(const int num)
 }
 
 
-std::vector <ref <message> > POP3Folder::getMessages(const int from, const int to)
+std::vector <ref <message> > POP3Folder::getMessages(const messageSet& msgs)
 {
 	ref <POP3Store> store = m_store.acquire();
 
-	const int to2 = (to == -1 ? m_messageCount : to);
-
 	if (!store)
 		throw exceptions::illegal_state("Store disconnected");
 	else if (!isOpen())
 		throw exceptions::illegal_state("Folder not open");
-	else if (to2 < from || from < 1 || to2 < 1 || from > m_messageCount || to2 > m_messageCount)
-		throw exceptions::message_not_found();
-
-	std::vector <ref <message> > v;
-	ref <POP3Folder> thisFolder = thisRef().dynamicCast <POP3Folder>();
-
-	for (int i = from ; i <= to2 ; ++i)
-		v.push_back(vmime::create <POP3Message>(thisFolder, i));
-
-	return (v);
-}
-
-
-ref <message> POP3Folder::getMessageByUID(const message::uid& /* uid */)
-{
-	throw exceptions::operation_not_supported();
-}
-
-
-std::vector <ref <message> > POP3Folder::getMessagesByUID(const std::vector <message::uid>& /* uids */)
-{
-	throw exceptions::operation_not_supported();
-}
 
+	if (msgs.isNumberSet())
+	{
+		const std::vector <int> numbers = POP3Utils::messageSetToNumberList(msgs);
 
-std::vector <ref <message> > POP3Folder::getMessages(const std::vector <int>& nums)
-{
-	ref <POP3Store> store = m_store.acquire();
+		std::vector <ref <message> > messages;
+		ref <POP3Folder> thisFolder = thisRef().dynamicCast <POP3Folder>();
 
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
+		for (std::vector <int>::const_iterator it = numbers.begin() ; it != numbers.end() ; ++it)
+		{
+			if (*it < 1|| *it > m_messageCount)
+				throw exceptions::message_not_found();
 
-	std::vector <ref <message> > v;
-	ref <POP3Folder> thisFolder = thisRef().dynamicCast <POP3Folder>();
+			messages.push_back(vmime::create <POP3Message>(thisFolder, *it));
+		}
 
-	for (std::vector <int>::const_iterator it = nums.begin() ; it != nums.end() ; ++it)
+		return messages;
+	}
+	else
 	{
-		if (*it < 1|| *it > m_messageCount)
-			throw exceptions::message_not_found();
-
-		v.push_back(vmime::create <POP3Message>(thisFolder, *it));
+		throw exceptions::operation_not_supported();
 	}
-
-	return (v);
 }
 
 
@@ -560,99 +534,11 @@ void POP3Folder::onStoreDisconnected()
 }
 
 
-void POP3Folder::deleteMessage(const int num)
+void POP3Folder::deleteMessages(const messageSet& msgs)
 {
 	ref <POP3Store> store = m_store.acquire();
 
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	POP3Command::DELE(num)->send(store->getConnection());
-
-	ref <POP3Response> response =
-		POP3Response::readResponse(store->getConnection());
-
-	if (!response->isSuccess())
-		throw exceptions::command_error("DELE", response->getFirstLine());
-
-	// Update local flags
-	for (std::map <POP3Message*, int>::iterator it =
-	     m_messages.begin() ; it != m_messages.end() ; ++it)
-	{
-		POP3Message* msg = (*it).first;
-
-		if (msg->getNumber() == num)
-			msg->m_deleted = true;
-	}
-
-	// Notify message flags changed
-	std::vector <int> nums;
-	nums.push_back(num);
-
-	ref <events::messageChangedEvent> event =
-		vmime::create <events::messageChangedEvent>
-			(thisRef().dynamicCast <folder>(),
-			 events::messageChangedEvent::TYPE_FLAGS, nums);
-
-	notifyMessageChanged(event);
-}
-
-
-void POP3Folder::deleteMessages(const int from, const int to)
-{
-	ref <POP3Store> store = m_store.acquire();
-
-	if (from < 1 || (to < from && to != -1))
-		throw exceptions::invalid_argument();
-
-	if (!store)
-		throw exceptions::illegal_state("Store disconnected");
-	else if (!isOpen())
-		throw exceptions::illegal_state("Folder not open");
-
-	const int to2 = (to == -1 ? m_messageCount : to);
-
-	for (int i = from ; i <= to2 ; ++i)
-	{
-		POP3Command::DELE(i)->send(store->getConnection());
-
-		ref <POP3Response> response =
-			POP3Response::readResponse(store->getConnection());
-
-		if (!response->isSuccess())
-			throw exceptions::command_error("DELE", response->getFirstLine());
-	}
-
-	// Update local flags
-	for (std::map <POP3Message*, int>::iterator it =
-	     m_messages.begin() ; it != m_messages.end() ; ++it)
-	{
-		POP3Message* msg = (*it).first;
-
-		if (msg->getNumber() >= from && msg->getNumber() <= to2)
-			msg->m_deleted = true;
-	}
-
-	// Notify message flags changed
-	std::vector <int> nums;
-
-	for (int i = from ; i <= to2 ; ++i)
-		nums.push_back(i);
-
-	ref <events::messageChangedEvent> event =
-		vmime::create <events::messageChangedEvent>
-			(thisRef().dynamicCast <folder>(),
-			 events::messageChangedEvent::TYPE_FLAGS, nums);
-
-	notifyMessageChanged(event);
-}
-
-
-void POP3Folder::deleteMessages(const std::vector <int>& nums)
-{
-	ref <POP3Store> store = m_store.acquire();
+	const std::vector <int> nums = POP3Utils::messageSetToNumberList(msgs);
 
 	if (nums.empty())
 		throw exceptions::invalid_argument();
@@ -702,14 +588,7 @@ void POP3Folder::deleteMessages(const std::vector <int>& nums)
 }
 
 
-void POP3Folder::setMessageFlags(const int /* from */, const int /* to */,
-	const int /* flags */, const int /* mode */)
-{
-	throw exceptions::operation_not_supported();
-}
-
-
-void POP3Folder::setMessageFlags(const std::vector <int>& /* nums */,
+void POP3Folder::setMessageFlags(const messageSet& /* msgs */,
 	const int /* flags */, const int /* mode */)
 {
 	throw exceptions::operation_not_supported();
@@ -736,19 +615,7 @@ void POP3Folder::addMessage(utility::inputStream& /* is */, const int /* size */
 }
 
 
-void POP3Folder::copyMessage(const folder::path& /* dest */, const int /* num */)
-{
-	throw exceptions::operation_not_supported();
-}
-
-
-void POP3Folder::copyMessages(const folder::path& /* dest */, const int /* from */, const int /* to */)
-{
-	throw exceptions::operation_not_supported();
-}
-
-
-void POP3Folder::copyMessages(const folder::path& /* dest */, const std::vector <int>& /* nums */)
+void POP3Folder::copyMessages(const folder::path& /* dest */, const messageSet& /* msgs */)
 {
 	throw exceptions::operation_not_supported();
 }
diff --git a/src/net/pop3/POP3Utils.cpp b/src/net/pop3/POP3Utils.cpp
index f239627f..e2722104 100644
--- a/src/net/pop3/POP3Utils.cpp
+++ b/src/net/pop3/POP3Utils.cpp
@@ -73,6 +73,38 @@ void POP3Utils::parseMultiListOrUidlResponse(ref <POP3Response> response, std::m
 }
 
 
+
+class POP3MessageSetEnumerator : public messageSetEnumerator
+{
+public:
+
+	void enumerateNumberMessageRange(const vmime::net::numberMessageRange& range)
+	{
+		for (int i = range.getFirst(), last = range.getLast() ; i <= last ; ++i)
+			list.push_back(i);
+	}
+
+	void enumerateUIDMessageRange(const vmime::net::UIDMessageRange& /* range */)
+	{
+		// Not supported
+	}
+
+public:
+
+	std::vector <int> list;
+};
+
+
+// static
+const std::vector <int> POP3Utils::messageSetToNumberList(const messageSet& msgs)
+{
+	POP3MessageSetEnumerator en;
+	msgs.enumerate(en);
+
+	return en.list;
+}
+
+
 } // pop3
 } // net
 } // vmime
diff --git a/tests/net/messageSetTest.cpp b/tests/net/messageSetTest.cpp
new file mode 100644
index 00000000..3aef7ab0
--- /dev/null
+++ b/tests/net/messageSetTest.cpp
@@ -0,0 +1,200 @@
+//
+// VMime library (http://www.vmime.org)
+// Copyright (C) 2002-2013 Vincent Richard <[email protected]>
+//
+// 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 3 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.
+//
+// Linking this library statically or dynamically with other modules is making
+// a combined work based on this library.  Thus, the terms and conditions of
+// the GNU General Public License cover the whole combination.
+//
+
+#include "tests/testUtils.hpp"
+
+#include "vmime/net/messageSet.hpp"
+
+
+VMIME_TEST_SUITE_BEGIN(messageSetTest)
+
+	VMIME_TEST_LIST_BEGIN
+		VMIME_TEST(testNumberSet_Single)
+		VMIME_TEST(testNumberSet_Range)
+		VMIME_TEST(testNumberSet_InfiniteRange)
+		VMIME_TEST(testNumberSet_Multiple)
+		VMIME_TEST(testUIDSet_Single)
+		VMIME_TEST(testUIDSet_Range)
+		VMIME_TEST(testUIDSet_InfiniteRange)
+		VMIME_TEST(testUIDSet_MultipleNumeric)
+		VMIME_TEST(testUIDSet_MultipleNonNumeric)
+		VMIME_TEST(testIsNumberSet)
+		VMIME_TEST(testIsUIDSet)
+	VMIME_TEST_LIST_END
+
+
+	class messageSetStringEnumerator : public vmime::net::messageSetEnumerator
+	{
+	public:
+
+		messageSetStringEnumerator()
+			: m_first(true)
+		{
+		}
+
+		void enumerateNumberMessageRange(const vmime::net::numberMessageRange& range)
+		{
+			if (!m_first)
+				m_oss << ",";
+
+			if (range.getFirst() == range.getLast())
+				m_oss << range.getFirst();
+			else
+				m_oss << range.getFirst() << ":" << range.getLast();
+
+			m_first = false;
+		}
+
+		void enumerateUIDMessageRange(const vmime::net::UIDMessageRange& range)
+		{
+			if (!m_first)
+				m_oss << ",";
+
+			if (range.getFirst() == range.getLast())
+				m_oss << range.getFirst();
+			else
+				m_oss << range.getFirst() << ":" << range.getLast();
+
+			m_first = false;
+		}
+
+		const std::string str() const
+		{
+			return m_oss.str();
+		}
+
+	private:
+
+		std::ostringstream m_oss;
+		bool m_first;
+	};
+
+
+	const std::string enumerateAsString(const vmime::net::messageSet& set)
+	{
+		messageSetStringEnumerator en;
+		set.enumerate(en);
+
+		return en.str();
+	}
+
+
+	void testNumberSet_Single()
+	{
+		VASSERT_EQ("str", "42", enumerateAsString(vmime::net::messageSet::byNumber(42)));
+	}
+
+	void testNumberSet_Range()
+	{
+		VASSERT_EQ("str", "42:100", enumerateAsString(vmime::net::messageSet::byNumber(42, 100)));
+	}
+
+	void testNumberSet_InfiniteRange()
+	{
+		VASSERT_EQ("str", "42:-1", enumerateAsString(vmime::net::messageSet::byNumber(42, -1)));
+	}
+
+	void testNumberSet_Multiple()
+	{
+		std::vector <int> numbers;
+		numbers.push_back(1);    // test grouping 1:3
+		numbers.push_back(89);   // test sorting
+		numbers.push_back(2);
+		numbers.push_back(3);
+		numbers.push_back(42);
+		numbers.push_back(53);   // test grouping 53:57
+		numbers.push_back(54);
+		numbers.push_back(55);
+		numbers.push_back(56);
+		numbers.push_back(56);   // test duplicates
+		numbers.push_back(57);
+		numbers.push_back(99);
+
+		VASSERT_EQ("str", "1:3,42,53:57,89,99", enumerateAsString(vmime::net::messageSet::byNumber(numbers)));
+	}
+
+
+	void testUIDSet_Single()
+	{
+		VASSERT_EQ("str", "abcdef", enumerateAsString(vmime::net::messageSet::byUID("abcdef")));
+	}
+
+	void testUIDSet_Range()
+	{
+		VASSERT_EQ("str", "abc:def", enumerateAsString(vmime::net::messageSet::byUID("abc:def")));
+	}
+
+	void testUIDSet_InfiniteRange()
+	{
+		VASSERT_EQ("str", "abc:*", enumerateAsString(vmime::net::messageSet::byUID("abc", "*")));
+	}
+
+	void testUIDSet_MultipleNumeric()
+	{
+		std::vector <vmime::net::message::uid> uids;
+		uids.push_back("1");    // test grouping 1:3
+		uids.push_back("89");   // test sorting
+		uids.push_back("2");
+		uids.push_back("3");
+		uids.push_back("42");
+		uids.push_back("53");   // test grouping 53:57
+		uids.push_back("54");
+		uids.push_back("55");
+		uids.push_back("56");
+		uids.push_back("56");   // test duplicates
+		uids.push_back("57");
+		uids.push_back("99");
+
+		VASSERT_EQ("str", "1:3,42,53:57,89,99", enumerateAsString(vmime::net::messageSet::byUID(uids)));
+	}
+
+	void testUIDSet_MultipleNonNumeric()
+	{
+		std::vector <vmime::net::message::uid> uids;
+		uids.push_back("12");
+		uids.push_back("34");
+		uids.push_back("ab56");
+		uids.push_back("78cd");
+
+		VASSERT_EQ("str", "12,34,ab56,78cd", enumerateAsString(vmime::net::messageSet::byUID(uids)));
+	}
+
+	void testIsNumberSet()
+	{
+		VASSERT_TRUE("number1", vmime::net::messageSet::byNumber(42).isNumberSet());
+		VASSERT_FALSE("uid1", vmime::net::messageSet::byUID("42").isNumberSet());
+
+		VASSERT_TRUE("number2", vmime::net::messageSet::byNumber(42, -1).isNumberSet());
+		VASSERT_FALSE("uid2", vmime::net::messageSet::byUID("42", "*").isNumberSet());
+	}
+
+	void testIsUIDSet()
+	{
+		VASSERT_FALSE("number1", vmime::net::messageSet::byNumber(42).isUIDSet());
+		VASSERT_TRUE("uid1", vmime::net::messageSet::byUID("42").isUIDSet());
+
+		VASSERT_FALSE("number2", vmime::net::messageSet::byNumber(42, -1).isUIDSet());
+		VASSERT_TRUE("uid2", vmime::net::messageSet::byUID("42", "*").isUIDSet());
+	}
+
+VMIME_TEST_SUITE_END
diff --git a/vmime/net/folder.hpp b/vmime/net/folder.hpp
index 4cb6bb1a..fc878fbf 100644
--- a/vmime/net/folder.hpp
+++ b/vmime/net/folder.hpp
@@ -38,6 +38,7 @@
 
 #include "vmime/message.hpp"
 #include "vmime/net/message.hpp"
+#include "vmime/net/messageSet.hpp"
 #include "vmime/net/events.hpp"
 #include "vmime/net/folderStatus.hpp"
 
@@ -186,38 +187,34 @@ public:
 	  */
 	virtual ref <message> getMessage(const int num) = 0;
 
-	/** Get new references to messages in this folder, given their numbers.
+	/** Get new references to messages in this folder, given either their
+	  * sequence numbers or UIDs.
 	  *
-	  * @param from sequence number of the first message to get
-	  * @param to sequence number of the last message to get
-	  * @return new objects referencing the specified messages
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual std::vector <ref <message> > getMessages(const int from = 1, const int to = -1) = 0;
-
-	/** Get new references to messages in this folder, given their numbers.
+	  * To retrieve messages by their number, use:
+	  * \code{.cpp}
+	  *    // Get messages from sequence number 5 to sequence number 8 (including)
+	  *    folder->getMessage(vmime::net::messageSet::byNumber(5, 8));
 	  *
-	  * @param nums sequence numbers of the messages to retrieve
-	  * @return new objects referencing the specified messages
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual std::vector <ref <message> > getMessages(const std::vector <int>& nums) = 0;
-
-	/** Get message in this folder, given its UID.
+	  *    // Get all messages in the folder, starting from number 42
+	  *    folder->getMessage(vmime::net::messageSet::byNumber(42, -1));
+	  * \endcode
+	  * Or, to retrieve messages by their UID, use:
+	  * \code{.cpp}
+	  *    // Get messages from UID 1000 to UID 1042 (including)
+	  *    folder->getMessage(vmime::net::messageSet::byUID(1000, 1042));
 	  *
-	  * @param uid UID of message to retrieve
-	  * @return a new object referencing the specified message
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual ref <message> getMessageByUID(const message::uid& uid) = 0;
-
-	/** Get messages in this folder, given their UIDs.
+	  *    // Get message with UID 1042
+	  *    folder->getMessage(vmime::net::messageSet::byUID(1042));
+	  *
+	  *    // Get all messages in the folder, starting from UID 1000
+	  *    folder->getMessage(vmime::net::messageSet::byUID(1000, "*"));
+	  * \endcode
 	  *
-	  * @param uids UIDs of messages to retrieve
+	  * @param msgs index set of messages to retrieve
 	  * @return new objects referencing the specified messages
 	  * @throw exceptions::net_exception if an error occurs
 	  */
-	virtual std::vector <ref <message> > getMessagesByUID(const std::vector <message::uid>& uids) = 0;
+	virtual std::vector <ref <message> > getMessages(const messageSet& msgs) = 0;
 
 	/** Return the number of messages in this folder.
 	  *
@@ -249,46 +246,21 @@ public:
 	  */
 	virtual void rename(const folder::path& newPath) = 0;
 
-	/** Remove a message in this folder.
-	  *
-	  * @param num sequence number of the message to delete
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual void deleteMessage(const int num) = 0;
-
-	/** Remove one or more messages from this folder.
-	  *
-	  * @param from sequence number of the first message to delete
-	  * @param to sequence number of the last message to delete
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual void deleteMessages(const int from = 1, const int to = -1) = 0;
-
 	/** Remove one or more messages from this folder.
 	  *
-	  * @param nums sequence numbers of the messages to delete
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual void deleteMessages(const std::vector <int>& nums) = 0;
-
-	/** Change the flags for one or more messages in this folder.
-	  *
-	  * @param from sequence number of the first message to modify
-	  * @param to sequence number of the last message to modify
-	  * @param flags set of flags (see message::Flags)
-	  * @param mode indicate how to treat old and new flags (see message::FlagsModes)
+	  * @param msgs index set of messages to delete
 	  * @throw exceptions::net_exception if an error occurs
 	  */
-	virtual void setMessageFlags(const int from, const int to, const int flags, const int mode = message::FLAG_MODE_SET) = 0;
+	virtual void deleteMessages(const messageSet& msgs) = 0;
 
 	/** Change the flags for one or more messages in this folder.
 	  *
-	  * @param nums sequence numbers of the messages to modify
+	  * @param msgs index set of messages on which to set the flags
 	  * @param flags set of flags (see message::Flags)
 	  * @param mode indicate how to treat old and new flags (see message::FlagsModes)
 	  * @throw exceptions::net_exception if an error occurs
 	  */
-	virtual void setMessageFlags(const std::vector <int>& nums, const int flags, const int mode = message::FLAG_MODE_SET) = 0;
+	virtual void setMessageFlags(const messageSet& msgs, const int flags, const int mode = message::FLAG_MODE_SET) = 0;
 
 	/** Add a message to this folder.
 	  *
@@ -311,30 +283,13 @@ public:
 	  */
 	virtual void addMessage(utility::inputStream& is, const int size, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL) = 0;
 
-	/** Copy a message from this folder to another folder.
-	  *
-	  * @param dest destination folder path
-	  * @param num sequence number of the message to copy
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual void copyMessage(const folder::path& dest, const int num) = 0;
-
-	/** Copy messages from this folder to another folder.
-	  *
-	  * @param dest destination folder path
-	  * @param from sequence number of the first message to copy
-	  * @param to sequence number of the last message to copy
-	  * @throw exceptions::net_exception if an error occurs
-	  */
-	virtual void copyMessages(const folder::path& dest, const int from = 1, const int to = -1) = 0;
-
 	/** Copy messages from this folder to another folder.
 	  *
 	  * @param dest destination folder path
-	  * @param nums sequence numbers of the messages to copy
+	  * @param msgs index set of messages to copy
 	  * @throw exceptions::net_exception if an error occurs
 	  */
-	virtual void copyMessages(const folder::path& dest, const std::vector <int>& nums) = 0;
+	virtual void copyMessages(const folder::path& dest, const messageSet& msgs) = 0;
 
 	/** Request folder status without opening it.
 	  *
diff --git a/vmime/net/imap/IMAPFolder.hpp b/vmime/net/imap/IMAPFolder.hpp
index c1d2d34a..b7fc46a1 100644
--- a/vmime/net/imap/IMAPFolder.hpp
+++ b/vmime/net/imap/IMAPFolder.hpp
@@ -91,11 +91,7 @@ public:
 	bool isOpen() const;
 
 	ref <message> getMessage(const int num);
-	std::vector <ref <message> > getMessages(const int from = 1, const int to = -1);
-	std::vector <ref <message> > getMessages(const std::vector <int>& nums);
-
-	ref <message> getMessageByUID(const message::uid& uid);
-	std::vector <ref <message> > getMessagesByUID(const std::vector <message::uid>& uids);
+	std::vector <ref <message> > getMessages(const messageSet& msgs);
 
 	std::vector <int> getMessageNumbersStartingOnUID(const message::uid& uid);
 
@@ -106,19 +102,14 @@ public:
 
 	void rename(const folder::path& newPath);
 
-	void deleteMessage(const int num);
-	void deleteMessages(const int from = 1, const int to = -1);
-	void deleteMessages(const std::vector <int>& nums);
+	void deleteMessages(const messageSet& msgs);
 
-	void setMessageFlags(const int from, const int to, const int flags, const int mode = message::FLAG_MODE_SET);
-	void setMessageFlags(const std::vector <int>& nums, const int flags, const int mode = message::FLAG_MODE_SET);
+	void setMessageFlags(const messageSet& msgs, const int flags, const int mode = message::FLAG_MODE_SET);
 
 	void addMessage(ref <vmime::message> msg, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL);
 	void addMessage(utility::inputStream& is, const int size, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL);
 
-	void copyMessage(const folder::path& dest, const int num);
-	void copyMessages(const folder::path& dest, const int from = 1, const int to = -1);
-	void copyMessages(const folder::path& dest, const std::vector <int>& nums);
+	void copyMessages(const folder::path& dest, const messageSet& msgs);
 
 	void status(int& count, int& unseen);
 	ref <folderStatus> getStatus();
diff --git a/vmime/net/imap/IMAPUtils.hpp b/vmime/net/imap/IMAPUtils.hpp
index 7a03fcac..1dfde7a9 100644
--- a/vmime/net/imap/IMAPUtils.hpp
+++ b/vmime/net/imap/IMAPUtils.hpp
@@ -73,29 +73,6 @@ public:
 
 	static const string messageFlagList(const int flags);
 
-	/** Build an "IMAP set" given a list of message numbers. The function tries
-	  * to group consecutive message numbers to reduce the list.
-	  *
-	  * Example:
-	  *    IN  = "1,2,3,4,5,7,8,13,15,16,17"
-	  *    OUT = "1:5,7:8,13,15:*" for a mailbox with a total of 17 messages (max = 17)
-	  *
-	  * @param list list of message numbers
-	  * @param max number of messages in the mailbox (or -1 if not known)
-	  * @param alreadySorted set to true if the list of message numbers is
-	  * already sorted in ascending order
-	  * @return a set corresponding to the message list
-	  */
-	static const string listToSet(const std::vector <int>& list,
-		const int max = -1, const bool alreadySorted = false);
-
-	/** Build an "IMAP set" set given a list of message UIDs.
-	  *
-	  * @param list list of message UIDs
-	  * @return a set corresponding to the list
-	  */
-	static const string listToSet(const std::vector <message::uid>& list);
-
 	/** Format a date/time to IMAP date/time format.
 	  *
 	  * @param date date/time to format
@@ -103,25 +80,16 @@ public:
 	  */
 	static const string dateTime(const vmime::datetime& date);
 
-	/** Construct a fetch request for the specified messages, designated by their sequence numbers.
-	  *
-	  * @param cnt connection
-	  * @param list list of message numbers
-	  * @param options fetch options
-	  * @return fetch request
-	  */
-	static const string buildFetchRequest
-		(ref <IMAPConnection> cnt, const std::vector <int>& list, const int options);
-
-	/** Construct a fetch request for the specified messages, designated by their UIDs.
+	/** Construct a fetch request for the specified messages, designated
+	  * either by their sequence numbers or their UIDs.
 	  *
 	  * @param cnt connection
-	  * @param list list of message UIDs
+	  * @param msgs message set
 	  * @param options fetch options
 	  * @return fetch request
 	  */
 	static const string buildFetchRequest
-		(ref <IMAPConnection> cnt, const std::vector <message::uid>& list, const int options);
+		(ref <IMAPConnection> cnt, const messageSet& msgs, const int options);
 
 	/** Convert a parser-style address list to a mailbox list.
 	  *
@@ -130,6 +98,20 @@ public:
 	  */
 	static void convertAddressList(const IMAPParser::address_list& src, mailboxList& dest);
 
+	/** Returns an IMAP-formatted sequence set given a message set.
+	  *
+	  * @param msgs message set
+	  * @return IMAP sequence set (eg. "1:5,7,15:*")
+	  */
+	static const string messageSetToSequenceSet(const messageSet& msgs);
+
+	/** Returns a list of message sequence numbers given a message set.
+	  *
+	  * @param msgs message set
+	  * @return list of message numbers
+	  */
+	static const std::vector <int> messageSetToNumberList(const messageSet& msgs);
+
 private:
 
 	static const string buildFetchRequestImpl
diff --git a/vmime/net/maildir/maildirFolder.hpp b/vmime/net/maildir/maildirFolder.hpp
index 940fcaae..2b6f8b4d 100644
--- a/vmime/net/maildir/maildirFolder.hpp
+++ b/vmime/net/maildir/maildirFolder.hpp
@@ -89,11 +89,7 @@ public:
 	bool isOpen() const;
 
 	ref <message> getMessage(const int num);
-	std::vector <ref <message> > getMessages(const int from = 1, const int to = -1);
-	std::vector <ref <message> > getMessages(const std::vector <int>& nums);
-
-	ref <message> getMessageByUID(const message::uid& uid);
-	std::vector <ref <message> > getMessagesByUID(const std::vector <message::uid>& uids);
+	std::vector <ref <message> > getMessages(const messageSet& msgs);
 
 	int getMessageCount();
 
@@ -102,19 +98,14 @@ public:
 
 	void rename(const folder::path& newPath);
 
-	void deleteMessage(const int num);
-	void deleteMessages(const int from = 1, const int to = -1);
-	void deleteMessages(const std::vector <int>& nums);
+	void deleteMessages(const messageSet& msgs);
 
-	void setMessageFlags(const int from, const int to, const int flags, const int mode = message::FLAG_MODE_SET);
-	void setMessageFlags(const std::vector <int>& nums, const int flags, const int mode = message::FLAG_MODE_SET);
+	void setMessageFlags(const messageSet& msgs, const int flags, const int mode = message::FLAG_MODE_SET);
 
 	void addMessage(ref <vmime::message> msg, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL);
 	void addMessage(utility::inputStream& is, const int size, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL);
 
-	void copyMessage(const folder::path& dest, const int num);
-	void copyMessages(const folder::path& dest, const int from = 1, const int to = -1);
-	void copyMessages(const folder::path& dest, const std::vector <int>& nums);
+	void copyMessages(const folder::path& dest, const messageSet& msgs);
 
 	void status(int& count, int& unseen);
 	ref <folderStatus> getStatus();
diff --git a/vmime/net/maildir/maildirUtils.hpp b/vmime/net/maildir/maildirUtils.hpp
index 22246fb7..072a2648 100644
--- a/vmime/net/maildir/maildirUtils.hpp
+++ b/vmime/net/maildir/maildirUtils.hpp
@@ -34,6 +34,8 @@
 #include "vmime/utility/file.hpp"
 #include "vmime/utility/path.hpp"
 
+#include "vmime/net/messageSet.hpp"
+
 
 namespace vmime {
 namespace net {
@@ -129,6 +131,13 @@ public:
 	  * @param dir directory to delete
 	  */
 	static void recursiveFSDelete(ref <utility::file> dir);
+
+	/** Returns a list of message numbers given a message set.
+	  *
+	  * @param msgs message set
+	  * @return list of message numbers
+	  */
+	static const std::vector <int> messageSetToNumberList(const messageSet& msgs);
 };
 
 
diff --git a/vmime/net/messageSet.hpp b/vmime/net/messageSet.hpp
new file mode 100644
index 00000000..2535ac25
--- /dev/null
+++ b/vmime/net/messageSet.hpp
@@ -0,0 +1,335 @@
+//
+// VMime library (http://www.vmime.org)
+// Copyright (C) 2002-2013 Vincent Richard <[email protected]>
+//
+// 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 3 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.
+//
+// Linking this library statically or dynamically with other modules is making
+// a combined work based on this library.  Thus, the terms and conditions of
+// the GNU General Public License cover the whole combination.
+//
+
+#ifndef VMIME_NET_MESSAGESET_HPP_INCLUDED
+#define VMIME_NET_MESSAGESET_HPP_INCLUDED
+
+
+#include "vmime/net/message.hpp"
+
+
+namespace vmime {
+namespace net {
+
+
+// Forward references
+class numberMessageRange;
+class UIDMessageRange;
+
+
+/** Enumerator used to retrieve the message number/UID ranges contained
+  * in a messageSet object.
+  */
+
+class VMIME_EXPORT messageSetEnumerator
+{
+public:
+
+	virtual void enumerateNumberMessageRange(const numberMessageRange& range) = 0;
+	virtual void enumerateUIDMessageRange(const UIDMessageRange& range) = 0;
+};
+
+
+/** A range of (continuous) messages, designated either by their
+  * sequence number, or by their UID.
+  */
+
+class messageRange : public object
+{
+public:
+
+	virtual ~messageRange();
+
+	/** Enumerates this range with the specified enumerator.
+	  *
+	  * @param en enumerator that will receive the method calls while
+	  * enumerating this range
+	  */
+	virtual void enumerate(messageSetEnumerator& en) const = 0;
+
+	/** Clones this message range.
+	  */
+	virtual messageRange* clone() const = 0;
+
+protected:
+
+	messageRange();
+	messageRange(const messageRange&);
+};
+
+
+/** A range of (continuous) messages designated by their sequence number.
+  */
+
+class numberMessageRange : public messageRange
+{
+public:
+
+	/** Constructs a message range containing a single message.
+	  *
+	  * @param number message number (numbering starts at 1, not 0)
+	  */
+	numberMessageRange(const int number);
+
+	/** Constructs a message range for multiple messages.
+	  *
+	  * @param first number of the first message in the range (numbering
+	  * starts at 1, not 0)
+	  * @param last number of the last message in the range, or use the
+	  * special value -1 to designate the last message in the folder
+	  */
+	numberMessageRange(const int first, const int last);
+
+	/** Constructs a message range by copying from another range.
+	  *
+	  * @param other range to copy
+	  */
+	numberMessageRange(const numberMessageRange& other);
+
+	/** Returns the number of the first message in the range.
+	  *
+	  * @return number of the first message
+	  */
+	int getFirst() const;
+
+	/** Returns the number of the last message in the range, or -1
+	  * to designate the last message in the folder
+	  *
+	  * @return number of the last message
+	  */
+	int getLast() const;
+
+	void enumerate(messageSetEnumerator& en) const;
+
+	messageRange* clone() const;
+
+private:
+
+	int m_first, m_last;
+};
+
+
+/** A range of (continuous) messages represented by their UID.
+  */
+
+class UIDMessageRange : public messageRange
+{
+public:
+
+	/** Constructs a message range containing a single message.
+	  *
+	  * @param uid message UID
+	  */
+	UIDMessageRange(const message::uid& uid);
+
+	/** Constructs a message range for multiple messages.
+	  *
+	  * @param first UID of the first message in the range
+	  * @param last UID of the last message in the range, or use the
+	  * special value '*' to designate the last message in the folder
+	  */
+	UIDMessageRange(const message::uid& first, const message::uid& last);
+
+	/** Constructs a message range by copying from another range.
+	  *
+	  * @param other range to copy
+	  */
+	UIDMessageRange(const UIDMessageRange& other);
+
+	/** Returns the UID of the first message in the range.
+	  *
+	  * @return UID of the first message
+	  */
+	const message::uid getFirst() const;
+
+	/** Returns the UID of the last message in the range, or '*'
+	  * to designate the last message in the folder
+	  *
+	  * @return UID of the last message
+	  */
+	const message::uid getLast() const;
+
+	void enumerate(messageSetEnumerator& en) const;
+
+	messageRange* clone() const;
+
+private:
+
+	message::uid m_first, m_last;
+};
+
+
+/** Represents a set of messages, designated either by their sequence
+  * number, or by their UID (but not both).
+  *
+  * Following is example code to designate messages by their number:
+  * \code{.cpp}
+  *    // Designate a single message with sequence number 42
+  *    vmime::net::messageSet::byNumber(42)
+  *
+  *    // Designate messages from sequence number 5 to sequence number 8 (including)
+  *    vmime::net::messageSet::byNumber(5, 8)
+  *
+  *    // Designate all messages in the folder, starting from number 42
+  *    vmime::net::messageSet::byNumber(42, -1)
+  * \endcode
+  * Or, to designate messages by their UID, use:
+  * \code{.cpp}
+  *    // Designate a single message with UID 1042
+  *    vmime::net::messageSet::byUID(1042)
+  *
+  *    // Designate messages from UID 1000 to UID 1042 (including)
+  *    vmime::net::messageSet::byUID(1000, 1042)
+  *
+  *    // Designate all messages in the folder, starting from UID 1000
+  *    vmime::net::messageSet::byUID(1000, "*")
+  * \endcode
+  */
+
+class VMIME_EXPORT messageSet : public object
+{
+public:
+
+	~messageSet();
+
+	messageSet(const messageSet& other);
+
+	/** Constructs a new message set and initializes it with a single
+	  * message represented by its sequence number.
+	  *
+	  * @param number message number (numbering starts at 1, not 0)
+	  * @return new message set
+	  */
+	static messageSet byNumber(const int number);
+
+	/** Constructs a new message set and initializes it with a range
+	  * of messages represented by their sequence number.
+	  *
+	  * @param first number of the first message in the range (numbering
+	  * starts at 1, not 0)
+	  * @param last number of the last message in the range, or use the
+	  * special value -1 to designate the last message in the folder
+	  * @return new message set
+	  */
+	static messageSet byNumber(const int first, const int last);
+
+	/** Constructs a new message set and initializes it with a possibly
+	  * unsorted list of messages represented by their sequence number.
+	  * Please note that numbering starts at 1, not 0.
+	  *
+	  * The function tries to group consecutive message numbers into
+	  * ranges to reduce the size of the resulting set.
+	  *
+	  * For example, given the list "1,2,3,4,5,7,8,13,15,16,17" it will
+	  * result in the following ranges: "1:5,7:8,13,15:17".
+	  *
+	  * @param numbers a vector containing numbers of the messages
+	  * @return new message set
+	  */
+	static messageSet byNumber(const std::vector <int>& numbers);
+
+	/** Constructs a new message set and initializes it with a single
+	  * message represented by its UID.
+	  *
+	  * @param uid message UID
+	  * @return new message set
+	  */
+	static messageSet byUID(const message::uid& uid);
+
+	/** Constructs a new message set and initializes it with a range
+	  * of messages represented by their sequence number.
+	  *
+	  * @param first UID of the first message in the range
+	  * @param last UID of the last message in the range, or use the
+	  * special value '*' to designate the last message in the folder
+	  * @return new message set
+	  */
+	static messageSet byUID(const message::uid& first, const message::uid& last);
+
+	/** Constructs a new message set and initializes it with a possibly
+	  * unsorted list of messages represented by their UID.
+	  *
+	  * For UIDs that actually are numbers (this is the case for IMAP), the
+	  * function tries to group consecutive UIDs into ranges to reduce the
+	  * size of the resulting set.
+	  *
+	  * For example, given the list "1,2,3,4,5,7,8,13,15,16,17" it will
+	  * result in the following ranges: "1:5,7:8,13,15:17".
+	  *
+	  * @param uids a vector containing UIDs of the messages
+	  * @return new message set
+	  */
+	static messageSet byUID(const std::vector <message::uid>& uids);
+
+	/** Adds the specified range to this set. The type of message range
+	  * (either number or UID) must match the type of the ranges already
+	  * contained in this set (ie. it's not possible to have a message
+	  * set which contains both number ranges and UID ranges).
+	  *
+	  * @param range range to add
+	  * @throw std::invalid_argument exception if the range type does
+	  * not match the type of the ranges in this set
+	  */
+	void addRange(const messageRange& range);
+
+	/** Enumerates this set with the specified enumerator.
+	  *
+	  * @param en enumerator that will receive the method calls while
+	  * enumerating the ranges in this set
+	  */
+	void enumerate(messageSetEnumerator& en) const;
+
+	/** Returns whether this set is empty (contains no range).
+	  *
+	  * @return true if this set is empty, or false otherwise
+	  */
+	bool isEmpty() const;
+
+	/** Returns whether this set references messages by their sequence
+	  * number.
+	  *
+	  * @return true if this set references messages by their sequence
+	  * number, or false otherwise
+	  */
+	bool isNumberSet() const;
+
+	/** Returns whether this set references messages by their UID.
+	  *
+	  * @return true if this set references messages by their UID,
+	  * or false otherwise
+	  */
+	bool isUIDSet() const;
+
+private:
+
+	messageSet();
+
+	std::vector <messageRange*> m_ranges;
+};
+
+
+} // net
+} // vmime
+
+
+#endif // VMIME_NET_MESSAGESET_HPP_INCLUDED
diff --git a/vmime/net/pop3/POP3Folder.hpp b/vmime/net/pop3/POP3Folder.hpp
index 8a97213c..93c1d257 100644
--- a/vmime/net/pop3/POP3Folder.hpp
+++ b/vmime/net/pop3/POP3Folder.hpp
@@ -86,11 +86,7 @@ public:
 	bool isOpen() const;
 
 	ref <message> getMessage(const int num);
-	std::vector <ref <message> > getMessages(const int from = 1, const int to = -1);
-	std::vector <ref <message> > getMessages(const std::vector <int>& nums);
-
-	ref <message> getMessageByUID(const message::uid& uid);
-	std::vector <ref <message> > getMessagesByUID(const std::vector <message::uid>& uids);
+	std::vector <ref <message> > getMessages(const messageSet& msgs);
 
 	int getMessageCount();
 
@@ -99,19 +95,14 @@ public:
 
 	void rename(const folder::path& newPath);
 
-	void deleteMessage(const int num);
-	void deleteMessages(const int from = 1, const int to = -1);
-	void deleteMessages(const std::vector <int>& nums);
+	void deleteMessages(const messageSet& msgs);
 
-	void setMessageFlags(const int from, const int to, const int flags, const int mode = message::FLAG_MODE_SET);
-	void setMessageFlags(const std::vector <int>& nums, const int flags, const int mode = message::FLAG_MODE_SET);
+	void setMessageFlags(const messageSet& msgs, const int flags, const int mode = message::FLAG_MODE_SET);
 
 	void addMessage(ref <vmime::message> msg, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL);
 	void addMessage(utility::inputStream& is, const int size, const int flags = message::FLAG_UNDEFINED, vmime::datetime* date = NULL, utility::progressListener* progress = NULL);
 
-	void copyMessage(const folder::path& dest, const int num);
-	void copyMessages(const folder::path& dest, const int from = 1, const int to = -1);
-	void copyMessages(const folder::path& dest, const std::vector <int>& nums);
+	void copyMessages(const folder::path& dest, const messageSet& msgs);
 
 	void status(int& count, int& unseen);
 	ref <folderStatus> getStatus();
diff --git a/vmime/net/pop3/POP3Utils.hpp b/vmime/net/pop3/POP3Utils.hpp
index 7a2376a1..9d20431c 100644
--- a/vmime/net/pop3/POP3Utils.hpp
+++ b/vmime/net/pop3/POP3Utils.hpp
@@ -35,6 +35,8 @@
 
 #include "vmime/types.hpp"
 
+#include "vmime/net/messageSet.hpp"
+
 
 namespace vmime {
 namespace net {
@@ -63,6 +65,13 @@ public:
 	  */
 	static void parseMultiListOrUidlResponse
 		(ref <POP3Response> response, std::map <int, string>& result);
+
+	/** Returns a list of message numbers given a message set.
+	  *
+	  * @param msgs message set
+	  * @return list of message numbers
+	  */
+	static const std::vector <int> messageSetToNumberList(const messageSet& msgs);
 };