public static long?FindNextMessagePosition(IPositionedMessagesReader reader,
long originalMessagePos)
{
// Validate the input.
if (originalMessagePos < reader.BeginPosition)
{
return(null);
}
if (originalMessagePos >= reader.EndPosition)
{
return(null);
}
using (IPositionedMessagesParser parser = reader.CreateParser(new CreateParserParams(originalMessagePos,
null, MessagesParserFlag.HintMessageContentIsNotNeeed | MessagesParserFlag.HintMessageTimeIsNotNeeded,
MessagesParserDirection.Forward, null)))
{
if (parser.ReadNext() == null)
{
return(null);
}
IMessage p = parser.ReadNext();
if (p == null)
{
return(null);
}
return(p.Position);
}
}
public static long?FindPrevMessagePosition(IPositionedMessagesReader reader,
long originalMessagePos)
{
long nextMessagePos;
using (IPositionedMessagesParser p = reader.CreateParser(new CreateParserParams(originalMessagePos, null,
MessagesParserFlag.HintMessageContentIsNotNeeed | MessagesParserFlag.HintMessageContentIsNotNeeed,
MessagesParserDirection.Forward)))
{
var msgAtOriginalPos = p.ReadNext();
if (msgAtOriginalPos != null)
{
nextMessagePos = msgAtOriginalPos.Position;
}
else
{
nextMessagePos = reader.EndPosition;
}
}
using (IPositionedMessagesParser p = reader.CreateParser(new CreateParserParams(nextMessagePos, null,
MessagesParserFlag.HintMessageContentIsNotNeeed | MessagesParserFlag.HintMessageContentIsNotNeeed,
MessagesParserDirection.Backward)))
{
IMessage msg = p.ReadNext();
if (msg != null)
{
return(msg.Position);
}
return(null);
}
}
/// <summary>
/// Finds the first and the last available messages in the reader.
/// </summary>
/// <param name="reader">Messages reader to read from</param>
/// <param name="cachedFirstMessage">When the caller passes non-null value
/// the function doesn't search for the first message in the reader and return the
/// value precalculated by the client instead. That can be user for optimization:
/// if the client is sure that the first message didn't change then it can
/// pass the value calculated before. If <paramref name="firstMessage"/> is <value>null</value>
/// the function will search for the first message in the reader.</param>
/// <param name="firstMessage">When the function returns <paramref name="firstMessage"/> receives
/// the message with the smallest available position.</param>
/// <param name="lastMessage">When the function returns
/// <paramref name="lastMessage"/> receives the message with the largest available position.</param>
public static void GetBoundaryMessages(
IPositionedMessagesReader reader,
IMessage cachedFirstMessage,
out IMessage firstMessage, out IMessage lastMessage)
{
if (cachedFirstMessage == null)
{
firstMessage = ReadNearestMessage(reader, reader.BeginPosition);
}
else
{
firstMessage = cachedFirstMessage;
}
lastMessage = firstMessage;
using (IPositionedMessagesParser parser = reader.CreateParser(new CreateParserParams(reader.EndPosition,
null, MessagesParserFlag.Default, MessagesParserDirection.Backward)))
{
IMessage tmp = parser.ReadNext();
if (tmp != null)
{
lastMessage = tmp;
}
}
}
public static IEnumerable <IMessage> ParserAsEnumerator(IPositionedMessagesParser parser, ParserAsEnumeratorFlag flags = ParserAsEnumeratorFlag.Default, Action <Exception> readExceptionHandler = null)
{
for (; ;)
{
IMessage msg = null;
try
{
msg = parser.ReadNext();
}
catch (Exception e)
{
if (readExceptionHandler != null)
{
readExceptionHandler(e);
}
else
{
throw;
}
}
if (msg == null)
{
if ((flags & ParserAsEnumeratorFlag.YieldLastNullMessage) != 0)
{
yield return(msg);
}
break;
}
yield return(msg);
}
}
static public IMessage ReadNearestMessage(IPositionedMessagesReader reader, long position, MessagesParserFlag flags)
{
using (IPositionedMessagesParser parser = reader.CreateParser(new CreateParserParams(position, null, flags, MessagesParserDirection.Forward)))
{
IMessage ret = parser.ReadNext();
return(ret);
}
}