/// <summary>
/// Writes the message to a memory mapped file, where the memory mapped file name is WebsocketPipe.Address + id.
/// mmf format: [wasread? 1 byte][datasize(int)][length(int)][msg][length(int)][msg]...
/// If wasread=0, then writes the new message to the end of the message list and advances the number of messages +1.
/// If wasread=1, clears the mmf and then writes the new message.
/// </summary>
/// <param name="wp">The calling WebsocketPipe</param>
/// <param name="msg">The message to write.</param>
/// <param name="to">The stream to write the mmf filename to.</param>
/// <param name="id">The id of the targer we are writing to, since there may be many we open a mmf for each</param>
public virtual void WriteMessage(WebsocketPipeMessageInfo msg, Stream to)
{
if (msg.Data.Length < this.UseInternalPacketDataSendingIfMsgByteSizeIsLessThen)
{
// write that this is an internal message.
to.WriteByte(1);
WebsocketAsInternalDataSocket.WriteMessage(msg, to);
return;
}
// write that this is a mmf msg.
to.WriteByte(0);
// make the id and write it to the stream.
string id = MakeValidMmfID(msg.DataSocketId);
byte[] mmfnamebuffer = ASCIIEncoding.ASCII.GetBytes(id);
to.Write(mmfnamebuffer, 0, mmfnamebuffer.Length);
Mutex mu = new Mutex(false, id + "_mutex");
if (!mu.WaitOne(MemoryMappedFileAccessTimeout))
{
throw new Exception("Memory mapped file access timedout.");
}
// The data size for a single message.
int totalDataSize = msg.Data.Length + sizeof(int) + 1;
// Creating/Opening the stream.
MemoryMappedViewStream strm = GetDataWritingMemoryMappedViewStream(id, ref totalDataSize);
// we are at the position of the write, and are ready for the message write.
msg.WriteToStream(strm);
strm.Flush();
strm.Close();
strm.Dispose();
strm = null;
// release the mutex.
mu.ReleaseMutex();
}
/// <summary>
/// Reads the pending messages in the memory mapped file, where the memory mapped file name is in the stream from.
/// mmf format: [wasread? 1 byte][datasize(int)][length(int)][msg][length(int)][msg]...
/// If wasread=1, then ignores the read since the mmf was not written to, or was already read.
/// If wasread=0, reads all pending messages and sets wasread to 1.
/// </summary>
/// <param name="wp"></param>
/// <param name="from"></param>
/// <returns></returns>
public virtual IEnumerable <WebsocketPipeMessageInfo> ReadMessages(Stream from)
{
// reading the memory mapped file name or the msg bytes.
if (from.ReadByte() == 1)
{
// internal message.
return(WebsocketAsInternalDataSocket.ReadMessages(from));
}
// read the id from the from stram.
StreamReader freader = new StreamReader(from, ASCIIEncoding.ASCII);
string id = freader.ReadToEnd();
// calling the mutex to verify reading.
Mutex mu = new Mutex(false, id + "_mutex");
if (!mu.WaitOne(MemoryMappedFileAccessTimeout))
{
throw new Exception("Wait timeout while attempting to read messages from mmf file with id: " + id);
}
MemoryMappedFile mmf = MemoryMappedFile.OpenExisting(id);
Stream strm = mmf.CreateViewStream(0, 0, MemoryMappedFileAccess.ReadWrite);
BinaryReader reader = new BinaryReader(strm);
strm.Seek(0, SeekOrigin.Begin);
BinaryReader msgreader = null;
int totalDataLength = 0;
if (strm.Length > MMFHeaderSize && reader.ReadByte() == 0)
{
// there is something we need to read.
// reading all the contents.
totalDataLength = reader.ReadInt32();
if (totalDataLength > 0)
{
msgreader = new BinaryReader(new MemoryStream(reader.ReadBytes(totalDataLength)));
}
// marking as read.
strm.Seek(0, SeekOrigin.Begin);
strm.WriteByte(1);
}
strm.Flush();
strm.Close();
strm.Dispose();
// clearing the newly created mmf.
mmf.Dispose();
mmf = null;
// release the mutex allowing others to write.
mu.ReleaseMutex();
mu.Dispose();
mu = null;
reader = null;
// return nothing...
if (msgreader == null)
{
return(new WebsocketPipeMessageInfo[0]);
}
// reading the messages.
strm = msgreader.BaseStream;
msgreader.BaseStream.Seek(0, SeekOrigin.Begin);
List <WebsocketPipeMessageInfo> msgs = new List <WebsocketPipeMessageInfo>();
while (strm.Position < totalDataLength)
{
WebsocketPipeMessageInfo info = WebsocketPipeMessageInfo.FromStream(msgreader);
if (info == null)
{
break; // something went wrong.
}
msgs.Add(info);
}
strm.Close();
strm.Dispose();
msgreader = null;
strm = null;
return(msgs);
}
