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/*
* Copyright (C) 2007-2012 Xagasoft, All rights reserved.
*
* This file is part of the libgats library and is released under the
* terms of the license contained in the file LICENSE.
*/
using System.IO;
using System.Net;
using System;
namespace Com.Xagasoft.Gats
{
/// <summary>
/// Main I/O interface. Use this to read and write GATS.
/// </summary>
/// <remarks>
/// GatsStream is not a traditional Stream class, it only can read and
/// write complete GATS packets. A GATS packet consists of a version,
/// size, and a single encoded GATS object (which can be a container).
///
/// This one class handles both reading and writing. Writing is fairly
/// straight forward, but for volatile streams like network sockets you'll
/// probably want to wrap your stream with a buffer before handing it to
/// GatsStream.
///
/// Reading handles it's own buffering, and will remember what has been
/// read between calls if it cannot get enough data at once to complete
/// a single packet. See the ReadObject docs for more details.
/// </remarks>
public class GatsStream
{
private Stream s;
private MemoryStream ReadBuf;
private int size = -1;
private int version;
private BinaryWriter bw = null;
private BinaryReader br = null;
/// <summary>
/// Construct a new GatsStream around a given Stream class.
/// </summary>
/// <remarks>
/// The provided Stream does not need to be opened for both reading and
/// writing, you can construct a GatsStream around a read only or
/// write only stream.
/// </remarks>
/// <param name="s">Stream to operate on.</param>
public GatsStream( Stream s )
{
this.s = s;
this.ReadBuf = new MemoryStream();
}
/// <summary>
/// Read a GATS packet and return the contained GatsObject.
/// </summary>
/// <remarks>
/// This reads a complete packet into an internal buffer, parses the
/// gats object within it, and returns it. This method will read as
/// much data as it needs from the stream, but no more. Not a single
/// extra byte will be read.
///
/// In the event that an end of stream is encountered, or a partial
/// packet has been read but no more data can be read at the moment,
/// this method will maintain it's buffer but return null to the caller.
/// </remarks>
/// <returns>
/// The read object, or null if no object could be read yet.
/// </returns>
public GatsObject ReadObject()
{
if( size == -1 )
{
for(;;)
{
version = s.ReadByte();
if( version == -1 )
return null;
if( version > 0 )
break;
}
}
if( br == null )
this.br = new BinaryReader( s );
switch( version )
{
case 1:
// Verion 1 of gats
if( size == -1 )
size = IPAddress.NetworkToHostOrder( br.ReadInt32() )-5;
byte[] buf = new byte[4096];
while( ReadBuf.Length < size )
{
int goal = (int)(size-ReadBuf.Length);
if( goal > 4096 )
goal = 4096;
int amnt = s.Read( buf, 0, goal );
if( amnt <= 0 )
return null;
ReadBuf.Write( buf, 0, amnt );
}
ReadBuf.Seek( 0, SeekOrigin.Begin );
GatsObject ret = GatsObject.Read( ReadBuf );
ReadBuf.SetLength( 0 );
size = version = -1;
return ret;
}
return null;
}
/// <summary>
/// Write a GatsObject to the stream in a proper GATS packet.
/// </summary>
/// <remarks>
/// The object passed in is first written to an internal buffer, and
/// then to the output in several write operations. This means that
/// for many applications you will want to buffer the output. In the
/// case of writing to files, it could be faster to buffer the output.
/// In the case of writing to a socket buffering could prevent sending
/// many small packets.
///
/// No flushing is done by this method, it is left to the caller to
/// determine the proper time to flush their streams.
/// </remarks>
/// <param name="obj">The object to be written.</param>
public void WriteObject( GatsObject obj )
{
MemoryStream ms = new MemoryStream();
obj.Write( ms );
if( bw == null )
this.bw = new BinaryWriter( s );
bw.Write( (byte)1 );
bw.Write( IPAddress.HostToNetworkOrder( (int)ms.Length+5 ) );
bw.Write( ms.GetBuffer(), 0, (int)ms.Length );
}
}
}
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