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/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
using System;
using log4net;
using Apache.Qpid.Buffer;
namespace Apache.Qpid.Codec
{
public abstract class CumulativeProtocolDecoder : IProtocolDecoder
{
static ILog _logger = LogManager.GetLogger(typeof(CumulativeProtocolDecoder));
ByteBuffer _remaining;
/// <summary>
/// Creates a new instance with the 4096 bytes initial capacity of
/// cumulative buffer.
/// </summary>
protected CumulativeProtocolDecoder()
{
_remaining = AllocateBuffer();
}
/// <summary>
/// Cumulates content of <tt>in</tt> into internal buffer and forwards
/// decoding request to {@link #doDecode(IoSession, ByteBuffer, ProtocolDecoderOutput)}.
/// <tt>doDecode()</tt> is invoked repeatedly until it returns <tt>false</tt>
/// and the cumulative buffer is compacted after decoding ends.
/// </summary>
/// <exception cref="Exception">
/// if your <tt>doDecode()</tt> returned <tt>true</tt> not consuming the cumulative buffer.
/// </exception>
public void Decode(ByteBuffer input, IProtocolDecoderOutput output)
{
if ( _remaining.Position != 0 ) // If there were remaining undecoded bytes
{
DecodeRemainingAndInput(input, output);
} else
{
DecodeInput(input, output);
}
}
private void DecodeInput(ByteBuffer input, IProtocolDecoderOutput output)
{
_logger.Debug(string.Format("DecodeInput: input {0}", input.Remaining));
// Just decode the input buffer and remember any remaining undecoded bytes.
try
{
DecodeAll(input, output);
} finally
{
if ( input.HasRemaining )
{
_remaining.Put(input);
}
}
}
private void DecodeRemainingAndInput(ByteBuffer input, IProtocolDecoderOutput output)
{
_logger.Debug(string.Format("DecodeRemainingAndInput: input {0}, remaining {1}", input.Remaining, _remaining.Position));
// replace the _remainder buffer, so that we can leave the
// original one alone. Necessary because some consumer splice
// the buffer and only consume it until later, causing
// a race condition if we compact it too soon.
ByteBuffer newRemainding = AllocateBuffer();
ByteBuffer temp = _remaining;
_remaining = newRemainding;
temp.Put(input);
temp.Flip();
try
{
DecodeAll(temp, output);
} finally
{
if ( temp.Remaining > 0 )
_remaining.Put(temp);
}
}
private void DecodeAll(ByteBuffer buf, IProtocolDecoderOutput output)
{
for ( ; ; )
{
int oldPos = buf.Position;
bool decoded = DoDecode(buf, output);
if ( decoded )
{
if ( buf.Position == oldPos )
{
throw new Exception(
"doDecode() can't return true when buffer is not consumed.");
}
if ( !buf.HasRemaining )
{
break;
}
} else
{
break;
}
}
}
/// <summary>
/// Implement this method to consume the specified cumulative buffer and
/// decode its content into message(s).
/// </summary>
/// <param name="input">the cumulative buffer</param>
/// <param name="output">decoder output</param>
/// <returns>
/// <tt>true</tt> if and only if there's more to decode in the buffer
/// and you want to have <tt>doDecode</tt> method invoked again.
/// Return <tt>false</tt> if remaining data is not enough to decode,
/// then this method will be invoked again when more data is cumulated.
/// </returns>
/// <exception cref="Exception">If cannot decode</exception>
protected abstract bool DoDecode(ByteBuffer input, IProtocolDecoderOutput output);
public void Dispose()
{
_remaining = null;
}
private ByteBuffer AllocateBuffer()
{
ByteBuffer buffer = ByteBuffer.Allocate(4096);
buffer.IsAutoExpand = true;
return buffer;
}
}
}
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