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//------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------
namespace System.ServiceModel.Channels
{
using System.IO;
using System.Xml;
using System.Diagnostics;
abstract class BufferedMessageWriter
{
int[] sizeHistory;
int sizeHistoryIndex;
const int sizeHistoryCount = 4;
const int expectedSizeVariance = 256;
BufferManagerOutputStream stream;
public BufferedMessageWriter()
{
this.stream = new BufferManagerOutputStream(SR.MaxSentMessageSizeExceeded);
InitMessagePredicter();
}
protected abstract XmlDictionaryWriter TakeXmlWriter(Stream stream);
protected abstract void ReturnXmlWriter(XmlDictionaryWriter writer);
public ArraySegment<byte> WriteMessage(Message message, BufferManager bufferManager, int initialOffset, int maxSizeQuota)
{
int effectiveMaxSize;
// make sure that maxSize has room for initialOffset without overflowing, since
// the effective buffer size is message size + initialOffset
if (maxSizeQuota <= int.MaxValue - initialOffset)
effectiveMaxSize = maxSizeQuota + initialOffset;
else
effectiveMaxSize = int.MaxValue;
int predictedMessageSize = PredictMessageSize();
if (predictedMessageSize > effectiveMaxSize)
predictedMessageSize = effectiveMaxSize;
else if (predictedMessageSize < initialOffset)
predictedMessageSize = initialOffset;
try
{
stream.Init(predictedMessageSize, maxSizeQuota, effectiveMaxSize, bufferManager);
stream.Skip(initialOffset);
XmlDictionaryWriter writer = TakeXmlWriter(stream);
OnWriteStartMessage(writer);
message.WriteMessage(writer);
OnWriteEndMessage(writer);
writer.Flush();
ReturnXmlWriter(writer);
int size;
byte[] buffer = stream.ToArray(out size);
RecordActualMessageSize(size);
return new ArraySegment<byte>(buffer, initialOffset, size - initialOffset);
}
finally
{
stream.Clear();
}
}
protected virtual void OnWriteStartMessage(XmlDictionaryWriter writer)
{
}
protected virtual void OnWriteEndMessage(XmlDictionaryWriter writer)
{
}
void InitMessagePredicter()
{
sizeHistory = new int[4];
for (int i = 0; i < sizeHistoryCount; i++)
sizeHistory[i] = 256;
}
int PredictMessageSize()
{
int max = 0;
for (int i = 0; i < sizeHistoryCount; i++)
if (sizeHistory[i] > max)
max = sizeHistory[i];
return max + expectedSizeVariance;
}
void RecordActualMessageSize(int size)
{
sizeHistory[sizeHistoryIndex] = size;
sizeHistoryIndex = (sizeHistoryIndex + 1) % sizeHistoryCount;
}
}
}
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