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ILRewriting for beginners

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27 Sep 2012Ms-PL11 min read 62.4K   1.4K   46  
Runtime IL-Rewriting can be used to add behavior such as logging to applications, or redirect calls from one API to another. This article and accompanying source code explains how to substitute a method call at runtime.
// ----------------------------------------------------------------------------------------------
// Copyright (c) Mattias H�gstr�m.
// ----------------------------------------------------------------------------------------------
// This source code is subject to terms and conditions of the Microsoft Public License. A 
// copy of the license can be found in the License.html file at the root of this distribution. 
// If you cannot locate the Microsoft Public License, please send an email to 
// dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
// by the terms of the Microsoft Public License.
// ----------------------------------------------------------------------------------------------
// You must not remove this notice, or any other, from this software.
// ----------------------------------------------------------------------------------------------

#include "stdafx.h"
#include "ILRewriteProfilerFactory.h"
#include "ILRewriteProfilerImpl.h"
#include "ProfilerLoggers.h"

using namespace std;

extern long g_comObjectsInUse;
ProfilerData g_profilerData;

ILRewriteProfilerFactory::ILRewriteProfilerFactory()
{
   m_nRefCount=0;
   InterlockedIncrement(&g_comObjectsInUse);
}

ILRewriteProfilerFactory::~ILRewriteProfilerFactory()
{
   g_debugLogger.WriteLine("ILRewriteProfilerFactory::~ILRewriteProfilerFactory");
   InterlockedDecrement(&g_comObjectsInUse);
}

HRESULT __stdcall ILRewriteProfilerFactory::QueryInterface(
   const IID& iid, 
   void** ppv)
{   
   g_debugLogger.WriteLine("ILRewriteProfilerFactory::QueryInterface");

   if ((iid == IID_IUnknown) || (iid == IID_IClassFactory))
   {
      *ppv = static_cast<IClassFactory*>(this) ; 
   }
   else
   {
      *ppv = NULL ;
      return E_NOINTERFACE ;
   }
   reinterpret_cast<IUnknown*>(*ppv)->AddRef() ;
   return S_OK ;
}

HRESULT __stdcall ILRewriteProfilerFactory::CreateInstance(IUnknown* pUnknownOuter,
   const IID& iid,
   void** ppv) 
{
   g_debugLogger.WriteLine("ILRewriteProfilerFactory::CreateInstance");
   if (!g_profilerData.m_outputLogger.IsOpen())
   {
      // DIAG_PRF_STACKTRACE must be defined
      // If not the stack will not be saved
      // It should have been opened in g_giagInit

      // Not true anymore
      // Added a server command to be able to set the stack log file
      // return E_INVALIDARG;
   }

   if (pUnknownOuter != NULL)
   {
      return CLASS_E_NOAGGREGATION ;
   }

   ILRewriteProfiler* pObject = new ILRewriteProfilerImpl();

   if (pObject == NULL)
   {
      return E_OUTOFMEMORY ;
   }

   return pObject->QueryInterface(iid, ppv) ;
}

ULONG __stdcall ILRewriteProfilerFactory::AddRef()
{
   return InterlockedIncrement(&m_nRefCount) ;
}

ULONG __stdcall ILRewriteProfilerFactory::Release()
{
   long nRefCount=0;
   nRefCount=InterlockedDecrement(&m_nRefCount) ;
   if (nRefCount == 0) delete this;
   return nRefCount;
}

HRESULT __stdcall ILRewriteProfilerFactory::LockServer(BOOL bLock) 
{
   return E_NOTIMPL;
}

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License

This article, along with any associated source code and files, is licensed under The Microsoft Public License (Ms-PL)


Written By
Architect Visma Software AB
Sweden Sweden
Mattias works at Visma, a leading Nordic ERP solution provider. He has good knowledge in C++/.Net development, test tool development, and debugging. His great passion is memory dump analysis. He likes giving talks and courses.

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