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IGlobalTraceEventProvider::GetTraceEvent Method

IIS 7.0

Retrieves the trace event for the provider.

virtual HRESULT GetTraceEvent(
   OUT HTTP_TRACE_EVENT** ppTraceEvent
) = 0;

ppTraceEvent

[OUT] A pointer to the address of an HTTP_TRACE_EVENT structure.

An HRESULT. Possible values include, but are not limited to, those in the following table.

Value

Definition

S_OK

Indicates that the operation was successful.

CGlobalModule derived classes that register for GL_TRACE_EVENT event types receive an IGlobalTraceEventProvider pointer as a parameter on the CGlobalModule::OnGlobalTraceEvent pure virtual method. Clients will usually call the GetTraceEvent method on that pointer only if the CheckSubscription method returns true.

GetTraceEvent behavior depends on implementation. You should use the following information as a guideline, but it may not be correct in all scenarios:

All IGlobalTraceEventProvider implementers declare a private HTTP_TRACE_EVENT pointer and initialize that pointer during construction to shared HTTP_TRACE_EVENT data that is passed to the constructors. The GetTraceEvent call sets the dereferenced ppTraceEvent pointer to this private data and then always returns S_OK.

IGlobalTraceEventProvider implementers are responsible for memory management with this data; therefore, IGlobalTraceEventProvider implementers that use dynamic memory allocation must release or call delete on the HTTP_TRACE_EVENT pointer when it is no longer needed.

IGlobalTraceEventProvider implementers are responsible for memory management with this data; therefore, IGlobalTraceEventProvider clients must not release or call delete on the returned HTTP_TRACE_EVENT pointer when this data is no longer needed.

The following code example demonstrates how to create a global module that listens for GL_TRACE_EVENT events and then writes the IGlobalTraceEventProvider information to the Event Viewer.

Caution noteCaution:

IIS 7 generates a large number of events in the Event Viewer. To avoid a log overflow error in a production environment, you should generally avoid writing cache information to the event log. For demonstration purposes, this code example writes an entry to the Event Viewer in debug mode only.

#pragma warning( disable : 4290 )
#pragma warning( disable : 4530 )

#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <tchar.h>
#include <initguid.h>
#include <httptrace.h>
#include <httpserv.h>
#include <httpcach.h>

#include <string>
using namespace std;

#import "msxml6.dll"
using namespace MSXML2;

// The CConvert class mirrors the Convert class that is 
// defined in the .NET Framework. It converts primitives 
// and other data types to wstring types.
class CConvert
{
public:
    // The ToString method converts a HANDLE to a wstring.
    // h: the HANDLE to convert to a wstring.
    // return: the HANDLE as a wstring.
    static wstring ToString(HANDLE h)
    {
        // If the HANDLE is NULL, return the "NULL" string.
        if (NULL == h)
        {
            return L"NULL";
        }

        // If the HANDLE is not valid, return 
        // the INVALID_HANDLE_VALUE as a string.
        if (INVALID_HANDLE_VALUE == h)
        {
            return L"INVALID_HANDLE_VALUE";
        }

        // The HANDLE is valid.
        return L"valid";
    }

    // The ToString method converts a FILETIME pointer to a wstring.
    // fileTime: the FILETIME pointer to convert to a wstring.
    // return: the FILETIME pointer as a wstring.
    static wstring ToString(FILETIME* fileTime)
    {
        // If fileTime is NULL, return the empty string.
        if (NULL == fileTime)
        {
            return L"NULL";
        }

        // Convert the FILETIME to a local time, and 
        // then convert that local time to a wstring.
        SYSTEMTIME stUTC;
        SYSTEMTIME stLocal;
        FileTimeToSystemTime(fileTime, &stUTC);
        SystemTimeToTzSpecificLocalTime(NULL, &stUTC, &stLocal);        

        // Create a wstring to return.  Note: wsprintf 
        // can be also used. However, it is more difficult 
        // to handle both UNICODE and non-UNICODE correctly.
        wstring timeString =
            ToString(stLocal.wMonth) +
            wstring(L"/")            +
            ToString(stLocal.wDay)   +
            wstring(L"/")            +
            ToString(stLocal.wYear)  +
            wstring(L"  ")           +
            ToString(stLocal.wHour)  +
            wstring(L":")            +
            ToString(stLocal.wMinute);

        // Return the FILETIME data as a wstring.
        return timeString;
    }

    // The ToString method converts a 
    // ULARGE_INTEGER pointer to a wstring.
    // ui: the ULARGE_INTEGER pointer to convert to a string.
    // return: the ULARGE_INTEGER pointer as a string.
    static wstring ToString(ULARGE_INTEGER* ui)
    {
        // Return the empty string if the 
        // ULARGE_INTEGER pointer is NULL.
        if (NULL == ui)
        {
            return L"NULL";
        }

        // Return the low-order part to a wstring.
        return (ToString(ui->LowPart));
    }

    // The ToString method converts a PCSTR to a wstring.
    // pcstr: the PCSTR to convert to a wstring.
    // return: the PCSTR as a wstring.
    static wstring ToString(PCSTR pcstr)
    {
        // Return the empty string 
        // if the PCSTR is NULL.
        if (NULL == pcstr)
        {
            return L"NULL";
        }

        // Get the length of the string to copy.
        size_t length = strlen(pcstr);
        // Create a new double-byte character 
        // array of length plus 1.
        wchar_t* newText = new wchar_t[length+1];

        // Copy the source into the sink string.
        for (size_t i = 0; i < length; ++i)
        {
            newText[i] = pcstr[i];
        }

        // Terminate the string with the NULL character.
        newText[length] = '\0';
        // Get a wstring from the new double-byte string.
        wstring wText = newText;
        // Call delete on the newText pointer 
        // and set this pointer to NULL.
        delete[] newText;
        newText = NULL;

        // Return the wstring copy.
        return wText;
    }

    // The ToString method converts a long to a wstring.
    // l: the long value to convert to a wstring.
    // return: the long as a wstring.
    static wstring ToString(long l)
    {
        WCHAR str[256];
        str[0] = '\0';        
        _ltow_s(l, str, 256, 10);
        return str;
    }

    // The ToString method converts a DWORD to a wstring.
    // d: the DWORD value to convert to a wstring.
    // return: the DWORD as a wstring.
    static wstring ToString(DWORD d)
    {
        return ToString((long)d);
    }

    // The ToString method converts an LPCGUID to a wstring.
    // guid: the LPCGUID value to convert to a wstring.
    // return: The LPCGUID as a wstring; otherwise, L"" if
    // guid is NULL.
    static wstring ToString(LPCGUID guid)
    {
        // If the GUID is NULL, return the empty string.
        if (NULL == guid)
        {
            return L"NULL";
        }

        // Create a WCHAR array to write the GUID to.
        WCHAR guidString[256];
        // Initialize the zero-based index of the 
        // guidString to the null-terminating character 
        // because the StringFromGUID2 may fail.
        guidString[0] = '\0';
        // Convert the GUID to a string of the form "{...}".
        int characters = StringFromGUID2(*guid, guidString, 256);
        // Return the guidString as a wstring.
        return guidString;
    }

    // The ToString method converts a BOOL to a wstring.
    // b: the BOOL value to convert to a wstring.
    // return: L"true" for true; otherwise, L"false" for false.
    static wstring ToString(BOOL b)
    {
        return (b) ? L"true" : L"false";
    }

    // The ToByteString converts a double-byte 
    // character string to a single-byte string.
    // str: the double-byte string to convert.
    // return: a single-byte string copied from str.
    static string ToByteString(const wstring& str)
    {
        // Get the length of the 
        // double-byte string.
        size_t length = str.length();

        // Create a temporary char pointer.
        char* byteChar = new char[length+1];
        byteChar[0] = '\0';
        // Copy the double-byte character string
        // into the single-byte string.        
        size_t charsReturned = 0;
        wcstombs_s(&charsReturned, byteChar, 
                   length+1, str.c_str(), length+1);
        // Create a string to return.
        string retString = byteChar;
        // Delete the temporary string and
        // set that string to NULL.
        delete[] byteChar;
        byteChar = NULL;

        // Return the single-byte string.
        return retString;
    }

    // The ToString method converts a USHORT to a wstring.
    // u: the USHORT value to convert to a wstring.
    // return: the value of u as a wstring.
    static wstring ToString(USHORT u)
    {
        return (ToString((long)u));
    }

    // The ToString method converts a 
    // const BYTE pointer to a wstring.
    // bytes: the BYTE pointer to convert.
    // return: the value of bytes as a wstring.
    static wstring ToString(const BYTE* bytes)
    {
        return (ToString((PCSTR)bytes));    
    }

    // The ToString method converts 
    // a PCWSTR to a wstring.
    // pcwstr: the PCWSTR to convert.
    // return: L"NULL" if the pcwstr
    // parameter is NULL; otherwise, 
    // pcwstr converted to a wstring.
    static wstring ToString(PCWSTR pcwstr)
    {
        // If the pcwstr parameter
        // is NULL, return L"NULL".
        if (NULL == pcwstr)
        {
            return L"NULL";
        }

        // Implicitly convert the 
        // PCWSTR to a wstring.
        return pcwstr;
    }

    // The ToString method converts 
    // a character to a wstring.
    // c: the character to convert.
    // return: c as a wstring.
    static wstring ToString(char c)
    {
        wstring str;
        str += c;
        return str;
    }

    // The ToString method converts
    // a short to a wstring.
    // s: the short to convert.
    // return: s as a wstring.
    static wstring ToString(short s)
    {
        return (ToString((long)s));
    }
};

// The CEventWriter class writes XML 
// documents and strings to the event log.
class CEventWriter
{
public:
    // Creates the CEventWriter class.
    // name: the name of the 
    // event log to open.
    CEventWriter(const wstring& name)
    {                
        #ifdef UNICODE
        m_eventLog = RegisterEventSource(NULL, name.c_str());
        #else
        string multiName = CConvert::ToByteString(name);
        m_eventLog = RegisterEventSource(NULL, multiName.c_str());
        #endif        
    }

    // Creates the destructor for the 
    // CEventWriter class. This destructor
    // closes the HANDLE to the event 
    // log if that HANDLE is open.
    virtual ~CEventWriter()
    {
        // If the HANDLE to the event 
        // log is open, close it.
        if (NULL != m_eventLog)
        {
            // Deregister the event log HANDLE.
            DeregisterEventSource(m_eventLog);
            // Set the HANDLE to NULL.
            m_eventLog = NULL;
        }
    }
    // The ReportInfo method writes the content
    // of the XML document to the event log.
    // doc: the XML document to write.
    // return: true if the event log is written.
    BOOL ReportInfo(MSXML2::IXMLDOMDocument3Ptr doc)
    {
        MSXML2::IXMLDOMElementPtr documentElement = 
            doc->documentElement;
        // Get the XML as a BSTR and place this XML into a 
        // _bstr_t wrapper. The client of the XML document 
        // is responsible for deleting the returned BSTR from 
        // the property, which the _bstr_t wrapper will do
        // automatically.
        _bstr_t bstrXml = documentElement->xml;
        // Convert the _bstr_t to a wstring.
        wstring xmlString = bstrXml;
        // Write the XML to the event writer.
        return ReportInfo(xmlString);        
    }

    // The ReportInfo method writes 
    // a wstring to the event log.
    // info: the wstring to write.
    // return: true if the event log is written.
    BOOL ReportInfo(const wstring& info)
    {
        return ReportEvent(EVENTLOG_INFORMATION_TYPE, info);
    }

    // The ReportError method writes 
    // a wstring to the event log.
    // error: the wstring to write.
    // return: true if the event log is written.
    BOOL ReportError(const wstring& error)
    {
        return ReportEvent(EVENTLOG_ERROR_TYPE, error);
    }
protected:
    // The ReportEvent method accepts an event type
    // and a wstring, and attempts to write that 
    // event to the event log.
    // type: the type of the event.
    // data: the wstring to write to the event log.
    // return: true if the event log is written;
    // otherwise, false.
    BOOL ReportEvent(WORD type, const wstring& data)
    {
        // If the m_eventLog HANDLE 
        // is NULL, return false.
        if (NULL == m_eventLog)
        {
            return FALSE;
        }

        #ifndef _DEBUG
        // If the current build is not debug,
        // return so the event log is not written.
        return TRUE;
        #endif

        #ifdef UNICODE
        // The unicode version of the ReportEvent
        // method requires double-byte strings.
        PCWSTR arr[1];
        arr[0] = data.c_str();
        return ::ReportEvent(m_eventLog,
                             type,
                             0, 0, NULL, 1, 
                             0, arr, (void*)arr);
        #else
        // The non-unicode version of the ReportEvent
        // method requires single-byte strings.
        string multiByte = 
            CConvert::ToByteString(data);
        LPCSTR arr[1];
        arr[0] = multiByte.c_str();
        return ::ReportEvent(m_eventLog,
                             type,
                             0, 0, NULL, 1,
                             0, arr, (void*)arr);
        #endif
    }
private:
    // Specify the HANDLE to the 
    // event log for writing.
    HANDLE m_eventLog;
};

// The CGlobalTraceModule class creates the CGlobalModule 
// class and registers for GL_TRACE_EVENT events.
class CGlobalTraceModule : public CGlobalModule
{
public:
    // Creates the destructor for the 
    // CGlobalTraceModule class.
    virtual ~CGlobalTraceModule()
    {

    }

    // The RegisterGlobalModule method creates and registers 
    // a new CGlobalTraceModule for GL_TRACE_EVENT events.
    // dwServerVersion: the current server version.
    // pModuleInfo: the current IHttpModuleRegistrationInfo pointer.
    // pGlobalInfo: the current IHttpServer pointer.
    // return: ERROR_NOT_ENOUGH_MEMORY if the heap is out of 
    // memory; otherwise, the value from the call to the 
    // SetGlobalNotifications method on the pModuleInfo pointer.
    static HRESULT RegisterGlobalModule
    (
        DWORD dwServerVersion,
        IHttpModuleRegistrationInfo* pModuleInfo,
        IHttpServer* pGlobalInfo
    )
    {        
        // The IHttpModuleRegistrationInfo and 
        // IHttpServer pointers must not be NULL.
        if ((NULL == pModuleInfo) || (NULL == pGlobalInfo))
        {
            return E_INVALIDARG;
        }

        // Get the IHttpTraceContext pointer 
        // from the IHttpServer pointer.
        IHttpTraceContext* traceContext =
            pGlobalInfo->GetTraceContext();

        // Get the HTTP_MODULE_ID from the 
        // IHttpModuleRegistrationInfo pointer.
        HTTP_MODULE_ID moduleId = 
            pModuleInfo->GetId();

        // The IHttpTraceContext pointer and 
        // HTTP_MODULE_ID both must not be NULL.
        if ((NULL == traceContext) || (NULL == moduleId))
        {
            return E_INVALIDARG;
        }

        // Create a new CGlobalTraceModule pointer
        // using the HTTP_MODULE_ID from the 
        // IHttpModuleRegistrationInfo pointer.
        CGlobalTraceModule* traceModule = 
            new CGlobalTraceModule(moduleId);

        // Return an out-of-memory error if the traceModule 
        // is NULL after the call to the new operator.
        if (NULL == traceModule)
        {            
            return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
        }    

        // Declare an HTTP_TRACE_CONFIGURATION structure 
        // to pass to the SetTraceConfiguration method.
        HTTP_TRACE_CONFIGURATION traceConfiguration;

        // Set the GUID on the HTTP_TRACE_CONFIGURATION
        // to GUID_IIS_ALL_TRACE_PROVIDERS.
        traceConfiguration.pProviderGuid = 
                                    &GUID_IIS_ALL_TRACE_PROVIDERS;
        // Register for all areas.
        traceConfiguration.dwAreas = 0xffffe;
        // Register for the maximum verbosity.
        traceConfiguration.dwVerbosity = 5;
        // Enable the provider.
        traceConfiguration.fProviderEnabled = TRUE;

        // Set the trace configuration on 
        // the IHttpTraceContext pointer.
        traceContext->SetTraceConfiguration(moduleId, &traceConfiguration);                                                  

        // Attempt to set global notification 
        // for an GL_TRACE_EVENT event by using 
        // the traceModule as a listener.
        HRESULT hr = pModuleInfo->SetGlobalNotifications
            (traceModule, GL_TRACE_EVENT);

        // Return the HRESULT from the call to 
        // the SetGlobalNotifications method.
        return hr;
    }

    // The OnGlobalTraceEvent method is the callback
    // method for GL_TRACE_EVENT events in the pipeline.
    // pProvider: the IGlobalTraceEventProvider pointer.
    // return: GL_NOTIFICATION_CONTINUE.
    virtual 
    GLOBAL_NOTIFICATION_STATUS
    OnGlobalTraceEvent
    (
        IN IGlobalTraceEventProvider*  pProvider
    )
    {
        // If the IGlobalTraceEventProvider 
        // pointer is NULL, return.
        if (NULL == pProvider)
        {
            return GL_NOTIFICATION_CONTINUE;
        }

        // Check if the this module has a 
        // subscription to the event.
        BOOL subscription = 
            pProvider->CheckSubscription(m_moduleId);

        // If the module is not subscribed,
        // return GL_NOTIFICATION_CONTINUE.
        if (!subscription)
        {
            return GL_NOTIFICATION_CONTINUE;
        }

        // The following code uses COM smart pointers. Wrap 
        // the code in one try/catch statement for _com_error
        // exceptions. Note: it is not necessary to call 
        // CoInitialize and CoUninitialize on this thread 
        // because IIS does this automatically.
        try
        {
            // Create an XML document in memory.
            MSXML2::IXMLDOMDocument3Ptr doc
                (__uuidof(MSXML2::DOMDocument60));

            // Create a eventProviderElement root element.            
            MSXML2::IXMLDOMElementPtr eventProviderElement =
                doc->createElement(L"eventProvider");

            // Append the eventProviderElement 
            // element to the XML document.
            doc->appendChild(eventProviderElement);

            // Declare an HRESULT and initialize
            // that HRESULT to E_FAIL.
            HRESULT hr = E_FAIL;

            // Declare an HTTP_TRACE_EVENT pointer
            // and initialize that pointer to NULL.
            HTTP_TRACE_EVENT* traceEvent = NULL;

            // Call the GetTraceEvent method on the
            // IGlobalTraceEventProvider pointer.
            hr = pProvider->GetTraceEvent(&traceEvent);        

            // Create an XML element for 
            // the HTTP_TRACE_EVENT pointer.
            MSXML2::IXMLDOMElementPtr traceEventElement =
                CreateElement(traceEvent, hr, doc);

            // Append the traceEventElement 
            // to the eventProviderElement.
            eventProviderElement->appendChild(traceEventElement);

            // Write the XML using the writer.        
            m_eventWriter.ReportInfo(doc);
        }
        // Catch any _com_error that occurs while 
        // writing to the XML document in memory.
        catch (_com_error& ce)
        {            
            // Get the description for the error.
            wstring description = ce.Description();
            // Write the error to the event writer.
            m_eventWriter.ReportError(description);
            // Set the error status on the
            // IGlobalTraceEventProvider pointer.
            pProvider->SetErrorStatus(ce.Error());
        }
        // Return GL_NOTIFICATION_CONTINUE.
        return GL_NOTIFICATION_CONTINUE;
    }

    // The Terminate method is required for
    // non-abstract CGlobalTraceModule classes.
    // This method calls delete on this.
    virtual VOID Terminate(VOID)
    {
        delete this;
    }
protected:
    // Creates the constructor for the CGlobalTraceModule 
    // class. This constructor initializes the CEventWriter
    // to write to the application event log.
    // moduleId: the current module identifier.
    CGlobalTraceModule(HTTP_MODULE_ID moduleId): 
         m_eventWriter(L"IISADMIN")
    {
        m_moduleId = moduleId;
    }

    // The AddAttribute method creates a 
    // new XML attribute and appends that 
    // attribute to an existing XML element.
    // name: the name of the attribute to create.
    // text: the text to set on the new attribute.
    // element: the XML element to 
    // append the new attribute to.
    // doc: the XML document to use for
    // creating XML elements and attributes.
    // return: a new MSXML2::IXMLDOMAttributePtr.
    // throws: a _com_error exception.
    static MSXML2::IXMLDOMAttributePtr AddAttribute
    (
        const wstring& name,
        const wstring& text,
        MSXML2::IXMLDOMElementPtr element,
        MSXML2::IXMLDOMDocument3Ptr doc
    ) throw (_com_error)
    {
        // Create an attribute with the name.
        MSXML2::IXMLDOMAttributePtr attribute = 
            doc->createAttribute(name.c_str());
        // Set the text of the attribute to the text value.
        attribute->text = text.c_str();
        // Add the attribute to the passed element.
        element->setAttributeNode(attribute);
        // Return the new attribute to the caller.
        return attribute;
    }

    // The CreateElement accepts an 
    // HTTP_TRACE_EVENT_ITEM pointer, and writes 
    // that pointer to a new XML element.
    // traceEventItem: the HTTP_TRACE_EVENT_ITEM 
    // pointer to write.
    // doc: the XML document for creating
    // elements and attributes.
    // return: a new MSXML2::IXMLDOMElementPtr.
    // throws: a _com_error exception.
    static MSXML2::IXMLDOMElementPtr CreateElement
    (
        HTTP_TRACE_EVENT_ITEM* traceEventItem,
        MSXML2::IXMLDOMDocument3Ptr doc
    ) throw (_com_error)    
    {
        // Create a new element to return.
        MSXML2::IXMLDOMElementPtr traceEventItemElement =
            doc->createElement(L"traceEventItem");

        // If the HTTP_TRACE_EVENT_ITEM pointer is
        // NULL, return the XML element.
        if (NULL == traceEventItem)
        {
            return traceEventItemElement;
        }

        // Get the cbData element from
        // the HTTP_TRACE_EVENT_ITEM pointer.
        DWORD data = traceEventItem->cbData;

        // Convert the DWORD to a wstring.
        wstring dataString =
            CConvert::ToString(data);

        // Add a data attribute to
        // the traceEventItemElement.
        AddAttribute(L"data", dataString,
                     traceEventItemElement, doc);

        // Get the HTTP_TRACE_TYPE from the
        // HTTP_TRACE_EVENT_ITEM pointer.
        HTTP_TRACE_TYPE traceType =
            traceEventItem->dwDataType;

        // Declare an empty string for 
        // the type of the request.
        wstring traceTypeString;

        // Declare a string that defaults
        // to NULL for the data type.        
        wstring pbDataString(L"NULL");

        // Get the data from the 
        // HTTP_TRACE_EVENT_ITEM pointer.
        PBYTE pbData =
            traceEventItem->pbData; 

        // A switch statement is necesary for
        // displaying the event type, but also
        // for downcasting the pbData to the
        // correct type based upon that type.
        switch (traceType)
        {
        case HTTP_TRACE_TYPE_BYTE:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_BYTE";
                // Cast the data to a character
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    char pbDataByte = 
                        reinterpret_cast<char>(pbData);    
                    pbDataString = 
                        CConvert::ToString(pbDataByte);
                }
                break;
            }
        case HTTP_TRACE_TYPE_USHORT:
            {
                // Set the type sring.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_USHORT";
                // Cast the data to a USHORT
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    USHORT uShort =                        
                        reinterpret_cast<USHORT>(pbData);
                    pbDataString =
                        CConvert::ToString(uShort);
                }
                break;
            }
        case HTTP_TRACE_TYPE_ULONG:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_ULONG";
                // Cast the data to a ULONG
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    ULONG uLong =                        
                        static_cast<ULONG>(*pbData);
                    pbDataString =
                        CConvert::ToString(uLong);
                }
                break;
            }
        case HTTP_TRACE_TYPE_ULONGLONG:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_ULONGLONG";
                // Cast the data to a long
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    long l =                        
                        static_cast<long>(*pbData);
                    pbDataString =
                        CConvert::ToString(l);
                }
                break;
            }
        case HTTP_TRACE_TYPE_CHAR:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_CHAR";
                // Cast the data to a char
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    char c =                        
                        reinterpret_cast<char>(pbData);
                    pbDataString =
                        CConvert::ToString(c);
                }
                break;
            }
        case HTTP_TRACE_TYPE_SHORT:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_SHORT";
                // Cast the data to a short 
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    short s =
                        reinterpret_cast<short>(pbData);                        
                    pbDataString =
                        CConvert::ToString(s);
                }
                break;
            }

        case HTTP_TRACE_TYPE_LONG:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_LONG";
                // Cast the data to a long
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    long l =                        
                        static_cast<long>(*pbData);
                    pbDataString =
                        CConvert::ToString(l);
                }
                break;
            }
        case HTTP_TRACE_TYPE_LONGLONG:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_LONGLONG";
                // Cast the data to a long
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    long l =                        
                        static_cast<long>(*pbData);
                    pbDataString =
                        CConvert::ToString(l);
                }
                break;
            }
        case HTTP_TRACE_TYPE_LPCWSTR:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_LPCWSTR";
                // Cast the data to a LPCWSTR
                // if the data is not NULL.
                if (NULL != pbData)
                {    
                    LPCWSTR str =
                        (LPCWSTR)(pbData);                        
                    pbDataString =
                        CConvert::ToString(str);    
                }        
                break;
            }
        case HTTP_TRACE_TYPE_LPCSTR:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_LPCSTR";
                // Cast the data to an LPCSTR
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    LPCSTR str =
                        (LPCSTR)(pbData);
                    pbDataString =
                        CConvert::ToString(str);
                }
                break;
            }
        case HTTP_TRACE_TYPE_LPCGUID:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_LPCGUID";
                // Cast the data to an LPCGUID
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    LPCGUID guid =                        
                        reinterpret_cast<LPCGUID>(pbData);
                    pbDataString =
                        CConvert::ToString(guid);
                }            
                break;
            }
        case HTTP_TRACE_TYPE_BOOL:
            {
                // Set the type string.
                traceTypeString = 
                    L"HTTP_TRACE_TYPE_BOOL";
                // Cast the data to a BOOL
                // if the data is not NULL.
                if (NULL != pbData)
                {
                    BOOL b =                                        
                        static_cast<BOOL>(*pbData);
                    pbDataString =
                        CConvert::ToString(b);
                }
                break;
            }
        default:
            {
                // Set the type string to
                // Unknown. The data string
                // is NULL which should be correct.
                traceTypeString = 
                    L"Unknown";
                break;
            }
        }

        // Add a traceType attribute to the
        // traceEventItemElement.
        AddAttribute(L"traceType", traceTypeString,
                     traceEventItemElement, doc);

        // Add a pbData attribute to the 
        // traceEventItemElement.
        AddAttribute(L"pbData", pbDataString,
                     traceEventItemElement, doc);

        // Get the description from the 
        // HTTP_TRACE_EVENT_ITEM pointer.
        LPCWSTR description = 
            traceEventItem->pszDataDescription;

        // Convert the LPCWSTR to a wstring.
        wstring descriptionString = 
            CConvert::ToString(description);

        // Add a description attribute 
        // to the traceEventItemElement.
        AddAttribute(L"description", descriptionString,
                     traceEventItemElement, doc);

        // Get the name from the 
        // HTTP_TRACE_EVENT_ITEM pointer.
        LPCWSTR name = traceEventItem->pszName;

        // Convert the LPCWSTR to a wstring.
        wstring nameString =
            CConvert::ToString(name);

        // Add a name attribute to
        // the traceEventItemElement.
        AddAttribute(L"name", nameString, 
                     traceEventItemElement, doc);

        // Return the XML element.
        return traceEventItemElement;
    }

    // The CreateElement method converts an 
    // HTTP_TRACE_EVENT to an IXMLDOMElementPtr.
    // traceEvent: the HTTP_TRACE_EVENT pointer 
    // to convert.
    // hr: the HRESULT returned from 
    // retrieving the HTTP_TRACE_EVENT pointer.
    // doc: the XML document to use for
    // creating elements and attributes.
    // throws: a _com_error exception.
    static MSXML2::IXMLDOMElementPtr CreateElement
    (
        HTTP_TRACE_EVENT* traceEvent,
        HRESULT hr,
        MSXML2::IXMLDOMDocument3Ptr doc
    ) throw (_com_error)
    {
        // Create a new element to return.
        MSXML2::IXMLDOMElementPtr traceEventElement =
            doc->createElement(L"traceEvent");

        // If the HTTP_TRACE_EVENT pointer is NULL, 
        // or the call to retrieve the HTTP_TRACE_EVENT
        // pointer failed, return an empty XML element.
        if ((NULL == traceEvent) ||
            (FAILED(hr)))
        {
            return traceEventElement;
        }

        // Get the dwArea from the 
        // HTTP_TRACE_EVENT pointer.
        DWORD area =
            traceEvent->dwArea;

        // Convert the DWORD to a wstring.
        wstring areaString = 
            CConvert::ToString(area);

        // Add an area attribute to
        // the traceEventElement.
        AddAttribute(L"area", areaString,
                     traceEventElement, doc);

        // Get the dwEvent from the 
        // HTTP_TRACE_EVENT pointer.
        DWORD eventDWORD =
            traceEvent->dwEvent;

        // Convert the DWORD to a wstring.
        wstring eventString =
            CConvert::ToString(eventDWORD);

        // Add an event attribute to
        // the traceEventElement.
        AddAttribute(L"event", eventString,
                     traceEventElement, doc);

        // Get the dwEventVersion from 
        // the HTTP_TRACE_EVENT pointer.
        DWORD eventVersion = 
            traceEvent->dwEventVersion;

        // Convert the DWORD to a wstring.
        wstring eventVersionString =
            CConvert::ToString(eventVersion);

        // Add an eventVersion attribute
        // to the traceEventElement.
        AddAttribute(L"eventVersion", eventVersionString,
                     traceEventElement, doc);

        // Get the dwFlags from the
        // HTTP_TRACE_EVENT pointer.
        DWORD flags = 
            traceEvent->dwFlags;

        // Convert the DWORD to a wstring.
        wstring flagsString =
            CConvert::ToString(flags);

        // Add a flags attribute to 
        // the traceEventElement.
        AddAttribute(L"flags", flagsString,
                     traceEventElement, doc);

        // Get the dwTimeStamp from
        // the HTTP_TRACE_EVENT pointer.
        DWORD timeStamp =
            traceEvent->dwTimeStamp;

        // Convert the DWORD to a wstring.
        wstring timeStampString = 
            CConvert::ToString(timeStamp);

        // Add a timeStamp attribute to
        // the traceEventElement.
        AddAttribute(L"timeStamp", timeStampString,
                     traceEventElement, doc);

        // Get the dwVerbosity from 
        // the HTTP_TRACE_EVENT pointer.
        DWORD verbosity = 
            traceEvent->dwVerbosity;

        // Convert the DWORD to a wstring.
        wstring verbosityString = 
            CConvert::ToString(verbosity);

        // Add a verbosity attribute to
        // the traceEventElement.
        AddAttribute(L"verbosity", verbosityString,
                     traceEventElement, doc);

        // Get the pActivityGuid from the
        // HTTP_TRACE_EVENT pointer.
        LPCGUID activityGuid =
            traceEvent->pActivityGuid;

        // Convert the LPCGUID to a wstring.
        wstring activityGuidString = 
            CConvert::ToString(activityGuid);

        // Add an activityGuid attribute 
        // to the traceEventElement.
        AddAttribute(L"activityGuid", activityGuidString,
                     traceEventElement, doc);

        // Get the pAreaGuid from the 
        // HTTP_TRACE_EVENT pointer.
        LPCGUID areaGuid = 
            traceEvent->pAreaGuid;

        // Convert the LPCGUID to a wstring.
        wstring areaGuidString =
            CConvert::ToString(areaGuid);

        // Add an areaGuid attribute to
        // the traceEventElement.
        AddAttribute(L"areaGuid", areaGuidString,
                     traceEventElement, doc);

        // Get the pProviderGuid from the
        // HTTP_TRACE_EVENT pointer.
        LPCGUID providerGuid =
            traceEvent->pProviderGuid;

        // Convert the LPCGUID to a wstring.
        wstring providerGuidString =
            CConvert::ToString(providerGuid);

        // Add a providerGuid attribute to
        // the traceEventElement.
        AddAttribute(L"providerGuid", providerGuidString,
                     traceEventElement, doc);

        // Get the pRelatedActivityGuid from
        // the HTTP_TRACE_EVENT pointer.
        LPCGUID relatedActivityGuid =
            traceEvent->pRelatedActivityGuid;

        // Convert the LPCGUID to a wstring.
        wstring relatedActivityGuidString =
            CConvert::ToString(relatedActivityGuid);

        // Add a relatedActivityGuid attribute
        // to the traceEventElement.
        AddAttribute(L"relatedActivityGuid", 
                     relatedActivityGuidString,
                     traceEventElement, doc);

        // Get the pszEventName from the
        // HTTP_TRACE_EVENT pointer.
        LPCWSTR eventName = traceEvent->pszEventName;

        // Convert the LPCWSTR to a wstring.
        wstring eventNameString =
            CConvert::ToString(eventName);

        // Add an eventName attribute to
        // the traceEventElement.
        AddAttribute(L"eventName", eventNameString,
                     traceEventElement, doc);

        // Get the number of event 
        // items in the array from the
        // HTTP_TRACE_EVENT pointer.
        DWORD eventItems = 
            traceEvent->cEventItems;

        // Convert the DWORD to a wstring.
        wstring eventItemsString =
            CConvert::ToString(eventItems);

        // Add an eventItems attribute to
        // the traceEventElement.
        AddAttribute(L"eventItems", eventItemsString, 
                     traceEventElement, doc);

        // Create a new traceEventItems element 
        // for placing the returned items in.
        MSXML2::IXMLDOMElementPtr traceEventItemsElement =
            doc->createElement(L"traceEventItems");

        // Append the traceEventItemsElement 
        // to the traceEventElement.
        traceEventElement->appendChild(traceEventItemsElement);

        // Get the HTTP_TRACE_EVENT_ITEM pointer 
        // array from the HTTP_TRACE_EVENT pointer.
        HTTP_TRACE_EVENT_ITEM* eventItemsArray =
            traceEvent->pEventItems;

        // Enumerate the array and add an XML element
        // for each HTTP_TRACE_EVENT_ITEM pointer.
        for (DWORD i = 0; i < eventItems; ++i)
        {
            // Get the current HTTP_TRACE_EVENT_ITEM
            // pointer from the array.
            HTTP_TRACE_EVENT_ITEM* traceEventItem =
                (&eventItemsArray[i]);

            // Create an IXMLDOMElementPtr for the
            // HTTP_TRACE_EVENT_ITEM pointer.
            MSXML2::IXMLDOMElementPtr traceEventItemElement =
                CreateElement(traceEventItem, doc);

            // Append the traceEventItemElement to
            // the traceEventItemsElement.
            traceEventItemsElement->appendChild(traceEventItemElement);
        }

        // Return the XML element.
        return traceEventElement;
    }
private:
    // Specify the private CEventWriter
    // for writing events.
    CEventWriter m_eventWriter;

    // Specify the HTTP_MODULE_ID
    // for this module.
    HTTP_MODULE_ID m_moduleId;
};

// The RegisterModule method is the 
// main entry point for the DLL.
// dwServerVersion: the current server version.
// pModuleInfo: the current 
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
// return: the value returned by calling the
// CGlobalCacheModule::RegisterGlobalModule
// method.
HRESULT
__stdcall
RegisterModule(
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo* pModuleInfo,
    IHttpServer* pGlobalInfo
)
{        
    // Call the static method for initialization.
    return CGlobalTraceModule::RegisterGlobalModule            
        (dwServerVersion, 
         pModuleInfo, 
         pGlobalInfo);             
}


The above code writes a new event to the Event Viewer, where the Data box contains XML similar to the following.

<eventProvider>
    <traceEvent 
        area="0" 
        event="1" 
        eventVersion="1" 
        flags="1" 
        timeStamp="7394953" 
        verbosity="0" 
        activityGuid="{00000000-0000-0000-5D00-0080000000FB}" 
        areaGuid="{D42CF7EF-DE92-473E-8B6C-621EA663113A}" 
        providerGuid="{3A2A4E84-4C21-4981-AE10-3FDA0D9B0F83}" 
        relatedActivityGuid="NULL" 
        eventName="GENERAL_REQUEST_START" 
        eventItems="7">
        <traceEventItems>
            <traceEventItem 
                data="16" 
                traceType="HTTP_TRACE_TYPE_LPCGUID" 
                pbData="NULL" 
                description="NULL" 
                name="ContextId"/>
            <traceEventItem 
                data="4" 
                traceType="HTTP_TRACE_TYPE_ULONG" 
                pbData="1" 
                description="NULL" 
                name="SiteId"/>
            <traceEventItem 
                data="30" 
                traceType="HTTP_TRACE_TYPE_LPCWSTR" 
                pbData="DefaultAppPool" 
                description="NULL" 
                name="AppPoolId"/>
            <traceEventItem 
                data="8" 
                traceType="HTTP_TRACE_TYPE_ULONGLONG" 
                pbData="92" 
                description="NULL" 
                name="ConnId"/>
            <traceEventItem 
                data="8" 
                traceType="HTTP_TRACE_TYPE_ULONGLONG" 
                pbData="0" 
                description="NULL" 
                name="RawConnId"/>
            <traceEventItem 
                data="48" 
                traceType="HTTP_TRACE_TYPE_LPCWSTR" 
                pbData="http://server:80/" 
                description="NULL" 
                name="RequestURL"/>
            <traceEventItem 
                data="4" 
                    traceType="HTTP_TRACE_TYPE_LPCSTR" 
                    pbData="GET" 
                    description="NULL" 
                    name="RequestVerb"/>
        </traceEventItems>
    </traceEvent>
</eventProvider>

Your module must export the RegisterModule function. You can export this function by creating a module definition (.def) file for your project, or you can compile the module by using the /EXPORT:RegisterModule switch. For more information, see Walkthrough: Creating a Request-Level HTTP Module By Using Native Code.

You can optionally compile the code by using the __stdcall (/Gz) calling convention instead of explicitly declaring the calling convention for each function.

Type

Description

Client

  • IIS 7.0 on Windows Vista

  • IIS 7.5 on Windows 7

  • IIS Express 7.5 on Windows XP, Windows Vista, Windows 7

  • IIS 8.0 on Windows 8 Client

Server

  • IIS 7.0 on Windows Server 2008

  • IIS 7.5 on Windows Server 2008 R2

  • IIS Express 7.5 on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2

  • IIS 8.0 on Windows Server 2012

Product

IIS 7.0, IIS 7.5, IIS Express 7.5, IIS 8.0

Header

Httpserv.h

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