ISAPI extensions that send long responses to the client may not transmit any output in Internet Information Services 7.0 until the session is closed

//	Copyright (c) 1997-2002  Microsoft Corporation
//
//	Module Name:
//
//	Simple.cpp
//
//	Abstract:
//
//	This module shows IIS 7 WriteClient buffering.

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <httpext.h>

// The following define is needed if httpext.h is pre-Windows:
#ifndef   HSE_REQ_SET_FLUSH_FLAG
#define   HSE_REQ_SET_FLUSH_FLAG                   (HSE_REQ_END_RESERVED+43)
#endif

DWORD SendOutputToClient(IN EXTENSION_CONTROL_BLOCK  *pecb, IN DWORD msecDelay);DWORD SendOutputToClient(IN EXTENSION_CONTROL_BLOCK  *pecb, IN DWORD msecDelay, char *szBuffering) ;

//  Function:  
//
//  DllMain
//
//  Description:
//
//  The initialization function for this DLL.
//
//  Arguments:
//
//  hinstDll - This parameter is the instance handle to the DLL.
//  dwReason - This parameter is the reason why this DLL is called.
//  lpvContext - This parameter is reserved for future use.
//
//  Return Value:
//
//  If this parameter is successful, a value of TRUE is returned. If this parameter is not successful, a value of FALSE is returned.
BOOL WINAPI DllMain(IN HINSTANCE hinstDll, IN DWORD dwReason, IN LPVOID lpvContext)
{
// Be aware that appropriate initialization and termination code
// is written within the switch statement that is shown here. Because
// this example is very simple, no additional code is currently needed.

	switch(dwReason) {

		case DLL_PROCESS_ATTACH :

			break;

		case DLL_PROCESS_DETACH :

			break;
	}

	return TRUE;
}

//  Function:
//
//  GetExtensionVersion
//
//  Description:
//
//  This function is the first function that is called after IIS successfully loads the DLL. The function should use the 
//  version structure that is provided by IIS to set the ISAPI architectural version number of this extension.
//
//  A simple text string is also set so that administrators can find the DLL.
//
//  The HSE_VERSION_MINOR constant and the HSE_VERSION_MAJOR constant are defined in the httpext.h header.
//
//  Arguments: 
//
//  pVer - This parameter points to the extension version structure.
//
//  Return Value:
//
//  If this parameter is successful, a value of TRUE is returned. If this parameter is not successful, a value of FALSE is returned.
BOOL WINAPI GetExtensionVersion(HSE_VERSION_INFO *pVer)
{
	pVer->dwExtensionVersion = MAKELONG(HSE_VERSION_MINOR, HSE_VERSION_MAJOR);

	lstrcpyn((LPSTR) pVer->lpszExtensionDesc, "WriteClient buffering demo", HSE_MAX_EXT_DLL_NAME_LEN);

	return TRUE;
}


//  Function:
//
//  HttpExtensionProc
//
//  Description:    
//
//  This function is called by the server that is runnning IIS when a request for the ISAPI DLL
//  arrives. The HttpExtensionProc function processes the request and then
//  sends the appropriate response to the Web client by using the WriteClient() call.
//
//  Argument:
//
//  pECB - This parameter points to the extension control block.
//
//  Return Value:
//
//  HSE_STATUS_SUCCESS

DWORD WINAPI HttpExtensionProc(IN EXTENSION_CONTROL_BLOCK *pECB)
{

	DWORD hseStatus;
	DWORD msecDelay;
	char *pszBuffering; 

	pszBuffering = "default (on)";
	msecDelay=25;
    
	// Any value in the query string turns off buffering.
	if ( (char)*(pECB->lpszQueryString) != '\0' ){
		pszBuffering="off";
	    pECB->ServerSupportFunction (pECB->ConnID,
			HSE_REQ_SET_FLUSH_FLAG,
			(LPVOID) TRUE,
			NULL,
			NULL
			);
	}
	hseStatus = SendOutputToClient(pECB, msecDelay, pszBuffering);
	
	return hseStatus;
}

//  Function:
//
//  TerminateExtension
//
//  Description:
//
//  This function is called when the World Wide Web Publishing Service is shut down.
//
//  Arguments:
//
//  dwFlags - HSE_TERM_ADVISORY_UNLOAD or HSE_TERM_MUST_UNLOAD
//
//  Return Value:
//
//  A value of TRUE is returned if the extension is ready to be unloaded. Otherwise, a value of FALSE is returned.
BOOL WINAPI TerminateExtension(IN DWORD dwFlags)
{
	// Note: This code cannot be unloaded if any pending requests exist.

	return TRUE;
}

DWORD SendHeaderToClient(IN EXTENSION_CONTROL_BLOCK *pecb, IN LPCSTR pszErrorMsg)
{
	HSE_SEND_HEADER_EX_INFO	SendHeaderExInfo;
	char szStatus[] = "200 OK";
	char szHeader[1024];

	/* Notice that the HTTP header block is terminated by a blank '\r\n' pair, followed by the document body. */

	wsprintf(szHeader, "Content-Type: text/html\r\n\r\n<head><title>WriteClient Buffering Demo</title></head>\n<body><h1>%s</h1>\n", pszErrorMsg);

	/* The following code populates the SendHeaderExInfo structure. */

	SendHeaderExInfo.pszStatus = szStatus;
	SendHeaderExInfo.pszHeader = szHeader;
	SendHeaderExInfo.cchStatus = lstrlen(szStatus);
	SendHeaderExInfo.cchHeader = lstrlen(szHeader);
	SendHeaderExInfo.fKeepConn = FALSE;

	/* Use the EX version to send the header contents */

	if (!pecb->ServerSupportFunction(pecb->ConnID, HSE_REQ_SEND_RESPONSE_HEADER_EX, &SendHeaderExInfo, NULL, NULL))
   		return HSE_STATUS_ERROR;
	
	return HSE_STATUS_SUCCESS;
}

DWORD SendOutput(IN EXTENSION_CONTROL_BLOCK  *pecb, IN DWORD msecDelay) {
	
	CHAR pchOutput[1024]; 
	DWORD hseStatus = HSE_STATUS_SUCCESS;
	int i;
	DWORD len;

	/* Write data to client. */
	for( i=0; i < 1000 ; i++ ) {
		len = wsprintfA(pchOutput, "WriteClient output %d\n", i);
		if ( !pecb->WriteClient(pecb->ConnID, pchOutput, &len, HSE_IO_SYNC) ){
			hseStatus = HSE_STATUS_ERROR;
			break;
		}
		Sleep(msecDelay);
	}
	return hseStatus;
}

DWORD SendOutputToClient(IN EXTENSION_CONTROL_BLOCK  *pecb, IN DWORD msecDelay, char *szBuffering) {
	CHAR    pchBuffer[1024];
	DWORD   hseStatus = HSE_STATUS_SUCCESS;

	wsprintfA(pchBuffer, "WriteClient buffering %s", szBuffering);

	hseStatus = SendHeaderToClient(pecb, pchBuffer);

	if (hseStatus == HSE_STATUS_SUCCESS) {

		hseStatus = SendOutput(pecb, msecDelay );

		if (hseStatus != HSE_STATUS_SUCCESS) {

			/* Error in sending output. Send error message. */

			wsprintfA(pchBuffer, "Send Failed: Error (%d)<\br>", GetLastError());
			SendHeaderToClient(pecb, pchBuffer);
		}
	}

	pecb->ServerSupportFunction( pecb->ConnID, HSE_REQ_DONE_WITH_SESSION, NULL, NULL, NULL);

	return (hseStatus);
}