1.Introduction

In CEHTTP, a dynamic page can be distributed by creating DLL. It resembles page performed by PHP or Perl running on Apache Web server.

In the current version of CEHTTP, Three kinds of extension was supported that is ".MOD" ".CHX" ".DLL".
Moreover, a log files extension can be customized by creating DLL.

Tow small class libraries are used for communication between CEHTTP and the extensions files.

Difference of WindowsCE from other OS

WindowsCE has not environment variable and stdin/stdout.

A HTTP request header is usually set to environment variable. these variable can be obtain by using ::getenv(). but WindowsCE doesn't support. For this reason, CEHTTP pass the environment variables through dynamically allocated memory.

The browser send the body data to the web server by using POST command. Usually, this body data can be read from pipe which was connected to stdin And CGI response the data by using stdout. The web server send this data to browser. In CEHTTP, these data is also passed through allocated memory.

2.Outline

CHX/DLL

Operation of CHX extension and DLL extension is almost the same. It is just DLL. When CHX/DLL called by the demand from browser, CEHTTP create the environment and loads CHX/DLL on the memory.
CHX/DLL create response dynamically and return it to browser through CEHTTP. CHX/DLL can create response any type of content such as GIF, bitmap, or HTML document.

MOD

MOD type extension can create response according to the MIME type of requested file. If the file which was registered extension is called, CEHTTP will scan a MIME type list, and will determine MOD extension to execute.
The called file name and path goes into the environment variable. MOD extension can create a response dynamically according to this information.

3.MyVarMem Class

MyVarMem is the memory buffer elongated dynamically. Binary data and text data can be added.

Refer to "MyVarMem specifications"

4.MyHash Class

MyHash is inherited class from MyVarMem. It held a key and value. Addition, reference, and acquisition are possible.

Refer to "MyHash specifications"

5.CHX extension

Description

It is possible to create dynamic page. This extension is more simply than DLL extension by using class library.
In WindowsCE. in order not to support PIPE and environment variables, those information is passed via a memory.

Create Windows DLL, and change the extension to ".CHX", and export the following function by using def file.

Prototype

int fnChx(MyHash* pEnv, MyVarMem* pBody, MyVarMem* pRes)

Parameters

in	*MyHash pEnv**	The environment variable entries.
in	*MyVarMem pBody**	If the HTTP request comannd is POST, a request body entries.
out	*MyVarMem pRes**	The contents to return to a client.

Return Value

The length of pRes. It is possible to obtain by using pRes->GetLength() function.

remark

none.

6.DLL Extension

Description

It is possible to obtain all reciving data from a client browser. And it is possible to send all response data to client browser. But treatment is a little difficult. It is like a ISAPI extension.
In WindowsCE. in order not to support PIPE and environment variables, those information is passed via a memory.

The environment variable is contained in the form of the following.

|key1|\0|value1|\0|key2|\0|value2|...|keyN|\0|valueN|\0|\0|
・Terminate is like "|\0|\0|".
・The value is possible to be "\0" like "|key1|\0|\0|key2|...".
・The kye does not permited "\0".

What is actually inputted is not different from CHX forms.

Create Windows DLL, and export the following function by using def file.

Prototype

int fnCAPI(const void* pEnv, int nEnvLen,const void* pHead, int nHeadLen,const void* pBody, int nBodyLen,void** ppResponce)

Parameters

in	*const void pEnv**	The environment variable.
in	int nEnvLen	The length of the environment variable.
in	*const void pHead**	The request header block.
in	int nHeadLen	The length of the request header block.
in	*const void pBody**	The request body.
in	int nBodyLen	The length of body block.
out	void ppResponce**	The content of response which is allocated by ::malloc().

From version 2.30, use
HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, size ) instead of ::malloc( size ).
HeapReAlloc( GetProcessHeap(), HEAP_ZERO_MEMORY, p, size ) instead of ::realloc( size ).

Return Value

The data length (byte unit) which transmits to be browser.

7.MOD Extension

Description

It is an extension module for a MIME type. The form of function is same as CHX extension.

It is determined by the file name which MIME type is extended. For example, When the file which has the extension ".txt" is requested by client browser, the extension named "text.mod" is invoked by CEHTTP.

The following code indicate to obtain the filename path.

strcpy( szFile, pEnv->GetValueI("DOCUMENT_ROOT") );
strcat( szFile, pEnv->GetValueI("SCRIPT_NAME") );
// '/' ->'\'
char* p = szFile;

while( *p != '\0' ) {
if(*p == '/' ) {
*p++ = '\\';
}

MOD extension can change the called file.

CEHTTP enumerates the ".mod" files which exist in a current directory. A MIME type list will be changed if a ".mod" file is dsicoverd here.

For example, if there is "txt.mod", MIME type list is added following record.

.txt \program files\cehttp\txt.mod

The same thing is possible if MIME type list file is written as mentioned above. This file is explained by "CEHTTP users manual".

8.Logfile Extension

Description

The log file is provided by DLL extension. It is possible to change the output of a log file.

The file name is "cehttplog.dll" and the function name is "fnCehttpLog".

Although an environment variable is given to a log file function, some information is added as follows.

remote_addr	The IP address of remote host.
request_line	Request line which remote host has sent.
send_bytes	Byte count of response. It is not set when HTTP status is except 200.

Prototype

typedef int (*CEHTTPLOGAPI)(WCHAR* pwszLogFile, int nLogSize, int nHttpStatus, MyHash* hashRequest);

Parameters

in	*WCHAR pwszLogFile**	The log file name specified by CEHTTP.
in	int nLogSize	Max size of log files
in	int nHttpStatus	The status code of CEHTTP.
in	*MyHash pHashHeaders**	The environment variables

Return Value

0 indicate failure. otherwise success.

9.eMVC3++

All source code was compiled with Microsoft eMbedded Visual Tools 3.0. It is gratuitously compiler of Windows CE provided by Microsoft Corp.

It is possible to download of English version. Refer to the following URL.

http://www.microsoft.com/japan/windows/embedded/ce/techinfo/default.asp

10.Development

DLL Debugging

The DLL cannot debug alone. It must be debugged with CEHTTP.

If the project of CEHTTP and the project of extension DLL is added to one workspace, it is possible to debug. And step debugging can be available.

Create new workspace. select. [file - new] menu, and select [workspace] tab.
Select [project - insert project] menu.
Insert both project CEHTTP and DLL.

It becomes possible to debug both of code.

As a point which it must be careful of in case DLL is dealt with on WindowsCE, once DLL is load on memory of CEHTTP process, is is never released. This point becomes the difference with a Windows.

The note of multithread programming

The extended module loaded from CEHTTP needs to be multithread safe. It must be careful of in case of a global variable are used. The writing of a global variable affects operation of the extended module which is operated by other threads.

Initialization and release of a system object are performed in the function of ::DllMain(). For example, in case CriticalSection is used, it describe as follows.

CRITICAL_SECTION cs;
BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved )
{
    switch( ul_reason_for_call )
    {
        case DLL_PROCESS_ATTACH:
        {
            InitializeCriticalSection(&cs);
            break;
        }
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
            break;
        case DLL_PROCESS_DETACH:
        {
            DeleteCriticalSection( &cs );
            break;
        }
    }

    return TRUE;
}

int fnChx(MyHash* pEnv, MyVarMem* pBody, MyVarMem* pRes)
{
    EnterCriticalSection( &cs );
    // critical section code here...

    LeaveCriticalSection( &cs );
}

By this way, while other threads perform this DLL, it can prevend opening a system object carelessly.

About UNICODE

As for WindowsCE, UNICODE is default character set. But HTTP protocol request and response is written by ASCII character. Cautions are required.

In CEHTTP, it has shifted to the programming style which uses WSTR clearly, without using TEXT macro.

About test

Although it is the best way which is actually seen by the browser, it is also effective to check the raw data by using telnet. Windows has useful telnet to use a test.

It can use with the command line as follows.

>telnet <server name> <port number>

>telnet localhost 80
GET / HTTP/1.0

HTTP/1.0 200 OK
Server: CEHTTP/2.2
Content-Length: 127
Last-Modified: Mon, 10 Feb 2003 04:28:49 GMT
Connection: Keep-Alive
Content-Type: text/html

<HTML><BODY><H1>Can you see me?</H1><BR><HR>CEHTTP2 by<A HREF="http://www001.upp.so-net.ne.jp/ishi/">IshiSoft</A></BODY></HTML>

About tools

IProxy

The tool for seeing the protocol between a Web server and a browser is provided on IshiSoft.

MS Web Application Stress Tool

WAS is convenient for multithread test or durability test. This is the gratuitously tool from Microsoft Corp. It operates by the multithread and can describe with macro.

It can download from the following URL.

http://www.microsoft.com/technet/treeview/default.asp?url=/technet/itsolutions/intranet/downloads/webstres.asp

appendix. A Sample code

// sample.chx

#include "stdafx.h"
#include "stdio.h"
#include "chx.h"

//*****************************************************************************
// fhChx
//*****************************************************************************
int fnChx(MyHash* pEnv, MyVarMem* pBody, MyVarMem* pRes)
{
    char work[2048];
    if((char*)pBody)
    {
        sprintf(work,
            "Content-Type: text/html\r\n\r\n"
            "<html>"
            "<head><title>CECGI</title></head>"
            "<u><b>BODY</b></u><br>"
            "%s<br>"
            "<u><b>environment</b></u><br>"
            ,
            pBody->GetBuffer()
            );
    }
    else
    {
        pRes->Add("(null)");
    }

    pRes->Add(work);

    pEnv->SeekToFirst();

    do{
        sprintf(work,
            "%s=%s<br>\n"
            ,pEnv->GetCurrentKey()
            ,pEnv->GetCurrentValue()
            );
        pRes->Add(work);
    }while(pEnv->SeekNext());

    pRes->Add("</html>");
    return pRes->GetLength();
}

//*****************************************************************************
// DllMain
//*****************************************************************************
BOOL APIENTRY DllMain( HANDLE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved )
{
    switch (ul_reason_for_call)
        {
        case DLL_PROCESS_ATTACH:
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
        case DLL_PROCESS_DETACH:
            break;
    }
    return TRUE;
}

Appendix. B Environment variables

CEHTTP sets the following environment variables. It will not be set if there is information which is not acquired.

parameters description

SCRIPT_NAME The extended file name currently performed

PATH_INFO Path information attached behind URI

PATH_TRANSLATED The position on the local file system of path information

CONTENT_LENGTH Body length at the time of POST command

QUERY_STRING The parameter of the URI

REMOTE_ADDR The IP address of a client

REMOTE_HOST The host name (need dnslookup option at registry)

REMOTE_PORT The port of a client

REQUEST_METHOD The method of client request

SERVER_NAME The address of the WEB server specified by the client

SERVER_PORT A server's port specified by the client

SERVER_PROTOCOL The HTTP protocol version specified by the client

SERVER_SOFTWARE Server soft name

HTTP_ACCEPT The receivable MIME type specified by the client

HTTP_USER_AGENT Client soft name

HTTP_COOKIE The Cookie name which the client transmitted

HTTP_REFERER The page by which the client came

DOCUMENT_ROOT The document route position on a local file system

GATEWAY_INTERFACE Extended gateway name

parameters	description
SCRIPT_NAME	The extended file name currently performed
PATH_INFO	Path information attached behind URI
PATH_TRANSLATED	The position on the local file system of path information
CONTENT_LENGTH	Body length at the time of POST command
QUERY_STRING	The parameter of the URI
REMOTE_ADDR	The IP address of a client
REMOTE_HOST	The host name (need dnslookup option at registry)
REMOTE_PORT	The port of a client
REQUEST_METHOD	The method of client request
SERVER_NAME	The address of the WEB server specified by the client
SERVER_PORT	A server's port specified by the client
SERVER_PROTOCOL	The HTTP protocol version specified by the client
SERVER_SOFTWARE	Server soft name
HTTP_ACCEPT	The receivable MIME type specified by the client
HTTP_USER_AGENT	Client soft name
HTTP_COOKIE	The Cookie name which the client transmitted
HTTP_REFERER	The page by which the client came
DOCUMENT_ROOT	The document route position on a local file system
GATEWAY_INTERFACE	Extended gateway name

All request header by client is upper cased, '-' is translated and added 'HTTP_'.
e.g. "Accept-Encoding" is translated to "HTTP_ACCEPT_ENCORDING".

Difference of WindowsCE from other OS

CHX/DLL

MOD

Description

Prototype

Parameters

Return Value

remark

Description

Prototype

Parameters

Return Value

Description

Description

Prototype

Parameters

Return Value

DLL Debugging

The note of multithread programming

About UNICODE

About test

About tools

IProxy

MS Web Application Stress Tool

appendix. A Sample code