谈谈在WebServer中如何实现CGI技术

谈谈在WebServer中如何实现CGI技术

在WebServer中，cgi技术的实现相信许多人很感兴趣，不过在一些开源软件如Apache中，由于软件规模大，相关模块多，直接去读懂是如何实现的比较费劲，下面就来谈谈CGI技术的实现方法。

要实现CGI技术，关键是要实现执行其他应用程序时，将应用程序的输出从屏幕重定向到SOCKET中去，实现了应用程序的输出重定向后，CGI实现就很简单了。

下面以windows平台为例来实现cgi技术。以下的cgi_writeclient()函数便实现了将CGI程序的输出结果重定向到socket的功能。

HANDLE cgi_exec( HANDLE hPipeWrite, char *exefile, char *cmdline, char *lpszCurrentPath )

{

BOOL bSucceed;

STARTUPINFO sui;

PROCESS_INFORMATION pi;

BOOL bTest;

memset(&sui,0,sizeof(STARTUPINFO));

sui.cb=sizeof(STARTUPINFO);

sui.dwXSize = 0;

sui.dwXSize = 0;

sui.wShowWindow = SW_HIDE;

sui.dwFlags= STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;

sui.hStdInput=NULL;

sui.hStdOutput=hPipeWrite;

sui.hStdError=hPipeWrite;

bSucceed = CreateProcess(exefile,

cmdline,

NULL,

NULL,

TRUE,

0,//CREATE_NEW_PROCESS_GROUP ,

NULL,

lpszCurrentPath,//lpszPath,//"\\Rose\\c\\",//NULL,//"d:\ip_progs\namepipe\child",

&sui,

&pi);

if ( bSucceed )

{

CloseHandle( pi.hThread );

return pi.hProcess;

}

// ShowErrorMessage( "CreateProcess()" );

return FALSE;

}

intcgi_writeclient( HTTPRequest *hr )

{

char *pszPath;

HANDLE hProcess;

BOOL bProcessDead = FALSE;

HANDLE hPipeRead, hPipeWrite;

SECURITY_ATTRIBUTES SecAttrib;

int ret;

int BytesInPipe;

char *buf;

DWORD dwRead;

SecAttrib.nLength = sizeof(SECURITY_ATTRIBUTES);

SecAttrib.lpSecurityDescriptor = NULL;

SecAttrib.bInheritHandle = TRUE;

if ( hr->http_mod != HTTP_GET )

{

return MODULE_RUN_CONTINUE;

}

if ( hr->mod != MOD_LOCAL )

{

return MODULE_RUN_CONTINUE;

}

pszPath = MemAlloc( hr->hMem, strlen( pszCgiRoot ) + strlen(hr->http_url) + 10 );

if ( !pszPath )

{

return MODULE_RUN_CONTINUE;

}

/* decide if it is the cgi path */

strcpy( pszPath, hr->http_url );

if ( pszPath[strlen(pszPath)-1] == '/' )

{

if ( *(hr->http_url) == '/' )

{

strcat( pszPath, hr->http_url+1 );

}

else

{

strcat( pszPath, hr->http_url );

}

}

else

{

strcpy( pszPath, pszRoot );

strcat( pszPath, hr->http_url );

ReplaceChar( pszPath, '\\', '/' );

}

if ( strnicmp( pszPath, pszCgiRoot, strlen(pszCgiRoot) ) != 0 )

{

return MODULE_RUN_CONTINUE;

}

ret = CreatePipe( &hPipeRead, &hPipeWrite, &SecAttrib, 65536 );

buf = MemAlloc( hr->hMem, 1024 );

hProcess = cgi_exec( hPipeWrite, NULL, pszPath, NULL );

while ( !bProcessDead )

{

int dwRet;

dwRet = WaitForSingleObject( hProcess, 1 );

if ( dwRet != WAIT_TIMEOUT )

{

bProcessDead = TRUE;

}

if (!PeekNamedPipe(hPipeRead, NULL, 0, NULL, &BytesInPipe, NULL))

{

break;

}

if ( BytesInPipe != 0 )

{

memset( buf, 0, sizeof(buf) );

dwRead = 0;

if ( ReadFile( hPipeRead, buf, 1024, &dwRead, NULL ) )

{

if ( dwRead > 0 )

{

send( hr->s, buf, dwRead, 0 );

}

}

}

}

do

{

if (!PeekNamedPipe(hPipeRead, NULL, 0, NULL, &BytesInPipe, NULL))

{

break;

}

if ( BytesInPipe != 0 )

{

memset( buf, 0, sizeof(buf) );

dwRead = 0;

if ( ReadFile( hPipeRead, buf, 1024, &dwRead, NULL ) )

{

if ( dwRead > 0 )

{

send( hr->s, buf, dwRead, 0 );

}

}

}

} while ( BytesInPipe != 0);

MemFree( hr->hMem, buf );

CloseHandle( hProcess );

CloseHandle( hPipeRead );

CloseHandle( hPipeWrite );

return MODULE_RUN_ENDSESSION;

}

在以上代码中，cgi_exec是实现创建进程，并将进程的输出定向到管道中，然后在cgi_writeclient()函数中，先创建管道，然后调用cgi_exec()函数创建cgi进程并将其输出定向到刚创建的管道中， 然后调用WaitForSingleObject()函数来等待CGI进程运行，注意不是等到进程结束后才从管道读数据。

在cgi进程的运行过程中，每等一段时间，就从管道中读取一部分数据，调用send()函数发送到socket中去。当等到cgi进程结束后，再从管道中将剩余的数据全部读出发送到socket中去。这样就实现了cgi的功能。