Returns the ISAPI extension block.
call "PC_ISAPI_GET_EXT"  using    ext-block
                            returning pc-status-code 
               	 01 extension-control-block typedef 03 cbsize DWORD 03 dwversion DWORD 03 connid HCONN 03 dwhttpstatuscode DWORD 03 lpszlogdata PIC x(hse-log-buffer-len) 03 lpszmethod LPSTR 03 lpszquerystring LPSTR 03 lpszpathinfo LPSTR 03 lpszpathtranslated LPSTR 03 cbtotalbytes DWORD 03 cbavailable DWORD 03 lpbdata LPBYTE 03 lpszcontenttype LPSTR 03 getservervariable procedure-pointer 03 writeclient procedure-pointer 03 readclient procedure-pointer 03 serversupportfunction procedure-pointer
| 0 | OK | 
| 1 | Non-ISAPI environment | 
| 2 | cbsize smaller than current ISAPI extension block |