Re: Check existence of data area in ILE C

Also my thanks to Chuck for _CTLA_HANDLE_NO_MSG.
I had no idea about this option. Of course a piece I shared was
written by someone here in the previous millenium.
And the fact that _CTLA_HANDLE does generate error message into the
log in our particular case was rather useful....

Jevgeni.

On Wed, Mar 11, 2015 at 9:56 AM, Zvi Kave <[email protected]> wrote:
>    Hi Chris,
>
>    I shall try it later because I need a quick solution.
>    In the meantime I need only to replace  _CTLA_HANDLE with
>    _CTLA_HANDLE_NO_MSG
>    in the exception handler.
>    Do I save CPU in your solution or it is the same, but without exception
>    handler ?
>
>    Thanks,
>
>    Zvi
>
>    On 10/03/2015 20:10, [1]chrish-lbwoW8fqX/3W0OUqm4st0/d9D2ou9A/[email protected] wrote:
>
>  Here is a quick sample for a data area which is a decimal data area (cannot
>  be retrieved using the QXX API's)
>
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <string.h>
>  #include <qusec.h>
>  #include <decimal.h>
>  #include <qwcrdtaa.h>
>
>
>  typedef _Packed struct DA_content_x {
>                         Qwc_Rdtaa_Data_Returned_t hdr;
>                         char data[10];
>                         } DA_content_t;
>
>  int main(int argc, char **argv) {
>  int rcvr_count = 0;
>  DA_content_t Dta_Content;                   /* data area content */
>  decimal(5,0) *d_ptr;
>  char DA_Name[20] = "NBROFRCV  CHLIB     ";  /* Name */
>  Qus_EC_t Error_Code = {0};                  /* error code struct */
>
>  Error_Code.Bytes_Provided = sizeof(Error_Code);
>
>  QWCRDTAA(&Dta_Content,
>           sizeof(Dta_Content),
>           DA_Name,
>           1,
>           5,
>           &Error_Code);
>  if(Error_Code.Bytes_Available > 0) {
>     // do something about the error
>     printf("Error received %.7s\n",Error_Code.Exception_Id);
>     return -1;
>     }
>  printf("Available = %d\n",Dta_Content.hdr.Bytes_Available);
>  printf("Returned = %d\n",Dta_Content.hdr.Bytes_Returned);
>  printf("Type = %.10s\n",Dta_Content.hdr.Type_Value_Returned);
>  printf("Length = %.10s\n",Dta_Content.hdr.Length_Value_Returned);
>  printf("Decimal pos = %d\n",Dta_Content.hdr.Number_Decimal_Positions);
>  d_ptr = (decimal(5,0)*)Dta_Content.data; printf("Content =
>  %D(5,0)\n",*d_ptr); return 1;
>  }
>
>  It's simple and easy to understand and does not require you to build in your
>  own error handler. Write it up as a generic handler for retrieving any data
>  area content.
>
>  Chris...
>
>  -----Original Message-----
>  From: C400-L [[2]mailto:c400-l-bounces-Zwy7GipZuJhWk0Htik3J/[email protected]] On Behalf Of Zvi Kave
>  Sent: March 10, 2015 12:04 PM
>  To: [3]c400-l-Zwy7GipZuJhWk0Htik3J/[email protected]
>  Subject: Re: [C400-L] Check existence of data area in ILE C
>
>     Very nice.
>     _CTLA_HANDLE_NO_MSG made the trick!!
>
>     Many thanks,
>
>     Zvi
>
>     On 10/03/2015 17:36, CRPence wrote:
>
>       On 10-Mar-2015 10:20 -0500, Zvi Kave wrote:
>
>         Sorry. It is too much complicated for me.
>         Waiting for simpler solution.
>         Perhaps a change in the exception handler?:
>          #pragma exception_handler(ERROR_OCCURED, ca, 0, _C2_MH_ESCAPE, \
>                                      _CTLA_HANDLE, "MCH3401")
>
>         Of course that would not resolve the issue of concurrency introduced
>       by performing a separate /check for existence/ test prior to invoking
>       the request to /Retrieve Data Area/ that itself performs the same
>       existence check.  Nevertheless...
>
>         I was unaware that the capability to suppress the messaging was
>       exposed externally in any of the HLLs, but a quick search of the
>       KnowledgeCenter revealed that there are both of the Exception Control
>       Actions available to the C language, "_CTLA_IGNORE_NO_MSG" and
>       "_CTLA_HANDLE_NO_MSG", which apparently provide the equivalent effect
>  of
>       the message suppression:
>
>  [1][4]<http://www.ibm.com/support/knowledgecenter/ssw_ibm_i_71/rzarf/prag_excep
>  tion_handler.htm%23prag_exception_handler>
>       "...
>       ctl_action
>
>           Specifies an integer constant to indicate what action should take
>       place for this exception handler. If handler is a function, the default
>       value is _CTLA_INVOKE. If handler is a label, the default value is
>       _CTLA_HANDLE. This parameter is optional.
>
>           The following are valid exception control actions that are defined
>       in the <except.h> header file:
>
>           #define name     Defined value and action
>       ...
>       _CTLA_HANDLE_NO_MSG     Defined to 3. The exception is handled but
>       messages are not logged before calling the handler. The exception will
>       no longer be active when the handler gets control. Exception messages
>       are not logged. Msg_Ref_Key in the typedef _INTRPT_Hndlr_Parms_T is set
>       to zero. Exception processing ends when the exception handler returns.
>       This is valid for functions and labels.
>        ...
>       _CTLA_IGNORE_NO_MSG     Defined to 132. The exception is handled and
>       messages are not logged. Control is not passed to the handler function
>       named on the directive and exception will no longer be active.
>  Execution
>       resumes at the instruction immediately following the instruction that
>       caused the exception. This is valid for functions only.
>        ..."
>
>  References
>
>     Visible links
>     1.
>  [5]http://www.ibm.com/support/knowledgecenter/ssw_ibm_i_71/rzarf/prag_exception
>  _handler.htm%23prag_exception_handler
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