Solved

Waitforsingleobject always results in a timeout !!!

Posted on 2004-08-03
1
2,054 Views
Last Modified: 2013-12-03
My waitforsingleobject always results in a timeout and i am unable to figure out why.. Please look at my code below..
i have a read file call .that gets called as soon as i receive a character in the input buffer. Hence i am waiting on waitcommevent and when a character appears, i issue a readfile to read all the characters that have come through my serial port.. However, waitcommevent is a blocking call. I had to make the waitcommevent timeout.. Hence, i moved to overlapped IO. But now..my waitcommevent always timeouts even though i know that there are characters to read. Please let me know what is wrong with my code..
/*********************************************************************************************/
int ReadProc1(char *str)
{
     
     /*
     Using the EV_RXCHAR flag will notify the thread that a byte arrived at the port. This event,
     used in combination with the ReadFile function, enables a program to read data only after
     it is in the receive buffer, as opposed to issuing a read that waits for the data to arrive*/


     DWORD dwCommEvent; //a variable that receives a mask indicating the type of event that occurred
     char chRead;          // Character read every time a read takes place.
     DWORD dwRead =0,Err,Bytes;          //Pointer to the variable that receives the number of bytes read
     char * str =calloc(100,sizeof(char));
     unsigned int i=0,j=2;
     BOOL fWaitingOnRead = FALSE,Ok= FALSE;

     OVERLAPPED osReader= {0};

     

     FillMemory(str, strlen(str), 0);
     //if((strcmp(p->PType,"13") == 0) && (strcmp(p->Data,"0") != 0)) stop = 0x06;
     if (stop == 0x06) terminate=1;
     if (stop == 0x03) terminate=0;
     
     
     memset(&osReader,0,sizeof(OVERLAPPED));
     osReader.hEvent = CreateEvent(
    NULL,   // no security attributes
    TRUE,  // auto reset event
    FALSE,  // not signaled
    NULL    // no name
    );
     if (osReader.hEvent == NULL)
     {
          LogEvent(hComm,"Error creating overlapped event");
     }

     for ( ; ; ) {
          if (!fWaitingOnRead)
          {

               if (!(WaitCommEvent(hComm, &dwCommEvent,&osReader)))
               {

                    if (GetLastError() != ERROR_IO_PENDING)
                    {
                         LogEvent (ghwnd," Error in Wait Comm Event");
                         return FALSE;
                    }
                    else
                    {
                         fWaitingOnRead = TRUE;
                         Err = WaitForSingleObject(hComm, READ_TIMEOUT);
                         
                         switch(Err)
                         {
                         case WAIT_TIMEOUT:
                              LogEvent(ghwnd,"Timed out waiting for response from device.. check connections/power");
                              return FALSE;
                              break;


                         case WAIT_OBJECT_0:
                          // Event triggered. Check the status.
                             
                              Ok = GetOverlappedResult(hComm, &osReader, &Bytes, TRUE);
                              if (Ok)
                              {
                       
                                   do
                                   {
                                                           
                                        if (ReadFile(hComm, &chRead, 1, &dwRead, NULL))
                                        {
                                   
                                             // A byte has been read; process it.
                                             str[i++]=chRead;
                                                                                     }
                                        else
                                        {
                                        // An error occurred in the ReadFile call.
                                             LogEvent(ghwnd," Read Failed With Error Code ");
                                             break;
                                        }
                         
                                   } while (dwRead );
                              }
                              else
                              {
                                   LogEvent(ghwnd,"Get Overlapped Result Failed ");
                                   return FALSE;
                              }
                              break;
                         default:

                              LogEvent (ghwnd," Error in wait for single object");
                              return FALSE;
                              break;
                         }//End of Switch
                    }//End of GetLastError
               }
               else
               {
                    LogEvent(ghwnd,"Read Completed Immedialtely");
                       /* So Proceed to readfile
                                 }//End of Wait Comm Event
          }// End of Waiting on Read
         
     
     }

         
     }
     
 
/*********************************************************************************************
0
Comment
Question by:shubha_mohan
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
1 Comment
 
LVL 48

Accepted Solution

by:
AlexFM earned 250 total points
ID: 11704971
0

Featured Post

Creating Instructional Tutorials  

For Any Use & On Any Platform

Contextual Guidance at the moment of need helps your employees/users adopt software o& achieve even the most complex tasks instantly. Boost knowledge retention, software adoption & employee engagement with easy solution.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In this article, I will show how to use the Ribbon IDs Tool Window to assign the built-in Office icons to a ribbon button.  This tool will help us to find the OfficeImageId that corresponds to our desired built-in Office icon. The tool is part of…
A theme is a collection of property settings that allow you to define the look of pages and controls, and then apply the look consistently across pages in an application. Themes can be made up of a set of elements: skins, style sheets, images, and o…
This is Part 3 in a 3-part series on Experts Exchange to discuss error handling in VBA code written for Excel. Part 1 of this series discussed basic error handling code using VBA. http://www.experts-exchange.com/videos/1478/Excel-Error-Handlin…
How to Install VMware Tools in Red Hat Enterprise Linux 6.4 (RHEL 6.4) Step-by-Step Tutorial

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question