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Problem with char protocol validation

 
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Schneider



Joined: 20 Nov 2006
Posts: 8

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Problem with char protocol validation
PostPosted: Mon Jan 22, 2007 9:03 pm     Reply with quote
I wrote a function that should return true or false dependind on a string received from the rs232.

Code:


boolean isCmd(char *pStr[]){
  char sTmp[] = {"#CMD:"};
  int iTmp;

  iTmp = (strlen(*pStr)-1);

  printf("strPar: %s\r\n", *pStr);
  printf("strCom: %s\r\n", sTmp);
  printf("Match: %u\r\n", strspn(*pStr, sTmp));
  printf("Index: %u\r\n", iTmp);
  printf("Close: %c\r\n", *pStr[iTmp]);

  if ((strspn(*pStr,sTmp)==5) & (*pStr[iTmp] == ';')){
    return true;
  }else{
    return false;
  }
}



the printf in the function is to trace the values while testing the function.

I use it this way:

Code:

   
   char strBuffer[];

   // receive data trough rs232 #CMD:123;

    gets(strBuffer);
    if(isCmd(&strBuffer)){
      printf("CMD is valid!\r\n");
    }else{
      printf("CMD is invalid!\r\n");
    }



everything works fine until the *pStr[iTmp]. it doesn't return the last character in the array. what am i doing whrong?


thanks for any help.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Jan 22, 2007 9:28 pm     Reply with quote
I didn't review your code in detail, but this statement here has got a
few problems:
Quote:
if ((strspn(*pStr,sTmp)==5) & (*pStr[iTmp] == ';')){

The strspn() function takes two pointers as arguments. You've got
a dereferenced pointer as the first argument. It should be a pointer.
The 2nd thing I see is that your intention is to do a logical operation
on the two expressions but you have a bitwise AND operator.
You should be using the logical AND operator, which is &&.
There might be other problems. Those are just two that I spotted.

This is from the Help file from my old QuickC for Windows:
Code:

Syntax:  size_t strspn( char *string1, char *string2 );
Returns: The position of the first nonmatching character in string1.

/*
STRSPN.C: This program uses strspn to determine the
length of the segment in the string "cabbage" consisting
of a's, b's, and c's.  In other words, it finds the first
non-abc letter.
*/

void main()
{
   char string[] = "cabbage";
   int  result;

   result = strspn( string, "abc" );
   printf( "The portion of '%s' containing only a, b, or c "
           "is %d bytes long\n", string, result );
}
Schneider



Joined: 20 Nov 2006
Posts: 8

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PostPosted: Tue Jan 23, 2007 6:34 am     Reply with quote
the strspn() is working fine. The only problem in the function is that I'm not obtaining the last char in the parameter string.

when I call the function, i get this feedback on the terminal screen:

assuming that the parameter passed to the function is #CMD:123

strPar: #CMD:123
strCom: #CMD:
Match: 5
Index: 7
Close: ??? (sometimes show some garbadge)

this should return false

and if the parameter passed to the function was #CMD:123;

the function should return true

i don't know why the 'Close' character is not returned when i try to get the *pStr[iTmp] value.

I realy missed the bitwise AND. I will try with the &&, butt the biggest problem is beffore the AND test.
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Tue Jan 23, 2007 7:06 am     Reply with quote
Try this:
Code:

boolean isCmd(char *pStr)
{
  char sTmp[] = {"#CMD:"};
  int iTmp;

  iTmp = (strlen(pStr)-1);

  printf("strPar: %s\r\n", pStr);
  printf("strCom: %s\r\n", sTmp);
  printf("Match: %u\r\n", strspn(pStr, sTmp));
  printf("Index: %u\r\n", iTmp);
  printf("Close: %c\r\n", pStr[iTmp]);

  if ((strspn(pStr,sTmp)==5) && (pStr[iTmp] == ';'))
  {
    return true;
  }
  else
  {
    return false;
  }
}

char *pStr[] is an array of pointers to strings which is not what you have. You just need a pointer to a string
Schneider



Joined: 20 Nov 2006
Posts: 8

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PostPosted: Tue Jan 23, 2007 11:41 pm     Reply with quote
you're the best dude.. the problem is solved.. thanks a lot..
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