C18 how to manage pointers

[cherreram]

Hi,
due to my work, recently I moved from CCS to C18 and everything ok, except for one thing: I dont know how to manage pointers in C18.

Time ago I built a string search routine who worked similar to "find" python instruction.
So, I wanted to use it now, in C18, but I have -- Error [1131] type mismatch in assignment-- in return.

this is the code:

signed short int finds(char *string1, char *string2){
//Funcion para buscar string2 en string1. La max. longitud de string1 y string2
// es 128 caracteres.Devuelve la posicion del inicio de string2 en string1.
//Si no lo encuentra, devuelve un -1.
//
   unsigned int counter1=0;
   unsigned int counter2=0;
   unsigned int startostring2=0;
   unsigned int startostring1=0;
   startostring2=string2;  //this is to hold the start address of string2 and str1 
   startostring1=string1;  //and here is where error [1131] type begin.
   while(*string1!=0){
      counter2=counter2+1;
      string1=string1+1;
   }
   string1=startostring1;
   while(counter1!=counter2){
      if(*string2!=*string1){
         string1=string1+1;
         counter1=counter1+1;
      }
      else{
         do{
            string1=string1+1;
            string2=string2+1;
            }while((*string2==*string1)&&(*string2!=0));
         if(*string2==0){
            return counter1;
         }
         else{
            counter1=string1-startostring1;
            string2=startostring2;
         }
      }
   }
   return -1;
}

this routine search for string2 into string1 and return the position, on string1, where string2 start to match. If string2 is not contained in string1, -1 is returned.

this is the way I use it:

signed short res=0;
char Buffer[]="this is a test only";
res=finds(&Buffer,"test");

in MikroC or CCS it works perfect, but C18 dont.

any advice?..I know there are ram and rom pointers, but when I have to use it?

 

[nostrildamus]

Could you elaborate a bit on the trouble you're having?

Is there some reason you're not treating strings as char*'s or char[]'s?

I've used C18 for all of my PIC18 development and haven't had trouble with pointers, so a bit more information would be very helpful to understand the problem.

 

[cherreram]

Hi again,

Thanks for your cooperation and problem solved.
In C18 is not possible to assign pointer's value to a variable. In the code above I had:

startostring2=string2; -->Error

startostring is a ram variable who retain the address contained in string2 (a pointer).
Even startostring is a 16 bit value and it is able to manage the 16 bit value stored in string2, there was an Error [1131] type mismatch in assignment.

The problem is, startostring2 is a variable and string2 is a pointer.
what to do?, simple, let's startostring be a pointer.

char *startostring2;

startostring is a pointer now and, it has to be declared exactly as string was. I mean, if string2 is a char, startostring2 has to be a char. If string2 is a unsigned char, startostring2 has to be a unsigned char and so on.

If we declare string2 as a char and startofstring2 as a unsigned char, we will get the same error code: mismatch in assignment.

Well, my code, now turns into:

signed short int finds(char *string1, char *string2){
   unsigned int counter1=0;
   unsigned int counter2=0;
   char *startostring2;
   char *startostring1;
   startostring2=string2;   
   startostring1=string1; 
   while(*string1!=0){
      counter2=counter2+1;
      string1=string1+1;
   }
   string1=startostring1;
   while(counter1!=counter2){
      if(*string2!=*string1){
         string1=string1+1;
         counter1=counter1+1;
      }
      else{
         do{
            string1=string1+1;
            string2=string2+1;
            }while((*string2==*string1)&&(*string2!=0));
         if(*string2==0){
            return counter1;
         }
         else{
            counter1=string1-startostring1;
            string2=startostring2;
         }
      }
   }
   return -1;
}

well, now works fine for me.

Hope it can help somebody.