C pointer char array to char array

Question

How do I access individual chars in a pointer char array? I have an array which might look something like this:

In the function calling my function in question:

char *parsedString[9];
getParsedString(parsedString);

size_t len = strlen(parsedString[3]);
pos.latitude = parseCoordinatePart(len, parsedString[3]);

Heres the function where I have problem understanding how to do:

double parseCoordinatePart(int len, char partArray[]){
   if(len == 8){
       degrees = 10 * partArray[0] - '0';
       degrees += partArray[1] - '0';

   }else if(len == 9){
       indexAdd = 1;
       degrees = 100 * partArray[0] - '0';
       degrees += 10 * partArray[1] - '0';
       degrees += partArray[2] - '0';
   }
   //More calculations to get longitude or latitude 
}

While parseCoordinatePart() does not give any compile errors I can not call it from my function above. My first thought was to dereference parsedString[3] but anyway I tried it always gave me "illegal conversion of integer to pointer"

Update: Heres the code for setting parsedString data:

void splitNmeaString(char *parsedString[]){
char *token;
// remove the first token
token = strtok(receivedData, ",");

int tokenIndex = 0;
while( token != NULL )
{
    token = strtok(NULL, ","); // works when 1st arg is NULL. But why?!
    if(tokenIndex < 10 ){
        parsedString[tokenIndex] = token;
    }else{
        break;
    }
}
}

I'm not sure what you mean by 'cannot call'. What happens when you try to call the function? Did you try to run it through gdb? Also, your array seems to have floating point data which makes no sense. — darnir
– darnir, Commented May 12, 2014 at 14:47
Does getParsedString() allocate memory for char *parsedString[9];? — ryyker
– ryyker, Commented May 12, 2014 at 14:50
When I compile the code it gives me "illegal conversion of integer to pointer". The array does not have floating points data. They are all "strings" or char array or what to say in c. What is gdb? I use MPLAB X with the xc8 compiler — user1842278
– user1842278, Commented May 12, 2014 at 14:51

ryyker · Accepted Answer · 2014-05-12 15:07:03Z

1

Too much for a comment, but:

Unless you are doing it in getParsedString(), Somewhere in your code char *parsedString[9]; has to be allocated memory for all 9 elements of the char *[9]

for(i=0;i<9;i++)
    {
         parsedString[i] = malloc(20);
    }

Are you doing this?

Edit (per comment)

When I allocated memory, and populated at least one string to test, function called without error, as shown:

int main ()
{
    //char *parsedString[9];
     //given that your system may not support malloc/calloc
    char parsedString[9][20];  //adjust second index if need more space

    parsedString[1] = malloc(20);
    //getParsedString(parsedString);  //not defined for me, comment

    strcpy(parsedString[1], "sdfgsd"); //fill with anything to test call

    size_t len = strlen(parsedString[1]);
     parseCoordinatePart(len, parsedString[1]); //calls without error given previous lines
     return 0;
}

Note, I have only allocated memory for, and populated one of the nine elements of char *parsedString[9]; to test the function call. It now calls without error as shown.

I do not see the definition of getParsedString(parsedString);, but suspect that you are doing memory allocation and string propulation there? If not, that may be where part of the problem lies.

edited May 12, 2014 at 15:07

answered May 12, 2014 at 14:54

ryyker

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7 Comments

user1842278 Over a year ago

Thank you, had no idea about that. Its updated now in my code but still same behavior

ryyker Over a year ago

When I add the malloc, and populate the string properly, the function calls without error. I will edit my code to show.

user1842278 Over a year ago

This time when compiling I did get another error. error: undefined symbol:_malloc(stuff/.../). When googling it, it seems that "Dynamic memory allocation, (heap-based allocation using malloc, etc.) is not supported on any 8-bit device". How do I do it not dynamic?

ryyker Over a year ago

What compiler are you using? i.e. what dev environment?

user1842278 Over a year ago

MPLAB X, compiler xc8. Using a PIC18

|

Pablo Francisco Pérez Hidalgo · Accepted Answer · 2014-05-12 15:08:14Z

1

One problem is you are multiplying an invalid value by its positional factor. Since multiplication has a higher precedence than subtraction, you should subtract '0' to your digit character before multiplying it:

double parseCoordinatePart(int len, char partArray[]){
   if(len == 8){
       degrees = 10 * (partArray[0] - '0'); //Here
       degrees += partArray[1] - '0';

   }else if(len == 9){
       indexAdd = 1;
       degrees = 100 * (partArray[0] - '0');
       degrees += 10 * (partArray[1] - '0');
       degrees += partArray[2] - '0';
   }
   //More calculations to get longitude or latitude 
}

Did you notice that parsedString[3] is not a string representation of a number but a cardinal point? N. None of your parseCoordinatePart if branches will be executed.

edited May 12, 2014 at 15:08

answered May 12, 2014 at 14:45

Pablo Francisco Pérez Hidalgo

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2 Comments

user1842278 Over a year ago

Of course! Did not notice that as the function could not be called. The degrees are defined above, did cut away some to make the code smaller. It is an interger

Pablo Francisco Pérez Hidalgo Over a year ago

@user1842278 Just edited my answer to include another observation. It may happen that is parseCoordinatePart called but none of its if branches is executed?

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