Thread: Need help returning -1 in function

Hi all, I should have signed up here about a year ago, as I could use help from time to time.

My current issue is that the following function if 'NUL', 'ETK' or 'NAK' are found in a string (containing up to 1500 characters), the function is to return -1 and a signal[] string is to have "NOT-VALID."

The issue I am having is the return value not being -1 but 4294967295 and the signal string even though it appears to be correct isnt' (I think i may have to do with '\0'.

I've tried casting, signed long, etc but nothing seems to work and I don't understand why.

Yes I know the code is crappy, but I'm still a student. I'd appreciate any help I can get.
Thanks.

Code:

long analyze(const char rawData[ ], char signal[ ], int frequency, int a, int b)
{

    long rv = 0,i = 0,st = 0;
    int found = 0;
    int invalid = 0;

    while(rawData[i] != '\0' && invalid != 1)
    {

        if (rawData[i] >= frequency + 48 && rawData[i] <= 57)
        {
            if (rawData[i+61] == rawData[i])
            {
                if (rawData[i+122] == rawData[i])
                {
                    found = 1;
                    i += 123;
                }
            }
        }

        if (found)
        {
            switch(rawData[i])
            {
            case 'E':
                if (rawData[i+1] == 'T' && rawData[i+2] == 'X')
                {
                    rv = -1;
                    strcpy(signal, "NON-SEQUITOR");
                    invalid = 1;
                }
                break;
            case 'N':
                if (rawData[i+1] == 'U' && rawData[i+2] == 'L')
                {
                    rv = -1;
                    strcpy(signal, "NON-SEQUITOR");
                    invalid = 1;
                }
                break;
            case 'A':
                if (rawData[i-1] == 'N' && rawData[i+2] == 'K')
                {
                    rv = -1;
                    strcpy(signal, "NON-SEQUITOR");
                    invalid = 1;
                }
                break;
            case '<':
                if (rawData[i+1] == '<')
                    signal[st] = rawData[i + 2] - frequency;
                break;
            case '>' :
                if(rawData[i + 1] == '>')
                    signal[st] += rawData[i + 2] + frequency;
                break;
            case ' ':
                signal[st] = ' ';
                st++;
                while(rawData[i + 1] == ' ')
                    i++;
                break;
            case '\0':
                signal[st] = '\0';
                break;
            default:
                if(rawData[i] >= a && rawData[i] <= b)
                {
                    signal[st] = rawData[i];
                    st++;
                    rv = strlen(signal);
                 }
                break;
            }
        }
        i++;
    }
    return rv;
}

Well, not to say that the function works, but the problem wouldn't be here since the function returns signed long. What could be happening is that the type changes when you use the return value. If in a larger expression the type becomes unsigned, that would explain things.

Code:

#include <stdio.h>

long foo(void) {
   return -1;
}

int main(void) {
   printf("return value = %lu\n", foo());
   return 0;
}

C code - 10 lines - codepad

Alright I fixed the return -1 issue, but I can't seem to figure out why signal[] is printing out a blank when using my profs main.

Its not making sense to me at all. When result = -1, NON-SEQUITOR should be in signal[], but the test is returning ' '.

Any ideas?

Originally Posted by compile_

Alright I fixed the return -1 issue, but I can't seem to figure out why signal[] is printing out a blank when using my profs main.

Its not making sense to me at all. When result = -1, NON-SEQUITOR should be in signal[], but the test is returning ' '.

Any ideas?

Originally Posted by c99tutorial

You should also provide a minimal main() function which calls your analyze function with some input of your choice. This is the way to test whether your function behaves as intended.

Please.

Originally Posted by whiteflags

Please.

Code:

#include <string.h>
#include <stdio.h>
long analyze(const char rawData[ ], char signal[ ], int frequency, int a, int b);
int main ()
{
    int frequency=0;
    signed long result;
    int a=0, b=0;
    char signal[121], rawData[ ] =
      ""; /* NO SIGNAL (empty string) f=0,a=0,b=0 */;
    result = analyze(rawData, signal, frequency, a, b);
    printf("Result = %lu\n", result);
    printf("Signal = %s", signal);


    return 0;
}

There you go.

the char signal[] = " ";
I can't figure out a way of setting signal[] to "NON-SEQUITOR" when the string is only that big. I think it has to do with the Case ' ': but i'm unsure.

I just got done telling you that you showed me a special case for input to the function. I don't know why you don't believe me.