Question

I have the following function:

int strpos(const char *needle, const char *haystack)
{
    int neLen, haLen, foundPos, nePos, i;
    char temp;

    neLen = strlen(needle);
    haLen = strlen(haystack);

    if(haLen < neLen)
        return -1;

    nePos    = 0;
    foundPos = -1;
    i        = 0;

    while((temp = *haystack++) != '\0'
          && (i < (haLen-neLen+1) || foundPos > -1)
          && nePos < neLen)
    {
        if(temp == *needle+nePos)
        {
            if(nePos == 0)
                foundPos = i;
            nePos++;
        }
        else
        {
            nePos = 0;
            foundPos = -1;
        }

        i++;
    }

    return foundPos;
}

It works properly when I search for a single character:

printf("Strpos: %d\n", strpos("a", "laoo")); // Result: "Strpos: 1"

But it improperly with longer string:

printf("Strpos: %d\n", strpos("ao", "laoo")); // Result: "Strpos: -1"

What is the problem?

Bonus question: is the while loop properly broken into multiple lines? What is the accepted way to do this?

EDIT: strlen() is, naturally, a custom function that returns the length of the string. This works properly.

Answer 1

The solution is of the standard bang-your-head-against-the-wall-in-an-infinite-loop-and-wonder-why-the-hell-you’re-a-programmer variety.

if(temp == *needle+nePos)

Should be:

if(temp == *(needle+nePos))