storing characters in char data type C language

Question

Hi,

I can store string of few length in char data type.

But when it exceeds its capacity what can be the alternative way to store string.

I am using char data type.

void setString(char* inPoints)
{
if (strcmp(mPoints, inPoints)!= ZERO) {

    if (mPoints) {

        free(mPoints);
    }

    mPoints = (char*)malloc((strlen(inPoints) + 1)  * sizeof(char));

    strcpy(mPoints, inPoints);
}
}

Answer 1

You can allocate a new, bigger array and copy the old string into it (and delete the old to prevent memory leaks), appending more characters. Or (if possible) switch to C++ string class, which makes this process easier.

Answer 2

realloc() should resize your string

Answer 3

Using strncpy instead of strcpy is normally safer, but here you alloc eachtime the right amount of memory needed to store inPoint into mPoint, so I cant see what's the point. The max length of a string you can store in mPoint is limited by the amount of malloc-able memory.

Add: you can realloc as suggested, and likely you can add a check on the length to avoid realloc-ing if the string is shorter; so mPoint would be able to hold always strings less than the longest string met so far, or equal to:

// somewhere altogether with mPoints
size_t mPointsCurrenStorage = INITVAL;
// e.g. INITVAL is 256, and you pre-malloc-ate mPoints to 256 chars
// ... in the func
size_t cl = strlen(inPoints);
if ( cl >= mPointsCurrentStorage ) {
  mPoints = realloc(mPoints, cl+1);
  mPointsCurrentStorage = cl+1;
}
strcpy(mPoints, inPoints);

this way the storage grows only...

Answer 4

• strcmp with mPoints=NULL is not allowed.
• ZERO as a constant?
• free() accepts NULL pointers.
• malloc() doesn't need a cast in C.
• sizeof(char) is 1.
• Always check the return of malloc().

Modified version:

void setString(char* inPoints)
{
    if ((mPoints == NULL) || (strcmp(mPoints, inPoints) != 0)) 
    {
        free(mPoints);

        mPoints = malloc(strlen(inPoints) + 1);

        if (mPoints != NULL)
        {
            strcpy(mPoints, inPoints);
        }
    }
}

And you're using a global variable mPoints, there are better solutions. But this and the error handling for malloc()=NULL aside, you're always allocating the needed amount, so what exactly do you mean by "exceeds its capacity"?