how to find actual end of char array in c containing zeros in the middle

Question

I am trying to find size of char array in c. There are zeros in between, so strlen does not give the right answer. An example scenario is below.

char buffData[256];
buffData[0] = 0x89;
buffData[1] = 0x32;
buffData[2] = 0x00;
buffData[3] = 0x02;
buffData[4] = 0x01;

How can I find the right length. ps: strlen would give 2 which is wrong

I want the answer 5 !

Answer 1

Even better than

int len = sizeof(buffData) / sizeof(char);

you can write more generally:

int len = sizeof(buffData) / sizeof(buffData[0]);

which will still work if you (or someone else) change the declaration of buffData, e.g:

double buffData[256];

---

If you want to know how many actually elements are in the array at some moment in time, there are at least 2 options:

1. keep track of elements count, each time you insert element increment the counter, decrement on element removal

   char buffData[256];
   int buffData_n = 0;
   
   buffData[0] = 0x32;
   buffData_n++;
   

2. memset memory to zero, or zero-initialize it, so then you can count non-zero elements explicitly:

   int i = 0;
   for ( ; i < 256 && buffData[i]; i++);
   printf("There is %d elements in the array now
   ", i);
   

If you want to allow for gaps filled by 0, and you can specify the size of a gap:

    int n = 0, i = 0;
    // gap size 2 max
    for ( ; i < 255; i++)
    {
        if (buffData[i]==0 && buffData[i+1]==0) break;
        if (buffData[i]) n++;
    }
    printf("There is %d elements in the array now
", n);