equivalent of fgets() but works on string instead of file

sgets.c

// equivalent to fgets() but works on string instead of file
/*
 * Equivalent to fgets() but operate on string instead of file.
 * It will read string upto `dst_size` or stop reading whenever find newline character,
 * then return string so far as read via `dst_str`.
 *
 * `offset` will be updated according to the current number of bytes read.
 * First call should always set it to 0, then consecutive call will be automatically updated by
 * this function, just re-supply it in the function call.
 *
 * At last, it will stop whenever it has read all of the bytes from the `input_str`.
 *
 * \param dst_str destination string as output
 * \param dst_size up to number of size to read for destination string
 * \param input_str input string to read
 * \param offset pointer to offset number for consecutive call
 * \return string as read starting from `offset` and up to `dst_size`. It returns NULL when all of `input_str`'s bytes has been read.
 */
static char* sgets(char* dst_str, int dst_size, const char* input_str, int* offset)
{
	int size_count = 0;

	const int of = *offset;

	if (of > strlen(input_str))
		return NULL;

	for (int i = 0; i<dst_size; ++i)
	{
		char c = input_str[of + i];

		if (c == '\n')
		{
			dst_str[i] = c;
			dst_str[i+1] = '\0';
			++size_count;
			break;
		}
		else if (c == '\0')
		{
			dst_str[i] = c;
			++size_count;
			break;
		}
		else
		{
			dst_str[i] = c;
			++size_count;
		}
	}

	// set offset back for future calls
	*offset = *offset + size_count;

	return dst_str;
}