convert String to unsigned long long

Projects Programming
1

i want to convert string for example "68976543210" to unsigned long long(64 bit) in mega2560, do is possible?

String x="68976543210";
unsigned long long y=?;
2

How about this way to do the conversion(s).

I deliberately use no Strings.

long long atoll(const char* ptr) {
  long long result = 0;
  while (*ptr && isdigit(*ptr)) {
    result *= 10;
    result += *ptr++ - '0';
  }
  return result;
}

void setup() {
  Serial.begin(115200);
  char buf[7];
  unsigned long long y = atoll("68976543210");
  sprintf(buf, "%06ld", (long)(y % 1000000));
  Serial.print(F("y = "));
  Serial.print((long)(y / 1000000));
  Serial.print(buf);
  Serial.println();
}

void loop() {}

y = 68976543210