AZ_NODISCARD az_result az_span_atou64()

in sdk/src/azure/core/az_span.c [103:154]

• 38 lines of code
• 8 McCabe index (conditional complexity)

AZ_NODISCARD az_result az_span_atou64(az_span source, uint64_t* out_number)
{
  _az_PRECONDITION_VALID_SPAN(source, 1, false);
  _az_PRECONDITION_NOT_NULL(out_number);

  int32_t const span_size = az_span_size(source);

  if (span_size < 1)
  {
    return AZ_ERROR_UNEXPECTED_CHAR;
  }

  // If the first character is not a digit or an optional + sign, return error.
  int32_t starting_index = 0;
  uint8_t* source_ptr = az_span_ptr(source);
  uint8_t next_byte = source_ptr[0];

  if (!isdigit(next_byte))
  {
    // There must be another byte after a sign.
    // The loop below checks that it must be a digit.
    if (next_byte != '+' || span_size < 2)
    {
      return AZ_ERROR_UNEXPECTED_CHAR;
    }
    starting_index++;
  }

  uint64_t value = 0;

  for (int32_t i = starting_index; i < span_size; ++i)
  {
    next_byte = source_ptr[i];
    if (!isdigit(next_byte))
    {
      return AZ_ERROR_UNEXPECTED_CHAR;
    }
    uint64_t const d = (uint64_t)next_byte - '0';

    // Check whether the next digit will cause an integer overflow.
    // Before actually doing the math below, this is checking whether value * 10 + d > UINT64_MAX.
    if ((UINT64_MAX - d) / _az_NUMBER_OF_DECIMAL_VALUES < value)
    {
      return AZ_ERROR_UNEXPECTED_CHAR;
    }

    value = value * _az_NUMBER_OF_DECIMAL_VALUES + d;
  }

  *out_number = value;
  return AZ_OK;
}