Function d2string

src/pstd/src/pstd_string.cc:479–516

Convert a double to a string representation. Returns the number of bytes * required. The representation should always be parsable by strtod(3). */

/* Convert a double to a string representation. Returns the number of bytes
 * required. The representation should always be parsable by strtod(3). */
int d2string(char* buf, size_t len, double value) {
  if (std::isnan(value)) {
    len = snprintf(buf, len, "nan");
  } else if (std::isinf(value)) {
    if (value < 0) {
      len = snprintf(buf, len, "-inf");
    } else {
      len = snprintf(buf, len, "inf");
    }
  } else if (value == 0) {
    /* See: http://en.wikipedia.org/wiki/Signed_zero, "Comparisons". */
    if (1.0 / value < 0) {
      len = snprintf(buf, len, "-0");
    } else {
      len = snprintf(buf, len, "0");
    }
  } else {
#if (DBL_MANT_DIG >= 52) && (LLONG_MAX == 0x7fffffffffffffffLL)
    /* Check if the float is in a safe range to be casted into a
     * long long. We are assuming that long long is 64 bit here.
     * Also we are assuming that there are no implementations around where
     * double has precision < 52 bit.
     *
     * Under this assumptions we test if a double is inside an interval
     * where casting to long long is safe. Then using two castings we
     * make sure the decimal part is zero. If all this is true we use
     * integer printing function that is much faster. */
    double min = -4503599627370495; /* (2^52)-1 */
    double max = 4503599627370496;  /* -(2^52) */
    if (value > min && value < max && value == (static_cast<double>(static_cast<long long>(value)))) {
      len = ll2string(buf, len, static_cast<long long>(value));
    } else  // NOLINT
#endif
      len = snprintf(buf, len, "%.17g", value);
  }

  return static_cast<int32_t>(len);
}

int string2d(const char* s, size_t slen, double* dval) {
  char* pEnd;