Function Atof

include/LightGBM/utils/common.h:180–270

}

inline static const char* Atof(const char* p, double* out) {
  int frac;
  double sign, value, scale;
  *out = NAN;
  // Skip leading white space, if any.
  while (*p == ' ') {
    ++p;
  }
  // Get sign, if any.
  sign = 1.0;
  if (*p == '-') {
    sign = -1.0;
    ++p;
  } else if (*p == '+') {
    ++p;
  }

  // is a number
  if ((*p >= '0' && *p <= '9') || *p == '.' || *p == 'e' || *p == 'E') {
    // Get digits before decimal point or exponent, if any.
    for (value = 0.0; *p >= '0' && *p <= '9'; ++p) {
      value = value * 10.0 + (*p - '0');
    }

    // Get digits after decimal point, if any.
    if (*p == '.') {
      double right = 0.0;
      int nn = 0;
      ++p;
      while (*p >= '0' && *p <= '9') {
        right = (*p - '0') + right * 10.0;
        ++nn;
        ++p;
      }
      value += right / Pow(10.0, nn);
    }

    // Handle exponent, if any.
    frac = 0;
    scale = 1.0;
    if ((*p == 'e') || (*p == 'E')) {
      uint32_t expon;
      // Get sign of exponent, if any.
      ++p;
      if (*p == '-') {
        frac = 1;
        ++p;
      } else if (*p == '+') {
        ++p;
      }
      // Get digits of exponent, if any.
      for (expon = 0; *p >= '0' && *p <= '9'; ++p) {
        expon = expon * 10 + (*p - '0');
      }
      if (expon > 308) expon = 308;
      // Calculate scaling factor.
      while (expon >= 50) { scale *= 1E50; expon -= 50; }
      while (expon >= 8) { scale *= 1E8;  expon -= 8; }