fast_float::detail Namespace Reference

Functions
fastfloat_really_inline int	power (int q) noexcept
void	trim (decimal &h)
uint32_t	number_of_digits_decimal_left_shift (const decimal &h, uint32_t shift)
uint64_t	round (decimal &h)
void	decimal_left_shift (decimal &h, uint32_t shift)
void	decimal_right_shift (decimal &h, uint32_t shift)
template<typename T >
from_chars_result	parse_infnan (const char *first, const char *last, T &value) noexcept
template<typename T >
fastfloat_really_inline void	to_float (bool negative, adjusted_mantissa am, T &value)

Function Documentation

decimal_left_shift()

void fast_float::detail::decimal_left_shift ( decimal &  h, uint32_t  shift  )

inline

                                                           {
  if (h.num_digits == 0) {
    return;
  }
  uint32_t num_new_digits = number_of_digits_decimal_left_shift(h, shift);
  int32_t read_index = int32_t(h.num_digits - 1);
  uint32_t write_index = h.num_digits - 1 + num_new_digits;
  uint64_t n = 0;
 
  while (read_index >= 0) {
    n += uint64_t(h.digits[read_index]) << shift;
    uint64_t quotient = n / 10;
    uint64_t remainder = n - (10 * quotient);
    if (write_index < max_digits) {
      h.digits[write_index] = uint8_t(remainder);
    } else if (remainder > 0) {
      h.truncated = true;
    }
    n = quotient;
    write_index--;
    read_index--;
  }
  while (n > 0) {
    uint64_t quotient = n / 10;
    uint64_t remainder = n - (10 * quotient);
    if (write_index < max_digits) {
      h.digits[write_index] = uint8_t(remainder);
    } else if (remainder > 0) {
      h.truncated = true;
    }
    n = quotient;
    write_index--;
  }
  h.num_digits += num_new_digits;
  if (h.num_digits > max_digits) {
    h.num_digits = max_digits;
  }
  h.decimal_point += int32_t(num_new_digits);
  trim(h);
}

References fast_float::decimal::decimal_point, fast_float::decimal::digits, fast_float::decimal::num_digits, number_of_digits_decimal_left_shift(), trim(), and fast_float::decimal::truncated.

Referenced by fast_float::compute_float().

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decimal_right_shift()

void fast_float::detail::decimal_right_shift ( decimal &  h, uint32_t  shift  )

inline

                                                            {
  uint32_t read_index = 0;
  uint32_t write_index = 0;
 
  uint64_t n = 0;
 
  while ((n >> shift) == 0) {
    if (read_index < h.num_digits) {
      n = (10 * n) + h.digits[read_index++];
    } else if (n == 0) {
      return;
    } else {
      while ((n >> shift) == 0) {
        n = 10 * n;
        read_index++;
      }
      break;
    }
  }
  h.decimal_point -= int32_t(read_index - 1);
  if (h.decimal_point < -decimal_point_range) { // it is zero
    h.num_digits = 0;
    h.decimal_point = 0;
    h.negative = false;
    h.truncated = false;
    return;
  }
  uint64_t mask = (uint64_t(1) << shift) - 1;
  while (read_index < h.num_digits) {
    uint8_t new_digit = uint8_t(n >> shift);
    n = (10 * (n & mask)) + h.digits[read_index++];
    h.digits[write_index++] = new_digit;
  }
  while (n > 0) {
    uint8_t new_digit = uint8_t(n >> shift);
    n = 10 * (n & mask);
    if (write_index < max_digits) {
      h.digits[write_index++] = new_digit;
    } else if (new_digit > 0) {
      h.truncated = true;
    }
  }
  h.num_digits = write_index;
  trim(h);
}

References fast_float::decimal::decimal_point, fast_float::decimal::digits, fast_float::decimal::negative, fast_float::decimal::num_digits, trim(), and fast_float::decimal::truncated.

Referenced by fast_float::compute_float().

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number_of_digits_decimal_left_shift()

uint32_t fast_float::detail::number_of_digits_decimal_left_shift ( const decimal &  h, uint32_t  shift  )

inline

                                                                                      {
  shift &= 63;
  const static uint16_t number_of_digits_decimal_left_shift_table[65] = {
    0x0000, 0x0800, 0x0801, 0x0803, 0x1006, 0x1009, 0x100D, 0x1812, 0x1817,
    0x181D, 0x2024, 0x202B, 0x2033, 0x203C, 0x2846, 0x2850, 0x285B, 0x3067,
    0x3073, 0x3080, 0x388E, 0x389C, 0x38AB, 0x38BB, 0x40CC, 0x40DD, 0x40EF,
    0x4902, 0x4915, 0x4929, 0x513E, 0x5153, 0x5169, 0x5180, 0x5998, 0x59B0,
    0x59C9, 0x61E3, 0x61FD, 0x6218, 0x6A34, 0x6A50, 0x6A6D, 0x6A8B, 0x72AA,
    0x72C9, 0x72E9, 0x7B0A, 0x7B2B, 0x7B4D, 0x8370, 0x8393, 0x83B7, 0x83DC,
    0x8C02, 0x8C28, 0x8C4F, 0x9477, 0x949F, 0x94C8, 0x9CF2, 0x051C, 0x051C,
    0x051C, 0x051C,
  };
  uint32_t x_a = number_of_digits_decimal_left_shift_table[shift];
  uint32_t x_b = number_of_digits_decimal_left_shift_table[shift + 1];
  uint32_t num_new_digits = x_a >> 11;
  uint32_t pow5_a = 0x7FF & x_a;
  uint32_t pow5_b = 0x7FF & x_b;
  const static uint8_t
    number_of_digits_decimal_left_shift_table_powers_of_5[0x051C] = {
        5, 2, 5, 1, 2, 5, 6, 2, 5, 3, 1, 2, 5, 1, 5, 6, 2, 5, 7, 8, 1, 2, 5, 3,
        9, 0, 6, 2, 5, 1, 9, 5, 3, 1, 2, 5, 9, 7, 6, 5, 6, 2, 5, 4, 8, 8, 2, 8,
        1, 2, 5, 2, 4, 4, 1, 4, 0, 6, 2, 5, 1, 2, 2, 0, 7, 0, 3, 1, 2, 5, 6, 1,
        0, 3, 5, 1, 5, 6, 2, 5, 3, 0, 5, 1, 7, 5, 7, 8, 1, 2, 5, 1, 5, 2, 5, 8,
        7, 8, 9, 0, 6, 2, 5, 7, 6, 2, 9, 3, 9, 4, 5, 3, 1, 2, 5, 3, 8, 1, 4, 6,
        9, 7, 2, 6, 5, 6, 2, 5, 1, 9, 0, 7, 3, 4, 8, 6, 3, 2, 8, 1, 2, 5, 9, 5,
        3, 6, 7, 4, 3, 1, 6, 4, 0, 6, 2, 5, 4, 7, 6, 8, 3, 7, 1, 5, 8, 2, 0, 3,
        1, 2, 5, 2, 3, 8, 4, 1, 8, 5, 7, 9, 1, 0, 1, 5, 6, 2, 5, 1, 1, 9, 2, 0,
        9, 2, 8, 9, 5, 5, 0, 7, 8, 1, 2, 5, 5, 9, 6, 0, 4, 6, 4, 4, 7, 7, 5, 3,
        9, 0, 6, 2, 5, 2, 9, 8, 0, 2, 3, 2, 2, 3, 8, 7, 6, 9, 5, 3, 1, 2, 5, 1,
        4, 9, 0, 1, 1, 6, 1, 1, 9, 3, 8, 4, 7, 6, 5, 6, 2, 5, 7, 4, 5, 0, 5, 8,
        0, 5, 9, 6, 9, 2, 3, 8, 2, 8, 1, 2, 5, 3, 7, 2, 5, 2, 9, 0, 2, 9, 8, 4,
        6, 1, 9, 1, 4, 0, 6, 2, 5, 1, 8, 6, 2, 6, 4, 5, 1, 4, 9, 2, 3, 0, 9, 5,
        7, 0, 3, 1, 2, 5, 9, 3, 1, 3, 2, 2, 5, 7, 4, 6, 1, 5, 4, 7, 8, 5, 1, 5,
        6, 2, 5, 4, 6, 5, 6, 6, 1, 2, 8, 7, 3, 0, 7, 7, 3, 9, 2, 5, 7, 8, 1, 2,
        5, 2, 3, 2, 8, 3, 0, 6, 4, 3, 6, 5, 3, 8, 6, 9, 6, 2, 8, 9, 0, 6, 2, 5,
        1, 1, 6, 4, 1, 5, 3, 2, 1, 8, 2, 6, 9, 3, 4, 8, 1, 4, 4, 5, 3, 1, 2, 5,
        5, 8, 2, 0, 7, 6, 6, 0, 9, 1, 3, 4, 6, 7, 4, 0, 7, 2, 2, 6, 5, 6, 2, 5,
        2, 9, 1, 0, 3, 8, 3, 0, 4, 5, 6, 7, 3, 3, 7, 0, 3, 6, 1, 3, 2, 8, 1, 2,
        5, 1, 4, 5, 5, 1, 9, 1, 5, 2, 2, 8, 3, 6, 6, 8, 5, 1, 8, 0, 6, 6, 4, 0,
        6, 2, 5, 7, 2, 7, 5, 9, 5, 7, 6, 1, 4, 1, 8, 3, 4, 2, 5, 9, 0, 3, 3, 2,
        0, 3, 1, 2, 5, 3, 6, 3, 7, 9, 7, 8, 8, 0, 7, 0, 9, 1, 7, 1, 2, 9, 5, 1,
        6, 6, 0, 1, 5, 6, 2, 5, 1, 8, 1, 8, 9, 8, 9, 4, 0, 3, 5, 4, 5, 8, 5, 6,
        4, 7, 5, 8, 3, 0, 0, 7, 8, 1, 2, 5, 9, 0, 9, 4, 9, 4, 7, 0, 1, 7, 7, 2,
        9, 2, 8, 2, 3, 7, 9, 1, 5, 0, 3, 9, 0, 6, 2, 5, 4, 5, 4, 7, 4, 7, 3, 5,
        0, 8, 8, 6, 4, 6, 4, 1, 1, 8, 9, 5, 7, 5, 1, 9, 5, 3, 1, 2, 5, 2, 2, 7,
        3, 7, 3, 6, 7, 5, 4, 4, 3, 2, 3, 2, 0, 5, 9, 4, 7, 8, 7, 5, 9, 7, 6, 5,
        6, 2, 5, 1, 1, 3, 6, 8, 6, 8, 3, 7, 7, 2, 1, 6, 1, 6, 0, 2, 9, 7, 3, 9,
        3, 7, 9, 8, 8, 2, 8, 1, 2, 5, 5, 6, 8, 4, 3, 4, 1, 8, 8, 6, 0, 8, 0, 8,
        0, 1, 4, 8, 6, 9, 6, 8, 9, 9, 4, 1, 4, 0, 6, 2, 5, 2, 8, 4, 2, 1, 7, 0,
        9, 4, 3, 0, 4, 0, 4, 0, 0, 7, 4, 3, 4, 8, 4, 4, 9, 7, 0, 7, 0, 3, 1, 2,
        5, 1, 4, 2, 1, 0, 8, 5, 4, 7, 1, 5, 2, 0, 2, 0, 0, 3, 7, 1, 7, 4, 2, 2,
        4, 8, 5, 3, 5, 1, 5, 6, 2, 5, 7, 1, 0, 5, 4, 2, 7, 3, 5, 7, 6, 0, 1, 0,
        0, 1, 8, 5, 8, 7, 1, 1, 2, 4, 2, 6, 7, 5, 7, 8, 1, 2, 5, 3, 5, 5, 2, 7,
        1, 3, 6, 7, 8, 8, 0, 0, 5, 0, 0, 9, 2, 9, 3, 5, 5, 6, 2, 1, 3, 3, 7, 8,
        9, 0, 6, 2, 5, 1, 7, 7, 6, 3, 5, 6, 8, 3, 9, 4, 0, 0, 2, 5, 0, 4, 6, 4,
        6, 7, 7, 8, 1, 0, 6, 6, 8, 9, 4, 5, 3, 1, 2, 5, 8, 8, 8, 1, 7, 8, 4, 1,
        9, 7, 0, 0, 1, 2, 5, 2, 3, 2, 3, 3, 8, 9, 0, 5, 3, 3, 4, 4, 7, 2, 6, 5,
        6, 2, 5, 4, 4, 4, 0, 8, 9, 2, 0, 9, 8, 5, 0, 0, 6, 2, 6, 1, 6, 1, 6, 9,
        4, 5, 2, 6, 6, 7, 2, 3, 6, 3, 2, 8, 1, 2, 5, 2, 2, 2, 0, 4, 4, 6, 0, 4,
        9, 2, 5, 0, 3, 1, 3, 0, 8, 0, 8, 4, 7, 2, 6, 3, 3, 3, 6, 1, 8, 1, 6, 4,
        0, 6, 2, 5, 1, 1, 1, 0, 2, 2, 3, 0, 2, 4, 6, 2, 5, 1, 5, 6, 5, 4, 0, 4,
        2, 3, 6, 3, 1, 6, 6, 8, 0, 9, 0, 8, 2, 0, 3, 1, 2, 5, 5, 5, 5, 1, 1, 1,
        5, 1, 2, 3, 1, 2, 5, 7, 8, 2, 7, 0, 2, 1, 1, 8, 1, 5, 8, 3, 4, 0, 4, 5,
        4, 1, 0, 1, 5, 6, 2, 5, 2, 7, 7, 5, 5, 5, 7, 5, 6, 1, 5, 6, 2, 8, 9, 1,
        3, 5, 1, 0, 5, 9, 0, 7, 9, 1, 7, 0, 2, 2, 7, 0, 5, 0, 7, 8, 1, 2, 5, 1,
        3, 8, 7, 7, 7, 8, 7, 8, 0, 7, 8, 1, 4, 4, 5, 6, 7, 5, 5, 2, 9, 5, 3, 9,
        5, 8, 5, 1, 1, 3, 5, 2, 5, 3, 9, 0, 6, 2, 5, 6, 9, 3, 8, 8, 9, 3, 9, 0,
        3, 9, 0, 7, 2, 2, 8, 3, 7, 7, 6, 4, 7, 6, 9, 7, 9, 2, 5, 5, 6, 7, 6, 2,
        6, 9, 5, 3, 1, 2, 5, 3, 4, 6, 9, 4, 4, 6, 9, 5, 1, 9, 5, 3, 6, 1, 4, 1,
        8, 8, 8, 2, 3, 8, 4, 8, 9, 6, 2, 7, 8, 3, 8, 1, 3, 4, 7, 6, 5, 6, 2, 5,
        1, 7, 3, 4, 7, 2, 3, 4, 7, 5, 9, 7, 6, 8, 0, 7, 0, 9, 4, 4, 1, 1, 9, 2,
        4, 4, 8, 1, 3, 9, 1, 9, 0, 6, 7, 3, 8, 2, 8, 1, 2, 5, 8, 6, 7, 3, 6, 1,
        7, 3, 7, 9, 8, 8, 4, 0, 3, 5, 4, 7, 2, 0, 5, 9, 6, 2, 2, 4, 0, 6, 9, 5,
        9, 5, 3, 3, 6, 9, 1, 4, 0, 6, 2, 5,
  };
  const uint8_t *pow5 =
      &number_of_digits_decimal_left_shift_table_powers_of_5[pow5_a];
  uint32_t i = 0;
  uint32_t n = pow5_b - pow5_a;
  for (; i < n; i++) {
    if (i >= h.num_digits) {
      return num_new_digits - 1;
    } else if (h.digits[i] == pow5[i]) {
      continue;
    } else if (h.digits[i] < pow5[i]) {
      return num_new_digits - 1;
    } else {
      return num_new_digits;
    }
  }
  return num_new_digits;
}

References fast_float::decimal::digits, and fast_float::decimal::num_digits.

Referenced by decimal_left_shift().

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parse_infnan()

template<typename T >

from_chars_result fast_float::detail::parse_infnan ( const char *  first, const char *  last, T &  value  )

noexcept

Special case +inf, -inf, nan, infinity, -infinity. The case comparisons could be made much faster given that we know that the strings a null-free and fixed.

                                                                                         {
  from_chars_result answer;
  answer.ptr = first;
  answer.ec = std::errc(); // be optimistic
  bool minusSign = false;
  if (*first == '-') { // assume first < last, so dereference without checks; C++17 20.19.3.(7.1) explicitly forbids '+' here
      minusSign = true;
      ++first;
  }
  if (last - first >= 3) {
    if (fastfloat_strncasecmp(first, "nan", 3)) {
      answer.ptr = (first += 3);
      value = minusSign ? -std::numeric_limits<T>::quiet_NaN() : std::numeric_limits<T>::quiet_NaN();
      // Check for possible nan(n-char-seq-opt), C++17 20.19.3.7, C11 7.20.1.3.3. At least MSVC produces nan(ind) and nan(snan).
      if(first != last && *first == '(') {
        for(const char* ptr = first + 1; ptr != last; ++ptr) {
          if (*ptr == ')') {
            answer.ptr = ptr + 1; // valid nan(n-char-seq-opt)
            break;
          }
          else if(!(('a' <= *ptr && *ptr <= 'z') || ('A' <= *ptr && *ptr <= 'Z') || ('0' <= *ptr && *ptr <= '9') || *ptr == '_'))
            break; // forbidden char, not nan(n-char-seq-opt)
        }
      }
      return answer;
    }
    if (fastfloat_strncasecmp(first, "inf", 3)) {
      if ((last - first >= 8) && fastfloat_strncasecmp(first + 3, "inity", 5)) {
        answer.ptr = first + 8;
      } else {
        answer.ptr = first + 3;
      }
      value = minusSign ? -std::numeric_limits<T>::infinity() : std::numeric_limits<T>::infinity();
      return answer;
    }
  }
  answer.ec = std::errc::invalid_argument;
  return answer;
}

References fast_float::from_chars_result::ec, fast_float::fastfloat_strncasecmp(), and fast_float::from_chars_result::ptr.

Referenced by fast_float::from_chars_advanced().

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power()

fastfloat_really_inline int fast_float::detail::power ( int  q )

noexcept

For q in (0,350), we have that f = (((152170 + 65536) * q ) >> 16); is equal to floor(p) + q where p = log(5**q)/log(2) = q * log(5)/log(2)

For negative values of q in (-400,0), we have that f = (((152170 + 65536) * q ) >> 16); is equal to -ceil(p) + q where p = log(5**-q)/log(2) = -q * log(5)/log(2)

                                                      {
    return (((152170 + 65536) * q) >> 16) + 63;
  }

Referenced by fast_float::compute_float().

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round()

uint64_t fast_float::detail::round ( decimal &  h )

inline

                                  {
  if ((h.num_digits == 0) || (h.decimal_point < 0)) {
    return 0;
  } else if (h.decimal_point > 18) {
    return UINT64_MAX;
  }
  // at this point, we know that h.decimal_point >= 0
  uint32_t dp = uint32_t(h.decimal_point);
  uint64_t n = 0;
  for (uint32_t i = 0; i < dp; i++) {
    n = (10 * n) + ((i < h.num_digits) ? h.digits[i] : 0);
  }
  bool round_up = false;
  if (dp < h.num_digits) {
    round_up = h.digits[dp] >= 5; // normally, we round up  
    // but we may need to round to even!
    if ((h.digits[dp] == 5) && (dp + 1 == h.num_digits)) {
      round_up = h.truncated || ((dp > 0) && (1 & h.digits[dp - 1]));
    }
  }
  if (round_up) {
    n++;
  }
  return n;
}

References fast_float::decimal::decimal_point, fast_float::decimal::digits, fast_float::decimal::num_digits, and fast_float::decimal::truncated.

Referenced by fast_float::compute_float().

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to_float()

template<typename T >

fastfloat_really_inline void fast_float::detail::to_float	(	bool	negative,
		adjusted_mantissa	am,
		T &	value
	)

                                                                                     {
  uint64_t word = am.mantissa;
  word |= uint64_t(am.power2) << binary_format<T>::mantissa_explicit_bits();
  word = negative
  ? word | (uint64_t(1) << binary_format<T>::sign_index()) : word;
#if FASTFLOAT_IS_BIG_ENDIAN == 1
   if (std::is_same<T, float>::value) {
     ::memcpy(&value, (char *)&word + 4, sizeof(T)); // extract value at offset 4-7 if float on big-endian
   } else {
     ::memcpy(&value, &word, sizeof(T));
   }
#else
   // For little-endian systems:
   ::memcpy(&value, &word, sizeof(T));
#endif
}

References fast_float::adjusted_mantissa::mantissa, fast_float::binary_format< T >::mantissa_explicit_bits(), fast_float::adjusted_mantissa::power2, and fast_float::binary_format< T >::sign_index().

Referenced by fast_float::from_chars_advanced().

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trim()

void fast_float::detail::trim ( decimal &  h )

inline

                             {
  while ((h.num_digits > 0) && (h.digits[h.num_digits - 1] == 0)) {
    h.num_digits--;
  }
}

References fast_float::decimal::digits, and fast_float::decimal::num_digits.

Referenced by decimal_left_shift(), and decimal_right_shift().

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