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* documentation in the code updated, fixed errors with parsing some special very big exponent numbers.

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This commit is contained in:
IRainman 2025-12-27 12:56:51 +03:00
parent 6cefbb53ba
commit 3745f4b009
3 changed files with 31 additions and 24 deletions
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23
include/fast_float/ascii_number.h
View File

@ -435,7 +435,7 @@ parse_number_string(UC const *p, UC const *pend,
} else {
// Now let's parse the explicit exponent.
while ((p != pend) && is_integer(*p)) {
if (exp_number < std::numeric_limits<am_pow_t>::max()) {
if (exp_number < am_bias_limit) {
// check for exponent overflow if we have too many digits.
auto const digit = uint8_t(*p - UC('0'));
exp_number = 10 * exp_number + digit;
@ -561,7 +561,7 @@ parse_int_string(UC const *p, UC const *pend, T &value,
auto const *const start_digits = p;
FASTFLOAT_IF_CONSTEXPR17((std::is_same<T, std::uint8_t>::value)) {
const size_t len = (size_t)(pend - p);
const auto len = static_cast<am_digits>(pend - p);
if (len == 0) {
if (has_leading_zeros) {
value = 0;
@ -581,7 +581,7 @@ parse_int_string(UC const *p, UC const *pend, T &value,
if (cpp20_and_in_constexpr()) {
digits.as_int = 0;
for (size_t j = 0; j < 4 && j < len; ++j) {
for (uint_fast8_t j = 0; j < 4 && j < len; ++j) {
digits.as_str[j] = static_cast<uint8_t>(p[j]);
}
} else if (len >= 4) {
@ -598,12 +598,13 @@ parse_int_string(UC const *p, UC const *pend, T &value,
#endif
}
uint32_t magic =
const uint32_t magic =
((digits.as_int + 0x46464646u) | (digits.as_int - 0x30303030u)) &
0x80808080u;
uint32_t tz = (uint32_t)countr_zero_32(magic); // 7, 15, 23, 31, or 32
const auto tz =
static_cast<uint32_t>(countr_zero_32(magic)); // 7, 15, 23, 31, or 32
uint32_t nd = (tz == 32) ? 4 : (tz >> 3);
nd = (uint32_t)std::min((size_t)nd, len);
nd = std::min(nd, len);
if (nd == 0) {
if (has_leading_zeros) {
value = 0;
@ -617,7 +618,7 @@ parse_int_string(UC const *p, UC const *pend, T &value,
}
if (nd > 3) {
const UC *q = p + nd;
size_t rem = len - nd;
uint_fast8_t rem = len - nd;
while (rem) {
if (*q < UC('0') || *q > UC('9'))
break;
@ -632,15 +633,15 @@ parse_int_string(UC const *p, UC const *pend, T &value,
digits.as_int ^= 0x30303030u;
digits.as_int <<= ((4 - nd) * 8);
uint32_t check = ((digits.as_int >> 24) & 0xff) |
((digits.as_int >> 8) & 0xff00) |
((digits.as_int << 8) & 0xff0000);
const uint32_t check = ((digits.as_int >> 24) & 0xff) |
((digits.as_int >> 8) & 0xff00) |
((digits.as_int << 8) & 0xff0000);
if (check > 0x00020505) {
answer.ec = std::errc::result_out_of_range;
answer.ptr = p + nd;
return answer;
}
value = (uint8_t)((0x640a01 * digits.as_int) >> 24);
value = static_cast<uint8_t>((0x640a01 * digits.as_int) >> 24);
answer.ec = std::errc();
answer.ptr = p + nd;
return answer;

16
include/fast_float/fast_float.h
View File

@ -59,11 +59,11 @@ from_chars_advanced(UC const *first, UC const *last, T &value,
* `new` or `malloc`).
*/
FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(uint64_t const mantissa,
int_fast16_t const decimal_exponent) noexcept;
integer_times_pow10(am_mant_t const mantissa,
am_pow_t const decimal_exponent) noexcept;
FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(int64_t const mantissa,
int_fast16_t const decimal_exponent) noexcept;
integer_times_pow10(am_sign_mant_t const mantissa,
am_pow_t const decimal_exponent) noexcept;
/**
* This function is a template overload of `integer_times_pow10()`
@ -73,13 +73,13 @@ integer_times_pow10(int64_t const mantissa,
template <typename T>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value, T>::type
integer_times_pow10(uint64_t const mantissa,
int_fast16_t const decimal_exponent) noexcept;
integer_times_pow10(am_mant_t const mantissa,
am_pow_t const decimal_exponent) noexcept;
template <typename T>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value, T>::type
integer_times_pow10(int64_t const mantissa,
int_fast16_t const decimal_exponent) noexcept;
integer_times_pow10(am_sign_mant_t const mantissa,
am_pow_t const decimal_exponent) noexcept;
/**
* from_chars for integer types.

16
include/fast_float/float_common.h
View File

@ -500,18 +500,24 @@ full_multiplication(uint64_t a, uint64_t b) noexcept {
return answer;
}
// Value of the mantissa. An unsigned int avoids signed overflows (which are
// bad)
// 64 bit integer is used because mantissa can be up to 53 bits for double.
// Value of the int mantissa in the API.
typedef int_fast64_t am_sign_mant_t;
// An unsigned int avoids signed overflows (which are bad)
typedef uint_fast64_t am_mant_t;
// Size of bits in the mantissa and path and rounding shifts
typedef int_fast8_t am_bits_t;
// 16 bit signed integer is used for power to cover all double exponents.
// Power bias is signed for handling a denormal float
// or an invalid mantissa.
typedef int_fast64_t am_pow_t;
typedef int_fast16_t am_pow_t;
// Bias so we can get the real exponent with an invalid adjusted_mantissa.
constexpr static am_pow_t invalid_am_bias = -0x8000;
constexpr static am_pow_t invalid_am_bias =
std::numeric_limits<int16_t>::min() + 1;
constexpr static am_pow_t am_bias_limit =
(std::numeric_limits<int16_t>::max() + 1) / 8;
struct alignas(16) adjusted_mantissa {
am_mant_t mantissa;