mirror of
https://github.com/fastfloat/fast_float.git
synced 2025-12-06 16:56:57 +08:00
295 lines
9.3 KiB
C++
295 lines
9.3 KiB
C++
#ifndef FASTFLOAT_FLOAT_COMMON_H
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#define FASTFLOAT_FLOAT_COMMON_H
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#include <cfloat>
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#include <cstdint>
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#if defined(_MSC_VER) && !defined(__clang__)
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#define FASTFLOAT_VISUAL_STUDIO 1
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#endif
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#ifdef FASTFLOAT_VISUAL_STUDIO
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#define fastfloat_really_inline __forceinline
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#else
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#define fastfloat_really_inline inline __attribute__((always_inline))
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#endif
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namespace fast_float {
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// Compares two ASCII strings in a case insensitive manner.
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inline bool fastfloat_strncasecmp(const char *input1, const char *input2,
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size_t length) {
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char running_diff{0};
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for (size_t i = 0; i < length; i++) {
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running_diff |= (input1[i] ^ input2[i]);
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}
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return (running_diff == 0) || (running_diff == 32);
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}
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#ifndef FLT_EVAL_METHOD
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#error "FLT_EVAL_METHOD should be defined, please include cfloat."
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#endif
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inline bool is_space(uint8_t c) {
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static const bool table[] = {
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0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
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return table[c];
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}
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namespace {
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constexpr uint32_t max_digits = 768;
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constexpr uint32_t max_digit_without_overflow = 19;
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constexpr int32_t decimal_point_range = 2047;
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} // namespace
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struct value128 {
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uint64_t low;
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uint64_t high;
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value128(uint64_t _low, uint64_t _high) : low(_low), high(_high) {}
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value128() : low(0), high(0) {}
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};
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/* result might be undefined when input_num is zero */
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fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
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#ifdef FASTFLOAT_VISUAL_STUDIO
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unsigned long leading_zero = 0;
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// Search the mask data from most significant bit (MSB)
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// to least significant bit (LSB) for a set bit (1).
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if (_BitScanReverse64(&leading_zero, input_num))
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return (int)(63 - leading_zero);
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else
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return 64;
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#else
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return __builtin_clzll(input_num);
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#endif
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}
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#if defined(_WIN32) && !defined(__clang__)
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// Note MinGW falls here too
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#include <intrin.h>
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#if !defined(_M_X64) && !defined(_M_ARM64) // _umul128 for x86, arm
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// this is a slow emulation routine for 32-bit Windows
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//
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fastfloat_really_inline uint64_t __emulu(uint32_t x, uint32_t y) {
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return x * (uint64_t)y;
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}
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fastfloat_really_inline uint64_t _umul128(uint64_t ab, uint64_t cd,
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uint64_t *hi) {
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uint64_t ad = __emulu((uint32_t)(ab >> 32), (uint32_t)cd);
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uint64_t bd = __emulu((uint32_t)ab, (uint32_t)cd);
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uint64_t adbc = ad + __emulu((uint32_t)ab, (uint32_t)(cd >> 32));
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uint64_t adbc_carry = !!(adbc < ad);
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uint64_t lo = bd + (adbc << 32);
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*hi = __emulu((uint32_t)(ab >> 32), (uint32_t)(cd >> 32)) + (adbc >> 32) +
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(adbc_carry << 32) + !!(lo < bd);
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return lo;
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}
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#endif
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fastfloat_really_inline value128 full_multiplication(uint64_t value1,
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uint64_t value2) {
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value128 answer;
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#ifdef _M_ARM64
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// ARM64 has native support for 64-bit multiplications, no need to emultate
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answer.high = __umulh(value1, value2);
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answer.low = value1 * value2;
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#else
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answer.low =
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_umul128(value1, value2, &answer.high); // _umul128 not available on ARM64
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#endif // _M_ARM64
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return answer;
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}
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#else
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// compute value1 * value2
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fastfloat_really_inline value128 full_multiplication(uint64_t value1,
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uint64_t value2) {
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value128 answer;
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__uint128_t r = ((__uint128_t)value1) * value2;
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answer.low = uint64_t(r);
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answer.high = uint64_t(r >> 64);
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return answer;
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}
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#endif
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struct adjusted_mantissa {
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uint64_t mantissa;
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int power2; // a negative value indicate an invalid result
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adjusted_mantissa() = default;
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// bool operator==(const adjusted_mantissa &o) const = default;
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bool operator==(const adjusted_mantissa &o) const {
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return mantissa == o.mantissa && power2 == o.power2;
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}
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};
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struct decimal {
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uint32_t num_digits;
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int32_t decimal_point;
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bool negative;
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bool truncated;
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uint8_t digits[max_digits];
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decimal() = default;
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// Copies are not allowed since this is a fat object.
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decimal(const decimal &) = delete;
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// Copies are not allowed since this is a fat object.
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decimal &operator=(const decimal &) = delete;
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// Moves are allowed:
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decimal(decimal &&) = default;
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decimal &operator=(decimal &&other) = default;
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// Generates a mantissa by truncating to 19 digits.
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// This function should be reasonably fast.
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// Note that the user is responsible to ensure that digits are
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// initialized to zero when there are fewer than 19.
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inline uint64_t to_truncated_mantissa() {
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uint64_t val;
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// 8 first digits
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::memcpy(&val, digits, sizeof(uint64_t));
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val = val * 2561 >> 8;
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val = (val & 0x00FF00FF00FF00FF) * 6553601 >> 16;
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uint64_t mantissa =
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uint32_t((val & 0x0000FFFF0000FFFF) * 42949672960001 >> 32);
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// 8 more digits for a total of 16
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::memcpy(&val, digits + sizeof(uint64_t), sizeof(uint64_t));
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val = val * 2561 >> 8;
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val = (val & 0x00FF00FF00FF00FF) * 6553601 >> 16;
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uint32_t eight_digits_value =
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uint32_t((val & 0x0000FFFF0000FFFF) * 42949672960001 >> 32);
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mantissa = 100000000 * mantissa + eight_digits_value;
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for (uint32_t i = 2 * sizeof(uint64_t); i < max_digit_without_overflow;
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i++) {
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mantissa = mantissa * 10 + digits[i]; // can be accelerated
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}
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return mantissa;
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}
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// Generate san exponent matching to_truncated_mantissa()
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inline int32_t to_truncated_exponent() {
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return decimal_point - int32_t(max_digit_without_overflow);
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}
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};
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constexpr static double powers_of_ten_double[] = {
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1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
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1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22};
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constexpr static float powers_of_ten_float[] = {1e0, 1e1, 1e2, 1e3, 1e4, 1e5,
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1e6, 1e7, 1e8, 1e9, 1e10};
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template <typename T> struct binary_format {
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static constexpr int mantissa_explicit_bits();
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static constexpr int minimum_exponent();
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static constexpr int infinite_power();
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static constexpr int sign_index();
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static constexpr int min_exponent_fast_path();
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static constexpr int max_exponent_fast_path();
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static constexpr int max_exponent_round_to_even();
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static constexpr int min_exponent_round_to_even();
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static constexpr uint64_t max_mantissa_fast_path();
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static constexpr T exact_power_of_ten(int64_t power);
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};
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template <> constexpr int binary_format<double>::mantissa_explicit_bits() {
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return 52;
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}
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template <> constexpr int binary_format<float>::mantissa_explicit_bits() {
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return 23;
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}
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template <> constexpr int binary_format<double>::max_exponent_round_to_even() {
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return 23;
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}
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template <> constexpr int binary_format<float>::max_exponent_round_to_even() {
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return 10;
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}
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template <> constexpr int binary_format<double>::min_exponent_round_to_even() {
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return -4;
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}
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template <> constexpr int binary_format<float>::min_exponent_round_to_even() {
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return -17;
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}
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template <> constexpr int binary_format<double>::minimum_exponent() {
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return -1023;
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}
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template <> constexpr int binary_format<float>::minimum_exponent() {
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return -127;
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}
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template <> constexpr int binary_format<double>::infinite_power() {
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return 0x7FF;
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}
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template <> constexpr int binary_format<float>::infinite_power() {
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return 0xFF;
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}
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template <> constexpr int binary_format<double>::sign_index() { return 63; }
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template <> constexpr int binary_format<float>::sign_index() { return 31; }
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template <> constexpr int binary_format<double>::min_exponent_fast_path() {
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#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
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return 0;
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#else
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return -22;
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#endif
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}
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template <> constexpr int binary_format<float>::min_exponent_fast_path() {
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#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
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return 0;
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#else
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return -10;
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#endif
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}
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template <> constexpr int binary_format<double>::max_exponent_fast_path() {
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return 22;
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}
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template <> constexpr int binary_format<float>::max_exponent_fast_path() {
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return 10;
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}
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template <> constexpr uint64_t binary_format<double>::max_mantissa_fast_path() {
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return uint64_t(2) << mantissa_explicit_bits();
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}
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template <> constexpr uint64_t binary_format<float>::max_mantissa_fast_path() {
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return uint64_t(2) << mantissa_explicit_bits();
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}
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template <>
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constexpr double binary_format<double>::exact_power_of_ten(int64_t power) {
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return powers_of_ten_double[power];
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}
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template <>
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constexpr float binary_format<float>::exact_power_of_ten(int64_t power) {
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return powers_of_ten_float[power];
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}
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} // namespace fast_float
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// for convenience:
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#include <ostream>
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inline std::ostream &operator<<(std::ostream &out, const fast_float::decimal &d) {
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out << "0.";
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for (size_t i = 0; i < d.num_digits; i++) {
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out << int32_t(d.digits[i]);
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}
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out << " * 10 ** " << d.decimal_point;
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return out;
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}
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#endif
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