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65 lines
2.0 KiB
C++
65 lines
2.0 KiB
C++
// Copyright (c) 2021 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include <util/serfloat.h>
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#include <cmath>
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#include <limits>
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double DecodeDouble(uint64_t v) noexcept {
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static constexpr double NANVAL = std::numeric_limits<double>::quiet_NaN();
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static constexpr double INFVAL = std::numeric_limits<double>::infinity();
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double sign = 1.0;
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if (v & 0x8000000000000000) {
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sign = -1.0;
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v ^= 0x8000000000000000;
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}
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// Zero
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if (v == 0) return copysign(0.0, sign);
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// Infinity
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if (v == 0x7ff0000000000000) return copysign(INFVAL, sign);
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// Other numbers
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int exp = (v & 0x7FF0000000000000) >> 52;
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uint64_t man = v & 0xFFFFFFFFFFFFF;
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if (exp == 2047) {
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// NaN
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return NANVAL;
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} else if (exp == 0) {
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// Subnormal
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return copysign(ldexp((double)man, -1074), sign);
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} else {
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// Normal
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return copysign(ldexp((double)(man + 0x10000000000000), -1075 + exp), sign);
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}
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}
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uint64_t EncodeDouble(double f) noexcept {
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int cls = std::fpclassify(f);
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uint64_t sign = 0;
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if (copysign(1.0, f) == -1.0) {
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f = -f;
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sign = 0x8000000000000000;
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}
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// Zero
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if (cls == FP_ZERO) return sign;
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// Infinity
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if (cls == FP_INFINITE) return sign | 0x7ff0000000000000;
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// NaN
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if (cls == FP_NAN) return 0x7ff8000000000000;
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// Other numbers
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int exp;
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uint64_t man = std::round(std::frexp(f, &exp) * 9007199254740992.0);
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if (exp < -1021) {
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// Too small to represent, encode 0
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if (exp < -1084) return sign;
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// Subnormal numbers
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return sign | (man >> (-1021 - exp));
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} else {
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// Too big to represent, encode infinity
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if (exp > 1024) return sign | 0x7ff0000000000000;
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// Normal numbers
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return sign | (((uint64_t)(1022 + exp)) << 52) | (man & 0xFFFFFFFFFFFFF);
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}
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}
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