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| 1 | +// Copyright (c) 2021 The Bitcoin Core developers |
| 2 | +// Distributed under the MIT software license, see the accompanying |
| 3 | +// file COPYING or http://www.opensource.org/licenses/mit-license.php. |
| 4 | + |
| 5 | +#include <util/serfloat.h> |
| 6 | + |
| 7 | +#include <cmath> |
| 8 | +#include <limits> |
| 9 | + |
| 10 | +double DecodeDouble(uint64_t v) noexcept { |
| 11 | + static constexpr double NANVAL = std::numeric_limits<double>::quiet_NaN(); |
| 12 | + static constexpr double INFVAL = std::numeric_limits<double>::infinity(); |
| 13 | + double sign = 1.0; |
| 14 | + if (v & 0x8000000000000000) { |
| 15 | + sign = -1.0; |
| 16 | + v ^= 0x8000000000000000; |
| 17 | + } |
| 18 | + // Zero |
| 19 | + if (v == 0) return copysign(0.0, sign); |
| 20 | + // Infinity |
| 21 | + if (v == 0x7ff0000000000000) return copysign(INFVAL, sign); |
| 22 | + // Other numbers |
| 23 | + int exp = (v & 0x7FF0000000000000) >> 52; |
| 24 | + uint64_t man = v & 0xFFFFFFFFFFFFF; |
| 25 | + if (exp == 2047) { |
| 26 | + // NaN |
| 27 | + return NANVAL; |
| 28 | + } else if (exp == 0) { |
| 29 | + // Subnormal |
| 30 | + return copysign(ldexp((double)man, -1074), sign); |
| 31 | + } else { |
| 32 | + // Normal |
| 33 | + return copysign(ldexp((double)(man + 0x10000000000000), -1075 + exp), sign); |
| 34 | + } |
| 35 | +} |
| 36 | + |
| 37 | +uint64_t EncodeDouble(double f) noexcept { |
| 38 | + int cls = std::fpclassify(f); |
| 39 | + uint64_t sign = 0; |
| 40 | + if (copysign(1.0, f) == -1.0) { |
| 41 | + f = -f; |
| 42 | + sign = 0x8000000000000000; |
| 43 | + } |
| 44 | + // Zero |
| 45 | + if (cls == FP_ZERO) return sign; |
| 46 | + // Infinity |
| 47 | + if (cls == FP_INFINITE) return sign | 0x7ff0000000000000; |
| 48 | + // NaN |
| 49 | + if (cls == FP_NAN) return 0x7ff8000000000000; |
| 50 | + // Other numbers |
| 51 | + int exp; |
| 52 | + uint64_t man = std::round(std::frexp(f, &exp) * 9007199254740992.0); |
| 53 | + if (exp < -1021) { |
| 54 | + // Too small to represent, encode 0 |
| 55 | + if (exp < -1084) return sign; |
| 56 | + // Subnormal numbers |
| 57 | + return sign | (man >> (-1021 - exp)); |
| 58 | + } else { |
| 59 | + // Too big to represent, encode infinity |
| 60 | + if (exp > 1024) return sign | 0x7ff0000000000000; |
| 61 | + // Normal numbers |
| 62 | + return sign | (((uint64_t)(1022 + exp)) << 52) | (man & 0xFFFFFFFFFFFFF); |
| 63 | + } |
| 64 | +} |
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