double-conversion-diy-fp.h (5541B)
1 // © 2018 and later: Unicode, Inc. and others. 2 // License & terms of use: http://www.unicode.org/copyright.html 3 // 4 // From the double-conversion library. Original license: 5 // 6 // Copyright 2010 the V8 project authors. All rights reserved. 7 // Redistribution and use in source and binary forms, with or without 8 // modification, are permitted provided that the following conditions are 9 // met: 10 // 11 // * Redistributions of source code must retain the above copyright 12 // notice, this list of conditions and the following disclaimer. 13 // * Redistributions in binary form must reproduce the above 14 // copyright notice, this list of conditions and the following 15 // disclaimer in the documentation and/or other materials provided 16 // with the distribution. 17 // * Neither the name of Google Inc. nor the names of its 18 // contributors may be used to endorse or promote products derived 19 // from this software without specific prior written permission. 20 // 21 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 24 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 25 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 26 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 27 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 31 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 33 // ICU PATCH: ifdef around UCONFIG_NO_FORMATTING 34 #include "unicode/utypes.h" 35 #if !UCONFIG_NO_FORMATTING 36 37 #ifndef DOUBLE_CONVERSION_DIY_FP_H_ 38 #define DOUBLE_CONVERSION_DIY_FP_H_ 39 40 // ICU PATCH: Customize header file paths for ICU. 41 42 #include "double-conversion-utils.h" 43 44 // ICU PATCH: Wrap in ICU namespace 45 U_NAMESPACE_BEGIN 46 47 namespace double_conversion { 48 49 // This "Do It Yourself Floating Point" class implements a floating-point number 50 // with a uint64 significand and an int exponent. Normalized DiyFp numbers will 51 // have the most significant bit of the significand set. 52 // Multiplication and Subtraction do not normalize their results. 53 // DiyFp store only non-negative numbers and are not designed to contain special 54 // doubles (NaN and Infinity). 55 class DiyFp { 56 public: 57 static const int kSignificandSize = 64; 58 59 DiyFp() : f_(0), e_(0) {} 60 DiyFp(const uint64_t significand, const int32_t exponent) : f_(significand), e_(exponent) {} 61 62 // this -= other. 63 // The exponents of both numbers must be the same and the significand of this 64 // must be greater or equal than the significand of other. 65 // The result will not be normalized. 66 void Subtract(const DiyFp& other) { 67 DOUBLE_CONVERSION_ASSERT(e_ == other.e_); 68 DOUBLE_CONVERSION_ASSERT(f_ >= other.f_); 69 f_ -= other.f_; 70 } 71 72 // Returns a - b. 73 // The exponents of both numbers must be the same and a must be greater 74 // or equal than b. The result will not be normalized. 75 static DiyFp Minus(const DiyFp& a, const DiyFp& b) { 76 DiyFp result = a; 77 result.Subtract(b); 78 return result; 79 } 80 81 // this *= other. 82 void Multiply(const DiyFp& other) { 83 // Simply "emulates" a 128 bit multiplication. 84 // However: the resulting number only contains 64 bits. The least 85 // significant 64 bits are only used for rounding the most significant 64 86 // bits. 87 const uint64_t kM32 = 0xFFFFFFFFU; 88 const uint64_t a = f_ >> 32; 89 const uint64_t b = f_ & kM32; 90 const uint64_t c = other.f_ >> 32; 91 const uint64_t d = other.f_ & kM32; 92 const uint64_t ac = a * c; 93 const uint64_t bc = b * c; 94 const uint64_t ad = a * d; 95 const uint64_t bd = b * d; 96 // By adding 1U << 31 to tmp we round the final result. 97 // Halfway cases will be rounded up. 98 const uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32) + (1U << 31); 99 e_ += other.e_ + 64; 100 f_ = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); 101 } 102 103 // returns a * b; 104 static DiyFp Times(const DiyFp& a, const DiyFp& b) { 105 DiyFp result = a; 106 result.Multiply(b); 107 return result; 108 } 109 110 void Normalize() { 111 DOUBLE_CONVERSION_ASSERT(f_ != 0); 112 uint64_t significand = f_; 113 int32_t exponent = e_; 114 115 // This method is mainly called for normalizing boundaries. In general, 116 // boundaries need to be shifted by 10 bits, and we optimize for this case. 117 const uint64_t k10MSBits = DOUBLE_CONVERSION_UINT64_2PART_C(0xFFC00000, 00000000); 118 while ((significand & k10MSBits) == 0) { 119 significand <<= 10; 120 exponent -= 10; 121 } 122 while ((significand & kUint64MSB) == 0) { 123 significand <<= 1; 124 exponent--; 125 } 126 f_ = significand; 127 e_ = exponent; 128 } 129 130 static DiyFp Normalize(const DiyFp& a) { 131 DiyFp result = a; 132 result.Normalize(); 133 return result; 134 } 135 136 uint64_t f() const { return f_; } 137 int32_t e() const { return e_; } 138 139 void set_f(uint64_t new_value) { f_ = new_value; } 140 void set_e(int32_t new_value) { e_ = new_value; } 141 142 private: 143 static const uint64_t kUint64MSB = DOUBLE_CONVERSION_UINT64_2PART_C(0x80000000, 00000000); 144 145 uint64_t f_; 146 int32_t e_; 147 }; 148 149 } // namespace double_conversion 150 151 // ICU PATCH: Close ICU namespace 152 U_NAMESPACE_END 153 154 #endif // DOUBLE_CONVERSION_DIY_FP_H_ 155 #endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING