1 // Copyright 2010 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #ifndef DOUBLE_CONVERSION_DIY_FP_H_ 29 #define DOUBLE_CONVERSION_DIY_FP_H_ 30 31 #include "utils.h" 32 33 namespace WTF { 34 35 namespace double_conversion { 36 37 // This "Do It Yourself Floating Point" class implements a floating-point number 38 // with a uint64 significand and an int exponent. Normalized DiyFp numbers will 39 // have the most significant bit of the significand set. 40 // Multiplication and Subtraction do not normalize their results. 41 // DiyFp are not designed to contain special doubles (NaN and Infinity). 42 class DiyFp { 43 public: 44 static const int kSignificandSize = 64; 45 DiyFp()46 DiyFp() : f_(0), e_(0) {} DiyFp(uint64_t f,int e)47 DiyFp(uint64_t f, int e) : f_(f), e_(e) {} 48 49 // this = this - other. 50 // The exponents of both numbers must be the same and the significand of this 51 // must be bigger than the significand of other. 52 // The result will not be normalized. Subtract(const DiyFp & other)53 void Subtract(const DiyFp& other) { 54 ASSERT(e_ == other.e_); 55 ASSERT(f_ >= other.f_); 56 f_ -= other.f_; 57 } 58 59 // Returns a - b. 60 // The exponents of both numbers must be the same and this must be bigger 61 // than other. The result will not be normalized. Minus(const DiyFp & a,const DiyFp & b)62 static DiyFp Minus(const DiyFp& a, const DiyFp& b) { 63 DiyFp result = a; 64 result.Subtract(b); 65 return result; 66 } 67 68 69 // this = this * other. 70 void Multiply(const DiyFp& other); 71 72 // returns a * b; Times(const DiyFp & a,const DiyFp & b)73 static DiyFp Times(const DiyFp& a, const DiyFp& b) { 74 DiyFp result = a; 75 result.Multiply(b); 76 return result; 77 } 78 Normalize()79 void Normalize() { 80 ASSERT(f_ != 0); 81 uint64_t f = f_; 82 int e = e_; 83 84 // This method is mainly called for normalizing boundaries. In general 85 // boundaries need to be shifted by 10 bits. We thus optimize for this case. 86 const uint64_t k10MSBits = UINT64_2PART_C(0xFFC00000, 00000000); 87 while ((f & k10MSBits) == 0) { 88 f <<= 10; 89 e -= 10; 90 } 91 while ((f & kUint64MSB) == 0) { 92 f <<= 1; 93 e--; 94 } 95 f_ = f; 96 e_ = e; 97 } 98 Normalize(const DiyFp & a)99 static DiyFp Normalize(const DiyFp& a) { 100 DiyFp result = a; 101 result.Normalize(); 102 return result; 103 } 104 f()105 uint64_t f() const { return f_; } e()106 int e() const { return e_; } 107 set_f(uint64_t new_value)108 void set_f(uint64_t new_value) { f_ = new_value; } set_e(int new_value)109 void set_e(int new_value) { e_ = new_value; } 110 111 private: 112 static const uint64_t kUint64MSB = UINT64_2PART_C(0x80000000, 00000000); 113 114 uint64_t f_; 115 int e_; 116 }; 117 118 } // namespace double_conversion 119 120 } // namespace WTF 121 122 #endif // DOUBLE_CONVERSION_DIY_FP_H_ 123