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| 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_DOUBLE_H_ | |
| 29 #define DOUBLE_CONVERSION_DOUBLE_H_ | |
| 30 | |
| 31 #include "diy-fp.h" | |
| 32 | |
| 33 namespace WTF { | |
| 34 | |
| 35 namespace double_conversion { | |
| 36 | |
| 37 // We assume that doubles and uint64_t have the same endianness. | |
| 38 static uint64_t double_to_uint64(double d) { return BitCast<uint64_t>(d); } | |
| 39 static double uint64_to_double(uint64_t d64) { return BitCast<double>(d64);
} | |
| 40 | |
| 41 // Helper functions for doubles. | |
| 42 class Double { | |
| 43 public: | |
| 44 static const uint64_t kSignMask = UINT64_2PART_C(0x80000000, 00000000); | |
| 45 static const uint64_t kExponentMask = UINT64_2PART_C(0x7FF00000, 0000000
0); | |
| 46 static const uint64_t kSignificandMask = UINT64_2PART_C(0x000FFFFF, FFFF
FFFF); | |
| 47 static const uint64_t kHiddenBit = UINT64_2PART_C(0x00100000, 00000000); | |
| 48 static const int kPhysicalSignificandSize = 52; // Excludes the hidden
bit. | |
| 49 static const int kSignificandSize = 53; | |
| 50 | |
| 51 Double() : d64_(0) {} | |
| 52 explicit Double(double d) : d64_(double_to_uint64(d)) {} | |
| 53 explicit Double(uint64_t d64) : d64_(d64) {} | |
| 54 explicit Double(DiyFp diy_fp) | |
| 55 : d64_(DiyFpToUint64(diy_fp)) {} | |
| 56 | |
| 57 // The value encoded by this Double must be greater or equal to +0.0. | |
| 58 // It must not be special (infinity, or NaN). | |
| 59 DiyFp AsDiyFp() const { | |
| 60 ASSERT(Sign() > 0); | |
| 61 ASSERT(!IsSpecial()); | |
| 62 return DiyFp(Significand(), Exponent()); | |
| 63 } | |
| 64 | |
| 65 // The value encoded by this Double must be strictly greater than 0. | |
| 66 DiyFp AsNormalizedDiyFp() const { | |
| 67 ASSERT(value() > 0.0); | |
| 68 uint64_t f = Significand(); | |
| 69 int e = Exponent(); | |
| 70 | |
| 71 // The current double could be a denormal. | |
| 72 while ((f & kHiddenBit) == 0) { | |
| 73 f <<= 1; | |
| 74 e--; | |
| 75 } | |
| 76 // Do the final shifts in one go. | |
| 77 f <<= DiyFp::kSignificandSize - kSignificandSize; | |
| 78 e -= DiyFp::kSignificandSize - kSignificandSize; | |
| 79 return DiyFp(f, e); | |
| 80 } | |
| 81 | |
| 82 // Returns the double's bit as uint64. | |
| 83 uint64_t AsUint64() const { | |
| 84 return d64_; | |
| 85 } | |
| 86 | |
| 87 // Returns the next greater double. Returns +infinity on input +infinity
. | |
| 88 double NextDouble() const { | |
| 89 if (d64_ == kInfinity) return Double(kInfinity).value(); | |
| 90 if (Sign() < 0 && Significand() == 0) { | |
| 91 // -0.0 | |
| 92 return 0.0; | |
| 93 } | |
| 94 if (Sign() < 0) { | |
| 95 return Double(d64_ - 1).value(); | |
| 96 } else { | |
| 97 return Double(d64_ + 1).value(); | |
| 98 } | |
| 99 } | |
| 100 | |
| 101 int Exponent() const { | |
| 102 if (IsDenormal()) return kDenormalExponent; | |
| 103 | |
| 104 uint64_t d64 = AsUint64(); | |
| 105 int biased_e = | |
| 106 static_cast<int>((d64 & kExponentMask) >> kPhysicalSignificandSize); | |
| 107 return biased_e - kExponentBias; | |
| 108 } | |
| 109 | |
| 110 uint64_t Significand() const { | |
| 111 uint64_t d64 = AsUint64(); | |
| 112 uint64_t significand = d64 & kSignificandMask; | |
| 113 if (!IsDenormal()) { | |
| 114 return significand + kHiddenBit; | |
| 115 } else { | |
| 116 return significand; | |
| 117 } | |
| 118 } | |
| 119 | |
| 120 // Returns true if the double is a denormal. | |
| 121 bool IsDenormal() const { | |
| 122 uint64_t d64 = AsUint64(); | |
| 123 return (d64 & kExponentMask) == 0; | |
| 124 } | |
| 125 | |
| 126 // We consider denormals not to be special. | |
| 127 // Hence only Infinity and NaN are special. | |
| 128 bool IsSpecial() const { | |
| 129 uint64_t d64 = AsUint64(); | |
| 130 return (d64 & kExponentMask) == kExponentMask; | |
| 131 } | |
| 132 | |
| 133 bool IsNan() const { | |
| 134 uint64_t d64 = AsUint64(); | |
| 135 return ((d64 & kExponentMask) == kExponentMask) && | |
| 136 ((d64 & kSignificandMask) != 0); | |
| 137 } | |
| 138 | |
| 139 bool IsInfinite() const { | |
| 140 uint64_t d64 = AsUint64(); | |
| 141 return ((d64 & kExponentMask) == kExponentMask) && | |
| 142 ((d64 & kSignificandMask) == 0); | |
| 143 } | |
| 144 | |
| 145 int Sign() const { | |
| 146 uint64_t d64 = AsUint64(); | |
| 147 return (d64 & kSignMask) == 0? 1: -1; | |
| 148 } | |
| 149 | |
| 150 // Precondition: the value encoded by this Double must be greater or equ
al | |
| 151 // than +0.0. | |
| 152 DiyFp UpperBoundary() const { | |
| 153 ASSERT(Sign() > 0); | |
| 154 return DiyFp(Significand() * 2 + 1, Exponent() - 1); | |
| 155 } | |
| 156 | |
| 157 // Computes the two boundaries of this. | |
| 158 // The bigger boundary (m_plus) is normalized. The lower boundary has th
e same | |
| 159 // exponent as m_plus. | |
| 160 // Precondition: the value encoded by this Double must be greater than 0
. | |
| 161 void NormalizedBoundaries(DiyFp* out_m_minus, DiyFp* out_m_plus) const { | |
| 162 ASSERT(value() > 0.0); | |
| 163 DiyFp v = this->AsDiyFp(); | |
| 164 bool significand_is_zero = (v.f() == kHiddenBit); | |
| 165 DiyFp m_plus = DiyFp::Normalize(DiyFp((v.f() << 1) + 1, v.e() - 1)); | |
| 166 DiyFp m_minus; | |
| 167 if (significand_is_zero && v.e() != kDenormalExponent) { | |
| 168 // The boundary is closer. Think of v = 1000e10 and v- = 9999e9. | |
| 169 // Then the boundary (== (v - v-)/2) is not just at a distance o
f 1e9 but | |
| 170 // at a distance of 1e8. | |
| 171 // The only exception is for the smallest normal: the largest de
normal is | |
| 172 // at the same distance as its successor. | |
| 173 // Note: denormals have the same exponent as the smallest normal
s. | |
| 174 m_minus = DiyFp((v.f() << 2) - 1, v.e() - 2); | |
| 175 } else { | |
| 176 m_minus = DiyFp((v.f() << 1) - 1, v.e() - 1); | |
| 177 } | |
| 178 m_minus.set_f(m_minus.f() << (m_minus.e() - m_plus.e())); | |
| 179 m_minus.set_e(m_plus.e()); | |
| 180 *out_m_plus = m_plus; | |
| 181 *out_m_minus = m_minus; | |
| 182 } | |
| 183 | |
| 184 double value() const { return uint64_to_double(d64_); } | |
| 185 | |
| 186 // Returns the significand size for a given order of magnitude. | |
| 187 // If v = f*2^e with 2^p-1 <= f <= 2^p then p+e is v's order of magnitud
e. | |
| 188 // This function returns the number of significant binary digits v will
have | |
| 189 // once it's encoded into a double. In almost all cases this is equal to | |
| 190 // kSignificandSize. The only exceptions are denormals. They start with | |
| 191 // leading zeroes and their effective significand-size is hence smaller. | |
| 192 static int SignificandSizeForOrderOfMagnitude(int order) { | |
| 193 if (order >= (kDenormalExponent + kSignificandSize)) { | |
| 194 return kSignificandSize; | |
| 195 } | |
| 196 if (order <= kDenormalExponent) return 0; | |
| 197 return order - kDenormalExponent; | |
| 198 } | |
| 199 | |
| 200 static double Infinity() { | |
| 201 return Double(kInfinity).value(); | |
| 202 } | |
| 203 | |
| 204 static double NaN() { | |
| 205 return Double(kNaN).value(); | |
| 206 } | |
| 207 | |
| 208 private: | |
| 209 static const int kExponentBias = 0x3FF + kPhysicalSignificandSize; | |
| 210 static const int kDenormalExponent = -kExponentBias + 1; | |
| 211 static const int kMaxExponent = 0x7FF - kExponentBias; | |
| 212 static const uint64_t kInfinity = UINT64_2PART_C(0x7FF00000, 00000000); | |
| 213 static const uint64_t kNaN = UINT64_2PART_C(0x7FF80000, 00000000); | |
| 214 | |
| 215 const uint64_t d64_; | |
| 216 | |
| 217 static uint64_t DiyFpToUint64(DiyFp diy_fp) { | |
| 218 uint64_t significand = diy_fp.f(); | |
| 219 int exponent = diy_fp.e(); | |
| 220 while (significand > kHiddenBit + kSignificandMask) { | |
| 221 significand >>= 1; | |
| 222 exponent++; | |
| 223 } | |
| 224 if (exponent >= kMaxExponent) { | |
| 225 return kInfinity; | |
| 226 } | |
| 227 if (exponent < kDenormalExponent) { | |
| 228 return 0; | |
| 229 } | |
| 230 while (exponent > kDenormalExponent && (significand & kHiddenBit) ==
0) { | |
| 231 significand <<= 1; | |
| 232 exponent--; | |
| 233 } | |
| 234 uint64_t biased_exponent; | |
| 235 if (exponent == kDenormalExponent && (significand & kHiddenBit) == 0
) { | |
| 236 biased_exponent = 0; | |
| 237 } else { | |
| 238 biased_exponent = static_cast<uint64_t>(exponent + kExponentBias
); | |
| 239 } | |
| 240 return (significand & kSignificandMask) | | |
| 241 (biased_exponent << kPhysicalSignificandSize); | |
| 242 } | |
| 243 }; | |
| 244 | |
| 245 } // namespace double_conversion | |
| 246 | |
| 247 } // namespace WTF | |
| 248 | |
| 249 #endif // DOUBLE_CONVERSION_DOUBLE_H_ | |
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Chromium Code Reviews
Issue 14238015:
Move Source/WTF/wtf to Source/wtf (Closed)
Base URL: svn://svn.chromium.org/blink/trunk