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1 // Copyright 2010 the V8 project authors. All rights reserved. | 1 // Copyright 2017 The Chromium Authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // modification, are permitted provided that the following conditions are | 3 // found in the LICENSE file. |
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 | 4 |
28 #ifndef DOUBLE_CONVERSION_DIY_FP_H_ | 5 #include "platform/wtf/dtoa/diy-fp.h" |
29 #define DOUBLE_CONVERSION_DIY_FP_H_ | |
30 | 6 |
31 #include "utils.h" | 7 // The contents of this header was moved to platform/wtf as part of |
32 | 8 // WTF migration project. See the following post for details: |
33 namespace WTF { | 9 // https://groups.google.com/a/chromium.org/d/msg/blink-dev/tLdAZCTlcAA/bYXVT8gY
CAAJ |
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 | |
46 DiyFp() : f_(0), e_(0) {} | |
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. | |
53 void Subtract(const DiyFp& other) { | |
54 DCHECK_EQ(e_, other.e_); | |
55 DCHECK_GE(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. | |
62 static DiyFp Minus(const DiyFp& a, const DiyFp& b) { | |
63 DiyFp result = a; | |
64 result.Subtract(b); | |
65 return result; | |
66 } | |
67 | |
68 // this = this * other. | |
69 void Multiply(const DiyFp& other); | |
70 | |
71 // returns a * b; | |
72 static DiyFp Times(const DiyFp& a, const DiyFp& b) { | |
73 DiyFp result = a; | |
74 result.Multiply(b); | |
75 return result; | |
76 } | |
77 | |
78 void Normalize() { | |
79 DCHECK_NE(f_, 0u); | |
80 uint64_t f = f_; | |
81 int e = e_; | |
82 | |
83 // This method is mainly called for normalizing boundaries. In general | |
84 // boundaries need to be shifted by 10 bits. We thus optimize for this case. | |
85 const uint64_t k10MSBits = UINT64_2PART_C(0xFFC00000, 00000000); | |
86 while ((f & k10MSBits) == 0) { | |
87 f <<= 10; | |
88 e -= 10; | |
89 } | |
90 while ((f & kUint64MSB) == 0) { | |
91 f <<= 1; | |
92 e--; | |
93 } | |
94 f_ = f; | |
95 e_ = e; | |
96 } | |
97 | |
98 static DiyFp Normalize(const DiyFp& a) { | |
99 DiyFp result = a; | |
100 result.Normalize(); | |
101 return result; | |
102 } | |
103 | |
104 uint64_t f() const { return f_; } | |
105 int e() const { return e_; } | |
106 | |
107 void set_f(uint64_t new_value) { f_ = new_value; } | |
108 void set_e(int new_value) { e_ = new_value; } | |
109 | |
110 private: | |
111 static const uint64_t kUint64MSB = UINT64_2PART_C(0x80000000, 00000000); | |
112 | |
113 uint64_t f_; | |
114 int e_; | |
115 }; | |
116 | |
117 } // namespace double_conversion | |
118 | |
119 } // namespace WTF | |
120 | |
121 #endif // DOUBLE_CONVERSION_DIY_FP_H_ | |
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