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Side by Side Diff: third_party/WebKit/Source/wtf/dtoa/diy-fp.h

Issue 2764243002: Move files in wtf/ to platform/wtf/ (Part 9). (Closed)
Patch Set: Rebase. Created 3 years, 9 months ago
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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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