119 lines
3.9 KiB
C++
119 lines
3.9 KiB
C++
// Copyright 2010 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef DOUBLE_CONVERSION_DIY_FP_H_
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#define DOUBLE_CONVERSION_DIY_FP_H_
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#include "utils.h"
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namespace double_conversion {
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// This "Do It Yourself Floating Point" class implements a floating-point number
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// with a uint64 significand and an int exponent. Normalized DiyFp numbers will
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// have the most significant bit of the significand set.
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// Multiplication and Subtraction do not normalize their results.
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// DiyFp are not designed to contain special doubles (NaN and Infinity).
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class DiyFp {
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public:
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static const int kSignificandSize = 64;
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DiyFp() : f_(0), e_(0) {}
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DiyFp(uint64_t f, int e) : f_(f), e_(e) {}
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// this = this - other.
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// The exponents of both numbers must be the same and the significand of this
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// must be bigger than the significand of other.
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// The result will not be normalized.
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void Subtract(const DiyFp& other) {
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ASSERT(e_ == other.e_);
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ASSERT(f_ >= other.f_);
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f_ -= other.f_;
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}
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// Returns a - b.
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// The exponents of both numbers must be the same and this must be bigger
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// than other. The result will not be normalized.
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static DiyFp Minus(const DiyFp& a, const DiyFp& b) {
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DiyFp result = a;
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result.Subtract(b);
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return result;
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}
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// this = this * other.
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void Multiply(const DiyFp& other);
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// returns a * b;
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static DiyFp Times(const DiyFp& a, const DiyFp& b) {
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DiyFp result = a;
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result.Multiply(b);
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return result;
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}
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void Normalize() {
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ASSERT(f_ != 0);
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uint64_t f = f_;
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int e = e_;
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// This method is mainly called for normalizing boundaries. In general
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// boundaries need to be shifted by 10 bits. We thus optimize for this case.
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const uint64_t k10MSBits = UINT64_2PART_C(0xFFC00000, 00000000);
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while ((f & k10MSBits) == 0) {
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f <<= 10;
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e -= 10;
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}
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while ((f & kUint64MSB) == 0) {
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f <<= 1;
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e--;
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}
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f_ = f;
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e_ = e;
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}
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static DiyFp Normalize(const DiyFp& a) {
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DiyFp result = a;
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result.Normalize();
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return result;
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}
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uint64_t f() const { return f_; }
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int e() const { return e_; }
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void set_f(uint64_t new_value) { f_ = new_value; }
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void set_e(int new_value) { e_ = new_value; }
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private:
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static const uint64_t kUint64MSB = UINT64_2PART_C(0x80000000, 00000000);
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uint64_t f_;
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int e_;
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};
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} // namespace double_conversion
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#endif // DOUBLE_CONVERSION_DIY_FP_H_
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