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