The Tor Browser: gfx/skia/trunk/src/utils/SkFloatUtils.h@129ffea94266 (annotated)

gfx/skia/trunk/src/utils/SkFloatUtils.h@129ffea94266 (annotated)

gfx/skia/trunk/src/utils/SkFloatUtils.h

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkFloatUtils_DEFINED
 #define SkFloatUtils_DEFINED
 #include "SkTypes.h"
 #include <limits.h>
 #include <float.h>
 template <size_t size>
 class SkTypeWithSize {
 public:
     // Prevents using SkTypeWithSize<N> with non-specialized N.
     typedef void UInt;
 };
 template <>
 class SkTypeWithSize<32> {
 public:
     typedef uint32_t UInt;
 };
 template <>
 class SkTypeWithSize<64> {
 public:
     typedef uint64_t UInt;
 };
 template <typename RawType>
 struct SkNumericLimits {
     static const int digits = 0;
 };
 template <>
 struct SkNumericLimits<double> {
     static const int digits = DBL_MANT_DIG;
 };
 template <>
 struct SkNumericLimits<float> {
     static const int digits = FLT_MANT_DIG;
 };
 //See
 //http://stackoverflow.com/questions/17333/most-effective-way-for-float-and-double-comparison/3423299#3423299
 //http://code.google.com/p/googletest/source/browse/trunk/include/gtest/internal/gtest-internal.h
 //http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm
 template <typename RawType, unsigned int ULPs>
 class SkFloatingPoint {
 public:
     /** Bits is a unsigned integer the same size as the floating point number. */
     typedef typename SkTypeWithSize<sizeof(RawType) * CHAR_BIT>::UInt Bits;
     /** # of bits in a number. */
     static const size_t kBitCount = CHAR_BIT * sizeof(RawType);
     /** # of fraction bits in a number. */
     static const size_t kFractionBitCount = SkNumericLimits<RawType>::digits - 1;
     /** # of exponent bits in a number. */
     static const size_t kExponentBitCount = kBitCount - 1 - kFractionBitCount;
     /** The mask for the sign bit. */
     static const Bits kSignBitMask = static_cast<Bits>(1) << (kBitCount - 1);
     /** The mask for the fraction bits. */
     static const Bits kFractionBitMask =
         ~static_cast<Bits>(0) >> (kExponentBitCount + 1);
     /** The mask for the exponent bits. */
     static const Bits kExponentBitMask = ~(kSignBitMask | kFractionBitMask);
     /** How many ULP's (Units in the Last Place) to tolerate when comparing. */
     static const size_t kMaxUlps = ULPs;
     /**
      *  Constructs a FloatingPoint from a raw floating-point number.
      *
      *  On an Intel CPU, passing a non-normalized NAN (Not a Number)
      *  around may change its bits, although the new value is guaranteed
      *  to be also a NAN.  Therefore, don't expect this constructor to
      *  preserve the bits in x when x is a NAN.
      */
     explicit SkFloatingPoint(const RawType& x) { fU.value = x; }
     /** Returns the exponent bits of this number. */
     Bits exponent_bits() const { return kExponentBitMask & fU.bits; }
     /** Returns the fraction bits of this number. */
     Bits fraction_bits() const { return kFractionBitMask & fU.bits; }
     /** Returns true iff this is NAN (not a number). */
     bool is_nan() const {
         // It's a NAN if both of the folloowing are true:
         // * the exponent bits are all ones
         // * the fraction bits are not all zero.
         return (exponent_bits() == kExponentBitMask) && (fraction_bits() != 0);
     }
     /**
      *  Returns true iff this number is at most kMaxUlps ULP's away from ths.
      *  In particular, this function:
      *   - returns false if either number is (or both are) NAN.
      *   - treats really large numbers as almost equal to infinity.
      *   - thinks +0.0 and -0.0 are 0 DLP's apart.
      */
     bool AlmostEquals(const SkFloatingPoint& rhs) const {
         // Any comparison operation involving a NAN must return false.
         if (is_nan() || rhs.is_nan()) return false;
         const Bits dist = DistanceBetweenSignAndMagnitudeNumbers(fU.bits,
                                                                  rhs.fU.bits);
         //SkDEBUGF(("(%f, %f, %d) ", u_.value_, rhs.u_.value_, dist));
         return dist <= kMaxUlps;
     }
 private:
     /** The data type used to store the actual floating-point number. */
     union FloatingPointUnion {
         /** The raw floating-point number. */
         RawType value;
         /** The bits that represent the number. */
         Bits bits;
     };
     /**
      *  Converts an integer from the sign-and-magnitude representation to
      *  the biased representation. More precisely, let N be 2 to the
      *  power of (kBitCount - 1), an integer x is represented by the
      *  unsigned number x + N.
      *
      *  For instance,
      *
      *    -N + 1 (the most negative number representable using
      *           sign-and-magnitude) is represented by 1;
      *    0      is represented by N; and
      *    N - 1  (the biggest number representable using
      *           sign-and-magnitude) is represented by 2N - 1.
      *
      *  Read http://en.wikipedia.org/wiki/Signed_number_representations
      *  for more details on signed number representations.
      */
     static Bits SignAndMagnitudeToBiased(const Bits &sam) {
         if (kSignBitMask & sam) {
             // sam represents a negative number.
             return ~sam + 1;
         } else {
             // sam represents a positive number.
             return kSignBitMask | sam;
         }
     }
     /**
      *  Given two numbers in the sign-and-magnitude representation,
      *  returns the distance between them as an unsigned number.
      */
     static Bits DistanceBetweenSignAndMagnitudeNumbers(const Bits &sam1,
                                                        const Bits &sam2) {
         const Bits biased1 = SignAndMagnitudeToBiased(sam1);
         const Bits biased2 = SignAndMagnitudeToBiased(sam2);
         return (biased1 >= biased2) ? (biased1 - biased2) : (biased2 - biased1);
     }
     FloatingPointUnion fU;
 };
 #endif

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gfx/skia/trunk/src/utils/SkFloatUtils.h@129ffea94266 (annotated)

gfx/skia/trunk/src/utils/SkFloatUtils.h