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

gfx/skia/trunk/include/utils/SkRandom.h@129ffea94266 (annotated)

gfx/skia/trunk/include/utils/SkRandom.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 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkRandom_DEFINED
 #define SkRandom_DEFINED
 #include "SkScalar.h"
 /** \class SkLCGRandom
     Utility class that implements pseudo random 32bit numbers using a fast
     linear equation. Unlike rand(), this class holds its own seed (initially
     set to 0), so that multiple instances can be used with no side-effects.
 */
 class SkLCGRandom {
 public:
     SkLCGRandom() : fSeed(0) {}
     SkLCGRandom(uint32_t seed) : fSeed(seed) {}
     /** Return the next pseudo random number as an unsigned 32bit value.
     */
     uint32_t nextU() { uint32_t r = fSeed * kMul + kAdd; fSeed = r; return r; }
     /** Return the next pseudo random number as a signed 32bit value.
     */
     int32_t nextS() { return (int32_t)this->nextU(); }
     /** Return the next pseudo random number as an unsigned 16bit value.
     */
     U16CPU nextU16() { return this->nextU() >> 16; }
     /** Return the next pseudo random number as a signed 16bit value.
     */
     S16CPU nextS16() { return this->nextS() >> 16; }
     /**
      *  Returns value [0...1) as a float
      */
     float nextF() {
         // const is 1 / (2^32 - 1)
         return (float)(this->nextU() * 2.32830644e-10);
     }
     /**
      *  Returns value [min...max) as a float
      */
     float nextRangeF(float min, float max) {
         return min + this->nextF() * (max - min);
     }
     /** Return the next pseudo random number, as an unsigned value of
         at most bitCount bits.
         @param bitCount The maximum number of bits to be returned
     */
     uint32_t nextBits(unsigned bitCount) {
         SkASSERT(bitCount > 0 && bitCount <= 32);
         return this->nextU() >> (32 - bitCount);
     }
     /** Return the next pseudo random unsigned number, mapped to lie within
         [min, max] inclusive.
     */
     uint32_t nextRangeU(uint32_t min, uint32_t max) {
         SkASSERT(min <= max);
         uint32_t range = max - min + 1;
         if (0 == range) {
             return this->nextU();
         } else {
             return min + this->nextU() % range;
         }
     }
     /** Return the next pseudo random unsigned number, mapped to lie within
         [0, count).
      */
     uint32_t nextULessThan(uint32_t count) {
         SkASSERT(count > 0);
         return this->nextRangeU(0, count - 1);
     }
     /** Return the next pseudo random number expressed as an unsigned SkFixed
         in the range [0..SK_Fixed1).
     */
     SkFixed nextUFixed1() { return this->nextU() >> 16; }
     /** Return the next pseudo random number expressed as a signed SkFixed
         in the range (-SK_Fixed1..SK_Fixed1).
     */
     SkFixed nextSFixed1() { return this->nextS() >> 15; }
     /** Return the next pseudo random number expressed as a SkScalar
         in the range [0..SK_Scalar1).
     */
     SkScalar nextUScalar1() { return SkFixedToScalar(this->nextUFixed1()); }
     /** Return the next pseudo random number expressed as a SkScalar
         in the range [min..max).
     */
     SkScalar nextRangeScalar(SkScalar min, SkScalar max) {
         return this->nextUScalar1() * (max - min) + min;
     }
     /** Return the next pseudo random number expressed as a SkScalar
         in the range (-SK_Scalar1..SK_Scalar1).
     */
     SkScalar nextSScalar1() { return SkFixedToScalar(this->nextSFixed1()); }
     /** Return the next pseudo random number as a bool.
     */
     bool nextBool() { return this->nextU() >= 0x80000000; }
     /** A biased version of nextBool().
      */
     bool nextBiasedBool(SkScalar fractionTrue) {
         SkASSERT(fractionTrue >= 0 && fractionTrue <= SK_Scalar1);
         return this->nextUScalar1() <= fractionTrue;
     }
     /**
      *  Return the next pseudo random number as a signed 64bit value.
      */
     int64_t next64() {
         int64_t hi = this->nextS();
         return (hi << 32) | this->nextU();
     }
     /**
      *  Return the current seed. This allows the caller to later reset to the
      *  same seed (using setSeed) so it can generate the same sequence.
      */
     int32_t getSeed() const { return fSeed; }
     /** Set the seed of the random object. The seed is initialized to 0 when the
         object is first created, and is updated each time the next pseudo random
         number is requested.
     */
     void setSeed(int32_t seed) { fSeed = (uint32_t)seed; }
 private:
     //  See "Numerical Recipes in C", 1992 page 284 for these constants
     enum {
         kMul = 1664525,
         kAdd = 1013904223
     };
     uint32_t fSeed;
 };
 /** \class SkRandom
  Utility class that implements pseudo random 32bit numbers using Marsaglia's
  multiply-with-carry "mother of all" algorithm. Unlike rand(), this class holds
  its own state, so that multiple instances can be used with no side-effects.
  Has a large period and all bits are well-randomized.
  */
 class SkRandom {
 public:
     SkRandom() { init(0); }
     SkRandom(uint32_t seed) { init(seed); }
     SkRandom(const SkRandom& rand) : fK(rand.fK), fJ(rand.fJ) {}
     SkRandom& operator=(const SkRandom& rand) {
         fK = rand.fK;
         fJ = rand.fJ;
         return *this;
     }
     /** Return the next pseudo random number as an unsigned 32bit value.
      */
     uint32_t nextU() {
         fK = kKMul*(fK & 0xffff) + (fK >> 16);
         fJ = kJMul*(fJ & 0xffff) + (fJ >> 16);
         return (((fK << 16) | (fK >> 16)) + fJ);
     }
     /** Return the next pseudo random number as a signed 32bit value.
      */
     int32_t nextS() { return (int32_t)this->nextU(); }
     /** Return the next pseudo random number as an unsigned 16bit value.
      */
     U16CPU nextU16() { return this->nextU() >> 16; }
     /** Return the next pseudo random number as a signed 16bit value.
      */
     S16CPU nextS16() { return this->nextS() >> 16; }
     /**
      *  Returns value [0...1) as an IEEE float
      */
     float nextF() {
         unsigned int floatint = 0x3f800000 | (this->nextU() >> 9);
         float f = SkBits2Float(floatint) - 1.0f;
         return f;
     }
     /**
      *  Returns value [min...max) as a float
      */
     float nextRangeF(float min, float max) {
         return min + this->nextF() * (max - min);
     }
     /** Return the next pseudo random number, as an unsigned value of
      at most bitCount bits.
      @param bitCount The maximum number of bits to be returned
      */
     uint32_t nextBits(unsigned bitCount) {
         SkASSERT(bitCount > 0 && bitCount <= 32);
         return this->nextU() >> (32 - bitCount);
     }
     /** Return the next pseudo random unsigned number, mapped to lie within
      [min, max] inclusive.
      */
     uint32_t nextRangeU(uint32_t min, uint32_t max) {
         SkASSERT(min <= max);
         uint32_t range = max - min + 1;
         if (0 == range) {
             return this->nextU();
         } else {
             return min + this->nextU() % range;
         }
     }
     /** Return the next pseudo random unsigned number, mapped to lie within
      [0, count).
      */
     uint32_t nextULessThan(uint32_t count) {
         SkASSERT(count > 0);
         return this->nextRangeU(0, count - 1);
     }
     /** Return the next pseudo random number expressed as an unsigned SkFixed
      in the range [0..SK_Fixed1).
      */
     SkFixed nextUFixed1() { return this->nextU() >> 16; }
     /** Return the next pseudo random number expressed as a signed SkFixed
      in the range (-SK_Fixed1..SK_Fixed1).
      */
     SkFixed nextSFixed1() { return this->nextS() >> 15; }
     /** Return the next pseudo random number expressed as a SkScalar
      in the range [0..SK_Scalar1).
      */
     SkScalar nextUScalar1() { return SkFixedToScalar(this->nextUFixed1()); }
     /** Return the next pseudo random number expressed as a SkScalar
      in the range [min..max).
      */
     SkScalar nextRangeScalar(SkScalar min, SkScalar max) {
         return this->nextUScalar1() * (max - min) + min;
     }
     /** Return the next pseudo random number expressed as a SkScalar
      in the range (-SK_Scalar1..SK_Scalar1).
      */
     SkScalar nextSScalar1() { return SkFixedToScalar(this->nextSFixed1()); }
     /** Return the next pseudo random number as a bool.
      */
     bool nextBool() { return this->nextU() >= 0x80000000; }
     /** A biased version of nextBool().
      */
     bool nextBiasedBool(SkScalar fractionTrue) {
         SkASSERT(fractionTrue >= 0 && fractionTrue <= SK_Scalar1);
         return this->nextUScalar1() <= fractionTrue;
     }
     /**
      *  Return the next pseudo random number as a signed 64bit value.
      */
     int64_t next64() {
         int64_t hi = this->nextS();
         return (hi << 32) | this->nextU();
     }
     /** Reset the random object.
      */
     void setSeed(uint32_t seed) { init(seed); }
 private:
     // Initialize state variables with LCG.
     // We must ensure that both J and K are non-zero, otherwise the
     // multiply-with-carry step will forevermore return zero.
     void init(uint32_t seed) {
         fK = NextLCG(seed);
         if (0 == fK) {
             fK = NextLCG(fK);
         }
         fJ = NextLCG(fK);
         if (0 == fJ) {
             fJ = NextLCG(fJ);
         }
         SkASSERT(0 != fK && 0 != fJ);
     }
     static uint32_t NextLCG(uint32_t seed) { return kMul*seed + kAdd; }
     //  See "Numerical Recipes in C", 1992 page 284 for these constants
     //  For the LCG that sets the initial state from a seed
     enum {
         kMul = 1664525,
         kAdd = 1013904223
     };
     // Constants for the multiply-with-carry steps
     enum {
         kKMul = 30345,
         kJMul = 18000,
     };
     uint32_t fK;
     uint32_t fJ;
 };
 #endif

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gfx/skia/trunk/include/utils/SkRandom.h@129ffea94266 (annotated)

gfx/skia/trunk/include/utils/SkRandom.h