SkRandom Class Reference

#include <SkRandom.h>

Public Member Functions
	SkRandom ()
	SkRandom (uint32_t seed)
	SkRandom (const SkRandom &rand)
SkRandom &	operator= (const SkRandom &rand)
uint32_t	nextU ()
int32_t	nextS ()
float	nextF ()
float	nextRangeF (float min, float max)
uint32_t	nextBits (unsigned bitCount)
uint32_t	nextRangeU (uint32_t min, uint32_t max)
uint32_t	nextULessThan (uint32_t count)
SkScalar	nextUScalar1 ()
SkScalar	nextRangeScalar (SkScalar min, SkScalar max)
SkScalar	nextSScalar1 ()
bool	nextBool ()
bool	nextBiasedBool (SkScalar fractionTrue)
void	setSeed (uint32_t seed)

Detailed Description

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.

Definition at line 27 of file SkRandom.h.

Constructor & Destructor Documentation

SkRandom() [1/3]

SkRandom::SkRandom ( )

inline

Definition at line 29 of file SkRandom.h.

{ init(0); }

SkRandom() [2/3]

SkRandom::SkRandom ( uint32_t  seed )

inline

Definition at line 30 of file SkRandom.h.

{ init(seed); }

SkRandom() [3/3]

SkRandom::SkRandom ( const SkRandom &  rand )

inline

Definition at line 31 of file SkRandom.h.

: fK(rand.fK), fJ(rand.fJ) {}

Member Function Documentation

nextBiasedBool()

bool SkRandom::nextBiasedBool ( SkScalar  fractionTrue )

inline

A biased version of nextBool().

Definition at line 121 of file SkRandom.h.

                                               {
        SkASSERT(fractionTrue >= 0 && fractionTrue <= 1);
        return this->nextUScalar1() <= fractionTrue;
    }

nextBits()

uint32_t SkRandom::nextBits ( unsigned  bitCount )

inline

Return the next pseudo random number, as an unsigned value of at most bitCount bits.

Parameters

bitCount

The maximum number of bits to be returned

Definition at line 72 of file SkRandom.h.

                                         {
        SkASSERT(bitCount > 0 && bitCount <= 32);
        return this->nextU() >> (32 - bitCount);
    }

nextBool()

bool SkRandom::nextBool ( )

inline

Return the next pseudo random number as a bool.

Definition at line 117 of file SkRandom.h.

{ return this->nextU() >= 0x80000000; }

nextF()

float SkRandom::nextF ( )

inline

Returns value [0...1) as an IEEE float

Definition at line 55 of file SkRandom.h.

                  {
        uint32_t floatint = 0x3f800000 | (this->nextU() >> 9);
        float f = SkBits2Float(floatint) - 1.0f;
        return f;
    }

nextRangeF()

float SkRandom::nextRangeF ( float  min, float  max  )

inline

Returns value [min...max) as a float

Definition at line 64 of file SkRandom.h.

                                           {
        return min + this->nextF() * (max - min);
    }

nextRangeScalar()

SkScalar SkRandom::nextRangeScalar ( SkScalar  min, SkScalar  max  )

inline

Return the next pseudo random number expressed as a SkScalar in the range [min..max).

Definition at line 106 of file SkRandom.h.

                                                         {
        return this->nextUScalar1() * (max - min) + min;
    }

nextRangeU()

uint32_t SkRandom::nextRangeU ( uint32_t  min, uint32_t  max  )

inline

Return the next pseudo random unsigned number, mapped to lie within [min, max] inclusive.

Definition at line 80 of file SkRandom.h.

                                                    {
        SkASSERT(min <= max);
        uint32_t range = max - min + 1;
        if (0 == range) {
            return this->nextU();
        } else {
            return min + this->nextU() % range;
        }
    }

nextS()

int32_t SkRandom::nextS ( )

inline

Return the next pseudo random number as a signed 32bit value.

Definition at line 50 of file SkRandom.h.

{ return (int32_t)this->nextU(); }

nextSScalar1()

SkScalar SkRandom::nextSScalar1 ( )

inline

Return the next pseudo random number expressed as a SkScalar in the range [-SK_Scalar1..SK_Scalar1).

Definition at line 113 of file SkRandom.h.

{ return SkFixedToScalar(this->nextSFixed1()); }

nextU()

uint32_t SkRandom::nextU ( )

inline

Return the next pseudo random number as an unsigned 32bit value.

Definition at line 42 of file SkRandom.h.

                     {
        fK = kKMul*(fK & 0xffff) + (fK >> 16);
        fJ = kJMul*(fJ & 0xffff) + (fJ >> 16);
        return (((fK << 16) | (fK >> 16)) + fJ);
    }

nextULessThan()

uint32_t SkRandom::nextULessThan ( uint32_t  count )

inline

Return the next pseudo random unsigned number, mapped to lie within [0, count).

Definition at line 93 of file SkRandom.h.

                                           {
        SkASSERT(count > 0);
        return this->nextRangeU(0, count - 1);
    }

nextUScalar1()

SkScalar SkRandom::nextUScalar1 ( )

inline

Return the next pseudo random number expressed as a SkScalar in the range [0..SK_Scalar1).

Definition at line 101 of file SkRandom.h.

{ return SkFixedToScalar(this->nextUFixed1()); }

operator=()

SkRandom & SkRandom::operator= ( const SkRandom &  rand )

inline

Definition at line 33 of file SkRandom.h.

                                              {
        fK = rand.fK;
        fJ = rand.fJ;
 
        return *this;
    }

setSeed()

void SkRandom::setSeed ( uint32_t  seed )

inline

Reset the random object.

Definition at line 128 of file SkRandom.h.

{ init(seed); }

---

The documentation for this class was generated from the following file:

• third_party/skia/src/base/SkRandom.h