mirror of https://github.com/axmolengine/axmol.git
111 lines
3.5 KiB
C++
111 lines
3.5 KiB
C++
/*
|
|
* Copyright (C) 2006 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
#ifndef SkRandom_DEFINED
|
|
#define SkRandom_DEFINED
|
|
|
|
#include "Sk64.h"
|
|
#include "SkScalar.h"
|
|
|
|
/** \class SkRandom
|
|
|
|
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 SkRandom {
|
|
public:
|
|
SkRandom() : fSeed(0) {}
|
|
SkRandom(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; }
|
|
|
|
/** 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);
|
|
return min + this->nextU() % (max - min + 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 (-SK_Scalar1..SK_Scalar1).
|
|
*/
|
|
SkScalar nextSScalar1() { return SkFixedToScalar(this->nextSFixed1()); }
|
|
|
|
/** Return the next pseudo random number as a signed 64bit value.
|
|
*/
|
|
void next64(Sk64* a) {
|
|
SkASSERT(a);
|
|
a->set(this->nextS(), this->nextU());
|
|
}
|
|
|
|
/** 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;
|
|
};
|
|
|
|
#endif
|
|
|