mirror of https://github.com/axmolengine/axmol.git
99 lines
3.1 KiB
C++
99 lines
3.1 KiB
C++
#ifndef _FAST_RNG_H__
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#define _FAST_RNG_H__
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#include <cmath>
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#include <limits.h>
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/** A fast more effective seeded random number generator struct, made by kiss rng.
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* It uses a simple algorithm to improve the speed of generating random numbers with a decent quality,
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* Use this if you're planning to generate large amounts of random numbers in a single frame.
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*
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* @since axmol-1.0.0b8
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*/
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struct FastRNG
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{
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const uint32_t RNG_RAND_MAX = std::numeric_limits<uint32_t>::max();
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uint32_t _x = 1;
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uint32_t _y = 2;
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uint32_t _z = 4;
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uint32_t _w = 8;
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uint32_t _carry = 0;
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uint32_t _k = 0;
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uint32_t _m = 0;
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uint64_t _seed = 0;
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FastRNG() { seed_rng((uint32_t)time(NULL)); }
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FastRNG(uint64_t seed) { seed_rng_64(seed); }
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// initialize this object with seed
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void seed_rng(uint64_t seed)
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{
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auto seed1 = static_cast<uint32_t>(seed);
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auto seed2 = static_cast<uint32_t>(seed >> 32);
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_seed = seed;
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_x = static_cast<int32_t>(seed1) | 1;
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_y = static_cast<int32_t>(seed2) | 2;
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_z = static_cast<int32_t>(seed1) | 4;
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_w = static_cast<int32_t>(seed2) | 8;
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_carry = 0;
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}
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// initialize this object with a uint64_t seed
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// DEPRECATED: use seed_rng instead
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void seed_rng_64(uint64_t seed) { seed_rng(seed); }
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// returns a random uint32_t value
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uint32_t rng()
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{
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_x = _x * 69069 + 12345;
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_y ^= _y << 13;
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_y ^= _y >> 17;
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_y ^= _y << 5;
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_k = (_z >> 2) + (_w >> 3) + (_carry >> 2);
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_m = _w + _w + _z + _carry;
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_z = _w;
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_w = _m;
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_carry = _k >> 30;
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return _x + _y + _w;
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}
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// returns a random integer from min to max
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int32_t range(int32_t min, int32_t max)
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{
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return static_cast<int32_t>(min + rng() / (RNG_RAND_MAX / (max - min)));
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}
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// returns a random unsigned integer from min to max
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uint32_t rangeu(uint32_t min, uint32_t max)
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{
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return static_cast<uint32_t>(min + rng() / (RNG_RAND_MAX / (max - min)));
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}
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// returns a random integer from 0 to max
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int32_t max(int32_t max = INT_MAX)
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{
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return static_cast<int32_t>(static_cast<float>(rng()) / static_cast<float>(RNG_RAND_MAX / (max - 0)));
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}
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// returns a random unsigned integer from 0 to max
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uint32_t maxu(uint32_t max = UINT_MAX) { return static_cast<uint32_t>(0 + rng() / (RNG_RAND_MAX / (max - 0))); }
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// returns a random float from min to max
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float rangef(float min = -1.0F, float max = 1.0F)
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{
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return min + static_cast<float>(rng()) / (static_cast<float>(RNG_RAND_MAX) / (max - min));
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}
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// returns a random float from 0.0 to max
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float maxf(float max) { return static_cast<float>(rng()) / (static_cast<float>(RNG_RAND_MAX) / (max - 0.0f)); }
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// returns a random float from 0.0 to 1.0
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float float01() { return static_cast<float>(rng()) / (static_cast<float>(RNG_RAND_MAX) / (1.0f - 0.0f)); }
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// returns either false or true randomly
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bool bool01() { return static_cast<bool>(rng() & 1); }
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};
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#endif // _FAST_RNG_H__
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