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fysx
144 lines
3.9 KiB
C++
144 lines
3.9 KiB
C++
/**
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* Copyright (c) 2006-2014 LOVE Development Team
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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**/
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#include "RandomGenerator.h"
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// C++
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#include <cmath>
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#include <sstream>
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#include <iomanip>
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// C
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#include <cstdlib>
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namespace love
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{
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namespace math
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{
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// 64 bit Xorshift implementation taken from the end of Sec. 3 (page 4) in
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// George Marsaglia, "Xorshift RNGs", Journal of Statistical Software, Vol.8 (Issue 14), 2003
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RandomGenerator::RandomGenerator()
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: last_randomnormal(std::numeric_limits<double>::infinity())
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{
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// because it is too big for some compilers to handle ... if you know what
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// i mean
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Seed newseed;
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newseed.b32.low = 0xCBBF7A44;
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newseed.b32.high = 0x0139408D;
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setSeed(newseed);
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}
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uint64 RandomGenerator::rand()
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{
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rng_state.b64 ^= (rng_state.b64 << 13);
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rng_state.b64 ^= (rng_state.b64 >> 7);
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rng_state.b64 ^= (rng_state.b64 << 17);
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return rng_state.b64;
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}
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// Box–Muller transform
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double RandomGenerator::randomNormal(double stddev)
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{
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// use cached number if possible
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if (last_randomnormal != std::numeric_limits<double>::infinity())
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{
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double r = last_randomnormal;
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last_randomnormal = std::numeric_limits<double>::infinity();
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return r * stddev;
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}
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double r = sqrt(-2.0 * log(1. - random()));
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double phi = 2.0 * LOVE_M_PI * (1. - random());
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last_randomnormal = r * cos(phi);
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return r * sin(phi) * stddev;
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}
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void RandomGenerator::setSeed(RandomGenerator::Seed newseed)
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{
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// 0 xor 0 is still 0, so Xorshift can't generate new numbers.
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if (newseed.b64 == 0)
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throw love::Exception("Invalid random seed.");
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seed = newseed;
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rng_state = seed;
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}
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RandomGenerator::Seed RandomGenerator::getSeed() const
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{
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return seed;
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}
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void RandomGenerator::setState(const std::string &statestr)
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{
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// For this implementation we'll accept a hex string representing the
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// 64-bit state integer xorshift uses.
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Seed state = {};
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// Hex string must start with 0x.
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if (statestr.find("0x") != 0 || statestr.size() < 3)
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throw love::Exception("Invalid random state.");
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// standardized strtoull (or 64 bit integer support for stringstream)
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// requires C++11's standard library, which we can't use yet.
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// I use strtol like this not because it's the best solution, but because
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// it's "good enough".
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// Convert the hex string to the state integer character-by-character.
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for (size_t i = 2; i < statestr.size(); i++)
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{
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char hex[2] = {statestr[i], 0};
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char *end = nullptr;
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// Convert the current hex character to a number.
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int nibble = strtol(hex, &end, 16);
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// Check if strtol failed to convert it.
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if (end != nullptr && *end != 0)
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throw love::Exception("Invalid random state.");
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state.b64 = (state.b64 << 4) + nibble;
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}
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rng_state = state;
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}
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std::string RandomGenerator::getState() const
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{
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// For this implementation we'll return a hex string representing the 64-bit
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// state integer xorshift uses.
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std::stringstream ss;
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ss << "0x";
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// Again with the stringstream not dealing with 64 bit integers...
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ss << std::setfill('0') << std::setw(8) << std::hex << rng_state.b32.high;
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ss << std::setfill('0') << std::setw(8) << std::hex << rng_state.b32.low;
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return ss.str();
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}
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} // math
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} // love
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