love2d.love/src/modules/math/wrap_RandomGenerator.cpp

/**
 * Copyright (c) 2006-2013 LOVE Development Team
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 **/

#include "wrap_RandomGenerator.h"

#include <cmath>

namespace love
{
namespace math
{

uint64 luax_checkrandomseed(lua_State *L, int idx)
{
	union
	{
		double seed_double;
		uint64 seed_uint;
	} s;

	s.seed_double = luaL_checknumber(L, idx);

	return s.seed_uint;
}

int luax_getrandom(lua_State *L, int startidx, double r)
{
	int l, u;
	// from lua 5.1.4 source code: lmathlib.c:185 ff.
	switch (lua_gettop(L) - (startidx - 1))
	{
	case 0:
		lua_pushnumber(L, r);
		break;
	case 1:
		u = luaL_checkint(L, startidx);
		luaL_argcheck(L, 1 <= u, startidx, "interval is empty");
		lua_pushnumber(L, floor(r * u) + 1);
		break;
	case 2:
		l = luaL_checkint(L, startidx);
		u = luaL_checkint(L, startidx + 1);
		luaL_argcheck(L, l <= u, startidx + 1, "interval is empty");
		lua_pushnumber(L, floor(r * (u - l + 1)) + l);
		break;
	default:
		return luaL_error(L, "wrong number of arguments");
	}
	return 1;
}

RandomGenerator *luax_checkrandomgenerator(lua_State *L, int idx)
{
	return luax_checktype<RandomGenerator>(L, idx, "RandomGenerator", MATH_RANDOM_GENERATOR_T);
}

int w_RandomGenerator_randomseed(lua_State *L)
{
	RandomGenerator *rng = luax_checkrandomgenerator(L, 1);
	uint64 seed = luax_checkrandomseed(L, 2);
	rng->randomseed(seed);
	return 0;
}

int w_RandomGenerator_random(lua_State *L)
{
	RandomGenerator *rng = luax_checkrandomgenerator(L, 1);
	return luax_getrandom(L, 2, rng->random());
}

int w_RandomGenerator_randnormal(lua_State *L)
{
	RandomGenerator *rng = luax_checkrandomgenerator(L, 1);

	double mean = 0.0, stddev = 1.0;
	if (lua_gettop(L) > 2)
	{
		mean = luaL_checknumber(L, 2);
		stddev = luaL_checknumber(L, 3);
	}
	else
	{
		stddev = luaL_optnumber(L, 2, 1.0);
	}

	double r = rng->randnormal(stddev);
	lua_pushnumber(L, r + mean);
	return 1;
}

static const luaL_Reg functions[] =
{
	{ "randomseed", w_RandomGenerator_randomseed },
	{ "random", w_RandomGenerator_random },
	{ "randnormal", w_RandomGenerator_randnormal },
	{ 0, 0 }
};

extern "C" int luaopen_randomgenerator(lua_State *L)
{
	return luax_register_type(L, "RandomGenerator", functions);
}

} // math
} // love