Lua Random Number Generation

lua_sfmt_random_number_generation.c with SFMT

// taken from http://snes9x-rr.googlecode.com/svn/trunk/snes9x-151/lua-engine.cpp
// http://snes9x-rr.googlecode.com/svn/trunk/snes9x-151/SFMT/SFMT.c

// same as math.random, but uses SFMT instead of C rand()
// FIXME: this function doesn't care multi-instance,
//        original math.random either though (Lua 5.1)
static int sfmt_random (lua_State *L) {
	lua_Number r = (lua_Number) genrand_real2();
	switch (lua_gettop(L)) {  // check number of arguments
		case 0: {  // no arguments
			lua_pushnumber(L, r);  // Number between 0 and 1
			break;
		}
		case 1: {  // only upper limit
			int u = luaL_checkint(L, 1);
			luaL_argcheck(L, 1<=u, 1, "interval is empty");
			lua_pushnumber(L, floor(r*u)+1);  // int between 1 and `u'
			break;
		}
		case 2: {  // lower and upper limits
			int l = luaL_checkint(L, 1);
			int u = luaL_checkint(L, 2);
			luaL_argcheck(L, l<=u, 2, "interval is empty");
			lua_pushnumber(L, floor(r*(u-l+1))+l);  // int between `l' and `u'
			break;
		}
		default: return luaL_error(L, "wrong number of arguments");
	}
	return 1;
}

// same as math.randomseed, but uses SFMT instead of C srand()
// FIXME: this function doesn't care multi-instance,
//        original math.randomseed either though (Lua 5.1)
static int sfmt_randomseed (lua_State *L) {
	init_gen_rand(luaL_checkint(L, 1));
	return 0;
}