Retro68/gcc/libphobos/libdruntime/rt/util/random.d
Wolfgang Thaller 6fbf4226da gcc-9.1
2019-06-20 20:10:10 +02:00

52 lines
954 B
D

/**
* Random number generators for internal usage.
*
* Copyright: Copyright Digital Mars 2014.
* License: $(WEB www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
*/
module rt.util.random;
struct Rand48
{
private ulong rng_state;
@safe @nogc nothrow:
void defaultSeed()
{
import ctime = core.stdc.time : time;
seed(cast(uint)ctime.time(null));
}
pure:
void seed(uint seedval)
{
assert(seedval);
rng_state = cast(ulong)seedval << 16 | 0x330e;
popFront();
}
auto opCall()
{
auto result = front;
popFront();
return result;
}
@property uint front()
{
return cast(uint)(rng_state >> 16);
}
void popFront()
{
immutable ulong a = 25214903917;
immutable ulong c = 11;
immutable ulong m_mask = (1uL << 48uL) - 1;
rng_state = (a*rng_state+c) & m_mask;
}
enum empty = false;
}