1 /** 2 * Random number generators for internal usage. 3 * 4 * Copyright: Copyright Digital Mars 2014. 5 * License: $(WEB www.boost.org/LICENSE_1_0.txt, Boost License 1.0). 6 */ 7 module rt.util.random; 8 9 struct Rand48 10 { 11 private ulong rng_state; 12 13 @safe @nogc nothrow: 14 defaultSeedRand4815 void defaultSeed() 16 { 17 import ctime = core.stdc.time : time; 18 seed(cast(uint)ctime.time(null)); 19 } 20 21 pure: 22 seedRand4823 void seed(uint seedval) 24 { 25 assert(seedval); 26 rng_state = cast(ulong)seedval << 16 | 0x330e; 27 popFront(); 28 } 29 opCallRand4830 auto opCall() 31 { 32 auto result = front; 33 popFront(); 34 return result; 35 } 36 frontRand4837 @property uint front() 38 { 39 return cast(uint)(rng_state >> 16); 40 } 41 popFrontRand4842 void popFront() 43 { 44 immutable ulong a = 25214903917; 45 immutable ulong c = 11; 46 immutable ulong m_mask = (1uL << 48uL) - 1; 47 rng_state = (a*rng_state+c) & m_mask; 48 } 49 50 enum empty = false; 51 } 52