ludde@2073: #include "stdafx.h"
ludde@2073: #include "openttd.h"
ludde@2073: 
ludde@2073: #ifdef MERSENNE_TWISTER
ludde@2073: 
ludde@2073: // Source code for Mersenne Twister.
ludde@2073: // A Random number generator with much higher quality random numbers.
ludde@2073: 
ludde@2073: #define N              (624)                 // length of _mt_state vector
ludde@2073: #define M              (397)                 // a period parameter
ludde@2073: #define K              (0x9908B0DFU)         // a magic constant
ludde@2073: #define hiBit(u)       ((u) & 0x80000000U)   // mask all but highest   bit of u
ludde@2073: #define loBit(u)       ((u) & 0x00000001U)   // mask all but lowest    bit of u
ludde@2073: #define loBits(u)      ((u) & 0x7FFFFFFFU)   // mask     the highest   bit of u
ludde@2073: #define mixBits(u, v)  (hiBit(u)|loBits(v))  // move hi bit of u to hi bit of v
ludde@2073: 
ludde@2073: static uint32   _mt_state[N+1];     // _mt_state vector + 1 extra to not violate ANSI C
ludde@2073: static uint32   *_mt_next;          // _mt_next random value is computed from here
ludde@2073: static int      _mt_left = -1;      // can *_mt_next++ this many times before reloading
ludde@2073: 
ludde@2073: void SeedMT(uint32 seed)
ludde@2073: {
ludde@2073:     register uint32 x = (seed | 1U) & 0xFFFFFFFFU, *s = _mt_state;
ludde@2073:     register int    j;
ludde@2073: 
ludde@2073:     for(_mt_left=0, *s++=x, j=N; --j;
ludde@2073:         *s++ = (x*=69069U) & 0xFFFFFFFFU);
ludde@2073:  }
ludde@2073: 
ludde@2073: 
ludde@2073: static uint32 ReloadMT(void)
ludde@2073:  {
ludde@2073:     register uint32 *p0=_mt_state, *p2=_mt_state+2, *pM=_mt_state+M, s0, s1;
ludde@2073:     register int    j;
ludde@2073: 
ludde@2073:     if(_mt_left < -1)
ludde@2073:         SeedMT(4357U);
ludde@2073: 
ludde@2073:     _mt_left=N-1, _mt_next=_mt_state+1;
ludde@2073: 
ludde@2073:     for(s0=_mt_state[0], s1=_mt_state[1], j=N-M+1; --j; s0=s1, s1=*p2++)
ludde@2073:         *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
ludde@2073: 
ludde@2073:     for(pM=_mt_state, j=M; --j; s0=s1, s1=*p2++)
ludde@2073:         *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
ludde@2073: 
ludde@2073:     s1=_mt_state[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
ludde@2073:     s1 ^= (s1 >> 11);
ludde@2073:     s1 ^= (s1 <<  7) & 0x9D2C5680U;
ludde@2073:     s1 ^= (s1 << 15) & 0xEFC60000U;
ludde@2073:     return(s1 ^ (s1 >> 18));
ludde@2073:  }
ludde@2073: 
ludde@2073: 
ludde@2073: uint32 RandomMT(void)
ludde@2073: {
ludde@2073: 	uint32 y;
ludde@2073: 
ludde@2073: 	if(--_mt_left < 0)
ludde@2073: 		return ReloadMT();
ludde@2073: 
ludde@2073: 	y  = *_mt_next++;
ludde@2073: 	y ^= (y >> 11);
ludde@2073: 	y ^= (y <<  7) & 0x9D2C5680U;
ludde@2073: 	y ^= (y << 15) & 0xEFC60000U;
ludde@2073: 	return y ^ (y >> 18);
ludde@2073: }
ludde@2073: #else
ludde@2073: 
ludde@2073: void SeedMT(uint32 seed) {}
ludde@2073: 
ludde@2073: #endif