cpp/openttd-patchpack/source Files · mersenne.c

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peter1138

(svn r6455) - Feature: Add 2cc (two company colours) livery schemes. This replaces the original colour selection window and bumps the saveload version. Liveries are supported for all vehicles, not just those with 2cc support. Thanks to lakie for GUI inspiration.

/* $Id$ */

#include "stdafx.h"
#include "openttd.h"

#ifdef MERSENNE_TWISTER

// Source code for Mersenne Twister.
// A Random number generator with much higher quality random numbers.

#define N              (624)                 // length of _mt_state vector
#define M              (397)                 // a period parameter
#define K              (0x9908B0DFU)         // a magic constant
#define hiBit(u)       ((u) & 0x80000000U)   // mask all but highest   bit of u
#define loBit(u)       ((u) & 0x00000001U)   // mask all but lowest    bit of u
#define loBits(u)      ((u) & 0x7FFFFFFFU)   // mask     the highest   bit of u
#define mixBits(u, v)  (hiBit(u)|loBits(v))  // move hi bit of u to hi bit of v

static uint32   _mt_state[N+1];     // _mt_state vector + 1 extra to not violate ANSI C
static uint32   *_mt_next;          // _mt_next random value is computed from here
static int      _mt_left = -1;      // can *_mt_next++ this many times before reloading

void SeedMT(uint32 seed)
{
    register uint32 x = (seed | 1U) & 0xFFFFFFFFU, *s = _mt_state;
    register int    j;

    for (_mt_left=0, *s++=x, j=N; --j;
        *s++ = (x*=69069U) & 0xFFFFFFFFU);
 }


static uint32 ReloadMT(void)
 {
    register uint32 *p0=_mt_state, *p2=_mt_state+2, *pM=_mt_state+M, s0, s1;
    register int    j;

    if (_mt_left < -1)
        SeedMT(4357U);

    _mt_left=N-1, _mt_next=_mt_state+1;

    for (s0=_mt_state[0], s1=_mt_state[1], j=N-M+1; --j; s0=s1, s1=*p2++)
        *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);

    for (pM=_mt_state, j=M; --j; s0=s1, s1=*p2++)
        *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);

    s1=_mt_state[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
    s1 ^= (s1 >> 11);
    s1 ^= (s1 <<  7) & 0x9D2C5680U;
    s1 ^= (s1 << 15) & 0xEFC60000U;
    return(s1 ^ (s1 >> 18));
 }


uint32 RandomMT(void)
{
	uint32 y;

	if (--_mt_left < 0)
		return ReloadMT();

	y  = *_mt_next++;
	y ^= (y >> 11);
	y ^= (y <<  7) & 0x9D2C5680U;
	y ^= (y << 15) & 0xEFC60000U;
	return y ^ (y >> 18);
}
#else

void SeedMT(uint32 seed) {}

#endif /* MERSENNE_TWISTER */