src/ptclib/random.cxx

   1 /*
   2  * random.cxx
   3  *
   4  * ISAAC random number generator by Bob Jenkins.
   5  *
   6  * Portable Windows Library
   7  *
   8  * Copyright (c) 1993-2001 Equivalence Pty. Ltd.
   9  *
  10  * The contents of this file are subject to the Mozilla Public License
  11  * Version 1.0 (the "License"); you may not use this file except in
  12  * compliance with the License. You may obtain a copy of the License at
  13  * http://www.mozilla.org/MPL/
  14  *
  15  * Software distributed under the License is distributed on an "AS IS"
  16  * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
  17  * the License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * The Original Code is Portable Windows Library.
  21  *
  22  * The Initial Developer of the Original Code is Equivalence Pty. Ltd.
  23  *
  24  * Contributor(s): ______________________________________.
  25  *
  26  * Based on code originally by Bob Jenkins.
  27  *
  28  * $Log$
  29  * Revision 1.5  2003/02/20 23:32:00  robertj
  30  * More RTEMS support patches, thanks Sebastian Meyer.
  31  *
  32  * Revision 1.4  2001/03/03 05:12:47  robertj
  33  * Fixed yet another transcription error of random number generator code.
  34  *
  35  * Revision 1.3  2001/02/28 04:27:35  robertj
  36  * Fixed stupid error in random number seeding, infinite loop.
  37  *
  38  * Revision 1.2  2001/02/27 03:33:44  robertj
  39  * Changed random number generator due to licensing issues.
  40  *
  41  * Revision 1.1  2000/02/17 12:05:02  robertj
  42  * Added better random number generator after finding major flaws in MSVCRT version.
  43  *
  44  */
  45
  46
  47 #ifdef __GNUC__
  48 #pragma implementation "random.h"
  49 #endif
  50
  51 #include <ptlib.h>
  52 #include <ptclib/random.h>
  53
  54
  55
  56 ///////////////////////////////////////////////////////////////////////////////
  57 // PRandom
  58
  59 PRandom::PRandom()
  60 {
  61   SetSeed((DWORD)(time(NULL)+clock()));
  62 }
  63
  64
  65 PRandom::PRandom(DWORD seed)
  66 {
  67   SetSeed(seed);
  68 }
  69
  70
  71 #define mix(a,b,c,d,e,f,g,h) \
  72 { \
  73    a^=b<<11; d+=a; b+=c; \
  74    b^=c>>2;  e+=b; c+=d; \
  75    c^=d<<8;  f+=c; d+=e; \
  76    d^=e>>16; g+=d; e+=f; \
  77    e^=f<<10; h+=e; f+=g; \
  78    f^=g>>4;  a+=f; g+=h; \
  79    g^=h<<8;  b+=g; h+=a; \
  80    h^=a>>9;  c+=h; a+=b; \
  81 }
  82
  83
  84 void PRandom::SetSeed(DWORD seed)
  85 {
  86    int i;
  87    DWORD a,b,c,d,e,f,g,h;
  88    DWORD *m,*r;
  89    randa = randb = randc = 0;
  90    m=randmem;
  91    r=randrsl;
  92
  93    for (i=0; i<RandSize; i++)
  94      r[i] = seed++;
  95
  96    a=b=c=d=e=f=g=h=0x9e3779b9;  /* the golden ratio */
  97
  98    for (i=0; i<4; ++i)          /* scramble it */
  99    {
 100      mix(a,b,c,d,e,f,g,h);
 101    }
 102
 103    /* initialize using the the seed */
 104    for (i=0; i<RandSize; i+=8)
 105    {
 106      a+=r[i  ]; b+=r[i+1]; c+=r[i+2]; d+=r[i+3];
 107      e+=r[i+4]; f+=r[i+5]; g+=r[i+6]; h+=r[i+7];
 108      mix(a,b,c,d,e,f,g,h);
 109      m[i  ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
 110      m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
 111    }
 112
 113    /* do a second pass to make all of the seed affect all of m */
 114    for (i=0; i<RandSize; i+=8)
 115    {
 116      a+=m[i  ]; b+=m[i+1]; c+=m[i+2]; d+=m[i+3];
 117      e+=m[i+4]; f+=m[i+5]; g+=m[i+6]; h+=m[i+7];
 118      mix(a,b,c,d,e,f,g,h);
 119      m[i  ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
 120      m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
 121    }
 122
 123    randcnt=0;
 124    Generate();            /* fill in the first set of results */
 125    randcnt=RandSize;  /* prepare to use the first set of results */
 126 }
 127
 128
 129 #define ind(mm,x)  (*(DWORD *)((BYTE *)(mm) + ((x) & ((RandSize-1)<<2))))
 130
 131 #define rngstep(mix,a,b,mm,m,m2,r,x) \
 132 { \
 133   x = *m;  \
 134   a = (a^(mix)) + *(m2++); \
 135   *(m++) = y = ind(mm,x) + a + b; \
 136   *(r++) = b = ind(mm,y>>RandBits) + x; \
 137 }
 138
 139 unsigned PRandom::Generate()
 140 {
 141   if (randcnt--)
 142     return randrsl[randcnt];
 143
 144   register DWORD a,b,x,y,*m,*mm,*m2,*r,*mend;
 145   mm=randmem; r=randrsl;
 146   a = randa; b = randb + (++randc);
 147   for (m = mm, mend = m2 = m+(RandSize/2); m<mend; )
 148   {
 149     rngstep( a<<13, a, b, mm, m, m2, r, x);
 150     rngstep( a>>6 , a, b, mm, m, m2, r, x);
 151     rngstep( a<<2 , a, b, mm, m, m2, r, x);
 152     rngstep( a>>16, a, b, mm, m, m2, r, x);
 153   }
 154   for (m2 = mm; m2<mend; )
 155   {
 156     rngstep( a<<13, a, b, mm, m, m2, r, x);
 157     rngstep( a>>6 , a, b, mm, m, m2, r, x);
 158     rngstep( a<<2 , a, b, mm, m, m2, r, x);
 159     rngstep( a>>16, a, b, mm, m, m2, r, x);
 160   }
 161   randb = b; randa = a;
 162
 163   randcnt = RandSize-1;
 164   return randrsl[randcnt];
 165 }
 166
 167
 168 #ifdef P_RTEMS
 169 static PMutex mutex;
 170 #endif
 171
 172 unsigned PRandom::Number()
 173 {
 174 #ifndef P_RTEMS
 175   static PMutex mutex;
 176 #endif
 177   PWaitAndSignal wait(mutex);
 178
 179   static PRandom rand;
 180   return rand;
 181 }
 182
 183
 184 // End Of File ///////////////////////////////////////////////////////////////