src/port/rand.c

   1 /*
   2  * $PostgreSQL:$
   3  *
   4  *-------------------------------------------------------------------------
   5  *
   6  * rand.c
   7  *        Missing rand implementations for Win32
   8  *
   9  *-------------------------------------------------------------------------
  10  */
  11 #include "c.h"
  12
  13 /*
  14  * Copyright (c) 1993 Martin Birgmeier
  15  * All rights reserved.
  16  *
  17  * You may redistribute unmodified or modified versions of this source
  18  * code provided that the above copyright notice and this and the
  19  * following conditions are retained.
  20  *
  21  * This software is provided ``as is'', and comes with no warranties
  22  * of any kind. I shall in no event be liable for anything that happens
  23  * to anyone/anything when using this software.
  24  */
  25 #define RAND48_SEED_0   (0x330e)
  26 #define RAND48_SEED_1   (0xabcd)
  27 #define RAND48_SEED_2   (0x1234)
  28 #define RAND48_MULT_0   (0xe66d)
  29 #define RAND48_MULT_1   (0xdeec)
  30 #define RAND48_MULT_2   (0x0005)
  31 #define RAND48_ADD              (0x000b)
  32
  33 unsigned short _rand48_seed[3] = {
  34         RAND48_SEED_0,
  35         RAND48_SEED_1,
  36         RAND48_SEED_2
  37 };
  38 unsigned short _rand48_mult[3] = {
  39         RAND48_MULT_0,
  40         RAND48_MULT_1,
  41         RAND48_MULT_2
  42 };
  43 unsigned short _rand48_add = RAND48_ADD;
  44
  45 static void
  46 _dorand48(unsigned short xseed[3])
  47 {
  48         unsigned long accu;
  49         unsigned short temp[2];
  50
  51         accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] +
  52                 (unsigned long) _rand48_add;
  53         temp[0] = (unsigned short) accu;        /* lower 16 bits */
  54         accu >>= sizeof(unsigned short) * 8;
  55         accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] +
  56                 (unsigned long) _rand48_mult[1] * (unsigned long) xseed[0];
  57         temp[1] = (unsigned short) accu;        /* middle 16 bits */
  58         accu >>= sizeof(unsigned short) * 8;
  59         accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0];
  60         xseed[0] = temp[0];
  61         xseed[1] = temp[1];
  62         xseed[2] = (unsigned short) accu;
  63 }
  64
  65 long
  66 lrand48(void)
  67 {
  68         _dorand48(_rand48_seed);
  69         return ((long) _rand48_seed[2] << 15) + ((long) _rand48_seed[1] >> 1);
  70 }
  71
  72 void
  73 srand48(long seed)
  74 {
  75         _rand48_seed[0] = RAND48_SEED_0;
  76         _rand48_seed[1] = (unsigned short) seed;
  77         _rand48_seed[2] = (unsigned short) (seed > 16);
  78         _rand48_mult[0] = RAND48_MULT_0;
  79         _rand48_mult[1] = RAND48_MULT_1;
  80         _rand48_mult[2] = RAND48_MULT_2;
  81         _rand48_add = RAND48_ADD;
  82 }