Category : C Source Code
Archive   : CM3.ZIP
Filename : LRANDOM.C

/* ================ Random Number Generator from BSD ======================= */

/*
* Copyright (c) 1983 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that: (1) source distributions retain this entire copyright
* notice and comment, and (2) distributions including binaries display
* the following acknowledgement: ``This product includes software
* developed by the University of California, Berkeley and its contributors''
* in the documentation or other materials provided with the distribution
* and in all advertising materials mentioning features or use of this
* software. Neither the name of the University nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

static long randtbl[32] = { 0L,
0x9a319039L, 0x32d9c024L, 0x9b663182L, 0x5da1f342L,
0xde3b81e0L, 0xdf0a6fb5L, 0xf103bc02L, 0x48f340fbL,
0x7449e56bL, 0xbeb1dbb0L, 0xab5c5918L, 0x946554fdL,
0x8c2e680fL, 0xeb3d799fL, 0xb11ee0b7L, 0x2d436b86L,
0xda672e2aL, 0x1588ca88L, 0xe369735dL, 0x904f35f7L,
0xd7158fd6L, 0x6fa6f051L, 0x616e6b96L, 0xac94efdcL,
0x36413f93L, 0xc622c298L, 0xf5a42ab8L, 0x8a88d77bL,
0xf5ad9d0eL, 0x8999220bL, 0x27fb47b9L
};

static long *fptr = &randtbl[4];
static long *rptr = &randtbl[1];
static long *state = &randtbl[1];
static long *end_ptr = &randtbl[32];
/*
* Returns a really good 31-bit random number.
*/
static long
lrandom()
{
long i;

*fptr += *rptr;
i = (*fptr >> 1) & 0x7fffffffUL; /* chucking least random bit */
if(++fptr >= end_ptr)
{
fptr = state;
++rptr;
}
else
{
if(++rptr >= end_ptr)
rptr = state;
}
return( i );
}
/* ========================= END Random Number Generator ==================== */