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_rand48.c revision 1.2 
      1 /*
      2  * Copyright (c) 1993 Martin Birgmeier
      3  * All rights reserved.
      4  *
      5  * You may redistribute unmodified or modified versions of this source
      6  * code provided that the above copyright notice and this and the
      7  * following conditions are retained.
      8  *
      9  * This software is provided ``as is'', and comes with no warranties
     10  * of any kind. I shall in no event be liable for anything that happens
     11  * to anyone/anything when using this software.
     12  */
     13 
     14 #include "rand48.h"
     15 
     16 unsigned short _rand48_seed[3] = {
     17 	RAND48_SEED_0,
     18 	RAND48_SEED_1,
     19 	RAND48_SEED_2
     20 };
     21 unsigned short _rand48_mult[3] = {
     22 	RAND48_MULT_0,
     23 	RAND48_MULT_1,
     24 	RAND48_MULT_2
     25 };
     26 unsigned short _rand48_add = RAND48_ADD;
     27 
     28 void
     29 __dorand48(unsigned short xseed[3])
     30 {
     31 	unsigned long accu;
     32 	unsigned short temp[2];
     33 
     34 	accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] +
     35 	 (unsigned long) _rand48_add;
     36 	temp[0] = (unsigned short) accu;	/* lower 16 bits */
     37 	accu >>= sizeof(unsigned short) * 8;
     38 	accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] +
     39 	 (unsigned long) _rand48_mult[1] * (unsigned long) xseed[0];
     40 	temp[1] = (unsigned short) accu;	/* middle 16 bits */
     41 	accu >>= sizeof(unsigned short) * 8;
     42 	accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0];
     43 	xseed[0] = temp[0];
     44 	xseed[1] = temp[1];
     45 	xseed[2] = (unsigned short) accu;
     46 }
     47