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random.c

/*
 * Copyright (c) 1993 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the Computer Systems
 *    Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * LBL random number generator.
 *
 * Written by Steve McCanne & Chris Torek (mccanne@ee.lbl.gov,
 * torek@ee.lbl.gov), November, 1992.
 *
 * This implementation is based on ``Two Fast Implementations of
 * the "Minimal Standard" Random Number Generator", David G. Carta,
 * Communications of the ACM, Jan 1990, Vol 33 No 1.
 */

static int randseed = 1;

void
srandom(int seed)
{
      randseed = seed;
}

#ifdef sparc
#ifdef __svr4__
#define RANDOM "random"
#define RANDSEED "randseed"
#else
#define RANDOM "_random"
#define RANDSEED "_randseed"
#endif
asm("\
      .global     " RANDOM "              ;\
" RANDOM ":                         ;\
      sethi %hi(16807), %o1               ;\
      wr    %o1, %lo(16807), %y           ;\
       sethi      %hi(" RANDSEED "), %g1        ;\
       ld   [%g1 + %lo(" RANDSEED ")], %o0      ;\
       andcc      %g0, 0, %o2             ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %o0, %o2               ;\
      mulscc  %o2, %g0, %o2               ;\
      rd    %y, %o3                       ;\
      srl   %o2, 16, %o1                  ;\
      set   0xffff, %o4             ;\
      and   %o4, %o2, %o0                 ;\
      sll   %o0, 15, %o0                  ;\
      srl   %o3, 17, %o3                  ;\
      or    %o3, %o0, %o0                 ;\
      addcc %o0, %o1, %o0                 ;\
      bneg  1f                      ;\
       sethi      %hi(0x7fffffff), %o1          ;\
      retl                          ;\
       st   %o0, [%g1 + %lo(" RANDSEED ")]      ;\
1:                                  ;\
      or    %o1, %lo(0x7fffffff), %o1     ;\
      add   %o0, 1, %o0             ;\
      and   %o1, %o0, %o0                 ;\
      retl                          ;\
       st   %o0, [%g1 + %lo(" RANDSEED ")] ");
#else
int
random()
{
      register int x = randseed;
      register int hi, lo, t;

      hi = x / 127773;
      lo = x % 127773;
      t = 16807 * lo - 2836 * hi;
      if (t <= 0)
            t += 0x7fffffff;
      randseed = t;
      return (t);
}
#endif

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