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/* Copyright (C) 1994 W. Schelter
This file is part of GNU Common Lisp, herein referred to as GCL
GCL is free software; you can redistribute it and/or modify it under
the terms of the GNU LIBRARY GENERAL PUBLIC LICENSE as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GCL is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU library general public
license along with GCL; see the file COPYING. If not, write to the
Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
ulong low,divisor,h,q;
if divisor!= 0 and if (hiremainder:low)/divisor (ie q)
is expressible in 32 bits,
then
(h = hiremainder, q = divll(low,divisor),
h:low == q * divisor + hiremainder && 0<= hiremainder && hiremainder < divisor)
is TRUE.
[the arithmetic is ordinary arithmetic among unsigned 64 bit integers]
A sufficient criteria for (hiremainder:low)/divisor
to be expressible in 32 bits,
is bfffo(divisor)-bfffo(hiremainder) <= 0
*/
#include "include.h"
#include "arith.h"
#define WORD_SIZE 32
/* SHIFT1BIT: shift h and l left by 1 as 64 bits. We don't care what
is coming into the bottom word */
#define shift1bit(h,l) \
l = (h = h << 1, ( l & (1<<(WORD_SIZE -1)) ? h +=1 : 0), l<<1)
ulong
divul3(x,y,hi)
ulong x,y,*hi;
{ulong q =0;
ulong h = *hi,l=x,hibit;
int count = WORD_SIZE;
/* if (y<=h) printf("error: the quotient will be more than 32 bits"); */
#ifdef QUICK_DIV
QUICK_DIV(x,y,h,hi)
#endif
do { q = q << 1;
hibit = h & (1 << (WORD_SIZE -1));
shift1bit(h,l);
if (hibit || (y <= h))
{ q += 1; h -= y;}
} while(--count > 0);
*hi = h;
return q;
}
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