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Language/OS - Multiplatform Resource Library
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LANGUAGE OS.iso
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lisp
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kcl
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akcl
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akcl1615.lha
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mp
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mp_mulul3.c
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C/C++ Source or Header
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1991-02-12
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953b
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50 lines
#include "include.h"
#include "arith.h"
/* ulong a,b,y;
(y = mulul3(a,b,&hiremainder), hiremainder:y == a*b) is TRUE.
*/
#ifdef USE_WORD_MULUL3
int mulul3(x,y,hiremainder)
ulong x,y,*hiremainder;
{
ulong xlo,xhi,ylo,yhi;
ulong z; TEMPVARS
xlo=x&65535;xhi=x>>16;ylo=y&65535;yhi=y>>16;
z=addll(xlo*yhi,xhi*ylo);
*hiremainder=(overflow)?xhi*yhi+65536+(z>>16):xhi*yhi+(z>>16);
z=addll(xlo*ylo,(z<<16));*hiremainder+=overflow;
return z;
}
#else
ulong
mulul3(a,b,h)
unsigned int a,b, *h;
{unsigned int temph,templ,ah,al,i;
ah=0;
al=0;
/* in case the shift by 32 does not zero an unsigned int..
we separate out the first step.*/
{if (b & 1)
{temph=0;templ=a;
lladd(temph,templ,ah,al);}
/* printf("\n%d b=%d a=%d (%d:%d)",i,b,a,ah,al); */
b=b>>1;
}
i=1;
while(b)
{if (b & 1)
{llshift(a,i,temph,templ);
lladd(temph,templ,ah,al);}
i++;b=b>>1;
}
*h=ah;
return al;
}
#endif