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Tricks of the Windows Gam…ming Gurus (2nd Edition)
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Disc2.iso
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vc98
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crt
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src
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xdnorm.c
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1998-06-16
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/* _Dnorm function -- IEEE 754 version */
#include "wctype.h"
#include "xmath.h"
_STD_BEGIN
_CRTIMP2 short _Dnorm(unsigned short *ps)
{ /* normalize double fraction */
short xchar;
unsigned short sign = ps[_D0] & _DSIGN;
xchar = 1;
if ((ps[_D0] &= _DFRAC) != 0 || ps[_D1]
|| ps[_D2] || ps[_D3])
{ /* nonzero, scale */
for (; ps[_D0] == 0; xchar -= 16)
{ /* shift left by 16 */
ps[_D0] = ps[_D1], ps[_D1] = ps[_D2];
ps[_D2] = ps[_D3], ps[_D3] = 0;
}
for (; ps[_D0] < 1<<_DOFF; --xchar)
{ /* shift left by 1 */
ps[_D0] = ps[_D0] << 1 | ps[_D1] >> 15;
ps[_D1] = ps[_D1] << 1 | ps[_D2] >> 15;
ps[_D2] = ps[_D2] << 1 | ps[_D3] >> 15;
ps[_D3] <<= 1;
}
for (; 1<<_DOFF+1 <= ps[_D0]; ++xchar)
{ /* shift right by 1 */
ps[_D3] = ps[_D3] >> 1 | ps[_D2] << 15;
ps[_D2] = ps[_D2] >> 1 | ps[_D1] << 15;
ps[_D1] = ps[_D1] >> 1 | ps[_D0] << 15;
ps[_D0] >>= 1;
}
ps[_D0] &= _DFRAC;
}
ps[_D0] |= sign;
return (xchar);
}
_STD_END
/*
* Copyright (c) 1994 by P.J. Plauger. ALL RIGHTS RESERVED.
* Consult your license regarding permissions and restrictions.
*/
/*
941029 pjp: added _STD machinery
*/