xfdnorm.c

来自「C标准库源代码」· C语言 代码 · 共 41 行

/* _FDnorm function -- IEEE 754 version */
#include "wctype.h"
#include "xmath.h"
_STD_BEGIN

_CRTIMP2 short _FDnorm(unsigned short *ps)
	{	/* normalize float fraction */
	short xchar;
	unsigned short sign = ps[_F0] & _FSIGN;

	xchar = 1;
	if ((ps[_F0] &= _FFRAC) != 0 || ps[_F1])
		{	/* nonzero, scale */
		if (ps[_F0] == 0)
			ps[_F0] = ps[_F1], ps[_F1] = 0, xchar -= 16;
		for (; ps[_F0] < 1<<_FOFF; --xchar)
			{	/* shift left by 1 */
			ps[_F0] = ps[_F0] << 1 | ps[_F1] >> 15;
			ps[_F1] <<= 1;
			}
		for (; 1<<_FOFF+1 <= ps[_F0]; ++xchar)
			{	/* shift right by 1 */
			ps[_F1] = ps[_F1] >> 1 | ps[_F0] << 15;
			ps[_F0] >>= 1;
			}
		ps[_F0] &= _FFRAC;
		}
	ps[_F0] |= 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
 */