s_isinf.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/*
 * isinf(x) returns 1 if x is infinity, else 0;
 * no branching!
 * Added by Cygnus Support.
 */

#include "fdlibm.h"

#ifdef __STDC__
	int isinf(double x)
#else
	int isinf(x)
	double x;
#endif
{
#ifndef _DOUBLE_IS_32BITS
	__int32_t hx,lx;
	EXTRACT_WORDS(hx,lx,x);
	hx &= 0x7fffffff;
	hx |= (__uint32_t)(lx|(-lx))>>31;	
	hx = 0x7ff00000 - hx;
	return 1 - (int)((__uint32_t)(hx|(-hx))>>31);
#else /* defined (_DOUBLE_IS_32BITS) */
	return isinff ((float) x);
#endif /* defined (_DOUBLE_IS_32BITS) */
}