s_finitef.c

glibc 库, 不仅可以学习使用库函数,还可以学习函数的具体实现,是提高功力的好资料

/* s_finitef.c -- float version of s_finite.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, [e-mail].
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: s_finitef.c,v 1.4 1995/05/10 20:47:18 jtc Exp $";
#endif

/*
 * finitef(x) returns 1 is x is finite, else 0;
 * no branching!
 */

#include "math.h"
#include "math_private.h"

#ifdef __STDC__
	int __finitef(float x)
#else
	int __finitef(x)
	float x;
#endif
{
	int32_t ix;
	GET_FLOAT_WORD(ix,x);
	return (int)((u_int32_t)((ix&0x7fffffff)-0x7f800000)>>31);
}
hidden_def (__finitef)
weak_alias (__finitef, finitef)