wf_log.c

Newlib 嵌入式 C库 标准实现代码

/* wf_log.c -- float version of w_log.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.
 * ====================================================
 */

/*
 * wrapper logf(x)
 */

#include "fdlibm.h"
#include <errno.h>

#ifdef __STDC__
	float logf(float x)		/* wrapper logf */
#else
	float logf(x)			/* wrapper logf */
	float x;
#endif
{
#ifdef _IEEE_LIBM
	return __ieee754_logf(x);
#else
	float z;
	struct exception exc;
	z = __ieee754_logf(x);
	if(_LIB_VERSION == _IEEE_ || isnanf(x) || x > (float)0.0) return z;
#ifndef HUGE_VAL 
#define HUGE_VAL inf
	double inf = 0.0;

	SET_HIGH_WORD(inf,0x7ff00000);	/* set inf to infinite */
#endif
	exc.name = "logf";
	exc.err = 0;
	exc.arg1 = exc.arg2 = (double)x;
	if (_LIB_VERSION == _SVID_)
           exc.retval = -HUGE;
	else
	   exc.retval = -HUGE_VAL;
	if(x==(float)0.0) {
	    /* logf(0) */
	    exc.type = SING;
	    if (_LIB_VERSION == _POSIX_)
	       errno = ERANGE;
	    else if (!matherr(&exc)) {
	       errno = ERANGE;
	    }
	} else { 
	    /* logf(x<0) */
	    exc.type = DOMAIN;
	    if (_LIB_VERSION == _POSIX_)
	       errno = EDOM;
	    else if (!matherr(&exc)) {
	       errno = EDOM;
	    }
            exc.retval = nan("");
        }
	if (exc.err != 0)
           errno = exc.err;
        return (float)exc.retval; 
#endif
}

#ifdef _DOUBLE_IS_32BITS

#ifdef __STDC__
	double log(double x)
#else
	double log(x)
	double x;
#endif
{
	return (double) logf((float) x);
}

#endif /* defined(_DOUBLE_IS_32BITS) */