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[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [math/] [s_ilogb.c] - Rev 1767
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/* @(#)s_ilogb.c 5.1 93/09/24 */ /* * ==================================================== * 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. * ==================================================== */ /* FUNCTION <<ilogb>>, <<ilogbf>>---get exponent of floating point number INDEX ilogb INDEX ilogbf ANSI_SYNOPSIS #include <math.h> int ilogb(double <[val]>); int ilogbf(float <[val]>); TRAD_SYNOPSIS #include <math.h> int ilogb(<[val]>) double <[val]>; int ilogbf(<[val]>) float <[val]>; DESCRIPTION All non zero, normal numbers can be described as <[m]> * 2**<[p]>. <<ilogb>> and <<ilogbf>> examine the argument <[val]>, and return <[p]>. The functions <<frexp>> and <<frexpf>> are similar to <<ilogb>> and <<ilogbf>>, but also return <[m]>. RETURNS <<ilogb>> and <<ilogbf>> return the power of two used to form the floating point argument. If <[val]> is <<0>>, they return <<- INT_MAX>> (<<INT_MAX>> is defined in limits.h). If <[val]> is infinite, or NaN, they return <<INT_MAX>>. PORTABILITY Neither <<ilogb>> nor <<ilogbf>> is required by ANSI C or by the System V Interface Definition (Issue 2). */ /* ilogb(double x) * return the binary exponent of non-zero x * ilogb(0) = 0x80000001 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised) */ #include "fdlibm.h" #include <limits.h> #ifndef _DOUBLE_IS_32BITS #ifdef __STDC__ int ilogb(double x) #else int ilogb(x) double x; #endif { __int32_t hx,lx,ix; EXTRACT_WORDS(hx,lx,x); hx &= 0x7fffffff; if(hx<0x00100000) { if((hx|lx)==0) return - INT_MAX; /* ilogb(0) = 0x80000001 */ else /* subnormal x */ if(hx==0) { for (ix = -1043; lx>0; lx<<=1) ix -=1; } else { for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; } return ix; } else if (hx<0x7ff00000) return (hx>>20)-1023; else return INT_MAX; } #endif /* _DOUBLE_IS_32BITS */
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