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Diffstat (limited to 'src/math/s_ilogb.c')
-rw-r--r-- | src/math/s_ilogb.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/src/math/s_ilogb.c b/src/math/s_ilogb.c new file mode 100644 index 0000000..f1ac498 --- /dev/null +++ b/src/math/s_ilogb.c @@ -0,0 +1,45 @@ +/* @(#)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. + * ==================================================== + */ + +/* ilogb(double x) + * return the binary exponent of non-zero x + * ilogb(0) = FP_ILOGB0 + * ilogb(NaN) = FP_ILOGBNAN (no signal is raised) + * ilogb(inf) = INT_MAX (no signal is raised) + */ + +#include <limits.h> + +#include <math.h> +#include "math_private.h" + +int ilogb(double x) +{ + int32_t hx,lx,ix; + + EXTRACT_WORDS(hx,lx,x); + hx &= 0x7fffffff; + if(hx<0x00100000) { + if((hx|lx)==0) + return FP_ILOGB0; + 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 if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN; + else return INT_MAX; +} |