| /* 2009 for Newlib: Sun's sf_ilogb.c converted to be sf_logb.c. */ |
| /* |
| * ==================================================== |
| * 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. |
| * ==================================================== |
| */ |
| |
| /* float logb(float x) |
| * return the binary exponent of non-zero x |
| * logbf(0) = -inf, raise divide-by-zero floating point exception |
| * logbf(+inf|-inf) = +inf (no signal is raised) |
| * logbf(NaN) = NaN (no signal is raised) |
| * Per C99 recommendation, a NaN argument is returned unchanged. |
| */ |
| |
| #include "fdlibm.h" |
| |
| float |
| #ifdef __STDC__ |
| logbf(float x) |
| #else |
| logbf(x) |
| float x; |
| #endif |
| { |
| __int32_t hx,ix; |
| |
| GET_FLOAT_WORD(hx,x); |
| hx &= 0x7fffffff; |
| if(FLT_UWORD_IS_ZERO(hx)) { |
| float xx; |
| /* arg==0: return -inf and raise divide-by-zero exception */ |
| SET_FLOAT_WORD(xx,hx); /* +0.0 */ |
| return -1./xx; /* logbf(0) = -inf */ |
| } |
| if(FLT_UWORD_IS_SUBNORMAL(hx)) { |
| for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1; |
| return (float) ix; |
| } |
| else if (FLT_UWORD_IS_INFINITE(hx)) return HUGE_VALF; /* x==+|-inf */ |
| else if (FLT_UWORD_IS_NAN(hx)) return x; |
| else return (float) ((hx>>23)-127); |
| } |
| |
| #ifdef _DOUBLE_IS_32BITS |
| |
| #ifdef __STDC__ |
| double logb(double x) |
| #else |
| double logb(x) |
| double x; |
| #endif |
| { |
| return (double) logbf((float) x); |
| } |
| |
| #endif /* defined(_DOUBLE_IS_32BITS) */ |