1 /* s_scalbnf.c -- float version of s_scalbn.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5 /* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16 #include <sys/cdefs.h> 17 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: s_scalbnf.c,v 1.9 2010/04/23 19:17:07 drochner Exp $"); 19 #endif 20 21 #include "namespace.h" 22 #include "math.h" 23 #include "math_private.h" 24 25 #ifdef __weak_alias 26 __weak_alias(scalbnf, _scalbnf) 27 #endif 28 29 static const float 30 two25 = 3.355443200e+07, /* 0x4c000000 */ 31 twom25 = 2.9802322388e-08, /* 0x33000000 */ 32 huge = 1.0e+30, 33 tiny = 1.0e-30; 34 35 float 36 scalbnf(float x, int n) 37 { 38 int32_t k,ix; 39 GET_FLOAT_WORD(ix,x); 40 k = (ix&0x7f800000)>>23; /* extract exponent */ 41 if (k==0) { /* 0 or subnormal x */ 42 if ((ix&0x7fffffff)==0) return x; /* +-0 */ 43 x *= two25; 44 GET_FLOAT_WORD(ix,x); 45 k = ((ix&0x7f800000)>>23) - 25; 46 if (n< -50000) return tiny*x; /*underflow*/ 47 } 48 if (k==0xff) return x+x; /* NaN or Inf */ 49 k = k+n; 50 if (k > 0xfe) return huge*copysignf(huge,x); /* overflow */ 51 if (k > 0) /* normal result */ 52 {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;} 53 if (k <= -25) { 54 if (n > 50000) /* in case integer overflow in n+k */ 55 return huge*copysignf(huge,x); /*overflow*/ 56 else return tiny*copysignf(tiny,x); /*underflow*/ 57 } 58 k += 25; /* subnormal result */ 59 SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); 60 return x*twom25; 61 } 62