s_scalbnf.c (1744B)
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 #ifndef lint 17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_scalbnf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 static const float 24 two25 = 3.355443200e+07, /* 0x4c000000 */ 25 twom25 = 2.9802322388e-08, /* 0x33000000 */ 26 huge = 1.0e+30, 27 tiny = 1.0e-30; 28 29 float 30 scalbnf (float x, int n) 31 { 32 int32_t k,ix; 33 GET_FLOAT_WORD(ix,x); 34 k = (ix&0x7f800000)>>23; /* extract exponent */ 35 if (k==0) { /* 0 or subnormal x */ 36 if ((ix&0x7fffffff)==0) return x; /* +-0 */ 37 x *= two25; 38 GET_FLOAT_WORD(ix,x); 39 k = ((ix&0x7f800000)>>23) - 25; 40 if (n< -50000) return tiny*x; /*underflow*/ 41 } 42 if (k==0xff) return x+x; /* NaN or Inf */ 43 k = k+n; 44 if (k > 0xfe) return huge*copysignf(huge,x); /* overflow */ 45 if (k > 0) /* normal result */ 46 {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;} 47 if (k <= -25) 48 if (n > 50000) /* in case integer overflow in n+k */ 49 return huge*copysignf(huge,x); /*overflow*/ 50 else return tiny*copysignf(tiny,x); /*underflow*/ 51 k += 25; /* subnormal result */ 52 SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); 53 return x*twom25; 54 }