1 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- 2 * 3 * ***** BEGIN LICENSE BLOCK ***** 4 * Version: MPL 1.1/GPL 2.0/LGPL 2.1 5 * 6 * The contents of this file are subject to the Mozilla Public License Version 7 * 1.1 (the "License"); you may not use this file except in compliance with 8 * the License. You may obtain a copy of the License at 9 * http://www.mozilla.org/MPL/ 10 * 11 * Software distributed under the License is distributed on an "AS IS" basis, 12 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License 13 * for the specific language governing rights and limitations under the 14 * License. 15 * 16 * The Original Code is Mozilla Communicator client code, released 17 * March 31, 1998. 18 * 19 * The Initial Developer of the Original Code is 20 * Sun Microsystems, Inc. 21 * Portions created by the Initial Developer are Copyright (C) 1998 22 * the Initial Developer. All Rights Reserved. 23 * 24 * Contributor(s): 25 * 26 * Alternatively, the contents of this file may be used under the terms of 27 * either of the GNU General Public License Version 2 or later (the "GPL"), 28 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), 29 * in which case the provisions of the GPL or the LGPL are applicable instead 30 * of those above. If you wish to allow use of your version of this file only 31 * under the terms of either the GPL or the LGPL, and not to allow others to 32 * use your version of this file under the terms of the MPL, indicate your 33 * decision by deleting the provisions above and replace them with the notice 34 * and other provisions required by the GPL or the LGPL. If you do not delete 35 * the provisions above, a recipient may use your version of this file under 36 * the terms of any one of the MPL, the GPL or the LGPL. 37 * 38 * ***** END LICENSE BLOCK ***** */ 39 40 /* @(#)s_scalbn.c 1.3 95/01/18 */ 41 /* 42 * ==================================================== 43 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 44 * 45 * Developed at SunSoft, a Sun Microsystems, Inc. business. 46 * Permission to use, copy, modify, and distribute this 47 * software is freely granted, provided that this notice 48 * is preserved. 49 * ==================================================== 50 */ 51 52 /* 53 * scalbn (double x, int n) 54 * scalbn(x,n) returns x* 2**n computed by exponent 55 * manipulation rather than by actually performing an 56 * exponentiation or a multiplication. 57 */ 58 59 #include "fdlibm.h" 60 61 #ifdef __STDC__ 62 static const double 63 #else 64 static double 65 #endif 66 two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ 67 twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ 68 really_big = 1.0e+300, 69 tiny = 1.0e-300; 70 71 #ifdef __STDC__ fd_scalbn(double x,int n)72 double fd_scalbn (double x, int n) 73 #else 74 double fd_scalbn (x,n) 75 double x; int n; 76 #endif 77 { 78 fd_twoints u; 79 int k,hx,lx; 80 u.d = x; 81 hx = __HI(u); 82 lx = __LO(u); 83 k = (hx&0x7ff00000)>>20; /* extract exponent */ 84 if (k==0) { /* 0 or subnormal x */ 85 if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ 86 x *= two54; 87 u.d = x; 88 hx = __HI(u); 89 k = ((hx&0x7ff00000)>>20) - 54; 90 if (n< -50000) return tiny*x; /*underflow*/ 91 } 92 if (k==0x7ff) return x+x; /* NaN or Inf */ 93 k = k+n; 94 if (k > 0x7fe) return really_big*fd_copysign(really_big,x); /* overflow */ 95 if (k > 0) /* normal result */ 96 {u.d = x; __HI(u) = (hx&0x800fffff)|(k<<20); x = u.d; return x;} 97 if (k <= -54) { 98 if (n > 50000) /* in case integer overflow in n+k */ 99 return really_big*fd_copysign(really_big,x); /*overflow*/ 100 else return tiny*fd_copysign(tiny,x); /*underflow*/ 101 } 102 k += 54; /* subnormal result */ 103 u.d = x; 104 __HI(u) = (hx&0x800fffff)|(k<<20); 105 x = u.d; 106 return x*twom54; 107 } 108