1b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project 2b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project/* @(#)s_scalbn.c 1.3 95/01/18 */ 3b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project/* 4b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * ==================================================== 5b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * 7b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * Developed at SunSoft, a Sun Microsystems, Inc. business. 8b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * Permission to use, copy, modify, and distribute this 9b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * software is freely granted, provided that this notice 10b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * is preserved. 11b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * ==================================================== 12b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project */ 13b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project 14b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project/* 15b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * ieee_scalbn (double x, int n) 16b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * ieee_scalbn(x,n) returns x* 2**n computed by exponent 17b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * manipulation rather than by actually performing an 18b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project * exponentiation or a multiplication. 19b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project */ 20b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project 21b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#include "fdlibm.h" 22b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project 23b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#ifdef __STDC__ 24b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Projectstatic const double 25b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#else 26b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Projectstatic double 27b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#endif 28b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Projecttwo54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ 29b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Projecttwom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ 30b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Projecthuge = 1.0e+300, 31b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Projecttiny = 1.0e-300; 32b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project 33b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#ifdef __STDC__ 34b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project double ieee_scalbn (double x, int n) 35b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#else 36b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project double ieee_scalbn (x,n) 37b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project double x; int n; 38b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project#endif 39b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project{ 40b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project int k,hx,lx; 41b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project hx = __HI(x); 42b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project lx = __LO(x); 43b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project k = (hx&0x7ff00000)>>20; /* extract exponent */ 44b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (k==0) { /* 0 or subnormal x */ 45b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ 46b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project x *= two54; 47b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project hx = __HI(x); 48b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project k = ((hx&0x7ff00000)>>20) - 54; 49b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (n< -50000) return tiny*x; /*underflow*/ 50b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project } 51b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (k==0x7ff) return x+x; /* NaN or Inf */ 52b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project k = k+n; 53b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (k > 0x7fe) return huge*ieee_copysign(huge,x); /* overflow */ 54b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (k > 0) /* normal result */ 55b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project {__HI(x) = (hx&0x800fffff)|(k<<20); return x;} 56b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (k <= -54) 57b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project if (n > 50000) /* in case integer overflow in n+k */ 58b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project return huge*ieee_copysign(huge,x); /*overflow*/ 59b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project else return tiny*ieee_copysign(tiny,x); /*underflow*/ 60b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project k += 54; /* subnormal result */ 61b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project __HI(x) = (hx&0x800fffff)|(k<<20); 62b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project return x*twom54; 63b07e1d9fd8d9e4e03698e0bd9bf77154c5390326The Android Open Source Project} 64