contrib/gdtoa/strtodI.c

   1 /****************************************************************
   2
   3 The author of this software is David M. Gay.
   4
   5 Copyright (C) 1998, 2000 by Lucent Technologies
   6 All Rights Reserved
   7
   8 Permission to use, copy, modify, and distribute this software and
   9 its documentation for any purpose and without fee is hereby
  10 granted, provided that the above copyright notice appear in all
  11 copies and that both that the copyright notice and this
  12 permission notice and warranty disclaimer appear in supporting
  13 documentation, and that the name of Lucent or any of its entities
  14 not be used in advertising or publicity pertaining to
  15 distribution of the software without specific, written prior
  16 permission.
  17
  18 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  19 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
  20 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
  21 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  22 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
  23 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
  24 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
  25 THIS SOFTWARE.
  26
  27 ****************************************************************/
  28
  29 /* Please send bug reports to
  30         David M. Gay
  31         Bell Laboratories, Room 2C-463
  32         600 Mountain Avenue
  33         Murray Hill, NJ 07974-0636
  34         U.S.A.
  35         dmg@bell-labs.com
  36  */
  37
  38 #include "gdtoaimp.h"
  39
  40  static double
  41 #ifdef KR_headers
  42 ulpdown(d) double *d;
  43 #else
  44 ulpdown(double *d)
  45 #endif
  46 {
  47         double u;
  48         ULong *L = (ULong*)d;
  49
  50         u = ulp(*d);
  51         if (!(L[_1] | L[_0] & 0xfffff)
  52          && (L[_0] & 0x7ff00000) > 0x00100000)
  53                 u *= 0.5;
  54         return u;
  55         }
  56
  57  int
  58 #ifdef KR_headers
  59 strtodI(s, sp, dd) CONST char *s; char **sp; double *dd;
  60 #else
  61 strtodI(CONST char *s, char **sp, double *dd)
  62 #endif
  63 {
  64 #ifdef Sudden_Underflow
  65         static FPI fpi = { 53, 1-1023-53+1, 2046-1023-53+1, 1, 1 };
  66 #else
  67         static FPI fpi = { 53, 1-1023-53+1, 2046-1023-53+1, 1, 0 };
  68 #endif
  69         ULong bits[2], sign;
  70         Long exp;
  71         int j, k;
  72         typedef union {
  73                 double d[2];
  74                 ULong L[4];
  75                 } U;
  76         U *u;
  77
  78         k = strtodg(s, sp, &fpi, &exp, bits);
  79         u = (U*)dd;
  80         sign = k & STRTOG_Neg ? 0x80000000L : 0;
  81         switch(k & STRTOG_Retmask) {
  82           case STRTOG_NoNumber:
  83                 u->d[0] = u->d[1] = 0.;
  84                 break;
  85
  86           case STRTOG_Zero:
  87                 u->d[0] = u->d[1] = 0.;
  88 #ifdef Sudden_Underflow
  89                 if (k & STRTOG_Inexact) {
  90                         if (sign)
  91                                 u->L[_0] = 0x80100000L;
  92                         else
  93                                 u->L[2+_0] = 0x100000L;
  94                         }
  95                 break;
  96 #else
  97                 goto contain;
  98 #endif
  99
 100           case STRTOG_Denormal:
 101                 u->L[_1] = bits[0];
 102                 u->L[_0] = bits[1];
 103                 goto contain;
 104
 105           case STRTOG_Normal:
 106                 u->L[_1] = bits[0];
 107                 u->L[_0] = (bits[1] & ~0x100000) | ((exp + 0x3ff + 52) << 20);
 108           contain:
 109                 j = k & STRTOG_Inexact;
 110                 if (sign) {
 111                         u->L[_0] |= sign;
 112                         j = STRTOG_Inexact - j;
 113                         }
 114                 switch(j) {
 115                   case STRTOG_Inexlo:
 116 #ifdef Sudden_Underflow
 117                         if ((u->L[_0] & 0x7ff00000) < 0x3500000) {
 118                                 u->L[2+_0] = u->L[_0] + 0x3500000;
 119                                 u->L[2+_1] = u->L[_1];
 120                                 u->d[1] += ulp(u->d[1]);
 121                                 u->L[2+_0] -= 0x3500000;
 122                                 if (!(u->L[2+_0] & 0x7ff00000)) {
 123                                         u->L[2+_0] = sign;
 124                                         u->L[2+_1] = 0;
 125                                         }
 126                                 }
 127                         else
 128 #endif
 129                         u->d[1] = u->d[0] + ulp(u->d[0]);
 130                         break;
 131                   case STRTOG_Inexhi:
 132                         u->d[1] = u->d[0];
 133 #ifdef Sudden_Underflow
 134                         if ((u->L[_0] & 0x7ff00000) < 0x3500000) {
 135                                 u->L[_0] += 0x3500000;
 136                                 u->d[0] -= ulpdown(u->d);
 137                                 u->L[_0] -= 0x3500000;
 138                                 if (!(u->L[_0] & 0x7ff00000)) {
 139                                         u->L[_0] = sign;
 140                                         u->L[_1] = 0;
 141                                         }
 142                                 }
 143                         else
 144 #endif
 145                         u->d[0] -= ulpdown(u->d);
 146                         break;
 147                   default:
 148                         u->d[1] = u->d[0];
 149                   }
 150                 break;
 151
 152           case STRTOG_Infinite:
 153                 u->L[_0] = u->L[2+_0] = sign | 0x7ff00000;
 154                 u->L[_1] = u->L[2+_1] = 0;
 155                 if (k & STRTOG_Inexact) {
 156                         if (sign) {
 157                                 u->L[2+_0] = 0xffefffffL;
 158                                 u->L[2+_1] = 0xffffffffL;
 159                                 }
 160                         else {
 161                                 u->L[_0] = 0x7fefffffL;
 162                                 u->L[_1] = 0xffffffffL;
 163                                 }
 164                         }
 165                 break;
 166
 167           case STRTOG_NaN:
 168                 u->L[_0] = u->L[2+_0] = 0x7fffffff | sign;
 169                 u->L[_1] = u->L[2+_1] = (ULong)-1;
 170                 break;
 171
 172           case STRTOG_NaNbits:
 173                 u->L[_0] = u->L[2+_0] = 0x7ff00000 | sign | bits[1];
 174                 u->L[_1] = u->L[2+_1] = bits[0];
 175           }
 176         return k;
 177         }