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 David M. Gay (dmg at acm dot org,
  30  * with " at " changed at "@" and " dot " changed to ".").      */
  31
  32 #include "gdtoaimp.h"
  33
  34  static double
  35 #ifdef KR_headers
  36 ulpdown(d) double *d;
  37 #else
  38 ulpdown(double *d)
  39 #endif
  40 {
  41         double u;
  42         ULong *L = (ULong*)d;
  43
  44         u = ulp(*d);
  45         if (!(L[_1] | L[_0] & 0xfffff)
  46          && (L[_0] & 0x7ff00000) > 0x00100000)
  47                 u *= 0.5;
  48         return u;
  49         }
  50
  51  int
  52 #ifdef KR_headers
  53 strtodI(s, sp, dd) CONST char *s; char **sp; double *dd;
  54 #else
  55 strtodI(CONST char *s, char **sp, double *dd)
  56 #endif
  57 {
  58         static FPI fpi = { 53, 1-1023-53+1, 2046-1023-53+1, 1, SI };
  59         ULong bits[2], sign;
  60         Long exp;
  61         int j, k;
  62         typedef union {
  63                 double d[2];
  64                 ULong L[4];
  65                 } U;
  66         U *u;
  67
  68         k = strtodg(s, sp, &fpi, &exp, bits);
  69         u = (U*)dd;
  70         sign = k & STRTOG_Neg ? 0x80000000L : 0;
  71         switch(k & STRTOG_Retmask) {
  72           case STRTOG_NoNumber:
  73                 u->d[0] = u->d[1] = 0.;
  74                 break;
  75
  76           case STRTOG_Zero:
  77                 u->d[0] = u->d[1] = 0.;
  78 #ifdef Sudden_Underflow
  79                 if (k & STRTOG_Inexact) {
  80                         if (sign)
  81                                 u->L[_0] = 0x80100000L;
  82                         else
  83                                 u->L[2+_0] = 0x100000L;
  84                         }
  85                 break;
  86 #else
  87                 goto contain;
  88 #endif
  89
  90           case STRTOG_Denormal:
  91                 u->L[_1] = bits[0];
  92                 u->L[_0] = bits[1];
  93                 goto contain;
  94
  95           case STRTOG_Normal:
  96                 u->L[_1] = bits[0];
  97                 u->L[_0] = (bits[1] & ~0x100000) | ((exp + 0x3ff + 52) << 20);
  98           contain:
  99                 j = k & STRTOG_Inexact;
 100                 if (sign) {
 101                         u->L[_0] |= sign;
 102                         j = STRTOG_Inexact - j;
 103                         }
 104                 switch(j) {
 105                   case STRTOG_Inexlo:
 106 #ifdef Sudden_Underflow
 107                         if ((u->L[_0] & 0x7ff00000) < 0x3500000) {
 108                                 u->L[2+_0] = u->L[_0] + 0x3500000;
 109                                 u->L[2+_1] = u->L[_1];
 110                                 u->d[1] += ulp(u->d[1]);
 111                                 u->L[2+_0] -= 0x3500000;
 112                                 if (!(u->L[2+_0] & 0x7ff00000)) {
 113                                         u->L[2+_0] = sign;
 114                                         u->L[2+_1] = 0;
 115                                         }
 116                                 }
 117                         else
 118 #endif
 119                         u->d[1] = u->d[0] + ulp(u->d[0]);
 120                         break;
 121                   case STRTOG_Inexhi:
 122                         u->d[1] = u->d[0];
 123 #ifdef Sudden_Underflow
 124                         if ((u->L[_0] & 0x7ff00000) < 0x3500000) {
 125                                 u->L[_0] += 0x3500000;
 126                                 u->d[0] -= ulpdown(u->d);
 127                                 u->L[_0] -= 0x3500000;
 128                                 if (!(u->L[_0] & 0x7ff00000)) {
 129                                         u->L[_0] = sign;
 130                                         u->L[_1] = 0;
 131                                         }
 132                                 }
 133                         else
 134 #endif
 135                         u->d[0] -= ulpdown(u->d);
 136                         break;
 137                   default:
 138                         u->d[1] = u->d[0];
 139                   }
 140                 break;
 141
 142           case STRTOG_Infinite:
 143                 u->L[_0] = u->L[2+_0] = sign | 0x7ff00000;
 144                 u->L[_1] = u->L[2+_1] = 0;
 145                 if (k & STRTOG_Inexact) {
 146                         if (sign) {
 147                                 u->L[2+_0] = 0xffefffffL;
 148                                 u->L[2+_1] = 0xffffffffL;
 149                                 }
 150                         else {
 151                                 u->L[_0] = 0x7fefffffL;
 152                                 u->L[_1] = 0xffffffffL;
 153                                 }
 154                         }
 155                 break;
 156
 157           case STRTOG_NaN:
 158                 u->L[0] = u->L[2] = d_QNAN0;
 159                 u->L[1] = u->L[3] = d_QNAN1;
 160                 break;
 161
 162           case STRTOG_NaNbits:
 163                 u->L[_0] = u->L[2+_0] = 0x7ff00000 | sign | bits[1];
 164                 u->L[_1] = u->L[2+_1] = bits[0];
 165           }
 166         return k;
 167         }