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) U *d;
  37 #else
  38 ulpdown(U *d)
  39 #endif
  40 {
  41         double u;
  42         ULong *L = d->L;
  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         U *u;
  63
  64         k = strtodg(s, sp, &fpi, &exp, bits);
  65         u = (U*)dd;
  66         sign = k & STRTOG_Neg ? 0x80000000L : 0;
  67         switch(k & STRTOG_Retmask) {
  68           case STRTOG_NoNumber:
  69                 dval(&u[0]) = dval(&u[1]) = 0.;
  70                 break;
  71
  72           case STRTOG_Zero:
  73                 dval(&u[0]) = dval(&u[1]) = 0.;
  74 #ifdef Sudden_Underflow
  75                 if (k & STRTOG_Inexact) {
  76                         if (sign)
  77                                 word0(&u[0]) = 0x80100000L;
  78                         else
  79                                 word0(&u[1]) = 0x100000L;
  80                         }
  81                 break;
  82 #else
  83                 goto contain;
  84 #endif
  85
  86           case STRTOG_Denormal:
  87                 word1(&u[0]) = bits[0];
  88                 word0(&u[0]) = bits[1];
  89                 goto contain;
  90
  91           case STRTOG_Normal:
  92                 word1(&u[0]) = bits[0];
  93                 word0(&u[0]) = (bits[1] & ~0x100000) | ((exp + 0x3ff + 52) << 20);
  94           contain:
  95                 j = k & STRTOG_Inexact;
  96                 if (sign) {
  97                         word0(&u[0]) |= sign;
  98                         j = STRTOG_Inexact - j;
  99                         }
 100                 switch(j) {
 101                   case STRTOG_Inexlo:
 102 #ifdef Sudden_Underflow
 103                         if ((u->L[_0] & 0x7ff00000) < 0x3500000) {
 104                                 word0(&u[1]) = word0(&u[0]) + 0x3500000;
 105                                 word1(&u[1]) = word1(&u[0]);
 106                                 dval(&u[1]) += ulp(&u[1]);
 107                                 word0(&u[1]) -= 0x3500000;
 108                                 if (!(word0(&u[1]) & 0x7ff00000)) {
 109                                         word0(&u[1]) = sign;
 110                                         word1(&u[1]) = 0;
 111                                         }
 112                                 }
 113                         else
 114 #endif
 115                         dval(&u[1]) = dval(&u[0]) + ulp(&u[0]);
 116                         break;
 117                   case STRTOG_Inexhi:
 118                         dval(&u[1]) = dval(&u[0]);
 119 #ifdef Sudden_Underflow
 120                         if ((word0(&u[0]) & 0x7ff00000) < 0x3500000) {
 121                                 word0(&u[0]) += 0x3500000;
 122                                 dval(&u[0]) -= ulpdown(u);
 123                                 word0(&u[0]) -= 0x3500000;
 124                                 if (!(word0(&u[0]) & 0x7ff00000)) {
 125                                         word0(&u[0]) = sign;
 126                                         word1(&u[0]) = 0;
 127                                         }
 128                                 }
 129                         else
 130 #endif
 131                         dval(&u[0]) -= ulpdown(u);
 132                         break;
 133                   default:
 134                         dval(&u[1]) = dval(&u[0]);
 135                   }
 136                 break;
 137
 138           case STRTOG_Infinite:
 139                 word0(&u[0]) = word0(&u[1]) = sign | 0x7ff00000;
 140                 word1(&u[0]) = word1(&u[1]) = 0;
 141                 if (k & STRTOG_Inexact) {
 142                         if (sign) {
 143                                 word0(&u[1]) = 0xffefffffL;
 144                                 word1(&u[1]) = 0xffffffffL;
 145                                 }
 146                         else {
 147                                 word0(&u[0]) = 0x7fefffffL;
 148                                 word1(&u[0]) = 0xffffffffL;
 149                                 }
 150                         }
 151                 break;
 152
 153           case STRTOG_NaN:
 154                 u->L[0] = (u+1)->L[0] = d_QNAN0;
 155                 u->L[1] = (u+1)->L[1] = d_QNAN1;
 156                 break;
 157
 158           case STRTOG_NaNbits:
 159                 word0(&u[0]) = word0(&u[1]) = 0x7ff00000 | sign | bits[1];
 160                 word1(&u[0]) = word1(&u[1]) = bits[0];
 161           }
 162         return k;
 163         }