contrib/gdtoa/g_ddfmt.c

   1 /****************************************************************
   2
   3 The author of this software is David M. Gay.
   4
   5 Copyright (C) 1998 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@acm.org). */
  30
  31 #include "gdtoaimp.h"
  32 #include <string.h>
  33
  34  char *
  35 #ifdef KR_headers
  36 g_ddfmt(buf, dd, ndig, bufsize) char *buf; double *dd; int ndig; size_t bufsize;
  37 #else
  38 g_ddfmt(char *buf, double *dd, int ndig, size_t bufsize)
  39 #endif
  40 {
  41         FPI fpi;
  42         char *b, *s, *se;
  43         ULong *L, bits0[4], *bits, *zx;
  44         int bx, by, decpt, ex, ey, i, j, mode;
  45         Bigint *x, *y, *z;
  46         double ddx[2];
  47 #ifdef Honor_FLT_ROUNDS /*{{*/
  48         int Rounding;
  49 #ifdef Trust_FLT_ROUNDS /*{{ only define this if FLT_ROUNDS really works! */
  50         Rounding = Flt_Rounds;
  51 #else /*}{*/
  52         Rounding = 1;
  53         switch(fegetround()) {
  54           case FE_TOWARDZERO:   Rounding = 0; break;
  55           case FE_UPWARD:       Rounding = 2; break;
  56           case FE_DOWNWARD:     Rounding = 3;
  57           }
  58 #endif /*}}*/
  59 #else /*}{*/
  60 #define Rounding FPI_Round_near
  61 #endif /*}}*/
  62
  63         if (bufsize < 10 || bufsize < ndig + 8)
  64                 return 0;
  65
  66         L = (ULong*)dd;
  67         if ((L[_0] & 0x7ff00000L) == 0x7ff00000L) {
  68                 /* Infinity or NaN */
  69                 if (L[_0] & 0xfffff || L[_1]) {
  70  nanret:
  71                         return strcp(buf, "NaN");
  72                         }
  73                 if ((L[2+_0] & 0x7ff00000) == 0x7ff00000) {
  74                         if (L[2+_0] & 0xfffff || L[2+_1])
  75                                 goto nanret;
  76                         if ((L[_0] ^ L[2+_0]) & 0x80000000L)
  77                                 goto nanret;    /* Infinity - Infinity */
  78                         }
  79  infret:
  80                 b = buf;
  81                 if (L[_0] & 0x80000000L)
  82                         *b++ = '-';
  83                 return strcp(b, "Infinity");
  84                 }
  85         if ((L[2+_0] & 0x7ff00000) == 0x7ff00000) {
  86                 L += 2;
  87                 if (L[_0] & 0xfffff || L[_1])
  88                         goto nanret;
  89                 goto infret;
  90                 }
  91         if (dd[0] + dd[1] == 0.) {
  92                 b = buf;
  93 #ifndef IGNORE_ZERO_SIGN
  94                 if (L[_0] & L[2+_0] & 0x80000000L)
  95                         *b++ = '-';
  96 #endif
  97                 *b++ = '0';
  98                 *b = 0;
  99                 return b;
 100                 }
 101         if ((L[_0] & 0x7ff00000L) < (L[2+_0] & 0x7ff00000L)) {
 102                 ddx[1] = dd[0];
 103                 ddx[0] = dd[1];
 104                 dd = ddx;
 105                 L = (ULong*)dd;
 106                 }
 107         z = d2b(dd[0], &ex, &bx);
 108         if (dd[1] == 0.)
 109                 goto no_y;
 110         x = z;
 111         y = d2b(dd[1], &ey, &by);
 112         if ( (i = ex - ey) !=0) {
 113                 if (i > 0) {
 114                         x = lshift(x, i);
 115                         ex = ey;
 116                         }
 117                 else
 118                         y = lshift(y, -i);
 119                 }
 120         if ((L[_0] ^ L[2+_0]) & 0x80000000L) {
 121                 z = diff(x, y);
 122                 if (L[_0] & 0x80000000L)
 123                         z->sign = 1 - z->sign;
 124                 }
 125         else {
 126                 z = sum(x, y);
 127                 if (L[_0] & 0x80000000L)
 128                         z->sign = 1;
 129                 }
 130         Bfree(x);
 131         Bfree(y);
 132  no_y:
 133         bits = zx = z->x;
 134         for(i = 0; !*zx; zx++)
 135                 i += 32;
 136         i += lo0bits(zx);
 137         if (i) {
 138                 rshift(z, i);
 139                 ex += i;
 140                 }
 141         fpi.nbits = z->wds * 32 - hi0bits(z->x[j = z->wds-1]);
 142         if (fpi.nbits < 106) {
 143                 fpi.nbits = 106;
 144                 if (j < 3) {
 145                         for(i = 0; i <= j; i++)
 146                                 bits0[i] = bits[i];
 147                         while(i < 4)
 148                                 bits0[i++] = 0;
 149                         bits = bits0;
 150                         }
 151                 }
 152         mode = 2;
 153         if (ndig <= 0) {
 154                 if (bufsize < (int)(fpi.nbits * .301029995664) + 10) {
 155                         Bfree(z);
 156                         return 0;
 157                         }
 158                 mode = 0;
 159                 }
 160         fpi.emin = 1-1023-53+1;
 161         fpi.emax = 2046-1023-106+1;
 162         fpi.rounding = Rounding;
 163         fpi.sudden_underflow = 0;
 164         i = STRTOG_Normal;
 165         s = gdtoa(&fpi, ex, bits, &i, mode, ndig, &decpt, &se);
 166         b = g__fmt(buf, s, se, decpt, z->sign, bufsize);
 167         Bfree(z);
 168         return b;
 169         }