contrib/gdtoa/g_dfmt.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 at acm dot org,
  30  * with " at " changed at "@" and " dot " changed to ".").      */
  31
  32 #include "gdtoaimp.h"
  33
  34  char*
  35 #ifdef KR_headers
  36 g_dfmt(buf, d, ndig, bufsize) char *buf; double *d; int ndig; size_t bufsize;
  37 #else
  38 g_dfmt(char *buf, double *d, int ndig, size_t bufsize)
  39 #endif
  40 {
  41         static FPI fpi0 = { 53, 1-1023-53+1, 2046-1023-53+1, 1, 0 };
  42         char *b, *s, *se;
  43         ULong bits[2], *L, sign;
  44         int decpt, ex, i, mode;
  45 #ifdef Honor_FLT_ROUNDS
  46 #include "gdtoa_fltrnds.h"
  47 #else
  48 #define fpi &fpi0
  49 #endif
  50
  51         if (ndig < 0)
  52                 ndig = 0;
  53         if (bufsize < ndig + 10)
  54                 return 0;
  55
  56         L = (ULong*)d;
  57         sign = L[_0] & 0x80000000L;
  58         if ((L[_0] & 0x7ff00000) == 0x7ff00000) {
  59                 /* Infinity or NaN */
  60                 if (bufsize < 10)
  61                         return 0;
  62                 if (L[_0] & 0xfffff || L[_1]) {
  63                         return strcp(buf, "NaN");
  64                         }
  65                 b = buf;
  66                 if (sign)
  67                         *b++ = '-';
  68                 return strcp(b, "Infinity");
  69                 }
  70         if (L[_1] == 0 && (L[_0] ^ sign) == 0 /*d == 0.*/) {
  71                 b = buf;
  72 #ifndef IGNORE_ZERO_SIGN
  73                 if (L[_0] & 0x80000000L)
  74                         *b++ = '-';
  75 #endif
  76                 *b++ = '0';
  77                 *b = 0;
  78                 return b;
  79                 }
  80         bits[0] = L[_1];
  81         bits[1] = L[_0] & 0xfffff;
  82         if ( (ex = (L[_0] >> 20) & 0x7ff) !=0)
  83                 bits[1] |= 0x100000;
  84         else
  85                 ex = 1;
  86         ex -= 0x3ff + 52;
  87         mode = 2;
  88         if (ndig <= 0)
  89                 mode = 0;
  90         i = STRTOG_Normal;
  91         s = gdtoa(fpi, ex, bits, &i, mode, ndig, &decpt, &se);
  92         return g__fmt(buf, s, se, decpt, sign, bufsize);
  93         }