misc/efgcvt_r.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995, 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <ctype.h>
  24 #include <math.h>
  25 #include <stdlib.h>
  26 #include <sys/param.h>
  27
  28 #ifndef FLOAT_TYPE
  29 # define FLOAT_TYPE double
  30 # define FUNC_PREFIX
  31 # define FLOAT_FMT_FLAG
  32 # define FLOAT_NAME_EXT
  33 # if DBL_MANT_DIG == 53
  34 #  define NDIGIT_MAX 17
  35 # elif DBL_MANT_DIG == 24
  36 #  define NDIGIT_MAX 9
  37 # elif DBL_MANT_DIG == 56
  38 #  define NDIGIT_MAX 18
  39 # else
  40 /* See IEEE 854 5.6, table 2 for this formula.  Unfortunately we need a
  41    compile time constant here, so we cannot use it.  */
  42 #  error "NDIGIT_MAX must be precomputed"
  43 #  define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * DBL_MANT_DIG + 1.0)))
  44 # endif
  45 #endif
  46
  47 #define APPEND(a, b) APPEND2 (a, b)
  48 #define APPEND2(a, b) a##b
  49
  50 #define FLOOR APPEND(floor, FLOAT_NAME_EXT)
  51 #define FABS APPEND(fabs, FLOAT_NAME_EXT)
  52 #define LOG10 APPEND(log10, FLOAT_NAME_EXT)
  53 #define EXP APPEND(exp, FLOAT_NAME_EXT)
  54
  55
  56 int
  57 APPEND (FUNC_PREFIX, fcvt_r) (value, ndigit, decpt, sign, buf, len)
  58      FLOAT_TYPE value;
  59      int ndigit, *decpt, *sign;
  60      char *buf;
  61      size_t len;
  62 {
  63   int n, i;
  64   int left;
  65
  66   if (buf == NULL)
  67     {
  68       __set_errno (EINVAL);
  69       return -1;
  70     }
  71
  72   left = 0;
  73   if (isfinite (value))
  74     {
  75       *sign = signbit (value) != 0;
  76       if (*sign)
  77         value = -value;
  78
  79       if (ndigit < 0)
  80         {
  81           /* Rounding to the left of the decimal point.  */
  82           while (ndigit < 0)
  83             {
  84               FLOAT_TYPE new_value = value * 0.1;
  85
  86               if (new_value < 1.0)
  87                 {
  88                   ndigit = 0;
  89                   break;
  90                 }
  91
  92               value = new_value;
  93               ++left;
  94               ++ndigit;
  95             }
  96         }
  97     }
  98   else
  99     /* Value is Inf or NaN.  */
 100     *sign = 0;
 101
 102   n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
 103                   value);
 104   /* Check for a too small buffer.  */
 105   if (n >= len)
 106     return -1;
 107
 108   i = 0;
 109   while (i < n && isdigit (buf[i]))
 110     ++i;
 111   *decpt = i;
 112
 113   if (i == 0)
 114     /* Value is Inf or NaN.  */
 115     return 0;
 116
 117   if (i < n)
 118     {
 119       do
 120         ++i;
 121       while (i < n && !isdigit (buf[i]));
 122
 123       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 124         {
 125           /* We must not have leading zeroes.  Strip them all out and
 126              adjust *DECPT if necessary.  */
 127           --*decpt;
 128           while (i < n && buf[i] == '0')
 129             {
 130               --*decpt;
 131               ++i;
 132             }
 133         }
 134
 135       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 136       buf[n - (i - MAX (*decpt, 0))] = '\0';
 137     }
 138
 139   if (left)
 140     {
 141       *decpt += left;
 142       if (--len > n)
 143         {
 144           while (left-- > 0 && n < len)
 145             buf[n++] = '0';
 146           buf[n] = '\0';
 147         }
 148     }
 149
 150   return 0;
 151 }
 152
 153 int
 154 APPEND (FUNC_PREFIX, ecvt_r) (value, ndigit, decpt, sign, buf, len)
 155      FLOAT_TYPE value;
 156      int ndigit, *decpt, *sign;
 157      char *buf;
 158      size_t len;
 159 {
 160   int exponent = 0;
 161
 162   if (isfinite (value) && value != 0.0)
 163     {
 164       /* Slow code that doesn't require -lm functions.  */
 165       FLOAT_TYPE d;
 166       FLOAT_TYPE f = 1.0;
 167       if (value < 0.0)
 168         d = -value;
 169       else
 170         d = value;
 171       if (d < 1.0)
 172         {
 173           do
 174             {
 175               f *= 10.0;
 176               --exponent;
 177             }
 178           while (d * f < 1.0);
 179
 180           value *= f;
 181         }
 182       else if (d >= 10.0)
 183         {
 184           do
 185             {
 186               f *= 10;
 187               ++exponent;
 188             }
 189           while (d >= f * 10.0);
 190
 191           value /= f;
 192         }
 193     }
 194   else if (value == 0.0)
 195     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 196        This could be changed to -1 if we want to return 0.  */
 197     exponent = 0;
 198
 199   if (ndigit <= 0 && len > 0)
 200     {
 201       buf[0] = '\0';
 202       *decpt = 1;
 203       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 204     }
 205   else
 206     if (APPEND (FUNC_PREFIX, fcvt_r) (value, MIN (ndigit, NDIGIT_MAX) - 1,
 207                                       decpt, sign, buf, len))
 208       return -1;
 209
 210   *decpt += exponent;
 211   return 0;
 212 }