misc/efgcvt_r.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995,1996,1997,1998,1999,2000,2001 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 <float.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24 #include <ctype.h>
  25 #include <math.h>
  26 #include <stdlib.h>
  27 #include <sys/param.h>
  28
  29 #ifndef FLOAT_TYPE
  30 # define FLOAT_TYPE double
  31 # define FUNC_PREFIX
  32 # define FLOAT_FMT_FLAG
  33 # define FLOAT_NAME_EXT
  34 # if DBL_MANT_DIG == 53
  35 #  define NDIGIT_MAX 17
  36 # elif DBL_MANT_DIG == 24
  37 #  define NDIGIT_MAX 9
  38 # elif DBL_MANT_DIG == 56
  39 #  define NDIGIT_MAX 18
  40 # else
  41 /* See IEEE 854 5.6, table 2 for this formula.  Unfortunately we need a
  42    compile time constant here, so we cannot use it.  */
  43 #  error "NDIGIT_MAX must be precomputed"
  44 #  define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * DBL_MANT_DIG + 1.0)))
  45 # endif
  46 #endif
  47
  48 #define APPEND(a, b) APPEND2 (a, b)
  49 #define APPEND2(a, b) a##b
  50
  51 #define FLOOR APPEND(floor, FLOAT_NAME_EXT)
  52 #define FABS APPEND(fabs, FLOAT_NAME_EXT)
  53 #define LOG10 APPEND(log10, FLOAT_NAME_EXT)
  54 #define EXP APPEND(exp, FLOAT_NAME_EXT)
  55
  56
  57 int
  58 APPEND (FUNC_PREFIX, fcvt_r) (value, ndigit, decpt, sign, buf, len)
  59      FLOAT_TYPE value;
  60      int ndigit, *decpt, *sign;
  61      char *buf;
  62      size_t len;
  63 {
  64   ssize_t n;
  65   ssize_t i;
  66   int left;
  67
  68   if (buf == NULL)
  69     {
  70       __set_errno (EINVAL);
  71       return -1;
  72     }
  73
  74   left = 0;
  75   if (isfinite (value))
  76     {
  77       *sign = signbit (value) != 0;
  78       if (*sign)
  79         value = -value;
  80
  81       if (ndigit < 0)
  82         {
  83           /* Rounding to the left of the decimal point.  */
  84           while (ndigit < 0)
  85             {
  86               FLOAT_TYPE new_value = value * 0.1;
  87
  88               if (new_value < 1.0)
  89                 {
  90                   ndigit = 0;
  91                   break;
  92                 }
  93
  94               value = new_value;
  95               ++left;
  96               ++ndigit;
  97             }
  98         }
  99     }
 100   else
 101     /* Value is Inf or NaN.  */
 102     *sign = 0;
 103
 104   n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
 105                   value);
 106   /* Check for a too small buffer.  */
 107   if (n >= (ssize_t) len)
 108     return -1;
 109
 110   i = 0;
 111   while (i < n && isdigit (buf[i]))
 112     ++i;
 113   *decpt = i;
 114
 115   if (i == 0)
 116     /* Value is Inf or NaN.  */
 117     return 0;
 118
 119   if (i < n)
 120     {
 121       do
 122         ++i;
 123       while (i < n && !isdigit (buf[i]));
 124
 125       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 126         {
 127           /* We must not have leading zeroes.  Strip them all out and
 128              adjust *DECPT if necessary.  */
 129           --*decpt;
 130           while (i < n && buf[i] == '0')
 131             {
 132               --*decpt;
 133               ++i;
 134             }
 135         }
 136
 137       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 138       buf[n - (i - MAX (*decpt, 0))] = '\0';
 139     }
 140
 141   if (left)
 142     {
 143       *decpt += left;
 144       if (--len > n)
 145         {
 146           while (left-- > 0 && n < len)
 147             buf[n++] = '0';
 148           buf[n] = '\0';
 149         }
 150     }
 151
 152   return 0;
 153 }
 154
 155 int
 156 APPEND (FUNC_PREFIX, ecvt_r) (value, ndigit, decpt, sign, buf, len)
 157      FLOAT_TYPE value;
 158      int ndigit, *decpt, *sign;
 159      char *buf;
 160      size_t len;
 161 {
 162   int exponent = 0;
 163
 164   if (isfinite (value) && value != 0.0)
 165     {
 166       /* Slow code that doesn't require -lm functions.  */
 167       FLOAT_TYPE d;
 168       FLOAT_TYPE f = 1.0;
 169       if (value < 0.0)
 170         d = -value;
 171       else
 172         d = value;
 173       if (d < 1.0)
 174         {
 175           do
 176             {
 177               f *= 10.0;
 178               --exponent;
 179             }
 180           while (d * f < 1.0);
 181
 182           value *= f;
 183         }
 184       else if (d >= 10.0)
 185         {
 186           do
 187             {
 188               f *= 10;
 189               ++exponent;
 190             }
 191           while (d >= f * 10.0);
 192
 193           value /= f;
 194         }
 195     }
 196   else if (value == 0.0)
 197     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 198        This could be changed to -1 if we want to return 0.  */
 199     exponent = 0;
 200
 201   if (ndigit <= 0 && len > 0)
 202     {
 203       buf[0] = '\0';
 204       *decpt = 1;
 205       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 206     }
 207   else
 208     if (APPEND (FUNC_PREFIX, fcvt_r) (value, MIN (ndigit, NDIGIT_MAX) - 1,
 209                                       decpt, sign, buf, len))
 210       return -1;
 211
 212   *decpt += exponent;
 213   return 0;
 214 }