misc/efgcvt_r.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995,96,97,98,99,2000,01,02 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    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 # define FLOAT_MIN_10_EXP DBL_MIN_10_EXP
  35 # if DBL_MANT_DIG == 53
  36 #  define NDIGIT_MAX 17
  37 # elif DBL_MANT_DIG == 24
  38 #  define NDIGIT_MAX 9
  39 # elif DBL_MANT_DIG == 56
  40 #  define NDIGIT_MAX 18
  41 # else
  42 /* See IEEE 854 5.6, table 2 for this formula.  Unfortunately we need a
  43    compile time constant here, so we cannot use it.  */
  44 #  error "NDIGIT_MAX must be precomputed"
  45 #  define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * DBL_MANT_DIG + 1.0)))
  46 # endif
  47 # if DBL_MIN_10_EXP == -37
  48 #  define FLOAT_MIN_10_NORM     1.0e-37
  49 # elif DBL_MIN_10_EXP == -307
  50 #  define FLOAT_MIN_10_NORM     1.0e-307
  51 # elif DBL_MIN_10_EXP == -4931
  52 #  define FLOAT_MIN_10_NORM     1.0e-4931
  53 # else
  54 /* libc can't depend on libm.  */
  55 #  error "FLOAT_MIN_10_NORM must be precomputed"
  56 #  define FLOAT_MIN_10_NORM     exp10 (DBL_MIN_10_EXP)
  57 # endif
  58 #endif
  59
  60 #define APPEND(a, b) APPEND2 (a, b)
  61 #define APPEND2(a, b) a##b
  62
  63 #define FLOOR APPEND(floor, FLOAT_NAME_EXT)
  64 #define FABS APPEND(fabs, FLOAT_NAME_EXT)
  65 #define LOG10 APPEND(log10, FLOAT_NAME_EXT)
  66 #define EXP APPEND(exp, FLOAT_NAME_EXT)
  67
  68
  69 int
  70 APPEND (FUNC_PREFIX, fcvt_r) (value, ndigit, decpt, sign, buf, len)
  71      FLOAT_TYPE value;
  72      int ndigit, *decpt, *sign;
  73      char *buf;
  74      size_t len;
  75 {
  76   ssize_t n;
  77   ssize_t i;
  78   int left;
  79
  80   if (buf == NULL)
  81     {
  82       __set_errno (EINVAL);
  83       return -1;
  84     }
  85
  86   left = 0;
  87   if (isfinite (value))
  88     {
  89       *sign = signbit (value) != 0;
  90       if (*sign)
  91         value = -value;
  92
  93       if (ndigit < 0)
  94         {
  95           /* Rounding to the left of the decimal point.  */
  96           while (ndigit < 0)
  97             {
  98               FLOAT_TYPE new_value = value * 0.1;
  99
 100               if (new_value < 1.0)
 101                 {
 102                   ndigit = 0;
 103                   break;
 104                 }
 105
 106               value = new_value;
 107               ++left;
 108               ++ndigit;
 109             }
 110         }
 111     }
 112   else
 113     /* Value is Inf or NaN.  */
 114     *sign = 0;
 115
 116   n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
 117                   value);
 118   /* Check for a too small buffer.  */
 119   if (n >= (ssize_t) len)
 120     return -1;
 121
 122   i = 0;
 123   while (i < n && isdigit (buf[i]))
 124     ++i;
 125   *decpt = i;
 126
 127   if (i == 0)
 128     /* Value is Inf or NaN.  */
 129     return 0;
 130
 131   if (i < n)
 132     {
 133       do
 134         ++i;
 135       while (i < n && !isdigit (buf[i]));
 136
 137       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 138         {
 139           /* We must not have leading zeroes.  Strip them all out and
 140              adjust *DECPT if necessary.  */
 141           --*decpt;
 142           while (i < n && buf[i] == '0')
 143             {
 144               --*decpt;
 145               ++i;
 146             }
 147         }
 148
 149       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 150       buf[n - (i - MAX (*decpt, 0))] = '\0';
 151     }
 152
 153   if (left)
 154     {
 155       *decpt += left;
 156       if ((ssize_t) --len > n)
 157         {
 158           while (left-- > 0 && n < (ssize_t) len)
 159             buf[n++] = '0';
 160           buf[n] = '\0';
 161         }
 162     }
 163
 164   return 0;
 165 }
 166 libc_hidden_def (APPEND (FUNC_PREFIX, fcvt_r))
 167
 168 int
 169 APPEND (FUNC_PREFIX, ecvt_r) (value, ndigit, decpt, sign, buf, len)
 170      FLOAT_TYPE value;
 171      int ndigit, *decpt, *sign;
 172      char *buf;
 173      size_t len;
 174 {
 175   int exponent = 0;
 176
 177   if (isfinite (value) && value != 0.0)
 178     {
 179       /* Slow code that doesn't require -lm functions.  */
 180       FLOAT_TYPE d;
 181       FLOAT_TYPE f = 1.0;
 182       if (value < 0.0)
 183         d = -value;
 184       else
 185         d = value;
 186       /* For denormalized numbers the d < 1.0 case below won't work,
 187          as f can overflow to +Inf.  */
 188       if (d < FLOAT_MIN_10_NORM)
 189         {
 190           value /= FLOAT_MIN_10_NORM;
 191           if (value < 0.0)
 192             d = -value;
 193           else
 194             d = value;
 195           exponent += FLOAT_MIN_10_EXP;
 196         }
 197       if (d < 1.0)
 198         {
 199           do
 200             {
 201               f *= 10.0;
 202               --exponent;
 203             }
 204           while (d * f < 1.0);
 205
 206           value *= f;
 207         }
 208       else if (d >= 10.0)
 209         {
 210           do
 211             {
 212               f *= 10;
 213               ++exponent;
 214             }
 215           while (d >= f * 10.0);
 216
 217           value /= f;
 218         }
 219     }
 220   else if (value == 0.0)
 221     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 222        This could be changed to -1 if we want to return 0.  */
 223     exponent = 0;
 224
 225   if (ndigit <= 0 && len > 0)
 226     {
 227       buf[0] = '\0';
 228       *decpt = 1;
 229       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 230     }
 231   else
 232     if (APPEND (FUNC_PREFIX, fcvt_r) (value, MIN (ndigit, NDIGIT_MAX) - 1,
 233                                       decpt, sign, buf, len))
 234       return -1;
 235
 236   *decpt += exponent;
 237   return 0;
 238 }
 239 libc_hidden_def (APPEND (FUNC_PREFIX, ecvt_r))