misc/efgcvt_r.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995,1996,1997,1998,1999,2000 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   ssize_t n;
  64   ssize_t i;
  65   int left;
  66
  67   if (buf == NULL)
  68     {
  69       __set_errno (EINVAL);
  70       return -1;
  71     }
  72
  73   left = 0;
  74   if (isfinite (value))
  75     {
  76       *sign = signbit (value) != 0;
  77       if (*sign)
  78         value = -value;
  79
  80       if (ndigit < 0)
  81         {
  82           /* Rounding to the left of the decimal point.  */
  83           while (ndigit < 0)
  84             {
  85               FLOAT_TYPE new_value = value * 0.1;
  86
  87               if (new_value < 1.0)
  88                 {
  89                   ndigit = 0;
  90                   break;
  91                 }
  92
  93               value = new_value;
  94               ++left;
  95               ++ndigit;
  96             }
  97         }
  98     }
  99   else
 100     /* Value is Inf or NaN.  */
 101     *sign = 0;
 102
 103   n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
 104                   value);
 105   /* Check for a too small buffer.  */
 106   if (n >= (ssize_t) len)
 107     return -1;
 108
 109   i = 0;
 110   while (i < n && isdigit (buf[i]))
 111     ++i;
 112   *decpt = i;
 113
 114   if (i == 0)
 115     /* Value is Inf or NaN.  */
 116     return 0;
 117
 118   if (i < n)
 119     {
 120       do
 121         ++i;
 122       while (i < n && !isdigit (buf[i]));
 123
 124       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 125         {
 126           /* We must not have leading zeroes.  Strip them all out and
 127              adjust *DECPT if necessary.  */
 128           --*decpt;
 129           while (i < n && buf[i] == '0')
 130             {
 131               --*decpt;
 132               ++i;
 133             }
 134         }
 135
 136       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 137       buf[n - (i - MAX (*decpt, 0))] = '\0';
 138     }
 139
 140   if (left)
 141     {
 142       *decpt += left;
 143       if (--len > n)
 144         {
 145           while (left-- > 0 && n < len)
 146             buf[n++] = '0';
 147           buf[n] = '\0';
 148         }
 149     }
 150
 151   return 0;
 152 }
 153
 154 int
 155 APPEND (FUNC_PREFIX, ecvt_r) (value, ndigit, decpt, sign, buf, len)
 156      FLOAT_TYPE value;
 157      int ndigit, *decpt, *sign;
 158      char *buf;
 159      size_t len;
 160 {
 161   int exponent = 0;
 162
 163   if (isfinite (value) && value != 0.0)
 164     {
 165       /* Slow code that doesn't require -lm functions.  */
 166       FLOAT_TYPE d;
 167       FLOAT_TYPE f = 1.0;
 168       if (value < 0.0)
 169         d = -value;
 170       else
 171         d = value;
 172       if (d < 1.0)
 173         {
 174           do
 175             {
 176               f *= 10.0;
 177               --exponent;
 178             }
 179           while (d * f < 1.0);
 180
 181           value *= f;
 182         }
 183       else if (d >= 10.0)
 184         {
 185           do
 186             {
 187               f *= 10;
 188               ++exponent;
 189             }
 190           while (d >= f * 10.0);
 191
 192           value /= f;
 193         }
 194     }
 195   else if (value == 0.0)
 196     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 197        This could be changed to -1 if we want to return 0.  */
 198     exponent = 0;
 199
 200   if (ndigit <= 0 && len > 0)
 201     {
 202       buf[0] = '\0';
 203       *decpt = 1;
 204       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 205     }
 206   else
 207     if (APPEND (FUNC_PREFIX, fcvt_r) (value, MIN (ndigit, NDIGIT_MAX) - 1,
 208                                       decpt, sign, buf, len))
 209       return -1;
 210
 211   *decpt += exponent;
 212   return 0;
 213 }