misc/efgcvt_r-template.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995-2024 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <ctype.h>
  23 #include <math.h>
  24 #include <stdlib.h>
  25 #include <sys/param.h>
  26 #include <math_ldbl_opt.h>
  27
  28 #ifndef SNPRINTF
  29 # define SNPRINTF __snprintf
  30 #endif
  31
  32
  33 #define APPEND(a, b) APPEND2 (a, b)
  34 #define APPEND2(a, b) a##b
  35
  36 int
  37 __FCVT_R (FLOAT_TYPE value, int ndigit, int *decpt, int *sign,
  38           char *buf, size_t len)
  39 {
  40   ssize_t n;
  41   ssize_t i;
  42   int left;
  43
  44   if (buf == NULL)
  45     {
  46       __set_errno (EINVAL);
  47       return -1;
  48     }
  49
  50   left = 0;
  51   if (isfinite (value))
  52     {
  53       *sign = signbit (value) != 0;
  54       if (*sign)
  55         value = -value;
  56
  57       if (ndigit < 0)
  58         {
  59           /* Rounding to the left of the decimal point.  */
  60           while (ndigit < 0)
  61             {
  62               FLOAT_TYPE new_value = value * 0.1;
  63
  64               if (new_value < 1.0)
  65                 {
  66                   ndigit = 0;
  67                   break;
  68                 }
  69
  70               value = new_value;
  71               ++left;
  72               ++ndigit;
  73             }
  74         }
  75     }
  76   else
  77     /* Value is Inf or NaN.  */
  78     *sign = 0;
  79
  80   n = SNPRINTF (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
  81                   value);
  82   /* Check for a too small buffer.  */
  83   if (n >= (ssize_t) len)
  84     return -1;
  85
  86   i = 0;
  87   while (i < n && isdigit (buf[i]))
  88     ++i;
  89   *decpt = i;
  90
  91   if (i == 0)
  92     /* Value is Inf or NaN.  */
  93     return 0;
  94
  95   if (i < n)
  96     {
  97       do
  98         ++i;
  99       while (i < n && !isdigit (buf[i]));
 100
 101       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 102         {
 103           /* We must not have leading zeroes.  Strip them all out and
 104              adjust *DECPT if necessary.  */
 105           --*decpt;
 106           while (i < n && buf[i] == '0')
 107             {
 108               --*decpt;
 109               ++i;
 110             }
 111         }
 112
 113       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 114       buf[n - (i - MAX (*decpt, 0))] = '\0';
 115     }
 116
 117   if (left)
 118     {
 119       *decpt += left;
 120       if ((ssize_t) --len > n)
 121         {
 122           while (left-- > 0 && n < (ssize_t) len)
 123             buf[n++] = '0';
 124           buf[n] = '\0';
 125         }
 126     }
 127
 128   return 0;
 129 }
 130
 131 int
 132 __ECVT_R (FLOAT_TYPE value, int ndigit, int *decpt, int *sign,
 133           char *buf, size_t len)
 134 {
 135   int exponent = 0;
 136
 137   if (isfinite (value) && value != 0.0)
 138     {
 139       /* Slow code that doesn't require -lm functions.  */
 140       FLOAT_TYPE d;
 141       FLOAT_TYPE f = 1.0;
 142       if (value < 0.0)
 143         d = -value;
 144       else
 145         d = value;
 146       /* For denormalized numbers the d < 1.0 case below won't work,
 147          as f can overflow to +Inf.  */
 148       if (d < FLOAT_MIN_10_NORM)
 149         {
 150           value /= FLOAT_MIN_10_NORM;
 151           if (value < 0.0)
 152             d = -value;
 153           else
 154             d = value;
 155           exponent += FLOAT_MIN_10_EXP;
 156         }
 157       if (d < 1.0)
 158         {
 159           do
 160             {
 161               f *= 10.0;
 162               --exponent;
 163             }
 164           while (d * f < 1.0);
 165
 166           value *= f;
 167         }
 168       else if (d >= 10.0)
 169         {
 170           do
 171             {
 172               f *= 10;
 173               ++exponent;
 174             }
 175           while (d >= f * 10.0);
 176
 177           value /= f;
 178         }
 179     }
 180   else if (value == 0.0)
 181     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 182        This could be changed to -1 if we want to return 0.  */
 183     exponent = 0;
 184
 185   if (ndigit <= 0 && len > 0)
 186     {
 187       buf[0] = '\0';
 188       *decpt = 1;
 189       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 190     }
 191   else
 192     if (__FCVT_R (value, MIN (ndigit, NDIGIT_MAX) - 1,
 193                   decpt, sign, buf, len))
 194       return -1;
 195
 196   *decpt += exponent;
 197   return 0;
 198 }