misc/efgcvt_r.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995-2019 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 <float.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 #include <math_ldbl_opt.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 #else
  59 # define LONG_DOUBLE_CVT
  60 #endif
  61
  62 #define APPEND(a, b) APPEND2 (a, b)
  63 #define APPEND2(a, b) a##b
  64 #define __APPEND(a, b) __APPEND2 (a, b)
  65 #define __APPEND2(a, b) __##a##b
  66
  67 #define FLOOR APPEND(floor, FLOAT_NAME_EXT)
  68 #define FABS APPEND(fabs, FLOAT_NAME_EXT)
  69 #define LOG10 APPEND(log10, FLOAT_NAME_EXT)
  70 #define EXP APPEND(exp, FLOAT_NAME_EXT)
  71
  72
  73 int
  74 __APPEND (FUNC_PREFIX, fcvt_r) (FLOAT_TYPE value, int ndigit, int *decpt,
  75                                 int *sign, char *buf, size_t len)
  76 {
  77   ssize_t n;
  78   ssize_t i;
  79   int left;
  80
  81   if (buf == NULL)
  82     {
  83       __set_errno (EINVAL);
  84       return -1;
  85     }
  86
  87   left = 0;
  88   if (isfinite (value))
  89     {
  90       *sign = signbit (value) != 0;
  91       if (*sign)
  92         value = -value;
  93
  94       if (ndigit < 0)
  95         {
  96           /* Rounding to the left of the decimal point.  */
  97           while (ndigit < 0)
  98             {
  99               FLOAT_TYPE new_value = value * 0.1;
 100
 101               if (new_value < 1.0)
 102                 {
 103                   ndigit = 0;
 104                   break;
 105                 }
 106
 107               value = new_value;
 108               ++left;
 109               ++ndigit;
 110             }
 111         }
 112     }
 113   else
 114     /* Value is Inf or NaN.  */
 115     *sign = 0;
 116
 117   n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
 118                   value);
 119   /* Check for a too small buffer.  */
 120   if (n >= (ssize_t) len)
 121     return -1;
 122
 123   i = 0;
 124   while (i < n && isdigit (buf[i]))
 125     ++i;
 126   *decpt = i;
 127
 128   if (i == 0)
 129     /* Value is Inf or NaN.  */
 130     return 0;
 131
 132   if (i < n)
 133     {
 134       do
 135         ++i;
 136       while (i < n && !isdigit (buf[i]));
 137
 138       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 139         {
 140           /* We must not have leading zeroes.  Strip them all out and
 141              adjust *DECPT if necessary.  */
 142           --*decpt;
 143           while (i < n && buf[i] == '0')
 144             {
 145               --*decpt;
 146               ++i;
 147             }
 148         }
 149
 150       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 151       buf[n - (i - MAX (*decpt, 0))] = '\0';
 152     }
 153
 154   if (left)
 155     {
 156       *decpt += left;
 157       if ((ssize_t) --len > n)
 158         {
 159           while (left-- > 0 && n < (ssize_t) len)
 160             buf[n++] = '0';
 161           buf[n] = '\0';
 162         }
 163     }
 164
 165   return 0;
 166 }
 167
 168 int
 169 __APPEND (FUNC_PREFIX, ecvt_r) (FLOAT_TYPE value, int ndigit, int *decpt,
 170                                 int *sign, char *buf, size_t len)
 171 {
 172   int exponent = 0;
 173
 174   if (isfinite (value) && value != 0.0)
 175     {
 176       /* Slow code that doesn't require -lm functions.  */
 177       FLOAT_TYPE d;
 178       FLOAT_TYPE f = 1.0;
 179       if (value < 0.0)
 180         d = -value;
 181       else
 182         d = value;
 183       /* For denormalized numbers the d < 1.0 case below won't work,
 184          as f can overflow to +Inf.  */
 185       if (d < FLOAT_MIN_10_NORM)
 186         {
 187           value /= FLOAT_MIN_10_NORM;
 188           if (value < 0.0)
 189             d = -value;
 190           else
 191             d = value;
 192           exponent += FLOAT_MIN_10_EXP;
 193         }
 194       if (d < 1.0)
 195         {
 196           do
 197             {
 198               f *= 10.0;
 199               --exponent;
 200             }
 201           while (d * f < 1.0);
 202
 203           value *= f;
 204         }
 205       else if (d >= 10.0)
 206         {
 207           do
 208             {
 209               f *= 10;
 210               ++exponent;
 211             }
 212           while (d >= f * 10.0);
 213
 214           value /= f;
 215         }
 216     }
 217   else if (value == 0.0)
 218     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 219        This could be changed to -1 if we want to return 0.  */
 220     exponent = 0;
 221
 222   if (ndigit <= 0 && len > 0)
 223     {
 224       buf[0] = '\0';
 225       *decpt = 1;
 226       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 227     }
 228   else
 229     if (__APPEND (FUNC_PREFIX, fcvt_r) (value, MIN (ndigit, NDIGIT_MAX) - 1,
 230                                         decpt, sign, buf, len))
 231       return -1;
 232
 233   *decpt += exponent;
 234   return 0;
 235 }
 236
 237 #if LONG_DOUBLE_COMPAT (libc, GLIBC_2_0)
 238 # ifdef LONG_DOUBLE_CVT
 239 #  define cvt_symbol(symbol) \
 240   cvt_symbol_1 (libc, __APPEND (FUNC_PREFIX, symbol), \
 241               APPEND (FUNC_PREFIX, symbol), GLIBC_2_4)
 242 #  define cvt_symbol_1(lib, local, symbol, version) \
 243     libc_hidden_def (local) \
 244     versioned_symbol (lib, local, symbol, version)
 245 # else
 246 #  define cvt_symbol(symbol) \
 247   cvt_symbol_1 (libc, __APPEND (FUNC_PREFIX, symbol), \
 248               APPEND (q, symbol), GLIBC_2_0); \
 249   weak_alias (__APPEND (FUNC_PREFIX, symbol), APPEND (FUNC_PREFIX, symbol))
 250 #  define cvt_symbol_1(lib, local, symbol, version) \
 251   libc_hidden_def (local) \
 252   compat_symbol (lib, local, symbol, version)
 253 # endif
 254 #else
 255 # define cvt_symbol(symbol) \
 256   cvt_symbol_1 (__APPEND (FUNC_PREFIX, symbol), APPEND (FUNC_PREFIX, symbol))
 257 #  define cvt_symbol_1(local, symbol) \
 258   libc_hidden_def (local) \
 259   weak_alias (local, symbol)
 260 #endif
 261 cvt_symbol(fcvt_r);
 262 cvt_symbol(ecvt_r);