misc/efgcvt_r.c

   1 /* Compatibility functions for floating point formatting, reentrant versions.
   2    Copyright (C) 1995-2015 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    <http://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) (value, ndigit, decpt, sign, buf, len)
  75      FLOAT_TYPE value;
  76      int ndigit, *decpt, *sign;
  77      char *buf;
  78      size_t len;
  79 {
  80   ssize_t n;
  81   ssize_t i;
  82   int left;
  83
  84   if (buf == NULL)
  85     {
  86       __set_errno (EINVAL);
  87       return -1;
  88     }
  89
  90   left = 0;
  91   if (isfinite (value))
  92     {
  93       *sign = signbit (value) != 0;
  94       if (*sign)
  95         value = -value;
  96
  97       if (ndigit < 0)
  98         {
  99           /* Rounding to the left of the decimal point.  */
 100           while (ndigit < 0)
 101             {
 102               FLOAT_TYPE new_value = value * 0.1;
 103
 104               if (new_value < 1.0)
 105                 {
 106                   ndigit = 0;
 107                   break;
 108                 }
 109
 110               value = new_value;
 111               ++left;
 112               ++ndigit;
 113             }
 114         }
 115     }
 116   else
 117     /* Value is Inf or NaN.  */
 118     *sign = 0;
 119
 120   n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", MIN (ndigit, NDIGIT_MAX),
 121                   value);
 122   /* Check for a too small buffer.  */
 123   if (n >= (ssize_t) len)
 124     return -1;
 125
 126   i = 0;
 127   while (i < n && isdigit (buf[i]))
 128     ++i;
 129   *decpt = i;
 130
 131   if (i == 0)
 132     /* Value is Inf or NaN.  */
 133     return 0;
 134
 135   if (i < n)
 136     {
 137       do
 138         ++i;
 139       while (i < n && !isdigit (buf[i]));
 140
 141       if (*decpt == 1 && buf[0] == '0' && value != 0.0)
 142         {
 143           /* We must not have leading zeroes.  Strip them all out and
 144              adjust *DECPT if necessary.  */
 145           --*decpt;
 146           while (i < n && buf[i] == '0')
 147             {
 148               --*decpt;
 149               ++i;
 150             }
 151         }
 152
 153       memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
 154       buf[n - (i - MAX (*decpt, 0))] = '\0';
 155     }
 156
 157   if (left)
 158     {
 159       *decpt += left;
 160       if ((ssize_t) --len > n)
 161         {
 162           while (left-- > 0 && n < (ssize_t) len)
 163             buf[n++] = '0';
 164           buf[n] = '\0';
 165         }
 166     }
 167
 168   return 0;
 169 }
 170
 171 int
 172 __APPEND (FUNC_PREFIX, ecvt_r) (value, ndigit, decpt, sign, buf, len)
 173      FLOAT_TYPE value;
 174      int ndigit, *decpt, *sign;
 175      char *buf;
 176      size_t len;
 177 {
 178   int exponent = 0;
 179
 180   if (isfinite (value) && value != 0.0)
 181     {
 182       /* Slow code that doesn't require -lm functions.  */
 183       FLOAT_TYPE d;
 184       FLOAT_TYPE f = 1.0;
 185       if (value < 0.0)
 186         d = -value;
 187       else
 188         d = value;
 189       /* For denormalized numbers the d < 1.0 case below won't work,
 190          as f can overflow to +Inf.  */
 191       if (d < FLOAT_MIN_10_NORM)
 192         {
 193           value /= FLOAT_MIN_10_NORM;
 194           if (value < 0.0)
 195             d = -value;
 196           else
 197             d = value;
 198           exponent += FLOAT_MIN_10_EXP;
 199         }
 200       if (d < 1.0)
 201         {
 202           do
 203             {
 204               f *= 10.0;
 205               --exponent;
 206             }
 207           while (d * f < 1.0);
 208
 209           value *= f;
 210         }
 211       else if (d >= 10.0)
 212         {
 213           do
 214             {
 215               f *= 10;
 216               ++exponent;
 217             }
 218           while (d >= f * 10.0);
 219
 220           value /= f;
 221         }
 222     }
 223   else if (value == 0.0)
 224     /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
 225        This could be changed to -1 if we want to return 0.  */
 226     exponent = 0;
 227
 228   if (ndigit <= 0 && len > 0)
 229     {
 230       buf[0] = '\0';
 231       *decpt = 1;
 232       *sign = isfinite (value) ? signbit (value) != 0 : 0;
 233     }
 234   else
 235     if (__APPEND (FUNC_PREFIX, fcvt_r) (value, MIN (ndigit, NDIGIT_MAX) - 1,
 236                                         decpt, sign, buf, len))
 237       return -1;
 238
 239   *decpt += exponent;
 240   return 0;
 241 }
 242
 243 #if LONG_DOUBLE_COMPAT (libc, GLIBC_2_0)
 244 # ifdef LONG_DOUBLE_CVT
 245 #  define cvt_symbol(symbol) \
 246   cvt_symbol_1 (libc, __APPEND (FUNC_PREFIX, symbol), \
 247               APPEND (FUNC_PREFIX, symbol), GLIBC_2_4)
 248 #  define cvt_symbol_1(lib, local, symbol, version) \
 249     versioned_symbol (lib, local, symbol, version)
 250 # else
 251 #  define cvt_symbol(symbol) \
 252   cvt_symbol_1 (libc, __APPEND (FUNC_PREFIX, symbol), \
 253               APPEND (q, symbol), GLIBC_2_0); \
 254   strong_alias (__APPEND (FUNC_PREFIX, symbol), APPEND (FUNC_PREFIX, symbol))
 255 #  define cvt_symbol_1(lib, local, symbol, version) \
 256   compat_symbol (lib, local, symbol, version)
 257 # endif
 258 #else
 259 # define cvt_symbol(symbol) \
 260   strong_alias (__APPEND (FUNC_PREFIX, symbol), APPEND (FUNC_PREFIX, symbol))
 261 #endif
 262 cvt_symbol(fcvt_r);
 263 cvt_symbol(ecvt_r);