gcc/m2/mc-boot-ch/Gdtoa.cc

   1 /* Gdtoa.cc provides access to double string conversion.
   2
   3 Copyright (C) 2016-2024 Free Software Foundation, Inc.
   4 Contributed by Gaius Mulley <gaius@glam.ac.uk>.
   5
   6 This file is part of GNU Modula-2.
   7
   8 GNU Modula-2 is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 3, or (at your option)
  11 any later version.
  12
  13 GNU Modula-2 is distributed in the hope that it will be useful, but
  14 WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Modula-2; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 #define GM2
  23
  24 #include "config.h"
  25 #include "system.h"
  26
  27
  28 #ifdef __cplusplus
  29 extern "C" {
  30 #endif
  31
  32 #define MAX_FP_DIGITS 500
  33
  34 typedef enum Mode { maxsignicant, decimaldigits } Mode;
  35
  36 /* maxsignicant: return a string containing max(1,ndigits)
  37    significant digits.  The return string contains the string
  38    produced by ecvt.  decimaldigits: return a string produced by
  39    fcvt.  The string will contain ndigits past the decimal point
  40    (ndigits may be negative).  */
  41
  42 double
  43 dtoa_strtod (const char *s, int *error)
  44 {
  45   char *endp;
  46   double d;
  47
  48   errno = 0;
  49   d = strtod (s, &endp);
  50   if (endp != NULL && (*endp == '\0'))
  51     *error = (errno != 0);
  52   else
  53     *error = TRUE;
  54   return d;
  55 }
  56
  57 /* dtoa_calcmaxsig - calculates the position of the decimal point it
  58    also removes the decimal point and exponent from string, p.  */
  59
  60 int
  61 dtoa_calcmaxsig (char *p, int ndigits)
  62 {
  63   char *e;
  64   char *o;
  65   int x;
  66
  67   e = index (p, 'E');
  68   if (e == NULL)
  69     x = 0;
  70   else
  71     {
  72       *e = (char)0;
  73       x = atoi (e + 1);
  74     }
  75
  76   o = index (p, '.');
  77   if (o == NULL)
  78     return strlen (p) + x;
  79   else
  80     {
  81       memmove (o, o + 1, ndigits - (o - p));
  82       return o - p + x;
  83     }
  84 }
  85
  86 /* dtoa_calcdecimal - calculates the position of the decimal point it
  87    also removes the decimal point and exponent from string, p.  It
  88    truncates the digits in p accordingly to ndigits.  Ie ndigits is
  89    the number of digits after the '.' */
  90
  91 int
  92 dtoa_calcdecimal (char *p, int str_size, int ndigits)
  93 {
  94   char *e;
  95   char *o;
  96   int x;
  97   int l;
  98
  99   e = index (p, 'E');
 100   if (e == NULL)
 101     x = 0;
 102   else
 103     {
 104       *e = (char)0;
 105       x = atoi (e + 1);
 106     }
 107
 108   l = strlen (p);
 109   o = index (p, '.');
 110   if (o == NULL)
 111     x += strlen (p);
 112   else
 113     {
 114       int m = strlen (o);
 115       memmove (o, o + 1, l - (o - p));
 116       if (m > 0)
 117         o[m - 1] = '0';
 118       x += o - p;
 119     }
 120   if ((x + ndigits >= 0) && (x + ndigits < str_size))
 121     p[x + ndigits] = (char)0;
 122   return x;
 123 }
 124
 125
 126 int
 127 dtoa_calcsign (char *p, int str_size)
 128 {
 129   if (p[0] == '-')
 130     {
 131       memmove (p, p + 1, str_size - 1);
 132       return TRUE;
 133     }
 134   else
 135     return FALSE;
 136 }
 137
 138
 139 char *
 140 dtoa_dtoa (double d, int mode, int ndigits, int *decpt, int *sign)
 141 {
 142   char format[50];
 143   char *p;
 144   int r;
 145   switch (mode)
 146     {
 147
 148     case maxsignicant:
 149       ndigits += 20; /* enough for exponent.  */
 150       p = (char *) malloc (ndigits);
 151       snprintf (format, 50, "%s%d%s", "%.", ndigits - 20, "E");
 152       snprintf (p, ndigits, format, d);
 153       *sign = dtoa_calcsign (p, ndigits);
 154       *decpt = dtoa_calcmaxsig (p, ndigits);
 155       return p;
 156     case decimaldigits:
 157       p = (char *) malloc (MAX_FP_DIGITS + 20);
 158       snprintf (format, 50, "%s%d%s", "%.", MAX_FP_DIGITS, "E");
 159       snprintf (p, MAX_FP_DIGITS + 20, format, d);
 160       *sign = dtoa_calcsign (p, MAX_FP_DIGITS + 20);
 161       *decpt = dtoa_calcdecimal (p, MAX_FP_DIGITS + 20, ndigits);
 162       return p;
 163     default:
 164       abort ();
 165     }
 166 }
 167
 168 #if defined(GM2)
 169 /* GNU Modula-2 hooks */
 170
 171 void
 172 _M2_dtoa_init (void)
 173 {
 174 }
 175
 176 void
 177 _M2_dtoa_fini (void)
 178 {
 179 }
 180 #endif
 181
 182 #ifdef __cplusplus
 183 }
 184 #endif