lib/strtol.c

   1 /* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
   2
   3    This program is free software; you can redistribute it and/or modify
   4    it under the terms of the GNU General Public License as published by
   5    the Free Software Foundation; either version 2, or (at your option)
   6    any later version.
   7
   8    This program is distributed in the hope that it will be useful,
   9    but WITHOUT ANY WARRANTY; without even the implied warranty of
  10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11    GNU General Public License for more details.
  12
  13    You should have received a copy of the GNU General Public License
  14    along with this program; if not, write to the Free Software
  15    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  16
  17 #ifdef HAVE_CONFIG_H
  18 #include <config.h>
  19 #endif
  20
  21 #include <ctype.h>
  22 #include <errno.h>
  23
  24 #if HAVE_LIMITS_H
  25 #include <limits.h>
  26 #endif
  27
  28 #ifndef ULONG_MAX
  29 #define ULONG_MAX ((unsigned long) ~(unsigned long) 0)
  30 #endif
  31
  32 #ifndef LONG_MAX
  33 #define LONG_MAX (~(1 << (sizeof (long) * 8 - 1)))
  34 #endif
  35
  36 #ifndef LONG_MIN
  37 #define LONG_MIN (-LONG_MAX - 1)
  38 #endif
  39
  40 #if STDC_HEADERS
  41 #include <stddef.h>
  42 #include <stdlib.h>
  43 #else
  44 #define NULL 0
  45 extern int errno;
  46 #endif
  47
  48 #ifndef UNSIGNED
  49 #define UNSIGNED        0
  50 #endif
  51
  52 /* Convert NPTR to an `unsigned long int' or `long int' in base BASE.
  53    If BASE is 0 the base is determined by the presence of a leading
  54    zero, indicating octal or a leading "0x" or "0X", indicating hexadecimal.
  55    If BASE is < 2 or > 36, it is reset to 10.
  56    If ENDPTR is not NULL, a pointer to the character after the last
  57    one converted is stored in *ENDPTR.  */
  58 #if     UNSIGNED
  59 unsigned long int
  60 #define strtol  strtoul
  61 #else
  62 long int
  63 #endif
  64 strtol (nptr, endptr, base)
  65      const char *nptr;
  66      char **endptr;
  67      int base;
  68 {
  69   int negative;
  70   register unsigned long int cutoff;
  71   register unsigned int cutlim;
  72   register unsigned long int i;
  73   register const char *s;
  74   register unsigned char c;
  75   const char *save;
  76   int overflow;
  77
  78   if (base < 0 || base == 1 || base > 36)
  79     base = 10;
  80
  81   s = nptr;
  82
  83   /* Skip white space.  */
  84   while (isspace (*s))
  85     ++s;
  86   if (*s == '\0')
  87     goto noconv;
  88
  89   /* Check for a sign.  */
  90   if (*s == '-')
  91     {
  92       negative = 1;
  93       ++s;
  94     }
  95   else if (*s == '+')
  96     {
  97       negative = 0;
  98       ++s;
  99     }
 100   else
 101     negative = 0;
 102
 103   if (base == 16 && s[0] == '0' && toupper (s[1]) == 'X')
 104     s += 2;
 105
 106   /* If BASE is zero, figure it out ourselves.  */
 107   if (base == 0)
 108     {
 109       if (*s == '0')
 110         {
 111           if (toupper (s[1]) == 'X')
 112             {
 113               s += 2;
 114               base = 16;
 115             }
 116           else
 117             base = 8;
 118         }
 119       else
 120         base = 10;
 121     }
 122
 123   /* Save the pointer so we can check later if anything happened.  */
 124   save = s;
 125
 126   cutoff = ULONG_MAX / (unsigned long int) base;
 127   cutlim = ULONG_MAX % (unsigned long int) base;
 128
 129   overflow = 0;
 130   i = 0;
 131   for (c = *s; c != '\0'; c = *++s)
 132     {
 133       if (isdigit (c))
 134         c -= '0';
 135       else if (isalpha (c))
 136         c = toupper (c) - 'A' + 10;
 137       else
 138         break;
 139       if (c >= base)
 140         break;
 141       /* Check for overflow.  */
 142       if (i > cutoff || (i == cutoff && c > cutlim))
 143         overflow = 1;
 144       else
 145         {
 146           i *= (unsigned long int) base;
 147           i += c;
 148         }
 149     }
 150
 151   /* Check if anything actually happened.  */
 152   if (s == save)
 153     goto noconv;
 154
 155   /* Store in ENDPTR the address of one character
 156      past the last character we converted.  */
 157   if (endptr != NULL)
 158     *endptr = (char *) s;
 159
 160 #if     !UNSIGNED
 161   /* Check for a value that is within the range of
 162      `unsigned long int', but outside the range of `long int'.  */
 163   if (i > (negative ?
 164            -(unsigned long int) LONG_MIN : (unsigned long int) LONG_MAX))
 165     overflow = 1;
 166 #endif
 167
 168   if (overflow)
 169     {
 170       errno = ERANGE;
 171 #if     UNSIGNED
 172       return ULONG_MAX;
 173 #else
 174       return negative ? LONG_MIN : LONG_MAX;
 175 #endif
 176     }
 177
 178   /* Return the result of the appropriate sign.  */
 179   return (negative ? -i : i);
 180
 181 noconv:;
 182   /* There was no number to convert.  */
 183   if (endptr != NULL)
 184     *endptr = (char *) nptr;
 185   return 0L;
 186 }