lib/strtol.c

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