compiler/clib/atol.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     ANSI C function atol().
   6 */
   7
   8 #include <limits.h>
   9 #include <ctype.h>
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14 #include <stdlib.h>
  15
  16         long atol (
  17
  18 /*  SYNOPSIS */
  19         const char * str)
  20
  21 /*  FUNCTION
  22         Convert a string of digits into an long integer.
  23
  24     INPUTS
  25         str - The string which should be converted. Leading
  26                 whitespace are ignored. The number may be prefixed
  27                 by a '+' or '-'.
  28
  29     RESULT
  30         The value of string str.
  31
  32     NOTES
  33
  34     EXAMPLE
  35         // returns 1
  36         atol ("  \t +1");
  37
  38         // returns 1
  39         atol ("1");
  40
  41         // returns -1
  42         atol ("  \n -1");
  43
  44     BUGS
  45
  46     SEE ALSO
  47         atof(), atoi(), strtod(), strtol(), strtoul()
  48
  49     INTERNALS
  50
  51 ******************************************************************************/
  52 {
  53     unsigned long   val   = 0;
  54     int             digit;
  55     char            c = 0;
  56     unsigned long   cutoff;
  57     int             cutlim;
  58     int             any;
  59
  60     while (isspace (*str))
  61         str ++;
  62
  63     if (*str)
  64     {
  65         if (*str == '+' || *str == '-')
  66             c = *str ++;
  67
  68         /*
  69             Conversion loop, from FreeBSD's src/lib/libc/stdlib/strtoul.c
  70
  71             The previous AROS loop was
  72             a) inefficient - it did a division each time around.
  73             b) buggy - it returned the wrong value in endptr on overflow.
  74         */
  75         cutoff = (unsigned long)ULONG_MAX / (unsigned long)10;
  76         cutlim = (unsigned long)ULONG_MAX % (unsigned long)10;
  77         val = 0;
  78         any = 0;
  79
  80         while (*str)
  81         {
  82             digit = *str;
  83
  84             if (!isdigit(digit))
  85                 break;
  86
  87             digit -= '0';
  88
  89             /*
  90                 any < 0 when we have overflowed. We still need to find the
  91                 end of the subject sequence
  92             */
  93             if (any < 0 || val > cutoff || (val == cutoff && digit > cutlim))
  94             {
  95                 any = -1;
  96             }
  97             else
  98             {
  99                 any = 1;
 100                 val = (val * 10) + digit;
 101             }
 102
 103             str++;
 104         }
 105
 106         /* Range overflow */
 107         if (any < 0)
 108         {
 109             val = ULONG_MAX;
 110         }
 111
 112         if (c == '-')
 113             val = -val;
 114     }
 115
 116     return val;
 117 } /* atol */