Python/mystrtoul.c

   1
   2 #include "Python.h"
   3
   4 #if defined(__sgi) && defined(WITH_THREAD) && !defined(_SGI_MP_SOURCE)
   5 #define _SGI_MP_SOURCE
   6 #endif
   7
   8 /* Convert a possibly signed character to a nonnegative int */
   9 /* XXX This assumes characters are 8 bits wide */
  10 #ifdef __CHAR_UNSIGNED__
  11 #define Py_CHARMASK(c)          (c)
  12 #else
  13 #define Py_CHARMASK(c)          ((c) & 0xff)
  14 #endif
  15
  16 /* strtol and strtoul, renamed to avoid conflicts */
  17
  18
  19 #include <ctype.h>
  20 #ifdef HAVE_ERRNO_H
  21 #include <errno.h>
  22 #endif
  23
  24 /* Static overflow check values for bases 2 through 36.
  25  * smallmax[base] is the largest unsigned long i such that
  26  * i * base doesn't overflow unsigned long.
  27  */
  28 static unsigned long smallmax[] = {
  29         0, /* bases 0 and 1 are invalid */
  30         0,
  31         ULONG_MAX / 2,
  32         ULONG_MAX / 3,
  33         ULONG_MAX / 4,
  34         ULONG_MAX / 5,
  35         ULONG_MAX / 6,
  36         ULONG_MAX / 7,
  37         ULONG_MAX / 8,
  38         ULONG_MAX / 9,
  39         ULONG_MAX / 10,
  40         ULONG_MAX / 11,
  41         ULONG_MAX / 12,
  42         ULONG_MAX / 13,
  43         ULONG_MAX / 14,
  44         ULONG_MAX / 15,
  45         ULONG_MAX / 16,
  46         ULONG_MAX / 17,
  47         ULONG_MAX / 18,
  48         ULONG_MAX / 19,
  49         ULONG_MAX / 20,
  50         ULONG_MAX / 21,
  51         ULONG_MAX / 22,
  52         ULONG_MAX / 23,
  53         ULONG_MAX / 24,
  54         ULONG_MAX / 25,
  55         ULONG_MAX / 26,
  56         ULONG_MAX / 27,
  57         ULONG_MAX / 28,
  58         ULONG_MAX / 29,
  59         ULONG_MAX / 30,
  60         ULONG_MAX / 31,
  61         ULONG_MAX / 32,
  62         ULONG_MAX / 33,
  63         ULONG_MAX / 34,
  64         ULONG_MAX / 35,
  65         ULONG_MAX / 36,
  66 };
  67
  68 /* maximum digits that can't ever overflow for bases 2 through 36,
  69  * calculated by [int(math.floor(math.log(2**32, i))) for i in range(2, 37)].
  70  * Note that this is pessimistic if sizeof(long) > 4.
  71  */
  72 static int digitlimit[] = {
  73         0,  0, 32, 20, 16, 13, 12, 11, 10, 10,  /*  0 -  9 */
  74         9,  9,  8,  8,  8,  8,  8,  7,  7,  7,  /* 10 - 19 */
  75         7,  7,  7,  7,  6,  6,  6,  6,  6,  6,  /* 20 - 29 */
  76         6,  6,  6,  6,  6,  6,  6};             /* 30 - 36 */
  77
  78 /*
  79 **      strtoul
  80 **              This is a general purpose routine for converting
  81 **              an ascii string to an integer in an arbitrary base.
  82 **              Leading white space is ignored.  If 'base' is zero
  83 **              it looks for a leading 0, 0x or 0X to tell which
  84 **              base.  If these are absent it defaults to 10.
  85 **              Base must be 0 or between 2 and 36 (inclusive).
  86 **              If 'ptr' is non-NULL it will contain a pointer to
  87 **              the end of the scan.
  88 **              Errors due to bad pointers will probably result in
  89 **              exceptions - we don't check for them.
  90 */
  91 unsigned long
  92 PyOS_strtoul(register char *str, char **ptr, int base)
  93 {
  94         register unsigned long result = 0; /* return value of the function */
  95         register int c;         /* current input character */
  96         register int ovlimit;   /* required digits to overflow */
  97
  98         /* skip leading white space */
  99         while (*str && isspace(Py_CHARMASK(*str)))
 100                 ++str;
 101
 102         /* check for leading 0 or 0x for auto-base or base 16 */
 103         switch (base) {
 104                 case 0:         /* look for leading 0, 0x or 0X */
 105                         if (*str == '0') {
 106                                 ++str;
 107                                 if (*str == 'x' || *str == 'X') {
 108                                         ++str;
 109                                         base = 16;
 110                                 }
 111                                 else
 112                                         base = 8;
 113                         }
 114                         else
 115                                 base = 10;
 116                         break;
 117
 118                 case 16:        /* skip leading 0x or 0X */
 119                         if (*str == '0') {
 120                                 ++str;
 121                                 if (*str == 'x' || *str == 'X')
 122                                         ++str;
 123                         }
 124                         break;
 125         }
 126
 127         /* catch silly bases */
 128         if (base < 2 || base > 36) {
 129                 if (ptr)
 130                         *ptr = str;
 131                 return 0;
 132         }
 133
 134         /* skip leading zeroes */
 135         while (*str == '0')
 136                 ++str;
 137
 138         /* base is guaranteed to be in [2, 36] at this point */
 139         ovlimit = digitlimit[base];
 140
 141         /* do the conversion until non-digit character encountered */
 142         while ((c = _PyLong_DigitValue[Py_CHARMASK(*str)]) < base) {
 143                 if (ovlimit > 0) /* no overflow check required */
 144                         result = result * base + c;
 145                 else { /* requires overflow check */
 146                         register unsigned long temp_result;
 147
 148                         if (ovlimit < 0) /* guaranteed overflow */
 149                                 goto overflowed;
 150
 151                         /* there could be an overflow */
 152                         /* check overflow just from shifting */
 153                         if (result > smallmax[base])
 154                                 goto overflowed;
 155
 156                         result *= base;
 157
 158                         /* check overflow from the digit's value */
 159                         temp_result = result + c;
 160                         if (temp_result < result)
 161                                 goto overflowed;
 162
 163                         result = temp_result;
 164                 }
 165
 166                 ++str;
 167                 --ovlimit;
 168         }
 169
 170         /* set pointer to point to the last character scanned */
 171         if (ptr)
 172                 *ptr = str;
 173
 174         return result;
 175
 176 overflowed:
 177         if (ptr) {
 178                 /* spool through remaining digit characters */
 179                 while (_PyLong_DigitValue[Py_CHARMASK(*str)] < base)
 180                         ++str;
 181                 *ptr = str;
 182         }
 183         errno = ERANGE;
 184         return (unsigned long)-1;
 185 }
 186
 187 long
 188 PyOS_strtol(char *str, char **ptr, int base)
 189 {
 190         long result;
 191         char sign;
 192
 193         while (*str && isspace(Py_CHARMASK(*str)))
 194                 str++;
 195
 196         sign = *str;
 197         if (sign == '+' || sign == '-')
 198                 str++;
 199
 200         result = (long) PyOS_strtoul(str, ptr, base);
 201
 202         /* Signal overflow if the result appears negative,
 203            except for the largest negative integer */
 204         if (result < 0 && !(sign == '-' && result == -result)) {
 205                 errno = ERANGE;
 206                 result = 0x7fffffff;
 207         }
 208
 209         if (sign == '-')
 210                 result = -result;
 211
 212         return result;
 213 }