diff options
Diffstat (limited to 'Python/mystrtoul.c')
| -rw-r--r-- | Python/mystrtoul.c | 238 |
1 files changed, 150 insertions, 88 deletions
diff --git a/Python/mystrtoul.c b/Python/mystrtoul.c index 8e60c0c..380b37d 100644 --- a/Python/mystrtoul.c +++ b/Python/mystrtoul.c @@ -15,6 +15,66 @@ /* strtol and strtoul, renamed to avoid conflicts */ + +#include <ctype.h> +#ifndef DONT_HAVE_ERRNO_H +#include <errno.h> +#endif + +/* Static overflow check values for bases 2 through 36. + * smallmax[base] is the largest unsigned long i such that + * i * base doesn't overflow unsigned long. + */ +static unsigned long smallmax[] = { + 0, /* bases 0 and 1 are invalid */ + 0, + ULONG_MAX / 2, + ULONG_MAX / 3, + ULONG_MAX / 4, + ULONG_MAX / 5, + ULONG_MAX / 6, + ULONG_MAX / 7, + ULONG_MAX / 8, + ULONG_MAX / 9, + ULONG_MAX / 10, + ULONG_MAX / 11, + ULONG_MAX / 12, + ULONG_MAX / 13, + ULONG_MAX / 14, + ULONG_MAX / 15, + ULONG_MAX / 16, + ULONG_MAX / 17, + ULONG_MAX / 18, + ULONG_MAX / 19, + ULONG_MAX / 20, + ULONG_MAX / 21, + ULONG_MAX / 22, + ULONG_MAX / 23, + ULONG_MAX / 24, + ULONG_MAX / 25, + ULONG_MAX / 26, + ULONG_MAX / 27, + ULONG_MAX / 28, + ULONG_MAX / 29, + ULONG_MAX / 30, + ULONG_MAX / 31, + ULONG_MAX / 32, + ULONG_MAX / 33, + ULONG_MAX / 34, + ULONG_MAX / 35, + ULONG_MAX / 36, +}; + +/* maximum digits that can't ever overflow for bases 2 through 36, + * calculated by [int(math.floor(math.log(2**32, i))) for i in range(2, 37)]. + * Note that this is pessimistic if sizeof(long) > 4. + */ +static int digitlimit[] = { + 0, 0, 32, 20, 16, 13, 12, 11, 10, 10, /* 0 - 9 */ + 9, 9, 8, 8, 8, 8, 8, 7, 7, 7, /* 10 - 19 */ + 7, 7, 7, 7, 6, 6, 6, 6, 6, 6, /* 20 - 29 */ + 6, 6, 6, 6, 6, 6, 6}; /* 30 - 36 */ + /* ** strtoul ** This is a general purpose routine for converting @@ -28,98 +88,100 @@ ** Errors due to bad pointers will probably result in ** exceptions - we don't check for them. */ - -#include <ctype.h> -#ifndef DONT_HAVE_ERRNO_H -#include <errno.h> -#endif - unsigned long PyOS_strtoul(register char *str, char **ptr, int base) { - register unsigned long result; /* return value of the function */ - register int c; /* current input character */ - register unsigned long temp; /* used in overflow testing */ - int ovf; /* true if overflow occurred */ + register unsigned long result = 0; /* return value of the function */ + register int c; /* current input character */ + register int ovlimit; /* required digits to overflow */ + + /* skip leading white space */ + while (*str && isspace(Py_CHARMASK(*str))) + ++str; - result = 0; - ovf = 0; + /* check for leading 0 or 0x for auto-base or base 16 */ + switch (base) { + case 0: /* look for leading 0, 0x or 0X */ + if (*str == '0') { + ++str; + if (*str == 'x' || *str == 'X') { + ++str; + base = 16; + } + else + base = 8; + } + else + base = 10; + break; -/* catch silly bases */ - if (base != 0 && (base < 2 || base > 36)) - { - if (ptr) - *ptr = str; - return 0; - } - -/* skip leading white space */ - while (*str && isspace(Py_CHARMASK(*str))) - str++; - -/* check for leading 0 or 0x for auto-base or base 16 */ - switch (base) - { - case 0: /* look for leading 0, 0x or 0X */ - if (*str == '0') - { - str++; - if (*str == 'x' || *str == 'X') - { - str++; - base = 16; - } - else - base = 8; + case 16: /* skip leading 0x or 0X */ + if (*str == '0') { + ++str; + if (*str == 'x' || *str == 'X') + ++str; + } + break; } - else - base = 10; - break; - - case 16: /* skip leading 0x or 0X */ - if (*str == '0' && (*(str+1) == 'x' || *(str+1) == 'X')) - str += 2; - break; - } - -/* do the conversion */ - while ((c = Py_CHARMASK(*str)) != '\0') - { - if (isdigit(c) && c - '0' < base) - c -= '0'; - else - { - if (isupper(c)) - c = tolower(c); - if (c >= 'a' && c <= 'z') - c -= 'a' - 10; - else /* non-"digit" character */ - break; - if (c >= base) /* non-"digit" character */ - break; + + /* catch silly bases */ + if (base < 2 || base > 36) { + if (ptr) + *ptr = str; + return 0; } - temp = result; - result = result * base + c; - if(base == 10) { - if(((long)(result - c) / base != (long)temp)) /* overflow */ - ovf = 1; + + /* skip leading zeroes */ + while (*str == '0') + ++str; + + /* base is guaranteed to be in [2, 36] at this point */ + ovlimit = digitlimit[base]; + + /* do the conversion until non-digit character encountered */ + while ((c = _PyLong_DigitValue[Py_CHARMASK(*str)]) < base) { + if (ovlimit > 0) /* no overflow check required */ + result = result * base + c; + else { /* requires overflow check */ + register unsigned long temp_result; + + if (ovlimit < 0) /* guaranteed overflow */ + goto overflowed; + + /* there could be an overflow */ + /* check overflow just from shifting */ + if (result > smallmax[base]) + goto overflowed; + + result *= base; + + /* check overflow from the digit's value */ + temp_result = result + c; + if (temp_result < result) + goto overflowed; + + result = temp_result; + } + + ++str; + --ovlimit; } - else { - if ((result - c) / base != temp) /* overflow */ - ovf = 1; + + /* set pointer to point to the last character scanned */ + if (ptr) + *ptr = str; + + return result; + +overflowed: + if (ptr) { + /* spool through remaining digit characters */ + while (_PyLong_DigitValue[Py_CHARMASK(*str)] < base) + ++str; + *ptr = str; } - str++; - } - -/* set pointer to point to the last character scanned */ - if (ptr) - *ptr = str; - if (ovf) - { - result = (unsigned long) ~0L; errno = ERANGE; - } - return result; + return (unsigned long)-1; } long @@ -127,25 +189,25 @@ PyOS_strtol(char *str, char **ptr, int base) { long result; char sign; - + while (*str && isspace(Py_CHARMASK(*str))) str++; - + sign = *str; if (sign == '+' || sign == '-') str++; - + result = (long) PyOS_strtoul(str, ptr, base); - + /* Signal overflow if the result appears negative, except for the largest negative integer */ if (result < 0 && !(sign == '-' && result == -result)) { errno = ERANGE; result = 0x7fffffff; } - + if (sign == '-') result = -result; - + return result; } |