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In rare cases of strings specifying true values near sys.maxint, and oddball bases (not decimal or a power of 2), int(string, base) could deliver insane answers. This repairs all such problems, and also speeds string->int significantly. On my box, here are % speedups for decimal strings of various lengths: length speedup ------ ------- 1 12.4% 2 15.7% 3 20.6% 4 28.1% 5 33.2% 6 37.5% 7 41.9% 8 46.3% 9 51.2% 10 19.5% 11 19.9% 12 23.9% 13 23.7% 14 23.3% 15 24.9% 16 25.3% 17 28.3% 18 27.9% 19 35.7% Note that the difference between 9 and 10 is the difference between short and long Python ints on a 32-bit box. The patch doesn't actually do anything to speed conversion to long: the speedup is due to detecting "unsigned long" overflow more quickly. This is a bugfix candidate, but it's a non-trivial patch and it would be painful to separate the "bug fix" from the "speed up" parts.
This commit is contained in:
Tim Peters
parent
b63588c188
commit
b713ec2531
4 changed files with 262 additions and 88 deletions
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@ -15,6 +15,94 @@
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/* strtol and strtoul, renamed to avoid conflicts */
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#include <ctype.h>
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#ifndef DONT_HAVE_ERRNO_H
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#include <errno.h>
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#endif
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/* Static overflow check values for bases 2 through 36.
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* smallmax[base] is the largest unsigned long i such that
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* i * base doesn't overflow unsigned long.
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*/
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static unsigned long smallmax[] = {
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0, /* bases 0 and 1 are invalid */
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0,
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ULONG_MAX / 2,
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ULONG_MAX / 3,
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ULONG_MAX / 4,
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ULONG_MAX / 5,
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ULONG_MAX / 6,
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ULONG_MAX / 7,
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ULONG_MAX / 8,
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ULONG_MAX / 9,
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ULONG_MAX / 10,
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ULONG_MAX / 11,
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ULONG_MAX / 12,
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ULONG_MAX / 13,
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ULONG_MAX / 14,
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ULONG_MAX / 15,
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ULONG_MAX / 16,
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ULONG_MAX / 17,
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ULONG_MAX / 18,
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ULONG_MAX / 19,
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ULONG_MAX / 20,
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ULONG_MAX / 21,
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ULONG_MAX / 22,
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ULONG_MAX / 23,
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ULONG_MAX / 24,
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ULONG_MAX / 25,
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ULONG_MAX / 26,
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ULONG_MAX / 27,
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ULONG_MAX / 28,
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ULONG_MAX / 29,
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ULONG_MAX / 30,
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ULONG_MAX / 31,
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ULONG_MAX / 32,
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ULONG_MAX / 33,
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ULONG_MAX / 34,
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ULONG_MAX / 35,
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ULONG_MAX / 36,
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};
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/* maximum digits that can't ever overflow for bases 2 through 36,
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* calculated by [int(math.floor(math.log(2**32, i))) for i in range(2, 37)].
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* Note that this is pessimistic if sizeof(long) > 4.
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*/
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static int digitlimit[] = {
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0, 0, 32, 20, 16, 13, 12, 11, 10, 10, /* 0 - 9 */
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9, 9, 8, 8, 8, 8, 8, 7, 7, 7, /* 10 - 19 */
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7, 7, 7, 7, 6, 6, 6, 6, 6, 6, /* 20 - 29 */
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6, 6, 6, 6, 6, 6, 6}; /* 30 - 36 */
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/* char-to-digit conversion for bases 2-36; all non-digits are 37 */
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static int digitlookup[] = {
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 37, 37, 37, 37, 37, 37,
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37, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
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25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 37, 37, 37, 37,
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37, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
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25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
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37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37
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};
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/*
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** strtoul
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** This is a general purpose routine for converting
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@ -28,98 +116,100 @@
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** Errors due to bad pointers will probably result in
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** exceptions - we don't check for them.
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*/
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#include <ctype.h>
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#ifndef DONT_HAVE_ERRNO_H
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#include <errno.h>
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#endif
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unsigned long
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PyOS_strtoul(register char *str, char **ptr, int base)
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{
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register unsigned long result; /* return value of the function */
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register int c; /* current input character */
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register unsigned long temp; /* used in overflow testing */
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int ovf; /* true if overflow occurred */
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register unsigned long result = 0; /* return value of the function */
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register int c; /* current input character */
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register int ovlimit; /* required digits to overflow */
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result = 0;
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ovf = 0;
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/* skip leading white space */
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while (*str && isspace(Py_CHARMASK(*str)))
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++str;
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/* catch silly bases */
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if (base != 0 && (base < 2 || base > 36))
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{
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/* check for leading 0 or 0x for auto-base or base 16 */
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switch (base) {
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case 0: /* look for leading 0, 0x or 0X */
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if (*str == '0') {
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++str;
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if (*str == 'x' || *str == 'X') {
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++str;
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base = 16;
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}
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else
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base = 8;
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}
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else
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base = 10;
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break;
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case 16: /* skip leading 0x or 0X */
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if (*str == '0') {
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++str;
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if (*str == 'x' || *str == 'X')
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++str;
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}
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break;
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}
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/* catch silly bases */
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if (base < 2 || base > 36) {
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if (ptr)
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*ptr = str;
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return 0;
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}
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/* skip leading zeroes */
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while (*str == '0')
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++str;
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/* base is guaranteed to be in [2, 36] at this point */
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ovlimit = digitlimit[base];
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/* do the conversion until non-digit character encountered */
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while ((c = digitlookup[Py_CHARMASK(*str)]) < base) {
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if (ovlimit > 0) /* no overflow check required */
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result = result * base + c;
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else { /* requires overflow check */
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register unsigned long temp_result;
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if (ovlimit < 0) /* guaranteed overflow */
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goto overflowed;
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/* there could be an overflow */
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/* check overflow just from shifting */
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if (result > smallmax[base])
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goto overflowed;
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result *= base;
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/* check overflow from the digit's value */
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temp_result = result + c;
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if (temp_result < result)
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goto overflowed;
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result = temp_result;
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}
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++str;
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--ovlimit;
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}
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/* set pointer to point to the last character scanned */
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if (ptr)
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*ptr = str;
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return 0;
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}
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*ptr = str;
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/* skip leading white space */
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while (*str && isspace(Py_CHARMASK(*str)))
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str++;
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return result;
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/* check for leading 0 or 0x for auto-base or base 16 */
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switch (base)
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{
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case 0: /* look for leading 0, 0x or 0X */
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if (*str == '0')
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{
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str++;
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if (*str == 'x' || *str == 'X')
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{
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str++;
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base = 16;
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}
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else
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base = 8;
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overflowed:
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if (ptr) {
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/* spool through remaining digit characters */
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while (digitlookup[Py_CHARMASK(*str)] < base)
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++str;
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*ptr = str;
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}
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else
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base = 10;
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break;
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case 16: /* skip leading 0x or 0X */
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if (*str == '0' && (*(str+1) == 'x' || *(str+1) == 'X'))
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str += 2;
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break;
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}
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/* do the conversion */
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while ((c = Py_CHARMASK(*str)) != '\0')
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{
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if (isdigit(c) && c - '0' < base)
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c -= '0';
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else
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{
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if (isupper(c))
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c = tolower(c);
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if (c >= 'a' && c <= 'z')
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c -= 'a' - 10;
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else /* non-"digit" character */
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break;
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if (c >= base) /* non-"digit" character */
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break;
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}
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temp = result;
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result = result * base + c;
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if(base == 10) {
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if(((long)(result - c) / base != (long)temp)) /* overflow */
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ovf = 1;
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}
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else {
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if ((result - c) / base != temp) /* overflow */
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ovf = 1;
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}
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str++;
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}
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/* set pointer to point to the last character scanned */
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if (ptr)
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*ptr = str;
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if (ovf)
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{
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result = (unsigned long) ~0L;
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errno = ERANGE;
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}
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return result;
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return (unsigned long)-1;
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}
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long
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@ -127,25 +217,25 @@ PyOS_strtol(char *str, char **ptr, int base)
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{
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long result;
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char sign;
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while (*str && isspace(Py_CHARMASK(*str)))
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str++;
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sign = *str;
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if (sign == '+' || sign == '-')
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str++;
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result = (long) PyOS_strtoul(str, ptr, base);
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/* Signal overflow if the result appears negative,
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except for the largest negative integer */
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if (result < 0 && !(sign == '-' && result == -result)) {
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errno = ERANGE;
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result = 0x7fffffff;
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}
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if (sign == '-')
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result = -result;
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return result;
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}
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