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Vladimir 'phcoder' Serbinenko a écrit :
> Duboucher Thomas wrote:
>> Bean a écrit :
>>> Hi,
>>> This one work:
>>> int
>>> auth_strcmp (const char *s1, const char *s2)
>>> {
>>> int result = 0;
>>> while (1)
>>> {
>>> result += (*s1 != *s2);
>>> if (*s1 == 0)
>>> break;
>>> s1++;
>>> s2++;
>>> }
>>> return (result != 0);
>>> }
>>> The trick is to compare the ending '\0' as well, so that partial match
>>> is not satisfied.
>>
>> Yep, I like this one, but I would prefer using an OR instead of an ADD
>> (with a highly hypothetical integer overflow :p) and because it's nicer
>> in terms of pure logic.
>> "The comparison beetwen s1 and s2 is false if *s1 is different from
>> *s2, or recursively if the comparison beetwen s1+1 and s2+1 is false"
>>
>> int
>> auth_strcmp (const char *s1, const char *s2)
>> {
>> int ret = 0;
>>
>> for (;;)
>> {
>> ret |= (*s1 != *s2);
>>
>> if (*s1 == '\0')
>> break;
>>
>> s1++;
>> s2++;
>> }
>>
>> return ret;
>> }
>>
> But now it has a technical problem: it may read post array definitions.
> If any of post-array memory is MMIO or absent reading from it may have
> peculiar consequences
Well, the only way to solve that problem would be IMHO to add a limit
to the size of s2, and use this maximum size as an end condition for the
'for' statement. Any better idea? :)
int
auth_strcmp (const char *s1, const char *s2)
{
int ret, n;
for (ret = n = 0; ret < PASSPHRASE_MAXSIZE; ret++)
{
ret |= (*s1 != *s2);
if (*s1 == '\0')
break;
s1++;
s2++;
}
return ret;
}
>> Also, because s1 and s2 have two differents roles, I think it would be
>> best to give them names that better suits them. ;)
>>
>> Thomas.
>
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