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From Nuutti Kotivuori <na...@iki.fi>
Subject Re: [PATCH] fixes for apr_vformatter and apr_snprintf
Date Thu, 11 Jul 2002 15:18:06 GMT
Jim Jagielski wrote:
> At 10:17 AM +0300 7/11/02, Nuutti Kotivuori wrote:
>> But back to the subject at hand.
>>
>> I'm a bit uncertain _how_ am I supposed to be using apr_snprintf so
>> code doesn't break the next time it's behaviour changes? I'm a bit
>> on a foul mood here, sorry, but this was supposed to be just a
>> minor checkup to see if the return value included the nul-byte or
>> not.
>>
>> So, if I want the length, without including the nul-byte - I need
>> to compare the return value against the buffer length I passed in,
>> and substract one if they are equal? I'd like to _depend_ on
>> something working this way, if I do it this way.
> 
> Hmmm... In the current code, if they are equal then it means either
> it fully fit the buffer or was truncated. So yes. Recall that
> ap(r)_snprintf() copies at most size-1, so the length of the
> returned string can only be a maximum of size-1.
> 
> I agree it looks like we're compromising vformatter for a bug in
> apr_psprintf...

OK, so if I make a fix to apr_psprintf to fix it, we can remove the
kludge in vformatter?

After that apr_snprintf returns len-1 if the data just fit and len if
it got truncated. Is this what is wanted?

If so, then the canonical code for getting the amount of chars written
would be:

#define SNPRINTF_MAXLEN

int chars = apr_snprintf(buffer, SNPRINTF_MAXLEN, format, ...);
if(chars >= SNPRINTF_MAXLEN) chars = SNPRINTF_MAXLEN-1;

I'll try and code the fix for this once I get a confirmation on this.

-- Naked

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