Re: Speedup usages of pg_*toa() functions

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От Ranier Vilela
Тема Re: Speedup usages of pg_*toa() functions
Дата
Msg-id CAEudQAp5o4sp=EoE-LNRneW=RcmQFfVZ0OKRP4RqMOcqJAy92w@mail.gmail.com
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Ответ на Re: Speedup usages of pg_*toa() functions  (Andrew Gierth <andrew@tao11.riddles.org.uk>)
Ответы Re: Speedup usages of pg_*toa() functions  (Andrew Gierth <andrew@tao11.riddles.org.uk>)
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Em ter., 9 de jun. de 2020 às 15:53, Andrew Gierth <andrew@tao11.riddles.org.uk> escreveu:
>>>>> "Ranier" == Ranier Vilela <ranier.vf@gmail.com> writes:

 Ranier> Where " ends up with two copies of pg_ultoa_n inlined into it",
 Ranier> in this simplified example?

The two references to sprintf are both inlined copies of your pg_utoa.

 Ranier> (b) I call this tail cut, I believe it saves time, for sure.

You seem to have missed the point that the pg_ultoa_n / pg_ulltoa_n
functions DO NOT ADD A TRAILING NUL. Which means that pg_ltoa / pg_lltoa
can't just tail call them, since they must add the NUL after.

 Ranier> Regarding bugs:

 Ranier> (c) your version don't check size of a var, when pg_ulltoa_n
 Ranier> warning about "least MAXINT8LEN bytes."

 Ranier> So in theory, I could blow it up, by calling pg_lltoa.

No. Callers of pg_lltoa are required to provide a buffer of at least
MAXINT8LEN+1 bytes.
Thanks for explanations.

So I would change, just the initialization (var uvalue), even though it is irrelevant.

int
pg_lltoa(int64 value, char *a)
{
int len = 0;
uint64 uvalue;

if (value < 0)
{
uvalue = (uint64) 0 - uvalue;
        a[len++] = '-';
}
else
uvalue = value;

len += pg_ulltoa_n(uvalue, a + len);
a[len] = '\0';

return len;
}
 
regards,
Ranier Vilela

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