Re: Patch: add conversion from pg_wchar to multibyte

> On Tue, May 22, 2012 at 3:27 PM, Tatsuo Ishii <ishii(at)postgresql(dot)org> wrote:
>
>> > Thanks for your comments. They clarify a lot.
>> > But I still don't realize how can we distinguish IS_LCPRV2 and IS_LC2?
>> > Isn't it possible for them to produce same pg_wchar?
>>
>> If LB is in 0x90 - 0x99 range, then they are LC2.
>> If LB is in 0xf0 - 0xff range, then they are LCPRV2.
>>
>
> Thanks. I rewrote inverse conversion from pg_wchar to mule. New version of
> patch is attached.

[forgot to cc: to the list]

I looked into your patch, especially: pg_wchar2euc_with_len(const
pg_wchar *from, unsigned char *to, int len)

I think there's a small room to enhance the function.

if (*from >> 24)
{
*to++ = *from >> 24;
*to++ = (*from >> 16) & 0xFF;
*to++ = (*from >> 8) & 0xFF;
*to++ = *from & 0xFF;
cnt += 4;
}

Since the function walk through this every single wchar, something like:

if ((c = *from >> 24))
{
*to++ = c;
*to++ = (*from >> 16) & 0xFF;
*to++ = (*from >> 8) & 0xFF;
*to++ = *from & 0xFF;
cnt += 4;
}

will save few cycles(I'm not sure the optimizer produces similar code
above anyway though).
--
Tatsuo Ishii
SRA OSS, Inc. Japan
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