Re: [Boost-users] Compress to buffer

Subject: Re: [Boost-users] Compress to buffer
From: Kenneth Adam Miller (kennethadammiller_at_[hidden])
Date: 2014-01-14 14:58:23

Thank you.

On Tue, Jan 14, 2014 at 1:55 PM, Krzysztof Czainski <1czajnik_at_[hidden]>wrote:

> 2014/1/14 Kenneth Adam Miller <kennethadammiller_at_[hidden]>
>
>> Ah ok. I apologize for posting too fast. I will be sure to go further in
>> exhausting all resources before I post in the future. However, I did find
>> some of the descriptions of the iostreams parts and how they compose
>> (especially examples, that's what I was really looking for) vague, IMHO.
>>
>> No, I haven't measured performance.
>>
> [...]
>
>>  Those unnecessary allocation copies would, in the worst case, result in
>> a 2-3x slowdown of the entire program
>>
>
> How do you know?
>
>
>>  due to the fact that it's literally pausing to repeat something that's
>> unnecessary.
>>
>> But actually, if this appends my 30k string, I didn't know it. The
>> back_insert_device<string> object wasn't something that I understood very
>> well from the description at
>> http://www.boost.org/doc/libs/1_45_0/libs/iostreams/doc/classes/back_inserter.html
>>
>> From what I had thought though, if my string was empty with 0's,
>>
>
> Right here's your mistake. string(30000,0) creates a non empty string.
> It's a string of 30k nulls.
>
>
>> and I appended to it, then I would end up with precisely my compressed
>> data. The idea of acquireStringFromPool is that it returns a large string
>> that is always cleared out for the filtering_ostream to fill up as though
>> it were a device. Is that incorrect? How can I get that functionality?
>>
>
> Like I said, you want std::vector::reserve().
>
> Perhaps, however, that reserve approach would be good. I apologize the
>> email was so long lol.
>>
>
> Btw, you're still top-posting. The idea is to leave the (minimal) context
> above your reply message ;-)
>
> By top posting you meant just the position of my text. I thought you meant
it to be me posting when I could have more fully investigated the issue. I
will follow this convention.

> Regards,
> Kris
>
>
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