Re: [RFC] CryptoAPI & Compression

Artem B. Bityuckiy
2005-04-03T09:20:28Z

Herbert Xu wrote:
> On Sun, Apr 03, 2005 at 12:22:12PM +0400, Artem B. Bityuckiy wrote:
>
>>The latter case is possible if the input isn't compressible and it is up
>>to user to detect that handle this situation properly (i.e., just not to
>>compress this). So, IMO, there are no problems here at least for the
>>crypto_comp_pcompress() function.
>

I meant here, that user a-priori doesn't always know how good will his
data be compressed. So, he *may* provide the output buffer of the same
size as the input buffer (as you wrote, both are of 1GiB). So, if the
input data *grows* after the compression, then crypto_comp_pcompress()
will fill the output buffer fully and return OK, indicating that not all
the input was compressed. And it is up to user to handle this situation.
Probably he will just leave his data uncompressed. Probably he will
provide more output buffers. I just wanted to say, that
crypto_comp_pcompress() will work OK even in the case of uncompressible
data because I thought something worries you in this case :-)

> Surely that defeats the purpose of pcompress? I thought the whole point
> was to compress as much of the input as possible into the output?
>
> So 1G into 1G doesn't make sense here. But 1G into 1M does and you
> want to put as much as you can in there. Otherwise we might as well
> delete crypto_comp_pcompress :)